HomeMy WebLinkAboutR-2013-133 Ahtanum-Wide Hollow Comprehensive Flood Hazard Management Plan AdoptionRESOLUTION NO. R-2013-133
A RESOLUTION of the City of Yakima, Washington adopting the Ahtanum-Wide
Hollow Comprehensive Flood Hazard Management Plan.
WHEREAS, Yakima County has experienced significant and repeated flood
damages throughout its history, was declared a Federal Disaster Area eight times in 27
years, and suffered 18 million dollars in damages to public infrastructure in the 1996 flood;
and
WHEREAS, Yakima County at the request of its constituents formed the
Countywide Flood Control Zone District (FCZD) in 1998 to carry out planning for flood risk
management and flood hazard reduction within the County's boundary and cities therein;
and
WHEREAS, in 2003 and 2005 (phases 1 and 2) Yakima County received State
Flood Control Assistance Account Program (FCAAP) funding to prepare a Comprehensive
Flood Hazard Management Plan (CFHMP) for streams in the Ahtanum and Wide Hollow
basins; and
WHEREAS, the FCZD, with the assistance of an advisory committee, which
included citizens, stakeholders (irrigation companies/districts), staff members of the cities
within the Yakima Valley (the City of Yakima and Union Gap), Yakima Nation, and
members of affected agencies have completed the Ahtanum-Wide Hollow CFHMP; and
WHEREAS, extensive public outreach was conducted by the Yakima County
FCZD including: (a) four public meetings, (b) five newsletter updates on plan progress, (c)
posting of progressive drafts of the plan on the County website, (d) 48 citizen and agency
Advisory Committee meetings over five years, (e) distribution of the plan to the library and
at the Yakima County public services customer counter for review, (f) conduction of six
public meetings on projects and revised flood maps which are recommended in the plan;
and
WHEREAS, environmental review under the State Environmental Protection Act
(SEPA) was completed by Yakima County on September 6, 2011, with issuance of a
Determination of Non -Significance; and
WHEREAS, the City of Yakima Planning Department adopted Yakima County's
SEPA Determination of Non -Significance on September 25, 2013; and
WHEREAS, the Ahtanum-Wide Hollow CFHMP was presented to the Yakima
Board of County Commissioners and Yakima City Council at a joint city -county study
session on April 24, 2012; and
WHEREAS, in some cases the contents of the CFHMP may overlap with the
contents of the City of Yakima Urban Area Comprehensive Plan 2025 (hereinafter "Plan
2025") and development regulations of the City of Yakima; and
WHEREAS, the CFHMP should not constitute an additional layer of potentially
inconsistent policies or regulations binding on and within the City of Yakima, but should
instead serve only as an advisory complement to other City of Yakima planning
endeavors, including Plan 2025 and/or the City of Yakima's development regulations
should be deemed authoritative and controlling within the City of Yakima for all purposes;
and
WHEREAS, the Yakima City Council finds and determines that it is in the pubic
interest to adopt the resolution set forth herein and that adoption for the purposes set forth
above will promote the general health, safety and welfare; now, therefore
BE IT RESOLVED BY THE CITY COUNCIL OF THE CITY OF YAKIMA:
The Ahtanum-Wide Hollow Comprehensive Flood Hazard Management Plan, copy
of which is on file with the City of Yakima and incorporated herein by this reference, is
adopted; provided, however, that the CFHMP shall by this resolution be limited in effect
solely to serve as an advisory complement to other City of Yakima planning endeavors,
including Plan 2025 and the City of Yakima's development regulations, and provided,
further, that in the event of any conflict between the CFHMP (including any policy, rule,
regulation, or requirement contained therein), and Plan 2025 and/or any of the City of
Yakima's development regulations, are and shall be deemed authoritative and controlling
within the City of Yakima for all purposes
ADOPTED BY THE CITY COUNCIL this 15th day of October, 2013.
ATTEST:
Micah Cawley/Mayor
BUSINESS OF THE CITY COUNCIL
YAKIMA, WASHINGTON
AGENDA STATEMENT
L-)
Item No./
For Meeting of: 10/15/2013
ITEM TITLE: Open record public hearing for consideration of the Ahtanum-
Wide Hollow Comprehensive Flood Hazard Management
Plan.
SUBMITTED BY: Steve Osguthorpe, AICP: Community Development Manager
- (509) 575-3533
Jeff Peters, Supervising Planner - (509) 575-6163
SUMMARY EXPLANATION:
The Ahtanum-Wide Hollow Comprehensive Flood Hazard Management Plan (CFHMP) is
a policy complement to other City of Yakima planning endeavors, including the City of Yakima's
Comprehensive Plan 2025, and the City of Yakima's development
regulations. The CFHMP contains recommended policy changes and flood actions, including
projects that reduce flood hazards. If adopted by local jurisdictions, the CFHMP allows the
jurisdiction to become eligible for state and federal funds for flood emergency response and
non -emergency activities to reduce property loss and threats to human life.
On April 24, 2012, the Yakima County Flood Control District presented its completed Ahtanum-
Wide Hollow Comprehensive Flood Hazard Management Plan to the Yakima City Council in a
study session. The Flood Control District at that time indicated that following the County's
adoption of the CFHMP which occurred on October 16, 2012, each participating jurisdiction
would be required to separately adopt the plan (the City of Yakima was a participating
jurisdiction). Therefore, this agenda item requests that the Yakima City Council hold the
required open record public hearing to consider the adoption of the Ahtanum-Wide Hollow Flood
Hazard Management Plan, and adopt the accompanying resolution.
For a complete copy of the plan please refer to the attached CD within your council packet
or the following Yakima County Flood Control District web page at
http://www.yakimacounty.us/surfacewater/Ahtanum-Wide Hollow CFHMP.php.
Resolution: X Ordinance:
Other (Specify):
Contract: Contract Term:
Start Date: End Date:
Item Budgeted: Amount:
Funding Source/Fiscal
Impact:
Strategic Priority: Public Safety
Insurance Required? No
Mail to:
Phone:
APPROVED FOR
SUBMITTAL:
RECOMMENDATION:
City Manager
The City of Yakima Planning Division recommends that City Council hold the required public
hearing and adopt the accompanying resolution adopting by reference the Ahtanum-Wide
HoIIow Comprehensive Flood Hazard Management PIan.
ATTACHMENTS:
Description
Upload Date
|| Ahtanum-WideHoUvwCFHMPResolution 10M/2013
El xmanumvWoeHollow Fact Sheet 1 10/6/2013
|| xmanumvWoeHollow Fact Sheet 2 10x6o013
Ty
Resolution
Backup Material
Backup Material
Comprehensive Flood Hazard Management Plan
(CFHMP)' Process
Establish Community Participation
Establish CFHMP Advisory Committee
Inventory Physical Conditions
& Public Workshops
v
Set Goals & Objectives
Determine the need for
flood hazard management measures
Identify alternate flood hazard management
alternatives - structural & non-structural
Review concurrent
FEMA restudy flood maps
Evaluate alternative measures with respect to
goals & objectives, cost, benefits & impacts
Develop a flood hazard
management strategy
Complete draft plan
Plan reviewed by°local jurisdictions
Local SEPA review & approval
Submit final plan to local jurisdictions
for public hearing & adoption
Submit plan to Ecology
AHTANUM-WIDE HOLLOW CFHMP
(COMPREHENSIVE FLOOD HAZARD MANAGEMENT PLAN)
MILESTONES & LINKS
Meetings and notifications:
Completed
DATE
JURISDICTION
Communication
AUDIENCE
11-10-10
Yakima
Discussion
Planning Commission — regarding flood maps
4-12-11
Yakima & County
Presentation
Intergovernmental Committee meeting
11-17-11
Yakima
Study Session
Yakima Transportation & Utilities Committee
12-2-12
Yakama Nation
Email notice
Offered to do presentation on CFHMP
1-19-12
Central Washington
Home Builders
Presentation
Presentation was for their governmental
committee.
1-23-12
Union Gap
Study Session
Council sub -committee
4-24-12
Yakima & BOCC
Study Session
Joint session organized by Yakima for their
Council and County Commissioners
6-11-12
Union Gap
Study Session
Presentation during their regular council
meeting, as they requested
6-14-12
Yakama Nation
Email Notice
Sent update on CFHMP adoption status and
renewed offer of presentation
9-18-12
BOCC
Hearing
To consider adoption
10-8-12
BOCC
Study Session
To consider public comments from hearing
10-16-12
BOCC
Regular Agenda
mtg.
Adopted the CFHMP, Reso. 388-2012
1-28-13
Union Gap
Hearing &
Adoption
Adopted the CFHMP, Reso No. 1043
10-15-13
Yakima
Hearing
Scheduled
To be Scheduled
DATE
JURISDICTION
Communication
AUDIENCE
2014?
Yakama Nation
Presentation
If requested
Other notable milestones:
June 2002 - Yakama Nation and Yakima County Memorandum of Agreement regarding
flood management for Ahtanum Creek and the Yakima River
April 2004 - approval of Phase 1 FCAAP grant (Flood Control Assistance Account
Program), Washington State program administered by Department of Ecology
August 2004 - Golder Associates, Inc. hired to provide assistance with public and
committee meetings; document and map flood history data; and gather current
field data on project area structures
(More on back...) Contact - Dianna Woods, 509-574-2300, dianna.woods®co.yakima.wa.us
November 2004 — the steering committee of staff members from the tribal, city and
county jurisdictions conducted their first meeting
February 2005 — completed the last of four public outreach meetings scheduled in
different locations throughout the plan area. More than 60 people total attended
these meetings - they identified 140 flood problems. The majority of attendees
were from rural or suburban areas.
March 2005 — more than 600 postcards were mailed to property owners in the urban
area seeking input on flooding and soliciting volunteers for the Advisory
Committee.
April 2005 — first newsletter mailed to interested members of the public
April 2005 — first Advisory Committee meeting which included property and business
owners from the jurisdictions and other stakeholders from engineering,
environmental, irrigation, regulatory, development, realty, historic, conservation
district and airport organizations
July 2005 — approval of Phase 2 FCAAP grant
August 2006 — last newsletter mailed — not continued due to large number of
alternatives which precluded the newsletter format, the 210 problems identified
by public and agencies yielded approximately 450 alternatives
October 2007 — Existing and Desired Conditions draft CFHMP submitted to Ecology for
fulfillment of grant deliverables
October 2010 — last combined Steering and Advisory Committee meeting (total of 48
meetings for Advisory Committee members)
September 2011— SEPA Determination of non -significance (DNS)
Internet links for more information:
• Yakima County Public Services Surface Water Division,
http://www.yakimacounty.us/su rfacewater/
• Surface Water flood control projects,
http://www.yakimacounty.us/surfacewater/Projects.htm
• Surface Water CFHMPs,
http://www.yakimacounty.us/su rfacewater/CFHMP.htm
• Surface Water flood map projects are included in this list,
http://www.yakimacounty.us/surfacewater/Projects List,php
(More on back...) Contact - Dianna Woods, 509-574-2300, dianna.woods®co.yakima.wa.us
AHTANUM-WIDE HOLLOW
COMPREHENSIVE FLOOD HAZARD
MANAGEMENT PLAN
Rutherford Road
September 2012
Rutherford Road
AHTANUM-WIDE HOLLOW
COMPREHENSIVE FLOOD HAZARD
MANAGEMENT PLAN
September 2012
February 1, 2003 - South 42nd — looking north
YAKIMA COUNTY • YAKAMA NATION
CITY OF YAKIMA • CITY OF UNION GAP
Adopted by the Board of Yakima County Commissioners
October 16, 2012
Resolution No. 388-2012
Cover Photos: Rutherford Road 1974 & 1996 Floods, 2010 Flood Hazard Mapping
for Wide Hollow, Spring, Bachelor & Ahtanum Creeks
ACKNOWLEDGEMENTS
This document was prepared by Yakima County Department of Public Services. Terry Keenhan, P.E.,
Manager of the Surface Water Management Division, served as the project manager for Yakima County.
Initial inventory data and assistance with public meetings and alternatives documentation was provided
by Golder Associates, Inc. Models for generation of the 10 and 25 year floodplain maps were provided by
WEST Consultants, Inc with the Yakima County GIS Department developing the maps
The two committees listed below created this plan, starting with developing the goals and objectives and
ending with prioritization of the recommendations. Chapter 2 has additional information about these
committees. It should be noted several members of the public volunteered large amounts of time and
attention over multiple years to work on the Advisory Committee. We thank all the committee members
and believe this plan is much improved due to their input.
Photographs were provided by Yakima County, Ahtanum Irrigation District, and local citizens.
AHTANUM-WIDE HOLLOW STEERING COMMITTEE
Steering Committee Member Representing
William Rathbone formerly City of Union Gap
Chris Waarvick City of Yakima
Dean Patterson formerly Yakima County Planning
Tom Ring Yakama Nation Water Resources
Virgil James Yakama Nation Zoning
Jeff Peters City of Yakima
Dennis Henne City of Union Gap
Brett Sheffield City of Yakima
Michael Kerins Yakima County Planning
Steve Erickson Yakima County Planning
John Knutson FCZD, previous Surface Water Manager
Terry Keenhan FCZD, Surface Water Manager
Dianna Woods Yakima County Surface Water
Keelan McPhee Yakima County Surface Water
Joel Freudenthal Yakima County Surface Water
Khalid Marcus Yakima County Surface Water
Andreas Kammereck Golder Associates, Consultants
AHTANUM-WIDE HOLLOW ADVISORY COMMITTEE
Advisory Committee Member Representing
Bill Goggin (deceased) Engineering - Private
Bill Koreski Business - Union Gap
Brandon Rogers Yakama Nation — Fisheries
Bruce Johnson Public — West Valley
Buck Taylor & Mike Redmond Yakima Air Terminal
Chuck Steele Department of Ecology
Dale Murphy Public - Wide Hollow
David Taylor
Ed Campbell
Eric Bartrand
Frank Glaspey
Joel Freudenthal
LaRayne Case-Malner
Lee Hacket
Ahtanum Irrigation District
Ahtanum Mission
WDFW
Business - Union Gap
Yakima County
Public- Emma Lane
Business - Union Gap
Leslie Wahl Audubon Society
Mark Herke Business — Ahtanum
Mathew Barnett Business - Union Gap
Merle Warehime Yakima Association of Realtors
Richard Visser WDFW
Robert Smoot Yakima Valley Canal Company
Ron Anderson Yakima Association of Realtors
Steve Simon Public - Union Gap
Steve Strosahl Development Community
Tim Critchlow West Valley School District
ADDENDA & ERRATA
Ahtanum-Wide Hollow CFHMP
September 2012
Changes from Final Draft June 2011
For Draft October 2011
0 Added "Acknowledgements" page
0 Edits to Executive Summary
0 Replaced second diagram & added figure number in Chapter 4
0 Conclusions from Appendix G added to Bridge Sediment Removal
Guidelines in Chapter 10
0 Edits to the section after recommendations in Chapter 11
0 Miscellaneous minor edits to improve readability throughout
0 Miscellaneous updates of dates throughout
0 Edits to Appendix G including discussion and conclusions
0 Added Ahtanum maps, map creation information and interpretation to
Appendix J
Changes from Draft October 2011
For September 2012
Detailed version:
01 -WHAT CFHMP Cover Changed date to September 2012
02 -WHAT CFHMP Title Page Changed date to September 2012
03a -Acknowledgements Deleted "Bill Goggin died during plan
formation."Added "(deceased)"
03b-Addendum.docx Changed title to "Addenda & Errata"
Note: numbers in front of document section titles are for maintaining printing order
04-CFHMP TOC 10-4-2011 Added to Appendix E "Preliminary" Fieldwork
Added "K - MOU Between Yakama Nation &
Yakima County" to appendices list
05-CFHMP TOC Tables & Figures 9-29 Pg 1- Changed "High Priority
Recommendations" to "Recommendations for
Further Flood Hazard Definition"; Changed
"Medium Priority Recommendations" to
"Recommendations for Flood Hazard Mitigation";
Deleted "Table ES -4 Low Priority
Recommendations" since incorporated into
other two tables
06 -Abbreviations
07 -Executive Summary Oct 3
08-Chapt 1 Introduction 9-30
Added "Chambers Creek" to other possible
names for Spring Creek East in "Stream Names
Key"
Pg I - Deleted "and", added "and planning"
Pg III - Added "by the Advisory and Steering
Committee", deleted "people" replaced with
"citizens / stakeholders"
Added "Key" for tables at end of pages
Pg XI - Added "PR22 & PR23" to tables from
Pg 11-8, added priorities also "M"
Pg XVIII - Inserted "(1% change of annual
flooding)"
Pg 1- Inserted "(see Figure 1-1)"
Pg 2 - Deleted "(Figure 1-1)"; Inserted "(Figure
1-1)" in another location
Pg 3 - Changed $17.7 to "$18"; Inserted "At the
request of county citizens,"; Inserted "(Appendix
K)"; Added "The Yakama Nation was involved in
development of the committees and selection of the
consultant."
Pg4 - Inserted "Ecology" and "(Modified, 1991
Guidebook)"
Note: numbers in front of document section titles are for maintaining printing order
09-Chapt 2 Public Involvement 9-30-11
10-Chapt 3 Previous & Related Studies
11-Chapt 4 Watershed Characteristics
Pg 3 - Added "(Chambers)"
Pg 10, 12, 13, 14, 15 - Added "Appendix C" to
maps
Pg 11- Deleted "History" replaced with
"Problem" Added "Appendix C" on map
Pg 1, 2, 3 - Added "(Chambers)" to Spring
Creek in 7 locations
Pg 6 - Corrected "Bain" to "Basin"
Pg 1, 18, 35, 43 - Added "(Chambers)" to
Spring Creek in 9 locations
Pg 16 - Added "g" to Condon; Changed
"Congden" to "Congdon"
Pg 22 - Added "a creek below the terrace at"
Pg 35 - Deleted "," after Shaw;
Pg 43 - Deleted "1940" replaced with "1932";
added "after 1940"; added "of the floodgate";
deleted "March"; added "in order to prevent
Yakima floodwater from entering Spring
(Chambers) Creek and"
14-Chapt 7 Basin Flooding Characteristics
Pg 9, 12 - deleted incorrect Spring Creek "2"
number and added "West"
15-Chapt 8 Flooding Issues
16-Chapt 9 Alternatives
Pg 12 - Added "(Chambers)" to Spring Creek
in 3 locations
Pg 12 - Inserted "(Chambers)" after Spring;
deleted "the 1980s" replaced with "1985";
added "(Chambers)"; deleted "East"
Pg 46, 48, 49, 50 - added total of 11
"(Chambers)" to Spring Creek entries
Pg 48 - Deleted brackets around regulations
and added "and"
Pg 54 - Added "to" so title matches the one on
the table
Note: numbers in front of document section titles are for maintaining printing order
18-Chapt 11 Recommendations
19-Chapt 12 Funding Strategy
Pg 67 — Deleted "Is also communicating"
replaced with "discussed"; deleted "about ...
possible"; added "The alignment in Figure 9-2
was dropped by FEMA in 2011."
Pg 8 — added "Public Works" to partners
column for PR -23
Pg 5-6 — Deleted "It is evident"; added "which
requires funding for planning and levee
maintenance"; deleted "and" replaced with
"plus the"; deleted "since" replaced with "as".
Deleted "There" replaced with "Below".
Pg 6 - Added "There is currently a stormwater
utility for NPDES Stormwater Permit within the
urbanized area of the county. This utility is focused
on water quality not water quality issues."
Note: For the following Appendices, "(Chambers)" was added to Spring Creek in the
text but not in the tables or Flood Problem Worksheets.
22- Appendix C Pg. 2, 4, 6, 8, corrected upside down pages and
table orientation also
24- Appendix E Table — corrected orientation
30 -Appendix K - MOU Btw Yakama Nation & Yakima County
Added this new appendix
31 -References Pg 4 — added complete citation information for
1901 soil survey that produced the 1901
Yakima Soil Map included in the CFHMP
Note: numbers in front of document section titles are for maintaining printing order
AHTANUM-WIDE HOLLOW
CFHMP
Table of Contents
Executive Summary ES -1
Chapter 1— Introduction 1-1
Background 1-2
Authority and Scope for the Ahtanum-Wide Hollow CFHMP 1-3
Plan Development Process 1-3
Growth Management Act 1-5
FCAAP Funding Requirements for CFHMPs 1-8
Involving the Public and Affected Agencies 1-9
Committees 1-10
Defining CFHMP Goals and Objectives 1-10
Related Programs and Actions 1-14
Chapter 2 - Public Involvement 2-1
Committees 2-1
Public Meetings, Open House, Advertisements, Interviews 2-7
Chapter 3 - Flood Related Studies 3-1
Upper Yakima River Comprehensive Flood Hazard Management Plan, 2007 3-1
Channel Migration Zone 3-1
Flood Insurance Studies 3-2
Yakima County Hazard Mitigation Grant Program Applications 3-4
Ahtanum Watershed Assessment & Programmatic EIS 3-5
National Water Quality Assessment 3-6
Total Maximum Daily Load 3-6
Chapter 4 - Watershed Characteristics 4-1
Geographic Setting 4-1
Geology 4-2
Surficial Geology 4-5
Drainage Improvement Districts 4-8
Climate 4-8
Stream Channel and Floodplain Morphology 4-18
Fisheries and Wildlife 4-22
Vegetation 4-23
Water Quality 4-33
Stream Structures 4-33
Chapter 5 — Development in Basin Floodplains 5-1
Current Development 5-1
Socioeconomic Characteristics 5-4
Land Use 5-4
Zoning 5-4
Economics of Floodplain Development 5-11
Economics of Flood Plain Zoning and Floodproofing 5-13
Planning for Future Floodplain Development 5-15
Chapter 6 — Planning and Regulatory Setting 6-1
Introduction 6-1
Summary of Existing Regulations 6-1
NFIP Planning and Community Development Considerations 6-9
Washington State Growth Management Act 6-13
Local Flood Hazard Reduction Administration Tools 6-20
Summary 6-26
Chapter 7 — Basin Flooding Characteristics 7-1
Introduction 7-1
Flood Peaks 7-1
FEMA Hydrology 7-5
Channel Routing of Flood Waters 7-6
Chapter 8 — Flooding Issues 8-1
Chapter 9 — Flood Action Alternatives & Priorities 9-1
Types of Flood Hazard Solutions 9-1
Flood Mitigation Approach Analysis 9-4
Alternative Generation 9-4
Alternatives Discussion by Flood Issues Categories 9-12
Channel Issues / River Function Flood Issues 9-26
Watershed Flood Issues 9-31
Bridges and Roads Flood Issues 9-33
Irrigation Flood Issues 9-37
Land Use Flood Issues 9-38
Development Standards / Enforcement Flood Issues 9-45
Union Gap Flood Issues 9-48
Information / Outreach Flood Issues 9-51
Flood Response Flood Issues 9-54
Shaw Creek Flood Issues 9-58
St Joseph's Mission at Ahtanum Flood Issues 9-63
Emma Lane Area Flood Issues 9-65
Monitoring & Inventories Flood Issues 9-69
Committee Selection of Alternatives 9-70
Chapter 10 — Supplemental Plan Studies 10-1
Stormwater Development Review 10-1
FIS Rate Map Review 10-1
Public Outreach for New FIS 10-2
10 and 25 -Year Flood Maps 10-2
Economic Flood Damage Data 10-2
Sediment Cleanout at County Bridges 10-3
Bridge Sediment Removal Guidelines 10-3
Inventory of Problematic Bridges 10-4
Bridge Design Guidelines for Ahtanum and Wide Hollow 10-4
Channel Sediment and Vegetation Control Pilot Projects 10-4
Sediment Budget for Creeks 10-4
Irrigation Infrastructure Inventory 10-5
Purchase and Elevate Repetitive Loss Homes 10-5
Initiate Emma Lane Channel Relocation Projects 10-5
Project and Planning Grant Applications 10-5
Insurance Reduction through Community Rating System 10-5
Wapato Dam Assessment 10-5
Flood Response Information Coordination 10-6
Future Findings 10-6
Chapter 11- Recommendations 11-1
Partners 11-1
Implementation Timelines 11-1
Discussion 11-13
Implementation Strategy 11-15
Chapter 12 - Funding Strategy 12-1
Inventory and Study Funding 12-2
Planning and Regulatory Funding Strategy 12-2
Ongoing Maintenance and Management Strategy 12-3
Structural Funding Strategy 12-3
Public Outreach Funding Plan 12-4
Flood Response Funding 12-4
Flood Control Sub -Zones 12-5
Local Funding Strategies 12-5
Appendices
A - Zoning & Land Use Tables
B - Photos
C - Flood Problems by Watershed Area
D - Golder CMZ Memo
E - Preliminary Fieldwork
F - Flood Problem Worksheets
G - Bridge Sediment Removal Guidelines
H - Wide Hollow Creek Profiles
I - Wide Hollow Creek 72nd to 80th
J - Ahtanum & Wide Hollow Creek 10 & 25 -Yr Flood Maps
K - MOU Between Yakama Nation & Yakima County
References
AHTANUM-WIDE HOLLOW
CFHMP
Table of Contents — Tables & Figures
Executive Summary ES -I
Table ES -1 Goals and Objectives for Ahtanum-Wide Hollow CFHMP ES -IV
Table ES -2 Recommendations for Further Flood Hazard Definition ES -VIII
Table ES -3 Recommendations for Flood Hazard Mitigation ES -X
Chapter 1 Introduction 1-1
Figure 1-1 Area Map and CFHMP Area Boundary 1-1
Figure 1-2 Comprehensive Flood Hazard Management Plan Process 1-4
Table 1-1 GMA Hazard Reduction Goals 1-5
Table 1-2 Goals and Objectives for Ahtanum-Wide Hollow CFHMP 1-11
Chapter 2 Public Involvement 2-1
Table 2-1 Ahtanum-Wide Hollow Steering Committee 2-2
Table 2-2 Steering Committee Meetings, 2004-2006 2-3
Table 2-3 Ahtanum-Wide Hollow Advisory Committee 2-5
Table 2-4 Advisory Committee Meetings, 2005-2010 2-5
Table 2-5 Public Workshops, 2005 2-7
Figure 2-1 Flood Problem Map Yakima/Union Gap 2-10
Figure 2-2 Flood History Map West Yakima 2-11
Figure 2-3 Flood Problem Map Southwest Yakima 2-12
Figure 2-4 Flood Problem Map West Valley North 2-13
Figure 2-5 Flood Problem Map West Valley South 2-14
Figure 2-6 Flood Problem Map Ahtanum 2-15
Chapter 3 Flood -Related Studies 3-1
Chapter 4 Watershed and Floodplain Characteristics 4-1
Figure 4-1 Ahtanum-Wide Hollow CFHMP Geologic Formations 4-3
Figure 4-2 Tilting Valley 4-4
Figure 4-3 Ahtanum-Wide Hollow CFHMP (West Half) Stream Typing & Geological
Hazards 4-5
Figure 4-4 Ahtanum-Wide Hollow CFHMP (East Half) Stream Typing & Geological
Hazards 4-7
Figure 4-5 Drainage Improvement Districts 4-9
Figure 4-6 Average Annual Precipitation 4-10
Table 4.1 Climate Data for the Yakima Area 4-11
Figure 4-7 Mean Monthly Precipitation in Yakima (Source: Naches CFHMP) 4-12
Figure 4-8 Combined Wet, Average & Dry Year Streamflows for Ahtanum Creek North and
South Forks (w/o irrigation diversion) (Source: Ahtanum Creek Watershed Restoration Program
EIS, Ecology, 2005) 4-13
Figure 4-9 Historic Stream & Canal Locations vs Current Stream & Channel Locations .4-15
Figure 4-10 Historic Stream & Canal Locations vs Current Stream & Channel Locations
(Shaw Creek) 4-17
Figure 4-11 1947 Stream & Irrigation Ditch Locations 4-17
Figure 4-12 The Ahtanum Mission Flow Diversion 4-20
Figure 4-13 1901 US Department of Soils Map 4-22
Figure 4-14 Effects to Channels due to Hybrid Willows 4-26
Figure 4-15 Effects to Structures due to Hybrid Willows 4-27
Figure 4-16 Wide Hollow Creek Vegetation - An example of the progression of willows 4-28
Figure 4-17A Wide Hollow Creek Draft Flood Study - Map 1 of 5 4-29
Figure 4-17B Wide Hollow Creek Draft Flood Study - Map 2 of 5 4-30
Figure 4-17C Wide Hollow Creek Draft Flood Study - Map 3 of 5 4-31
Figure 4-17D Wide Hollow Creek Draft Flood Study - Map 4 of 5 4-32
Figure 4-17E Wide Hollow Creek Draft Flood Study - Map 5 of 5 4-33
Table 4-2 Existing Structural Information Utilized 4-35
Figure 4-18 Structure Inventory Maps - Yakima/Union Gap 4-37
Figure 4-19 Structure Inventory Maps - West Yakima 4-38
Figure 4-20 Structure Inventory Maps - Southwest Yakima 4-39
Figure 4-21 Structure Inventory Maps - West Valley North 4-40
Figure 4-22 Structure Inventory Maps - West Valley South 4-41
Figure 4-23 Structure Inventory Maps - Ahtanum 4-42
Chapter 5 Basin Flooding Characteristics 5-1
Figure 5-1 Shallow Groundwater Areas 5-1
Figure 5-2 Urban Growth 1970-2011 5-2
Figure 5-3 City of Yakima & City of Union Gap Annexation History 5-3
Figure 5-4 Land Use, Yakima County and Yakima Combined 5-4
Figure 5-5 Ahtanum-Wide Hollow CFHMP Yakima County Zoning 5-6
Figure 5-6 Ahtanum-Wide Hollow CFHMP City of Yakima Zoning / City of Union Gap
Zoning 5-7
Figure 5-7 Zoning Yakama Nation 5-8
Figure 5-8 Yakima County Zoning in the Floodplain 5-10
Figure 5-9 City of Yakima Zoning in the Floodplain 5-10
Figure 5-10 City of Union Gap Zoning in the Floodplain 5-10
Figure 5-11 West Valley Neighborhood Plan 5-17
Chapter 6 Planning & Regulatory 6-1
Table 6-1 Surface Water Management Policies & Regulation in Yakima County 6-2
Table 6-2 Overview of Major Federal, State and Local Surface Water Management
Regulations 6-3
Table 6-3 Yakima County Involvement in the National Flood Insurance Program 6-8
Table 6-4 NFIP Planning Considerations (44 CFR 60.2) 6-9
Table 6-5 County Permit Requirements for Flood Control Work 6-30
Chapter 7 Basin Flooding Characteristics 7-1
Figure 7-1 Yakima Basin Peak Floods of Record 7-2
Table 7-1 FEMA Ahtanum Flood Discharges 7-5
Table 7-2 FEMA Flood Discharges for Wide Hollow Creek and Tributaries 7-5
Figure 7-2 1996 Ahtanum Flooding (Emma Ln & 42nd looking southeast / Rutherford Rd
looking northeast 7-10
Figure 7-3 1996 Ahtanum Flooding (Community of Ahtanum looking east / Wiley City
looking north) 7-11
Figure 7-4 Flood Extent in Union Gap 7-13
Figure 7-5 Example of a Bridge Constriction - Cottonwood Creek 7-14
Chapter 8 Flooding Issues 8-1
Figure 8-1 Flood History Map - Yakima/Union Gap 8-2
Figure 8-2 Flood History Map - West Yakima 8-3
Figure 8-3 Flood History Map - Southwest Yakima 8-4
Figure 8-4 Flood History Map - West Valley South 8-5
Figure 8-5 Flood History Map - West Valley North 8-6
Figure 8-6 Flood History Map - Ahtanum 8-7
Figure 8-7 Flood Mapping of Bachelor, Hatton & Ahtanum Creeks 8-11
Figure 8-8 Flood Mapping of Emma Lane Area 8-11
Figure 8-9 Flood Mapping of Spring Creek East 8-12
Figure 8-10 Flood Mapping of Shaw Creek 8-13
Figure 8-11 Preliminary FEMA Flood Mapping (09/30/2010) 8-16
Figure 8-12 Preliminary FEMA Flood Mapping (09/30/2010) 8-17
Figure 8-13 Preliminary FEMA Flood Mapping (09/30/2010) 8-18
Figure 8-14 Preliminary FEMA Flood Mapping (09/30/2010) 8-19
Figure 8-15 Preliminary FEMA Flood Mapping (09/30/2010) 8-20
Figure 8-16 Preliminary FEMA Flood Mapping (09/30/2010) 8-21
Chapter 9 Flood Action Alternatives & Priorities 9-1
Table 9-1 Typical Structural Flood Hazard Management Solutions 9-2
Table 9-2 Typical Non -Structural Flood Hazard Management Solutions 9-3
Table 9-3 Problem Addressed and Environmental Impact Associated with Flood Hazard
Management Measures 9-4
Table 9-4 Flood Problems 9-5
Table 9-5 Problem / Alternatives Worksheets 9-6
Table 9-6 Dropped Alternatives Identified During Alternative Tracking Process 9-8
Table 9-7 Flood Issue Categories 9-12
Table 9-8 Alternatives Summary by Flood Issue 9-13
Figure 9-1 100 -Yr Floodplain for High Flow Bypass Alternative #1 9-62
Figure 9-2 Emma Lane - January 2010 Draft Options 9-66
Figure 9-3 Emma Lane - January 2010 Draft Options 9-67
Table 9-9 Selected Flood Alternatives and Priorities 9-71
Chapter 11 Recommendations 11-1
Table 11-1 High Priority Recommendations 11-2
Table 11-2 Medium Priority Recommendations 11-7
Table 11-3 Low Priority Recommendations 11-10
STREAM NAMES KEY
County Stream Names
FEMA FIRM map
Stream Names
Comments
Spring Creek West
Spring Creek 1
Spring Creek East
Spring Creek 2
Older documents
may refer to this as
Chambers Creek
unnamed
Spring Creek 1 Trib 1
south tributary
unnamed
Spring Creek 1 Trib 2
north tributary
ABBREVIATIONS
1. AID — Ahtanum Irrigation District
2. BMP — Best Management Practice
3. BOR — Bureau of Reclamation
4. CAO — Critical Areas Ordinance
5. CFHMP — Comprehensive Flood Hazard Management Plan
6. DOE — Washington State Department of Ecology
7. DNR — Washington State Department of Natural Resources
8. Ecology — see DOE
9. ESA — Endangered Species Act
10. FCAAP - Flood Control Assistance Account Program
11. FEMA — Federal Emergency Management Agency
12. GMA — Washington State Growth Management Act
13. HCP — Habitat Conservation Plan
14. HMGP — Hazard Mitigation Grant Program
15. HPA — Hydraulic Project Approval
16. LB — left bank
17. LWD — large woody debris
18. NFIP — National Flood Insurance Program, administered by FEMA
19. RB — right bank
20. SEPA — State Environmental Policy Act
21. UG — Union Gap
22. Watersheds — for this document, watersheds = basins = drainages
23. WDFW — Washington State Department of Fish and Wildlife
24. WH — Wide Hollow
25. WIP — Wapato Irrigation Project
EXECUTIVE SUMMARY
The Comprehensive Flood Hazard Management Plan (CFHMP) for the Ahtanum and
Wide Hollow basins covers two urbanizing flood -prone basins in the cities of Yakima
and Union Gap, and Yakima County to the north of the Yakama Nation boundary. The
Ahtanum-Wide Hollow Comprehensive Flood Hazard Management Plan is the third
flood hazard plan to be developed in Yakima County by the County -wide Flood Control
Zone District (FCZD). The FCZD develops flood hazard management plans to prioritize
flood hazard mitigation actions, support County and City staff in the floodplain
communities, and develop partnerships across the various agencies and jurisdictions on
projects within floodplains.
The purpose of a CFHMP is to propose a suite of actions that will reduce identified flood
hazards over both the short and the long term. A CFHMP is a policy and planning
document which contains recommended policy changes and flood actions, including
projects that reduce flood hazard. Answers to the questions "What types of actions will
be effective?" and "Why will these actions be effective?" are the critical components of
an implementation strategy contained in the plan. The Plan provides a basis for flood
hazard risk management by the jurisdictions in the Ahtanum and Wide Hollow basins.
Flooding is a natural phenomenon, frequently exacerbated by human practices, that
cannot be entirely prevented. There are many approaches to protect lives and property
while protecting the environment and natural resources of the community. The
recommendations of this Plan sought to find the greatest public benefit at the least cost over
the short and long term.
A citizen and agency Advisory Committee was formed and 48 meetings held to assess
hazards, develop the CFHMP goals and objectives, and to develop the CFHMP
alternatives and recommendations. In addition, there were four public workshops,
providing extensive local contribution to the flood knowledge, potential solutions and
plan development by citizens, the two cities, Yakama Nation and all affected public
agencies.
Approval by the Washington State Department of Ecology and endorsement by FEMA
will allow local jurisdictions who adopt the plan to become eligible for state and federal
funds for flood emergency response and non -emergency activities to reduce property
loss and threats to human life. Infrastructure modification or replacement projects
identified within a CFHMP are eligible for funding through disaster grants. Without a
plan, infrastructure is normally replaced or repaired to pre -flood conditions and may fail
again. With the plan, infrastructure can be modified or replaced in a manner that
produces overall reduction in flood hazards to the structure and surrounding area.
The plan contains twelve chapters and supporting appendices. The chapters are divided
into four sections; Chapters 1 and 2 delineate plan process and community involvement,
Chapters 3 through 6 provide the physical and regulatory setting, Chapters 7 and 8
concentrate on flooding characteristics and Chapters 9 through 12 provide the plan
alternatives, recommendations, funding and strategy.
II Ahtanum-Wide Hollow CFHMP
Basin Flood Impacts
In 1974 the Ahtanum and Wide Hollow basins experienced a 200 -year flood, as
estimated from Ahtanum Creek stream records. In 1996, the Ahtanum basin
experienced an 80 -year flood while the flooding on Wide Hollow Creek was less severe.
These two major flood events, only twenty-two years apart, may turn out to be more
frequent than the above probability estimates would indicate.
The flood damages in 1996 were more severe than in 1974 since the basin and
floodplains had undergone more urban development. Total County -wide damages in
1996 were $18 million with severe public and private damages in these basins. In
response the County engineer designated these basins as flood prone and requires
higher drainage standards that the cities have also adopted. The continued conversion of
land use from rural to urban during the intervening period has increased flood risk
exposure. This has been demonstrated in recent economic analyses for federal flood
hazard grants that are noted in the plan.
Floodplain Land Use and Channel Conversion Impacts
The communities of Yakima, Union Gap, Ahtanum, Wiley City, and Gromore were
located near these creeks due to productive soils available for agricultural and easy
access to groundwater. These areas were settled before extensive flood experience had
been accumulated. The City of Union Gap is located at the Yakima River confluence of
these two creeks and encountered historic flooding and related development constraints.
The City of Yakima, protected by levees from the Naches and Yakima rivers built after
World War II, has more recently expanded into flood prone areas as a result of
westward annexations. Prior to the expansion, much of Yakima was located west of 16th
Avenue on high ground. A high proportion of the remaining developable land within
the Urban Growth Areas of Yakima and Union Gap is low lying former agricultural land
with high groundwater, in or near the floodplains.
Agriculture is very productive in the flat valley bottoms of these basins. With the
advent of large scale irrigation systems many channels were moved to the higher valley
side slopes. In this location, channels and ditches could be used to irrigate the adjacent
lower farmland. In other cases creeks were covered over or directly converted to
ditches. The designers of early irrigation systems took advantage of the geologic tilting
of these flat valleys to create irrigation systems extending across broad expanses of the
valley in both basins. These systems designed for irrigation also route flood waters. This
increased the number of flow paths and extent of shallow flooding over natural
conditions. These flood paths are only rarely active, and therefore the flood risks
associated with these areas are not easily recognized by the public, private institutions,
and public agencies, until after a flood occurs. Where flood paths remain in agricultural
use, only minimal damage occurs. When land is converted to higher density urban use
significant damage can, and has, occurred.
The use of the creeks to convey irrigation flows has led to "artificial hydrographs" and
the proliferation of vegetation in the channels that obstruct flow, trap sediment and
reduce channel capacity. Management of the irrigation systems themselves is also
increasingly difficult as large parcels are broken up through the urbanization process.
EXECUTIVE SUMMARY I III
This change reduces the frequency of maintenance and types of maintenance approaches
for irrigation channels. Both the increases in vegetation and changes in the level of
maintenance tend to reduce the capacity of irrigation channels, which include both
artificial channels and highly modified "natural" channels such as Wide Hollow,
Bachelor and Hatton Creeks. This increases the frequency and severity of "nuisance
flooding" in these drainages.
Urban road infrastructure also tends to exacerbate flooding, especially when located
across relocated channels that promote flood overflow paths. Flood waters may be
dammed or routed by roads or along roads. As the density of the road system has
increased to meet urban needs, more bridges have been required. There are the over 80
public bridges plus a larger number of private bridges in the basins that have the
capacity to deflect flow. Most of the road infrastructure was constructed and sized prior
to the 1974 flood.
Because of the above conditions, minor changes to the topography (road, fence, large
buildings, fill, and beaver dams) can, and often do, change how flood waters are routed
across the floodplains. The 100 -yr flood maps and history of flooding show the
redirection of flood flows across extensive tracts of land, that present a large flood
hazard. These channel flow redirection concerns were addressed in the development of
alternatives and recommendations. Economic implications of this progressive land use
change are also considered in the plan.
A compilation of flood location data is presented in Chapter 2.
Plan Scope and Process
The plan is comprehensive as it incorporates the entire watershed, as much community
input as possible and practical, and because it aims at short and long term solutions that
have been prioritized by the Advisory and Steering Committee. The structural flood
hazard solutions frequently chosen in the past to protect current development have
constrained the river at great community expense and exacerbate the extent of flooding
over the long term, or have impacted development downstream. Through a
comprehensive plan these effects are well understood before flood control actions are
taken that could worsen the situation through redirection of flows.
The CFHMP is guided by a Department of Ecology process that identifies flood
vulnerabilities and risk, and provides recommendations to mitigate community flood
impacts. The CFHMP process seeks to involve a broad spectrum of local citizens /
stakeholders and interests in the development of a plan and allows the community to
carefully consider and prioritize alternatives for flood hazard management.
Recommendations include both traditional structural solutions, such as channel
realignment, and non-structural solutions, such as regulations or elevation of homes, to
reduce flood exposure. CFHMPs address flood hazard only and review the current
community GMA and related mechanisms effecting flood management and regulation
within the plan geographic extent (see Chapter 8). The non-structural CFHMP
recommendations can be incorporated in the Growth Management Act (GMA)
Comprehensive Plans, including capital facilities plans, through inclusion of Hazard
IV Ahtanum-Wide Hollow CFHMP
goals (see Table 1.1 in Chapter 1) and through modification of planning requirements
and ordinances for development within floodplains.
CFHMP Goals and Objectives
Defining goals and objectives provides the framework for carrying out the CFHMP.
The goals and objectives were generated by the Advisory Committee following the
inventory of physical conditions, are provided in Table ES -1 below.
Goals reflect the broadest expression of the community's desires in preparing the plan;
objectives target specific results that fulfill the intent of the goals.
Table ES -1. GOALS AND OBJECTIVES FOR AHTANUM-WIDE HOLLOW CFHMP
Goals (to be achieved
through objectives) Objectives
1. Identify flood areas
and flood processes
• Identify the location of critical conveyance channel locations
• Identify stream reaches which have lost flood conveyance capacity due to
changes in streamside vegetation or by human activities
• Assess existing roads, bridges and culverts for barriers to flow-through and
potential abatement of flood damage
• Identify past erosion and stream migration processes and monitor after
storm events
• Understand and protect the natural function of the system to reduce flood
hazard
• Determine risks and potential mitigations for hollows
2. Reduce flood
damages to citizens,
property and
infrastructure while
maintaining natural
functions of stream
and floodplain
systems
• Identify structural and non-structural actions for reducing flood hazards that
recognize the corridor as a resource and are consistent with long-term river
corridor functioning
• Develop flood hazard management alternatives and strategies to reduce
long-term damages
• Develop short-term flood hazard reduction alternatives consistent with long-
term strategies
• Prefer mitigation recommendations that provide benefit for multiple problems
and/or locations or enhance the value of the stream corridor as an asset to
the community
• Improve predictability of channel response to flood events
• Evaluate impacts of present management of flood control and irrigation
diversion structures during flood events, such as the flood gate on Spring
Creek in Union Gap
• Create inundation maps for flood evacuation preparedness
• Conduct training at first responder and jurisdiction level using Flood
Response Plan
• Facilitate coordination with Emergency Management and Public Works
Agencies before, during and after floods (Flood Response Plan)
• Complete flood forecasting and warning projects in the basin and integrate
with Emergency Response
3. Work within the
physical and
biological processes
in the floodplain
• Protect existing, or enhance where possible, fish and wildlife habitat
• Protect the natural function of the system to reduce flood hazard
• Evaluate the use of setback dikes to allow for a more naturally functioning
floodplain
• Restore creeks to more natural channel (i.e. instream projects to address 90
degree angle corners and channels "perched" high on landscape)
• Consider mitigation at watershed level or at a minimum reach level across
jurisdictional boundaries
EXECUTIVE SUMMARY I V
Table ES -1. GOALS AND OBJECTIVES FOR AHTANUM-WIDE HOLLOW CFHMP
Goals (to be achieved
through objectives) Objectives
4. Achieve land use
practices that
respect floodplain
functions
• Use best available flood hazard data for regulation of land development and
permitting
• Show critical areas and floodplain areas on plat maps corresponding to
short/long plat developments (see City of Yakima regulations)
• Conduct restudies of FEMA floodplain maps
• Ensure that land use plans and regulations protect floodplain functions
• Evaluate and ensure County/City enforcement of land use regulations
• Coordinate with Yakama Nation on enforcement of land use regulations
• Evaluate other development requirements that may impact flood hazard
management, such as septic systems and water well siting
• Ensure consistency of floodplain regulations within jurisdictions and
investigate increasing the consistency between jurisdictions.
• Identify and implement incentive program for bioengineered structural
solutions to flood hazard mitigation
• Work with existing permitting agencies (such as, Fish and Wildlife, USACE,
Yakima County Shoreline, Ecology, and the Yakama Nation Water Code
Administration) on identifying ways to streamline project permitting process
• Encourage coordination and cooperation among all regulatory agencies
• Work in creative ways to streamline the regulatory process
5. Emphasize the value
of stream corridors
as an asset to the
community
• Encourage innovative development techniques where natural systems and
floodplain function exists
• Educate the public and development community on the value of allowing
floodplain and stream function to properties- investigate Smart Growth
concepts
• Encourage open space planning and acquisition, through incentives such as
leases, easements, acquisition, etc.
6. Quantify hazards in
our floodplain
• Identify erosion and stream migration hazards and evaluate mitigation
options as necessary
• Create and submit FEMA floodplain map for Shaw Creek
• Sustain the mapping program
• Compile varied available mapping data into a comprehensive
database/library resource that can be used to address future assessments
• Identify changing flood condition areas to support new floodplain mapping
work
• Identify draws that are prone to flash flooding
• Avoid contaminating land uses in the floodplain
• When designing a flood overflow area, make sure it is not a contaminated
area
• Minimize impacts of septic systems and other critical facilities on water
quality
VI Ahtanum-Wide Hollow CFHMP
Table ES -1. GOALS AND OBJECTIVES FOR AHTANUM-WIDE HOLLOW CFHMP
Goals (to be achieved
through objectives) Objectives
7.
Ensure a sustainable
flood plan through
public and agency
awareness,
acceptance,
involvement, and
education
• Communicate and coordinate with local governments and community groups
on flood issues/hazards
• Provide documented examples of positive steps being taken
• Highlight projects that will educate the public on sustainable flood hazard
mitigation
• Ensure an ongoing educational program that keeps up with current
understanding, science, and changes in the watershed
• Participate in the CRS (Community Rating System) program
• Flood safety preparedness education
• Determine where large numbers of animals may be kept during a flood event
and distribute information to the public
• Develop a stream corridor improvement program consistent with this plan
• Increase public awareness and understanding of flooding issues and
floodplain functions
8.
Ensure the
implementation of
the flood plan in a
timely manner for
both the short and
long term
• Seek grant funding
• Investigate possible cost savings through coordination with other multiple
objective projects
• Determine possible areas for flood control sub -zones
• Address the causes of problems as opposed to the symptoms
• Identify and utilize complementary Plans
• Consider flood related recommendations from large scale plans such as the
Ahtanum Watershed Assessment
• Integrate flood hazard reduction into ongoing planning, management
programs, and capital facilities plans
• Understanding how the landscape is managed
• Create and implement educational efforts to inform other organizations
about flood risks, plans, and possible mitigation approaches
These flood hazard goals and objectives are achieved by the plan development process
and subsequent implementation of the plan recommendations.
FEMA 100 -Yr Floodplain Remapping
During the development of the CFHMP the FEMA Flood Insurance Study (FIS) revised
the flood insurance rate maps (FIRMs). The accuracy of the old FIRMs for Ahtanum and
Wide Hollow Creeks had been under question following the 1996 flood. The previous
FIRMs were generated in the late 1970's and published in 1985. Remapping of these two
creeks was initiated under the nation-wide FEMA Map Modernization program starting
in 2004.
As part of the CFHMP the combined Steering and Citizens Advisory Committee, along
with the FCZD, municipalities and citizens, came forward to contribute to the accuracy
of the new FIRMs flood maps through direct input on historic flooding. A major focus
was the identification of overland flow paths.
This process also assisted in the development of the CFHMP. The flooding impact of
various factors such as vegetation, bridge sizing, sediment buildup at bridges and
agricultural infrastructure could be evaluated using the FEMA hydraulic models. The
EXECUTIVE SUMMARY I VII
draft CFHMP was initially delayed to allow the Advisory Committee to view the
preliminary FIRMs in order to refine CFHMP alternatives and recommendations.
The FIS Preliminary Maps for the new Wide Hollow Creek FIRMs were released to the
cities of Yakima and Union Gap in October 2010, followed by Ahtanum Creek FIRMS in
October 2011. The maps will be finalized in 2011 or 2012, respectively, depending on the
appeals process. The hydraulic models for both basins are available from the FCZD and
can be used for future studies and proposed or revised infrastructure.
Use of the FEMA models to evaluate sediment management at bridges revealed that
modifying the existing bridges would not resolve the overflow path problems for 100 -yr
floods, as originally hoped. A stronger non-structural approach than originally
envisioned during goals and objectives formulation, and one that addresses more
frequent floods at, or less than, the 25 -year flood, would be required in order to protect
future development.
Flood Hazard Management Recommendations
The plan recommendations focus on damage prevention to future and existing
development in order to reduce costs, including flood insurance fees. Many of the
recommendations will provide relief for both future and existing development. The plan
recommendations contained in Tables ES -2 and ES -3 were designed to incorporate
parallel objectives of multiple parties to facilitate implementation and maximize
benefits.
Partners have been added to the recommendations as a separate column in recognition
of the need to coordinate ongoing activities across agencies, to leverage funding, and
conduct long term planning of new and replacement infrastructure.
Priorities provided in the tables were based on issues of flood benefits, threat and
expediency. The jurisdictions and agencies will determine their final priorities in this
regard.
As priority does not fully convey the capability to implement, an onset timeline for
implementation was designated and added to the recommendations. The use of this
designation also provides an initial strategy for community implementation of the plan.
Actions completed by the FZCD are denoted "C" for "completed" and contained in
Chapter 10 and the Appendices. Actions already underway, usually by the FCZD (see
Chapter 10), are denoted IP for "in progress". Actions recommended to be initiated
shortly after Plan adoption are denoted S for "short term", while L is for "long term",
again referring to start date. Actions recommended within the next cycle of regulatory
update, such as Comprehensive Plan or Ordinance updates are denoted as AU for
"awaiting update". Actions recommended to be initiated as part of upcoming projects
or opportunities are denoted 0 for "opportunity".
VIII Ahtanum-Wide Hollow CFHMP
To guide implementation, recommendations were grouped into categories.
Recommendation categories indicate the work nature and main partners required for
implementation. The categories are: Inventory and Study, Planning and Regulatory,
Maintenance and Management, Structural, Public Outreach, and Flood Response. For
example, the FCZD cannot take the lead for Planning and Regulatory, a role that belongs
to the jurisdictions. The FCZD can facilitate Maintenance and Management for facilities
and lands that belong to landowners and jurisdictions. The FCZD has already taken a
major role in Public Outreach and Flood Response. Implementation of Public Outreach
recommendations will require an ongoing, coordinated approach to planning,
regulatory, structural, and maintenance actions and programs over the long term.
The flood hazard definition and mitigation recommendations are summarized in tables
ES -2 and ES -3, respectively. Inventory and Study recommendations within Table ES -2
will fill information gaps and may refine flood hazard mitigation recommendations
within Table ES -3. Many of these Inventory and Study recommendations are currently
in progress, and those complete are noted and included in the appendices. Additional
details on these recommendations and estimated costs are provided in Chapters 9 and
10, respectively. The largest proportion of costs is for structural recommendations; the
high priority structural recommendations are estimated at approximately $5 million
dollars.
ES -2 Recommendations for Further Flood Hazard Definition
INVENTORY AND STUDY
Description
Onset
Priority
Partners
IS -1 Establish technical work groups and pilot programs on a
reach by reach basis for channel, vegetation and sediment
maintenance (including Wide Hollow coarse sediment
budget), to develop criteria and enable appropriate larger scale
maintenance programs which meets flood and habitat needs.
(See Appendix J)
IP
H
FCZD/WDFW
Irrigation Districts,
Landowners,
Jurisdictions
IS -2 Establish cleanout guidelines and a pilot program bridge
sediment removal & maintenance. (See Appendices G & H)
C
H
FCZD/ Roads, Plan
Depts
IS -3 Inventory problematic bridges, roads and infrastructure
impacts and sediment buildup to generate action plan for
removals, etc. This includes areas of ponding.
IP
H
FCZD/ Roads Depts
IS -4 Inventory flooding impacts for existing and abandoned
irrigation structures.
IP
H
FCZD/
Irrigation
IS -5 Modify bridge crossing design to reduce flooding and
maintenance on case to case basis — wider spans, wider
easements upstream and downstream for channel design and
cleanout, deeper footings, to enable for scour, etc. (See
Appendix G)
IP
H
Roads/ Plan Depts
IS -6 Wapato dam impact assessment for Union Gap.
IP
H
FCZD
IS -7 Provide 10 and 25 year flood extent maps to show chronic
flooding areas where actions such as infrastructure sizing and
siting, proposed development and redevelopment can be
designed to guide flood hazard reduction. (See Appendix J)
C
H
FCZD
EXECUTIVE SUMMARY I IX
INVENTORY AND STUDY (cont)
Description
Onset
Priority
Partners
IS -8 Provide 10 and 25 year flood damage estimates using
established federal methods to guide economic and
environmental decisions.
IP
H
FCZD
IS -9 Study to identify Ahtanum avulsion scenarios and
existing flood issues at Mission.
S
H
FCZD
IS -10 Establish historical flooding areas —e.g. Wiley City &
Ahtanum-as special study areas to include all infrastructure.
S
H
FCZD/Plan Depts
IS -11 Establish historical map and identity flood risks in
Hollows.
S
H
FCZD
IS -12 Identify & prioritize emergency response access routes
during 10, 25 and 100 year floods to incorporate into
emergency transportation and planning.
S
H
City & County
Roads/YVOEM
IS -13 Resolve run-off issues presented by DIDs.
S
M
Jurisdictions
IS -14 Document floods including aerial photos, high water
marks, etc.
S
M
FCZD
IS -15 Identify high flood risk stream reaches where man-made
changes or proposed projects effect channel processes or
flooding including roads, perched channels and other
alterations
S
M
FCZD/ WDFW
IS -16 Design bridges and irrigation infrastructure to reduce
potential for accumulation of debris and sediment and creation
of un -natural overflow channels/paths.
L
M
Roads/FCZD Plan
Depts, WDFW
IS -17 Study use of ring dikes to protect St. Joseph's Mission
property.
IP
L
Landowners
IS -18 Consider major levee construction on Mission property
to alleviate headcuts, this may not be needed if
Recommendations A & B in Hatton section are successfully
implemented.
IP
L
FCZD
IS -19 Perform an Emma Lane flood study, and develop design
guidance on acceptable flood protection levels. (3-2). Address
Ahtanum Creek flood conveyance downstream of 42nd and
Ahtanum Rd.
IP
L
FCZD
IS -20 Develop a Coordinated Resource Management Group to
develop joint priorities for resource management (e.g. Wenas
working group).
L
L
NYCD/WDFW
IS -21 Investigate and recommend increased maintenance and
debris cleanout of culverts and ditches on public roads
(coordinate with road maintenance crews to optimize ditch
cleaning for flood purposes).
L
L
Roads
IS -22 Monitor effects of urbanization and land use
intensifications to the characteristics (runoff, time of
concentration, water quality) of the watershed over time. Take
action to mitigate for negative watershed scale effects.
L
L
FCZD
IS -23 Map non —mapped Channel Migration Zones (and other
hazards) (15G-4, 15D-3). Identify areas that are at risk for
channel migration in addition to identified CMZ, i.e. N.F.
Ahtanum, below the Narrows, at the Mission, Shaw Creek, etc.
O
L
FCZD/ plan Depts
IS -24 Alter drainage systems and easements, based on Emma
Lane floodplain remap study.
O
L
FCZD
Key:
ONSET:
C — Completed
IP — In Progress
PRIORITY: H — High
S — Short Term
L — Long Term
M — Medium
AU — Awaiting Updates
O — Opportunity
L — Low
X Ahtanum-Wide Hollow CFHMP
INVENTORY AND STUDY (cont)
Description
Onset
Priority
Partners
IS -25 Inventory of private roads acting as levees.
0
L
FCZD
IS -26 Private road culvert inventory.
0
L
FCZD
IS -27 Investigate funding sources or incentives for private
drainage infrastructure.
0
L
FCZD
ES -3 Recommendations for Flood Hazard Mitigation
PLANNING & REGULATORY
Policy Development
To be implemented in the policy processes associated with the broad scale Growth Management Act processes such as
County -Wide Planning Policies, Comprehensive Plans, Capital Facilities Plan Elements, and UGA expansion.
Description
Onset
Priority
Partners
PR -1 Ensure drainage infrastructure is properly sited, sized
and designed to minimize flood effects from stormwater run-
off. This includes establishing the relationship between
flooding and stormwater and determining detention/retention
and other stormwater standards.
IP
H
RSPG/Stormwater
Utilities
PR -2 Petition State Noxious Weed Control Board to list hybrid
willows as invasive species as designated in other states.
IP
H
FCZD
PR -3 Incorporate floodplain and economic impacts into SEPA
for subdivision layouts floodplain development (losses,
damages, safety, insurance, response and recovery) from the
planning to the project level, especially in urban and
urbanizing areas.
S
H
Plan Depts/FCZD
PR -4 Establish policies, such as a flood hazard audit and
hazard element using the flood problem inventory in this plan,
within County -wide planning policies and comprehensive
plans in flood hazard areas to direct preferred locations for
new infrastructure such as arterials, water and wastewater
distribution mainlines, regional stormwater facilities, parks
and greenbelts.
o New major arterials should be located outside of floodplains
where possible. If in floodplain, design to minimize flood
impacts.
AU
H
Plan Depts/FCZD
PR -5 Retain and provide Open Space land use in all
jurisdictions using zoning easements, acquisitions and
incentives within floodplains to provide multiple public
benefits such as preserving space for flooding, greenbelts and
trails.
AU
H
Plan Depts/ FCZD
PR -6 Provide open space incentives that target general
floodplain function, riparian and storage recommendations.
AU
H
Jurisdictions /Plan
Depts., Interest
Groups, FCZD
PR -7 Decide upon, designate (in flood response, transportation
and capital facilities plans) and maintain critical access routes
at 10, 25 and 100 year events.
S
H
Roads/YVOEM
PR -19 Develop flood abatement policies for high risk flood
prone areas of existing dense development in the floodplain.
o Design drainage to meet multiple objectives including flood
alleviation, in flood -prone areas, esp. in Wiley City and
Ahtanum.
0
L
M
Plan Depts/ FCZD
FCZD/Plan Depts
PR -20 Identify areas that are "islands" surrounded by
floodplain and develop standards to limit density, provide
emergency access and consider transportation networks
within the context of surrounding area.
L
M
FCZD/Plan Depts
EXECUTIVE SUMMARY I XI
PLANNING & REGULATORY (cont)
Description
Onset
Priority
Partners
PR -21 Seek land use examples for flood -prone areas from
other similar communities.
L
M
FCZD/Plan
Depts
PR -22 Ensure existing flood policies in the Yakima Urban Area
Comprehensive Plan are implemented through ordinances
and local jurisdiction land use decisions. Planning for flooding
is supported in Objective E7 (5.7.A [13A-41)
O
M
Plan Depts.
PR -23 Incorporated principle of floodplain planning into
infrastructure & similar facilities plans (5.4.D [8C-2, 12H-21)
L
M
Plan Depts.
PR -24 Preserve natural drainage including draws and mitigate
identified hollows that provide natural flood flow paths but
are not identified as FEMA floodplains. Implementation is
through drainage requirements within stormwater,
County/City drainage, grading, and long and short
subdivision ordinances.
S
M
Plan Depts
PR -25 Consider development moratoriums or high standards
of proof in place where development is outpacing flood
knowledge or tools available to keep the public safe (i.e. the
area has not been mapped, or conditions have changed since
the last mapping).
0
M
Plan Depts
PR -26 Maintain open areas near the mouth of Ahtanum Creek
for flooding such as Fulbright Park.
O
M
Plan Depts
PR -30 Take larger scale effects to the watershed into account
when designing new transportation systems: Minimize
number of roads — maximize efficiency and design roads in a
manner to minimize flooding.
AU
L
Roads / Plan Depts
PR -31 Assess the cumulative effect of road policies and
standards for new roads within the transportation element of
the comprehensive plan that act as dams or conveyances.
AU
L
Roads /Plan Depts
PR -32 Limit future development in the Emma Lane floodplain
area if structural alternatives not implemented.
AU
L
Plan Depts
PR -33 Place controls on building in the flood -prone areas in
and around Emma Lane (e.g. using zoning, utility hook-ups,
etc.).
AU
L
County Plan Dept
PR -34 Investigate geologic hazard area standards for
applicability to high flood risk hazard categories such as
channel migration zones and alluvial fans to address potential
regulatory gaps.
L
L
FCZD/ Plan Depts,
Bldg Officials
PR -8 Ensure all new development and redevelopment within
identified FEMA floodplains are adequately reviewed for
NFIP compliance and overall environmental (SEPA) impacts
through the use of additional review procedures which may
include; at minimum a public notice (type 2 for the County); a
signed checklist for all floodplain items; a floodplain
development permit independent of other required permits; or
establishing a floodplain overlay zone covering the above
concerns.
AU
H
Plans Depts/
FCZD
PR -9 Establish work groups to formalize regulatoryS
applicability of man-made and natural courses.
H
Plans Depts/
FCZD
Key:
ONSET:
C — Completed
IP — In Progress
PRIORITY: H — High
S — Short Term
L — Long Term
M — Medium
AU — Awaiting Updates
O — Opportunity
L — Low
XII Ahtanum-Wide Hollow CFHMP
PLANNING & REGULATORY (cont)
Description
Onset
Priority
Partners
PR -10 Ordinance increase for residential to at least one foot
above BFE for future development to reduce community costs
and damage.
AU
H
Bldg Officials/ Plan
Depts
PR -27 Work for consistency in zoning and development
standards across jurisdictions for developments and buildings
within floodplains. Determine gaps in the regulatory scheme.
AU
M
Plan Depts
PR -28 Reduce risks through subdivision development
standards to minimize new structures in harm's way.
o Integrate protection of floodplain functions
improvement/flood hazard reduction into subdivision
platting process.
o At a minimum, require a buildable area outside of the
floodplain including standards for lot size and housing
location.
O
O
M
Plan Depts
Plan Depts
PR -29 This includes special land use standards for industrial
uses relating to hazardous materials, storage, use, disposal and
flood -proofing for non-residential structures, including
elevating to make existing structures less flood damage prone.
Jurisdictions should adopt Appendix G of IBC.
SU
M
Plan Depts/
Bldg Officials
PR -35 Adopt and implement stricter building standards in
Emma Lane area -flood -proofed homes, buildings.
AU
L
County Plan &
Bldg Officials
PR -36 New traffic generating developments should be located
outside of floodplains (see also Bridges & Roads).
L
Jurisdictions, Plan &
FCZD
PR -11 Improve compliance with NFIP on all new and
replacement bridges and culverts.
IP
H
Bldg Officials
PR -12 Based on the 10 and 25 -year flood mapping, consider
them, for design requirement of land use designation decisions
in future floodplain development to minimize frequent
damages and economic impact.
S
H
Plan Depts/WDFW
PR -13 Use SEPA and Comprehensive Plan Policies and Goals
to address flood issues/impacts associated with larger scale
proposed developments where current zoning, subdivision or
building standards are not sufficient to mitigate flood risk.
S
H
Plan Depts
PR -14 Implement NPDES Regional stormwater to limit run-off
up to 100 yr flood.
IP
H
Local Jurisdictions
PR -15 Fully utilize new FEMA models and maps, and locally
developed 10 and 25 -yr map products, including loss data, forS
alternative analysis and infrastructure and land use decision
making, by providing models and mapping free of charge.
H
Plan Depts/
Roads
PR -16 Consolidate access for floodplain crossing to minimize
flood impacts.
AU
H
Plan Depts/
Roads
PR -17 Ensure floodplains and floodways are identified on final
plat maps — included would be text identifying effective map
date and disclosure regarding fact that the maps will change
over time. Also consider including identification of riverine
Critical Areas buffer on plats.
AU
H
Plan Depts
PR -18 Increase flood code enforcement through adequate
funding mechanisms 6.3.A.
S
H
Code
Enforcement
PR -18 Increase flood code enforcement through adequateS
funding mechanisms 6.3.A.
H
Code
Enforcement
EXECUTIVE SUMMARY I XIII
PLANNING & REGULATORY (cont)
Description
Onset
Priority
Partners
PR -37 Improve drainage throughout the entire Emma Lane
area — culverts, roads, etc.
IP
L
Roads
MAINTENANCE & MANAGEMENT
Continuous and stable Channel and Riparian Management
MM -1 Program for sediment and debris removal, invasive
species control, replacement species in plantings, sediment &
bank stabilization.
IP
H
WDFW/FCZD Plan
Depts,
NYCD
MM -2 Beaver management.
IP
H
WDFW/Landowners
MM -3 Riverine Infrastructure Management — debris and
sediment maintenance.
IP
H
Jurisdictions/
Irrigators
MM -4 Riparian restoration, mitigation and protection to
reduce flood impacts.
S
H
FCZD/WDFW
Jurisdictions
MM -5 Land acquisition in problem areas prior to development
(Emma Lane/Cottonwood/Shaw Creek/Union Gap, etc.).
IP
H
FCZD/ Jurisdictions
Landowners/ Interest
groups,
MM -6 Apply appropriate range management standards to elk
in confined feeding operations near riverine environment.
S
H
WDFW
MM -7 Obtain landowner access permission for problem
bridge channel maintenance.
IP
H
FCZD/ Jurisdictions
MM -8 Coordinate opening irrigation diversion gates for flood
relief, based on forecasts, channel maintenance needs, and
impact to diversion facility.
IP
H
FCZD/Irrigators
YVOEM
MM -9 Separate irrigation conveyances from streams as
practical and based on priority.
L
H
Irrigators/ Jurisdictions
MM -10 Consolidate irrigation diversions and remove as
become obsolete.
L
H
BOR/BPA/
Irrigators, Jurisdictions
MM -11 Community adoption of Community Rating System to
reduce insurance rates through CRS activities.
L
H
Jurisdictions
MM -12 Investigate irrigation infrastructure changes such as
flood gates or siphons to reduce flood routing through
irrigation systems.
L
M
Irrigators
MM -13 Modify drainage standards for existing roads in
overflow areas to minimize flood impacts (i.e. Emma Lane
area).
AU
M
Roads/FCZD
MM -14 Ensure replacement of damaged infrastructure
reduces future flood damage risks.
O
M
Roads
MM -15 Explore additional funding methods for mitigation or
reduce environmental effects (including flooding) from
existing roads or other infrastructure.
0
M
Roads
MM -16 The Spring Creek floodgate should generally be closed
except for habitat or flow enhancement for a limited time
period (see alternative F below also).
IP
L
Union Gap/FCZD
MM -17 Review DID management in relation to flood hazard
over the long term as land use changes.
L
L
DIDs (County)
MM -18 Investigate funding for enforcement and cleanup of
illegal dumps on private ground.
O
L
SW, DOE &
Health Dist
MM -19 Improve stormwater system on Ahtanum Road to
limit Emma Lane overflows into the airport area, and
downstream to 16th (which floods the intersection at Ahtanum
Road).
O
L
City of Yakima
Key:
ONSET:
C — Completed
IP — In Progress
PRIORITY: H — High
S — Short Term
L — Long Term
M — Medium
AU — Awaiting Updates
O — Opportunity
L — Low
XIV Ahtanum-Wide Hollow CFHMP
MAINTENANCE & MANAGEMENT (cont)
Continuous and stable Channel and Riparian Management
Description
Onset
Priority
Partners
MM -20 Investigate methods for the following:
- Research how other communities deal with dumping in
floodplains, particularly concrete, fill, etc.
- Research measures to deal with illegal/contaminated dumps
(meth labs, etc.)
- Examine statewide laws relating to dumping and streams to
establish authorities.
0
L
SW, FCZD,
Jurisdictions
MM -21 Utilize fence designs that prevent floodwaters from
backing up on fences, such as:
o Breakaway fence panels in locations that flood frequently.
o Suspension fences, which consist of steel pipe or cable hung
high above the creek, and hanging lighter materials down
from the cable. This works as a fence, but is not lost during
floods.
Fence setbacks — hold fences back some distance from the
creek (loss of traditional land usage).
0
L
NYCD/FCZD Bldg
Officials, Plan Depts
STRUCTURAL
Projects in Urban Growth Areas
Description
Onset
Priority
Partners
ST -1 Property acquisitions and home elevations for repetitive
loss properties.
IP
H
FCZD/
Jurisdictions
ST -2 Emma Lane channel improvements.
IP
H
FCZD/
Jurisdictions
ST -3 Bachelor Bridge at Ahtanum Rd. & Ahtanum Creek &
16th Avenue bridge replacements
0
H
County Roads/ Plan
Depts
ST -4 Wide Hollow flooding between 64th and 101st— channel
improvements and acquisitions — recommendations include
those for Shaw Creek, plus regional retention
IP
H
FCZD/
Jurisdictions
ST -5 Resolve Shaw Creek relocation/overflow to removeS
community damages and insurance
H
FCZD/ Jurisdictions,
Plan Depts.
ST -6 Wide Hollow relocation or overflow channel
incorporated in future development and proposed
infrastructure design in Union Gap
0
H
DOT/
Jurisdictions
ST -7 Improve grade for Spring Creek East to reduce floodingO
in Union Gap
H
DOT/
Jurisdictions
ST -8 Mill structure — Develop shelf ready open channel bypassO
design for grant application on, lower channel
H
FCZD/
Jurisdictions
Projects in City of Union Gap
Projects in areas which route floodwaters overland
ST -9 Reduce catastrophic flow captures at Mission
(infrastructure and town impacts — Rutherford Road) and
preventing avulsions into Hatton and capacity issues
S
H
FCD/Irrigators
landowners, Plan
Depts
ST -10 Flood design for John Cox diversion (new)
L
H
FCZD/Irrigators
ST -11 Make infrastructure improvements in Emma Lane area:
o Remove abandoned fill and infrastructure in Emma Lane
area to increase flood capacity and reduce redirection of
flood flows
o Widen bridge at 42nd Ave.
IP
IP
M
FCZD/
Landowners
Roads
ST -12 Evaluate not filling in the existing Ahtanum channel so
it can be used for habitat if the creek is relocated near Emma
Lane
IP
M
FCZD/
Landowners
EXECUTIVE SUMMARY I XV
STRUCTURAL (cont)
Projects in City of Union Gap
Projects in areas which route floodwaters overland
Description
Onset
Priority
Partners
ST -13 Perform a cost -benefit analysis for stream relocation
near Emma Lane
IP
M
FCZD
ST -14 Improve flood conveyance and predictability by
reconfiguring modified or "perched" streams and establishing
overflow channels if relocation is not feasible such as Shaw,
and Emma Lane
L
M
FCZD
ST -15 Maintain Wide Hollow flood mitigation methods in
Union Gap by retaining an overflow path along railroad right
of way and encouraging development of an 0 & M agreement
among appropriate parties for flood and fish structures the
Mill
0
M
City of Union
Gap
ST -16 Consider the following structural alternatives where
changes in the channel threaten homes, businesses,
agricultural land, or infrastructure.
o Levees, armor, buffers, CMZ (channel migration zones)
o Structural flood control measures either by individuals or
government
o Utilize "softer" solutions for bank stabilization, bio-
engineering.
o Levees constructed along perched channels (i.e. Cottonwood
Grove)
L
L
FCZD/ Plan Depts
ST -17 Expand diking along Shaw Creek to protect new and
existing development
L
L
Add Insurance
Costs
ST -18 In some locations, add wood to stream to "catch" wood
debris — this accomplishes multiple objectives — would benefit
habitat as well as reduce the volume of woody debris that
accumulates on bridges, diversions, and other structures.
0
L
FCZD
ST -19 Armoring:
- Provide armoring of roads with act as levees
(Ahtanum/Cottonwood Canyon Rd., etc.).
- Armor road ditches where road fill is going to contribute to
excess bedload and to protect road prism.
0
L
FCZD
ST -20 Culverts:
- Recognize the limitations of culverts as flood conveyance
structures
- Replace old culverts with higher capacity culverts based on
flood risk
0
L
FCZD & Jurisdictions
Roads
ST -21 Identify sources of funding for removal of abandoned
irrigation structures
0
L
FCZD & Agencies
ST -22 Preserve and restore natural floodplain in places that
retain some of the floodplain function. Prioritization - allow
for flexibility while identifying critical locations, based on
CFHMP and mapping.
0
L
FCZD
ST -23 Install a remote control floodgate that could be opened
some times of year, closed at others (on Spring Creek
floodgate)
0
L
City of UG
Key:
ONSET:
C — Completed
IP — In Progress
PRIORITY: H — High
S — Short Term
L — Long Term
M — Medium
AU — Awaiting Updates
O — Opportunity
L — Low
XVI Ahtanum-Wide Hollow CFHMP
STRUCTURAL (cont)
Projects in City of Union Gap
Description
Onset
Priority
Partners
ST -24 Protect natural floodplain functions in Shaw Creek's
watershed, especially before it is mapped.
O
L
FCZD
PUBLIC OUTREACH
PO -1 Information to public and local governments on New
FEMA Maps
IP
H
FCZD/
Jurisdictions
PO -2 Outreach to public regarding flood hazard related to
regulatory changes
IP
H
FCZD / Plan Depts
PO -3 Provide flood risk & regulatory constraints at beginning
of development process
S
H
Plan Depts
PO -4 Outreach to Realtors, lenders, etc. about flood risks
S
H
FCZD
PO -5 Provide information to the general public and property
owners to enhance their understanding of: specific flood risks,
beneficial functions of floodplain, and aesthetic values of
streams and floodplains for development
L
H
FCZD / Plan Depts
PO -6 Work with landowner assistance programs to improve
appropriate streamside vegetation and provide information
about flood resistant fencing
S
M
FCZD
PO -7 Utilize meetings and other methods of notification to
inform developers and current and prospective residents
about flood risks for Shaw Creek
IP
M
FCZD
PO -8 Encourage residents and property owners who are at
high risk for flooding to purchase flood insurance even if they
are not in a mapped floodplain
IP
M
Jurisdictions
PO -9 Provide public notice/disclosure/consultation about
planned flood projects
M
Jurisdictions/
FCZD
PO -10 Provide information for the public about culvert
maintenance and sizing
S
M
FCZD/Roads
PO -11 Yakima County Flood Control Zone District to provide
technical assistance and comments regarding flood hazards
and infrastructure design
IP
M
FCZD
PO -12 Encourage volunteer flood -watchers program to
provide information
S
M
FCZD
PO -13 Cooperate with other agencies to support or develop
public education programs, such as stream cleanup programs
and volunteer monitoring.
IP
L
FCZD
PO -14 Encourage citizens to report dumping in streams
(public outreach).
L
L
FCZD
FR -1 Designation of evacuation routes and notification of the
public and first responders
S
H
YVOEM/Roads
FR -2 Implement and participate in activities for the FloodS
Response Plan
H
YVOEM/
Jurisdictions
FR -3 EOC environmental coordination
L
H
EOC/WDFW
FR -4 Determine where large numbers of animals may be kept
during a flood event and distribute information to the public.
Work with Emergency Management and Red Cross to
establish animal food and shelter contingencies — discussions
may include Central Washington State Fairgrounds, farm feed
stores,
L
H
Conservation
Authorities
FR -5 Coordination between Emergency Management and the
Irrigation Districts such as AID and Yakima Valley Canal, for
management during floods. Include Irrigation Districts in
communications with the EOC
H
YVOEM/AID
YVCCo
EXECUTIVE SUMMARY I XVII
FLOOD RESPONSE
Description
Onset
Priority
Partners
FR -6 Public and agencies coordinate flood fight and post flood
actions with recommendations identified in the Ahtanum-
Wide Hollow CFHMP to provide a good basis for decision
whether to take emergency action
S
M
YVOEM
FR -7 Install gages on North Fork Ahtanum and Wide Hollow
Creeks, including telemetry
O
M
FCZD
FR -8 Develop warning systems including mass media
L
M
YVOEM
FR -9 Identify known problem locations so information is
available for first responders and include in the Flood
Response Plan (if appropriate)
S
M
YVOEM/ FCZD
FR -10 Provide special flood phone line for public to call in and
provide information about current flooding — EOC & FCZD
cooperate/coordinate
L
M
YVOEM/ FCZD
FR -11 Improve access to Bachelor diversion during floods
without diverting flood waters or making flood problems
worse
L
M
Irrigators/ BOR
FR -12 Improve communication, coordination and information
dissemination between various agencies and emergency
management office during flood emergencies
IP
M
YVOEM
FR -13 Coordinate between jurisdiction procedures in place for
expedited permit issuance during and period after a flood
event under State and County regulations.
0
L
OEM, Jurisdictions,
Agencies, FCZD
FR -14 Outline emergency response to ice jams in the Flood
Response Plan.
- Alert residences at risk. (new)
- Blast ice jams — (normally only done on very stable ice jams)
Facilitate regulatory approval by Ecology and Fish & Wildlife
and local jurisdictions due to short time frame. (new)
0
L
FCZD/Agencies
FR -14 Outline emergency response to ice jams in the Flood
Response Plan.
- Alert residences at risk. (new)
- Blast ice jams — (normally only done on very stable ice jams)
Facilitate regulatory approval by Ecology and Fish & Wildlife
and local jurisdictions due to short time frame. (new)
O
L
FCZD/Agencies
Key:
ONSET:
C — Completed
IP — In Progress
PRIORITY: H — High
S — Short Term
L — Long Term
M — Medium
AU — Awaiting Updates
O — Opportunity
L — Low
XVIII 1 Ahtanum-Wide Hollow CFHMP
Mapping Tools
The recently released (2011) Preliminary FIS maps for the 100 year flood increase
awareness of flood hazard. From the extent and nature of the flooding portrayed on the
FEMA maps it is evident that, despite the implementation of this plan, infrequent flood
events such as the 100 year (1% chance of annual flooding) event will continue to affect
large areas, causing substantial damage and economic disruption. Frequent floods, from
a five year interval up to the 25 year flood, produce the majority of property damage
and economic disruption to the community over time. As part of this plan, 10 and 25
year flood maps are provided that can serve as guidelines for future infrastructure
planning.
Preferred Implementation Order for Recommendation Categories
The Inventory and Study recommendation category should be implemented first as the
topics they cover increase awareness of flooding problems, problem causes and
locations, and may amend other recommendations. In particular the high priority
recommendations have been pursued by the FCZD to facilitate other recommendations.
The inventory results may change the focus of, or add to, some of the Planning and
Regulatory, Maintenance, and Structural recommendations, so that maximum public
benefit can be attained at reduced costs. Several of these inventories, including problem
bridges, and the effects of Drainage Improvement District facilities (DIDs) will improve
management of floods and allow tracking of changes to the basin into the future.
Recommendations to minimize future damages for new development require Planning
and Regulatory recommendations due to the widespread flooding nature (generally
shallow) of major floods (i.e., in the order of the 100 year), the general inability of
structural measures to remove such large affected areas from flooding, the relative effect
of minor changes to the landscape (fences, roads, emergency flood berms) on flood
routing and potential flood damage, and the impracticality of halting development or re-
development on large tracts of land.
For existing development floods between the 10 and 25 -year return period frequency
will cause the majority of long term property damage and economic disruption to the
community. For these floods, which are more frequent than the 100 -year flood, which
generally occur in the areas adjacent to stream and river channels, versus the overflow
paths, the Maintenance and Management plus the Structural recommendations will
provide the highest return. The plan has developed and provided flood maps for 10
and 25 year flood levels in Appendix J and sediment removal guidelines in appendix G
to enable the communities to guide these recommendations.
Reducing future and current damages across the range of flood events will require a
combination of modified design guidelines and standards, land use zoning, related
planning methods, flood response and channel maintenance.
Cornerstone to these mitigation recommendations is community involvement and a
cooperative approach involving agencies and the public. Recommendations for this
element are contained in the Public Outreach.
EXECUTIVE SUMMARY I XIX
Implementation Strategy
The purpose of a CFHMP is to propose a suite of actions that will reduce flood hazards
over both the short and long term. In order to develop a long term strategy it was
necessary to understand the underlying causes and obstacles to overcome. The most
relevant new understanding attained during development of this plan, apart from the
large extent of flooding, was the pervasive and historic nature of floodplain and channel
modifications to suit agricultural practices and the legacy that alteration presents for
future urbanization of the floodplains.
The greatest return on investment is to increase flood hazard awareness. Public
Outreach recommendations, including distribution of this Plan, will extend the
awareness of past and future floodplain changes. Development of the Plan increased
awareness of information needs to fill data gaps, therefore, the Inventory
recommendations received the highest implementation priority.
Answering what and why certain actions will be effective are the critical components of
an implementation strategy for the plan. The answers to these questions differ for new
and existing development. For new development, a higher priority is placed on
Planning and Regulatory recommendations. For existing development, a significant
specific issue is channel sediment and invasive vegetation, and the need for a
maintenance program to manage their effects. Studies to quantify the impacts of
sediment at bridges and in the channels have been initiated as a result of this Plan
(Appendix G) so that Maintenance recommendations can be more effective.
Recommendations for structural alternatives primarily act to route more water into the
main channels and transfer flow capacity issues from one location to another, where
channel capacity should be higher and impacts less. Many of the recommended
structural projects are located in the Urban Growth Areas and should be implemented
sooner rather than later — before development precludes the opportunity for these
structural alternatives and flood hazard conditions are fixed in place. Some of the
structural recommendations in the plan address critical locations in these watersheds
where overflow paths for large floods originate. These overflow points are usually
activated during frequent floods. Once identified, the projects focus on these locations
to reduce the frequent chronic, wide spread flooding.
Other structural recommendations are located in already urbanized areas, and will be
implemented in conjunction with planned infrastructure or redevelopment activities as
the opportunity arises.
The most economic action after the provision of selected Inventory recommendations is
to translate the new awareness into design and planning guidelines and building
restrictions that mitigate flood effects. Jurisdiction planning measures should
acknowledge the legacy of agricultural conversion of floodplains to more flood -prone
development. Building code revisions that reduce future economic burden to the
citizens through flood insurance reduction should be pursued to avoid subsidizing other
more flood prone communities.
XX 1 Ahtanum-Wide Hollow CFHMP
The next most economical action is to address existing flood issues specific to a cause
through wider actions such as channel maintenance.
The most expensive category is to address existing flood issues specific to a location.
Structural projects are typically very expensive; however, projects should be addressed
as soon as practical before the land is overdeveloped or under urbanization
development pressures. Structural projects, such as levees, also require maintenance
that is a continual commitment of resources, making them the least financially attractive.
In most cases the structural measures are more suited to 10 and 25—yr floods as they
encompass the majority of the community losses, as determined through economic
analysis.
A Funding Strategy is presented in Chapter 12.
CHAPTER 1
INTRODUCTION
The rivers and streams within the Yakima River watersheds are valuable resources for
Yakima County residents. The Ahtanum and Wide Hollow basins have been centers of
irrigation and orchards since the turn of the 20th century, contributing to the local economy
and receiving diverted flows from the Naches River. Ahtanum Creek also forms the
northern boundary of the Yakama Nation Reservation. Both basins are designated by the
County Engineer as "Flood Prone" as they have been subject to frequent and extensive
flooding.
The two basins experienced accelerating urban and suburban growth for the last 20 years for
the Cities of Yakima and Union Gap. Lower value agricultural land previously subject to
flood is now being converted to high value residential and commercial development. The
two basins have over 80 public bridges accommodating the urban road system and
numerous agricultural diversions creating entry paths for flood waters into unexpected
areas.
The Yakima County -Wide Flood Control Zone District (FCZD) is addressing this flood risk
need by preparing this Comprehensive Flood Hazard Management Plan (CFHMP) for the
Ahtanum and Wide Hollow basins. The Plan was developed by the FCZD and its consulting
firm, Golder Associates, with cooperation and input from the jurisdictions, the public and
all affected public agencies. It covers the entirety of the two basins (see Figure 1-1).
Figure 1-1 Area Map and CFHMP Area Boundary
Ahtanum-Wide Hollow CFHMP
City Limits ®aos
NORTH Study Area Boundary
Yakima
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2 1 Ahtanum-Wide Hollow CFHMP
CFHMPs are designed to help a community prevent future damages from flooding through
a short term and long term approach. Flood hazard reduction planning, to be successful,
must be comprehensive and take into account the entire river system. While flooding in
itself is a natural phenomenon that cannot be entirely prevented, there are many approaches
to protect lives and property. In addition, any activity in a river or its watershed can change
the nature of the river's flooding. Human intervention can exacerbate or reduce the extent of
flooding and its effects on human health, property, and the environment. These effects
should be well understood before flood control actions are taken as they can worsen the
situation.
This CFHMP seeks a balanced short and long-term approach to flood damage protection,
resource protection, environmental enhancement, and land development, and involved a
broad spectrum of local people and interests in the development of a plan. The process is
intended to allow the community to carefully consider and prioritize alternatives for flood
hazard management. The extensive local contribution to the flood knowledge and potential
solutions by citizens, the two cities, Yakama Nation and all affected public agencies, is
contained throughout the plan and discussed in detail in Chapters 2 and 9.
The plan contains 12 chapters and appendices. The chapters are divided into four sections;
chapters 1 to 2 delineate plan process and community involvement, chapters 3 through 6
provide the physical and regulatory setting, chapters 7 and 8 concentrate on flooding
characteristics and chapters 9 through 12 provide the plan alternatives, recommendations,
funding and strategy.
BACKGROUND
Yakima County is in Central Washington, spanning the width of the middle third of the
Yakima River basin, with its upland eastern border formed by the Cascade Mountain Ridge.
The county is the state's second largest county in land area, encompassing approximately
4,400 square miles and is bordered by Kittitas and Benton Counties along the Yakima River,
by Klickitat, Skamania, and Pierce Counties to the east and by Lewis County to the west.
The Ahtanum and Wide Hollow watersheds (Figure 1-1) extend east from the Cascade
Mountains to include the cities of Yakima and Union Gap, ending where the creeks flow
into the Yakima River. The northern boundary for the two adjoining basins is formed by
Cowiche Mountain, and the southern boundary by Ahtanum Ridge. The creeks, plus their
numerous tributaries, flow through this rapidly developing area.
Flooding in the basins normally occurs in winter or spring. Spring floods occur when warm
weather and rainstorms accelerate snow melt and runoff. Winter floods, which are often of
larger magnitude and less predictable, occur when a combination of rainfall and warm
winds on saturated or frozen ground produce large volumes of runoff from snowmelt and
rain.
The largest recent flood occurred on February 9, 1996, with damage amounting to several
million dollars in the Ahtanum and Wide Hollow drainages and over $18 million in Yakima
CHAPTER 1- INTRODUCTION 13
County as a whole (Lacey, E., 1 March 1996, personal communication). Numerous other
historical flood events resulted in significant damage, and are documented in this report. A
review of historical flood events, identifying recurring flood issues, is detailed in Chapters 5
and 7.
AUTHORITY AND SCOPE FOR THE AHTANUM-WIDE HOLLOW CFHMP
At the request of county citizens, Yakima County formed a County -wide Flood Control
Zone District (FCZD) in 1998 to address flooding issues, including the development of
CFHMPs for frequently flood damaged areas. The Ahtanum-Wide Hollow Comprehensive
Flood Hazard Management Plan (CFHMP) is the third to be developed in Yakima County
by the FCZD, following the Upper Yakima River and the Naches River CFHMPs.
Completion of the CFHMP makes the local jurisdictions eligible for state funds for
emergency and non -emergency activities that reduce property loss and threats to human life
and health from flooding.
The County also signed a Memorandum of Understanding with the Yakama Nation in
March 2001 for flood control issues (Appendix K). This MOU outlines the cooperative
relationship between Yakama Nation and Yakima County regarding flood planning on
Ahtanum Creek, which forms the northern boundary of the Yakama Nation Reservation.
The Yakama Nation was involved in development of the committees and selection of the
consultant.
Funding for the Ahtanum-Wide Hollow CFHMP was provided under an agreement
between Ecology and Yakima County, with Ecology contributing 75 percent of the initial
plan costs through the state's Flood Control Account Assistance Program (FCAAP) and the
Yakima County -wide Flood Control Zone District contributed the remainder of the funds.
Golder Associates was contracted as the consultant to assist in the development of the
CFHMP in June, 2004.
PLAN DEVELOPMENT PROCESS
Since 1986 state financial assistance for flood control works has been under the authority of
the Revised Code of Washington (RCW) Chapter 86.26: State Participation in Flood Control
Maintenance, and requires the development of a flood management plan. Since 1991 this
funding requires adoption of a plan development process in accordance with the 1991
guidebook from Department of Ecology, entitled "Comprehensive Planning for Flood
Hazard Management". A management plan, so developed, is referred to as a
"Comprehensive Flood Hazard Management Plan (CFHMP)" and, upon approval by the
Department of Ecology, qualifies the agency for funding under Washington Administrative
Code (WAC) Chapter 173-145: Administration of the Flood Control Assistance Account
Program (FCAAP).
The process for development of the CFHMP is shown on Figure 1-2
4 Ahtanum-Wide Hollow CFHMP
Comprehensive Flood Hazard Management Plan
(CFHMP) Process
Citizen Advisory Committee
Establish Community Participation
Establish CFHMP Advisory Committee
Inventory Physical Conditions
& Public Workshops
Set Goals & Objectives
Determine the need for
flood hazard management measures
•
Identify alternate flood hazard management
alternatives - structural & non-structural
Review concurrent
FEMA restudy flood maps
Evaluate alternative measures with respect to
goals & objectives, cost, benefits & impacts
Develop a flood hazard
management strategy
•
Complete draft plan
•
Plan reviewed by local jurisdictions
Local SEPA review & approval
•
Submit final plan to local jurisdictions
for public hearing & adoption
Submit plan to Ecology
Figure 1-2. Comprehensive Flood Hazard Management Plan Ecology Process (Modified,
1991 Guidebook)
CHAPTER 1- INTRODUCTION 15
GROWTH MANAGEMENT ACT
The Growth Management Act is a state statute, separate from CFHMPs, which requires
certain cities and counties to develop community comprehensive plans with public input to
direct and manage community development and growth. The CFHMPs are functional plans,
which are related to state and federal hazard mitigation plans that influence the
consideration of natural hazards within GMA Comprehensive Plans and urban growth. The
following Table 1-1 taken from "Optional Comprehensive Plan Element for Natural Hazard
Reduction", Washington State CTED, June 1999, provides guiding GMA Hazard Reduction
Goals that can be incorporated into the GMA Comprehensive Plan elements.
TABLE 1-1 GMA HAZARD REDUCTION GOALS
Land Use Element
GMA Criteria
Hazard Reduction Goals
• Land use designations
Residential
Commercial
Industrial
• Storm drainage / water quality
• Minimize residential uses in "harm's
way"
• Evaluate lands prone to repetitive
flooding in relation to open space uses
(wetland restoration, recreation, etc.)
• Ensure that all development can be
adequately provided with life safety
services (water pressure sufficient for
firefighting)
• Provide for comprehensive watershed
management and planning
• Require new development to control
generated runoff
• Mitigate increase hazard risk created by
development
• Adopt a sediment management strategy
Housing Element
GMA Criteria
Hazard Reduction Goals
• Market rate
• Low cost (including manufactured and
mobile homes
• RV parks
• Identification of land for new housing
• Minimize residences located in
designated areas
• Identify areas appropriate to
accommodate relocated units
• Develop programs to acquire high risk
homes
• Develop programs to retrofit high risk
homes
6 1 Ahtanum-Wide Hollow CFHMP
Capital Facilities Element
GMA Criteria
Hazard Reduction Goals
• Existing facilities
• Future needs
• Locations for new facilities including
parks and open space
• Acquire lands which have experienced
repetitive flooding
• Locate new facilities outside of areas
prone to flooding, landslides and wildfire
and maximize water storage attributes of
the site plan
• Assess impacts of capital facility
locations on emergency response
capabilities
Transportation Element
GMA Criteria
Hazard Reduction Goals
• Arterials and transit routes
• Forecasts of traffic for at least 10 years
• Maximize access to disrupted area
• Provide for redundancy during disasters
• Identify ways to reduce repetitive
damage (flood and landslide)
Utilities Element
GMA Criteria
Hazard Reduction Goals
• Existing and proposed locations
• Capacities of existing and proposed
utilities
• Reduce disruption and maximize
reliability
• Maximize firefighting capacity
Rural Element (county plans)
GMA Criteria
Hazard Reduction Goals
• Rural land designation
• Rural development densities
• Utilize tools such as agricultural setback
easements in flood -prone area to increase
flood storage and minimize
contamination of streams by livestock
• Adopt safe storage policies to minimize
contamination by loose barrels, fertilizers
and other products
Urban Growth Areas
GMA Criteria
Hazard Reduction Goals
• Designation of county -wide UGA
• Designation of city UGA
• 20 -year growth supply of land
• Review growth designations in terms of
maximizing flood storage and avoiding
potentially unstable slopes and flood
risks
• review growth designations in relation to
implications for fire response and fuel
load
CHAPTER 1- INTRODUCTION 17
Essential Public Facilities
GMA Criteria
Hazard Reduction Goals
• Designation process for siting
• Adopt siting criteria which avoid
hazardous areas
Designation of Resource Lands
GMA Criteria
Hazard Reduction Goals
• Agricultural lands
• Forest lands
• Mineral resource lands
• Adopt best management practices which
do not contribute to hazards
Designation of Critical Areas
GMA Criteria
Hazard Reduction Goals
• Wetlands
• Aquifer recharge areas
• Fish and wildlife habitat
• Frequently flooded areas
• Geologically hazardous areas
• Maximize water storage capacities of
wetlands
• Identify sites which could accommodate
water detention
• Preserve and supplement wildlife habitat
in such a way as to stabilize potentially
hazardous sites;
• Adopt vegetation management programs
which will stabilize unstable land and
enhance habitats
• Adopt vegetation management programs
which will enhance habitat and minimize
debris generation
• Adopt vegetation management programs
which will preserve essential habitat and
minimize exposure as "fuel" for potential
fires
The CFHMP identifies the community vulnerabilities and hazard issues to develop hazard -
related goals (refining the above guiding goals) specific to the plan area and
recommendations so that they can be incorporated into the Comprehensive Plans.
With the resulting clearer understanding of the level of hazard avoidance necessary to the
local area, cities and counties should define actions or strategies to achieve the goals. These
actions and strategies are applied in the implementation of vulnerable area mapping,
regulatory codes and standards, and capital investment means. Strategies which can satisfy
multiple objectives are important.
Coordination between jurisdictions is a critical tool for implementing watershed -wide
planning. It is also an important means to ensure that transportation evacuation route
redundancy is achieved, and that incursions into the floodplain can be minimized, while
appropriate resource utilization practices are applied in the upper watersheds.
8 1 Ahtanum-Wide Hollow CFHMP
FCAAP FUNDING REQUIREMENTS FOR CFHMPS
State funds from the FCAAP program can be used for emergency and non -emergency
activities that reduce property loss and threats to human health caused by flooding. The
existence and local jurisdiction adoption of a CFHMP also allows communities to obtain
state and federal funding to replace damaged infrastructure identified in the plan as
problematic in a manner consistent with the plan recommendations, as opposed to like for
like replacement.
To obtain funds for flood control maintenance and projects through the state FCAAP,
jurisdictions must prepare a CFHMP that, as discussed in RCW 86.26.105, determines:
• The need for flood control work
• Considers alternatives to in -stream flood control work
• Identify and consider potential impacts of in -stream flood control work on
the state's in -stream resources.
• Identify the river's meander belt or floodway
State law requires that a CFHMP describe the area where any proposed project is located
and the types and locations of existing flood problems. The area may include the entire
watershed or, at a minimum, the 100 -year floodplain within a reach of the watershed. The
reach must be of sufficient length that a comprehensive evaluation can be made of its flood
problems.
The CFHMP must also identify and rank appropriate structural and nonstructural measures
to reduce flood damage and provide the technical basis for these measures.
In addition the local emergency management organization must be administering an
acceptable comprehensive emergency operations plan in accordance with the Washington
Department of Commerce.
A complete description of the information that a CFHMP must include is contained in WAC
173-145-040.
RCW 86.26.105 allows local authorities up to three years to complete and adopt a CFHMP,
in order to be eligible for FCAAP grant funding for projects. A second two-year grant cycle
for Phase 2 is also possible, if needed to complete the plan. Ecology must approve the final
CFHMP, and the municipalities must subsequently adopt the plan to accrue the above
benefits.
Applications for project funding under FCAAP require the county engineer to certify a
CFHMP has been completed and adopted or is in preparation. Ecology considers the
following CFHMP aspects in FCAAP project funding:
• Consistency with the plan or plan recommendations,
• Priority of project as identified in the plan,
• Implementation of plan or plan recommendations,
• Potential impacts of instream uses and resources.
CHAPTER 1- INTRODUCTION 19
FCAAP project funding criteria include:
• Intensity of local flood control problems,
• Relationship of public benefits to total project cost,
• The priority established by the County.
INVOLVING THE PUBLIC AND AFFECTED AGENCIES
Public and inter -agency involvement is critical to the success of a CFHMP for the following
reasons (Ecology 1991):
• Proposed measures will affect local property owners, and their support will
be needed to take action.
• WAC 173-145-070 calls for review of all FCAAP projects by state agencies
including the Washington Department of Fish and Wildlife (WDFW) and
the Washington Department of Natural Resources (DNR), as well as by
affected Native American tribes and other public entities; all of these
parties should be involved in formulating the plan.
• Since watersheds typically cross jurisdictional lines, representatives from
neighboring local governments should be involved in the process.
• As the plan must be adopted by the local governments, it is important to
build support among the local constituencies.
• The planning process offers an opportunity to educate the public on the
issues, opportunities, and public responsibilities of flood hazard
management.
Required Consultation with Other Agencies
A variety of state and federal agencies are involved in key river issues such as fishery
resources, wildlife habitat, and public use. The presence of fishery resources, primarily
salmon and steelhead, is a primary consideration in performing any flood hazard
management activities in and around the waters of the State of Washington. The potential
loss of fish habitat resulting from construction in and next to rivers has been a major concern
of fisheries agencies, sports fishermen, and Native American groups.
To ensure that fishery resources are maintained, the WDFW has review authority for most
phases of FCAAP. Ecology is required to consult with WDFW before approving any
CFHMP. Applicants for FCAAP project funds must review their proposals with WDFW,
DNR, and affected Native American tribes.
Construction work to be performed in or adjacent to navigable waters of the United States,
including wetlands, must be approved by the COE. The COE permit process ensures that all
federal, state, and local regulatory agencies with jurisdiction over the project are properly
notified and have approved the project. The COE will not approve a project that has been
rejected by another permitting agency.
More information on public and agency involvement is contained in Chapter 2.
10 1 Ahtanum-Wide Hollow CFHMP
COMMITTEES
Two committees, a Steering and an Advisory Committee, were developed as part of the
CFHMP process outlined in Figure 1-2. The Advisory Committee developed goals and
objectives, then generated, evaluated and prioritized alternatives for inclusion in the plan
recommendations. The Steering Committee worked to form the Advisory Committee,
steering the early stages of the process including the development of plan goals and
objectives and assisted in the development of the flood hazard strategy.
The Steering Committee consisted of staff actively involved in representing the jurisdictions
participating in the plan. This included staff from the Yakama Nation, the City of Union
Gap, the City of Yakima, and Yakima County.
The Advisory Committee included members of the general public, the development
community, the business community, irrigation districts, the Department of Ecology, the
Department of Fish and Wildlife, the Yakama Nation, transportation agencies, and citizen
environmental and historic preservation groups.
The two committees were combined during the alternatives phase. The Steering and
Advisory committees are described in more detail in Chapter 2. An initial output from the
Committees was the definition of the plan goals and objectives.
DEFINING CFHMP GOALS AND OBJECTIVES
Defining goals and objectives provides a framework for carrying out the CFHMP. Goals
reflect the broadest expression of a community's desires in preparing the plan; objectives
target specific results that fulfill the intent of the goals.
The following mission statement describes the overall goal of the CFHMP:
The CFHMP is a systematic process to identify and prioritize areas and property
susceptible to flood damages, select alternatives to solve identified flood problems, and
implement solutions.
Goals and Objectives for this plan developed are provided in Table 1-1, and were generated
by the two committees following the inventory of physical conditions.
Following the basin inventory, the primary causes identified were limited channel capacity
that generated overland flow, and their contributing causes that would have to be
addressed in flood issue resolution. For example, increase bridge capacity at overflow
locations, or increasing flood plain function were considered useful.
From the FEMA hydraulic analyses it was realized during the plan period, that the
overflows could not be limited to bridge locations. The initial perspective during
development of the goals and objectives to concentrate on bridges was modified to
understand that a stronger non-structural approach would be required, i.e., land use zoning
vegetation management and utility location would be required.
CHAPTER 1- INTRODUCTION 111
Table 1-2. GOALS AND OBJECTIVES FOR AHTANUM-WIDE HOLLOW CFHMP
Goals (to be achieved
through objectives) Objectives
•
Identify the location of critical conveyance channel locations
•
Identify stream reaches which have lost flood conveyance capacity due
to changes in streamside vegetation or by human activities
•
Assess existing roads, bridges and culverts for barriers to flow-through
1. Identify flood areas
and potential abatement of flood damage
and flood processes
•
Identify past erosion and stream migration processes and monitor after
storm events
•
Understand and protect the natural function of the system to reduce
flood hazard
•
Determine risks and potential mitigations for hollows
•
Identify structural and non-structural actions for reducing flood hazards
that recognize the corridor as a resource and are consistent with long-
term river corridor functioning
•
Develop flood hazard management alternatives and strategies to
reduce long-term damages
•
Develop short-term flood hazard reduction alternatives consistent with
long-term strategies
2. Reduce flood
•
Prefer mitigation recommendations that provide benefit for multiple
damages to citizens,
property and
problems and/or locations or enhance the value of the stream corridor
as an asset to the community
infrastructure while
•
Improve predictability of channel response to flood events
maintaining natural
•
Evaluate impacts of present management of flood control and irrigation
functions of stream and
diversion structures during flood events, such as the flood gate on
floodplain systems
Spring Creek in Union Gap
•
Create inundation maps for flood evacuation preparedness
•
Conduct training at first responder and jurisdiction level using Flood
Response Plan
•
Facilitate coordination with Emergency Management and Public Works
Agencies before, during and after floods (Flood Response Plan)
•
Complete flood forecasting and warning projects in the basin and
integrate with Emergency Response
•
Protect existing, or enhance where possible, fish and wildlife habitat
•
Protect the natural function of the system to reduce flood hazard
3. Work within the
•
Evaluate the use of setback dikes to allow for a more naturally
physical and biological
functioning floodplain
processes in the
•
Restore creeks to more natural channel (i.e. instream projects to
floodplain
address 90 degree angle corners and channels "perched" high on
landscape)
•
Consider mitigation at watershed level or at a minimum reach level
across jurisdictional boundaries
12 Ahtanum-Wide Hollow CFHMP
Table 1-2. GOALS AND OBJECTIVES FOR AHTANUM-WIDE HOLLOW CFHMP
Goals (to be achieved
through objectives) Objectives
•
Use best available flood hazard data for regulation of land development
and permitting
•
Show critical areas and floodplain areas on plat maps corresponding to
short/long plat developments (see City of Yakima regulations)
•
Conduct restudies of FEMA floodplain maps
•
Ensure that land use plans and regulations protect floodplain functions
•
Evaluate and ensure County/City enforcement of land use regulations
•
Coordinate with Yakama Nation on enforcement of land use regulations
4. Achieve land use
•
Evaluate other development requirements that may impact flood hazard
practices that respect
management, such as septic systems and water well siting
floodplain functions
•
Ensure consistency of floodplain regulations within jurisdictions and
investigate increasing the consistency between jurisdictions.
•
Identify and implement incentive program for bioengineered structural
solutions to flood hazard mitigation
•
Work with existing permitting agencies (such as, Fish and Wildlife,
USACE, Yakima County Shoreline, Ecology, and the Yakama Nation
Water Code Administration) on identifying ways to streamline project
permitting process
•
Encourage coordination and cooperation among all regulatory agencies
•
Work in creative ways to streamline the regulatory process
•
Encourage innovative development techniques where natural systems
5. Emphasize the value
and floodplain function exists
of stream corridors as
•
Educate the public and development community on the value of
an asset to the
allowing floodplain and stream function to properties- investigate Smart
community
Growth concepts
•
Encourage open space planning and acquisition, through incentives
such as leases, easements, acquisition, etc.
•
Identify erosion and stream migration hazards and evaluate mitigation
options as necessary
•
Create and submit FEMA floodplain map for Shaw Creek
•
Sustain the mapping program
•
Compile varied available mapping data into a comprehensive
database/library resource that can be used to address future
6. Quantify hazards in
assessments
our floodplain
•
Identify changing flood condition areas to support new floodplain
mapping work
•
Identify draws that are prone to flash flooding
•
Avoid contaminating land uses in the floodplain
•
When designing a flood overflow area, make sure it is not a
contaminated area
•
Minimize impacts of septic systems and other critical facilities on water
quality
CHAPTER 1- INTRODUCTION 113
Table 1-2. GOALS AND OBJECTIVES FOR AHTANUM-WIDE HOLLOW CFHMP
Goals (to be achieved
through objectives) Objectives
•
Communicate and coordinate with local governments and community
groups on flood issues/hazards
•
Provide documented examples of positive steps being taken
•
Highlight projects that will educate the public on sustainable flood
hazard mitigation
7. Ensure a sustainable
•
Ensure an ongoing educational program that keeps up with current
flood plan through
understanding, science, and changes in the watershed
public and agency
awareness, acceptance,
•
Participate in the CRS (Community Rating System) program
involvement, and
•
Flood safety preparedness education
education
•
Determine where large numbers of animals may be kept during a flood
event and distribute information to the public
•
Develop a stream corridor improvement program consistent with this
plan
•
Increase public awareness and understanding of flooding issues and
floodplain functions
•
Seek grant funding
•
Investigate possible cost savings through coordination with other
multiple objective projects
•
Determine possible areas for flood control sub -zones
8. Ensure the
•
Address the causes of problems as opposed to the symptoms
implementation of the
•
Identify and utilize complementary Plans
flood plan in a timely
•
Consider flood related recommendations from large scale plans such as
manner for both the
the Ahtanum Watershed Assessment
short and long term
•
Integrate flood hazard reduction into ongoing planning, management
programs, and capital facilities plans
•
Understanding how the landscape is managed
•
Create and implement educational efforts to inform other organizations
about flood risks, plans, and possible mitigation approaches
The recommendations and implementation strategy contained in Chapter 11 of this CFHMP
were generated and are considered to achieve the above objectives. The ability to meet all
the objectives is dependent on cooperation amongst multiple jurisdiction and agencies and
the ability to fund the recommendations.
A discussion of funding and jurisdiction implementation strategies is contained in Chapter
12.
14 1 Ahtanum-Wide Hollow CFHMP
RELATED PROGRAMS AND ACTIONS
There are programs conducted in Yakima County and the jurisdictions which directly
affected CFHMP development, including the County's Comprehensive Plan, the County-
wide Flood Control Zone District activities, the FEMA flood map restudy and the Regional
Storm Water Program.
Plan 2015—Yakima County's Comprehensive Plan
Plan 2015 is mandated under the state's Growth Management Act (GMA), which requires
planning by all counties with a population of 50,000 or more, or a population increase of 10
percent or more over the last 10 years. Both apply to Yakima County. Plan 2015 was
approved by the Board of Yakima County Commissioners in 1997, and has gone through
several yearly amendments since that time. Plan 2015 expresses the county's growth,
development, and environmental objectives and guides growth in the entire county,
particularly in unincorporated areas outside of the Yakima and Union Gap Urban Growth
Areas (UGA).
The Yakima County Comprehensive Plan provides protection for water resources and for
flooded areas, including needed surface water runoff controls. Therefore, CFHMP and GMA
planning have common goals. The following elements of the GMA process will facilitate
CFHMP development (Ecology 1991):
• Population forecasts and development projections to predict increased
stormwater runoff and flooding problems.
• Floodplain information, such as the identification of critical areas.
• Definition of urban growth boundaries which, if properly located, can
minimize the need for flood control structures.
• Integration of flood hazard management measures into a capital
improvement program to adequately service new growth.
Yakima Urban Area Comprehensive Plan 2025
When a county is required to plan under the GMA, the cities and towns within that
county are likewise required to plan. The Yakima Urban Area Comprehensive Plan 2025
was adopted by the Yakima City Council and Board of Yakima County
Commissioners in December 2006 to guide development within the Yakima Urban
Growth Area, which includes the area of the City of Yakima and its unincorporated
UGA. The plan identifies hazards that have the greatest potential to threaten public
health and safety and includes floodplains as one of these hazards. The plan states
that FEMA and the City of Yakima provide guidelines to ensure that development in
or near these areas is compatible with surrounding properties and that risk to
upstream or downstream neighbors or the natural functions of floodplains is not
created.
CHAPTER 1- INTRODUCTION 115
Union Gap's Comprehensive Plan
Similarly, the Union Gap City Council has adopted the City of Union Gap
Comprehensive Plan as the guidance for growth and development within Union Gap.
The plan includes goals and policies to enhance the quantity and quality of surface
water, to prevent increased flooding from stormwater runoff, to improve water
quality through improved stormwater management, and to prevent the loss of life or
property and minimize public and private costs associated with repairing or
preventing flood damage from development in frequently flooded areas.
Shoreline Master Program for Ahtanum-Wide Hollow Jurisdictions
Yakima County and the Cities of Yakima and Union Gap implement the
requirements of Washington's Shoreline Management Act of 1971 (SMA) at the local
level. Yakima County completed an update of the regional Shoreline Master
Program (SMP) in December 2007, with State approval of the program on February
25, 2010. Union Gap adopted the regional Yakima County SMP on August 25, 2008.
Yakima is expected to have their SMP updated in 2010. Shoreline jurisdiction is
typically tied to the FEMA 100 -year flood plain or the floodway when they are
designated along the state's largest rivers and streams as identified by the SMA.
Ahtanum Creek is designated under the SMA, while Wide Hollow Creek is not.
More details are given in Chapter 8.
Yakima County Revised Flood Insurance Study
The Flood Insurance Study (FIS) defines the 100 -year floodplain and floodway, as mandated
by the National Flood Insurance Program (NFIP). The NFIP implements a comprehensive
set of regulations for mitigating flood damage. Yakima County and the cities of Union Gap
and Yakima participate in the NFIP by adopting zoning restrictions and enforcing building
standards to limit flood damage in the 100 -year floodplain.
The Flood Insurance Rate Maps (FIRMS) showing 100 and 500 -year flood extent and the FIS
for these basins were issued in 1985 based on data from the 1970's. In 2009 these maps were
converted to a digital format (DFIRMs) and adopted by the jurisdictions. The DFIRMs are
currently undergoing a restudy and remap using more recent data and anticipated for final
adoption in 2011. The current FEMA preliminary maps produced in the current FIS were
used as reference in this CFHMP. Committee members and the public at large commented
on the work maps, which were used by the consultant in preliminary maps generated in late
2010. The committee also had the opportunity to reprioritize or alter its recommendation
based on the FEMA work maps. Additional information about FIS's for jurisdictions
included in this CFHMP are included in Chapter 3.
Yakima County -Wide Flood Control Zone District Activities
As mentioned earlier, the FCZD was formed by Yakima County Commissioners in 1998 in
response to several years of damaging floods that severely affected county and city
infrastructure, private property and the county budget. Additional information about
formation of the district is provided in the Upper Yakima River CFHMP (revised 2007). The
district's mission is:
16 1 Ahtanum-Wide Hollow CFHMP
To reduce the risk of flood damage to public and private property through responsible and
efficient surface water management. These activities are provided through regulatory
activities, master planning, regional coordination, technical assistance, and implementation
and maintenance of structural and non-structural projects.
The first few years of the FCZD were used to build-up funds for flood emergencies, grant
matches, and demonstration projects. Staff was hired specifically for the FCZD beginning in
2001. Since that time the FCZD has been involved in numerous activities detailed in periodic
Project Updates. These activities include: production of CFHMPs; FEMA map restudies;
application and implementation of mitigation grants; removal of abandoned levees and
irrigation structures; work with County Roads on bridge conveyance; participation in
regional habitat and water resource plans; demonstration projects on vegetation
management; public outreach efforts; and the County Flood Response and Hazard
Mitigation (FEMA) Plans.
Most of the activities listed above occur in, or affect the Ahtanum and Wide Hollow
drainages. Some of the FCZD's benefit to the communities involves improving
communication and coordination of the various governments, agencies and organizations
involved with surface water management in Yakima County. These interactions and
relationships will help ensure the CFHMPs within Yakima County are effectively
implemented.
Regional Stormwater Programs
Due to the unique local soil and arid climate conditions of Yakima the Cities and County
have cooperated to create a Regional Stormwater Policy Group, which led to the adoption of
a Regional National Pollution and Discharge Elimination System, Phase II permit from
Ecology that has prescribed requirements for eliminating and reducing stormwater
pollution contribution from the urban areas. The Yakima County Surface Water Division
acts as the administrative lead. The three local jurisdictions that contain the Ahtanum and
Wide Hollow Creeks are within the regional program.
The standard practice within the "flood -prone" Ahtanum and Wide Hollow basins is to
retain and infiltrate the full 25 -year flood volume onsite. This has been demonstrated to
eliminate 100 -year flood peak flow increases from new urban development.
CHAPTER 2
PUBLIC INVOLVEMENT
Public involvement is an important aspect of the flood planning process, particularly in
complicated watersheds like Ahtanum and Wide Hollow. Input from the public was
necessary in order to gather a comprehensive record of past flooding and areas that are
particularly prone to flooding. This was important as little technical flood monitoring has
taken place historically in the watershed. Public involvement consisted of forming Steering
and Committees, holding public meetings, and conducting interviews of people with
knowledge of historical flooding conditions in the watershed.
COMMITTEES
Two committees were developed as part of the CFHMP process. The Advisory Committee
drafted goals, objectives, and the alternatives for the plan. The Steering Committee worked
to determine the feasibility of Plan alternatives. The Advisory Committee included members
of the general public, the development community, the business community, irrigation
districts, the Department of Ecology, the Department of Fish and Wildlife, the Yakama
Nation, transportation agencies, and citizen environmental and historic preservation
groups. The Steering Committee consisted of staff actively involved in representing the
jurisdictions participating in the plan. This included staff from the Yakama Nation, the City
of Union Gap, the City of Yakima, and Yakima County. The Steering Committee and
Advisory Committees were combined during the development of alternatives. Unless
otherwise noted, the use of the term Committee refers to the combined Steering and
Committees.
Steering Committee
The Steering Committee consisted of representatives from the four jurisdictions involved in
developing and implementing the plan: The Yakama Nation, the City of Yakima, the City of
Union Gap, and Yakima County. Steering Committee Membership is listed in Table 2-1.
2 Ahtanum-Wide Hollow CFHMP
Table 2-1
AHTANUM-WIDE HOLLOW STEERING COMMITTEE
Steering Committee Member Representing
William Rathbone City of Union Gap
Chris Waarvick City of Yakima
Dean Patterson Yakima County Planning
Tom Ring Yakama Nation Water Resources
Virgil James Yakama Nation Zoning
Jeff Peters City of Yakima
Dennis Henne City of Union Gap
Brett Sheffield City of Yakima
Michael Kerins Yakima County Planning
Steve Erickson Yakima County Planning
John Knutson FCZD, Surface Water Manager
Terry Keenhan FCZD, Surface Water Manager
Dianna Woods Yakima County Surface Water
Keelan McPhee Yakima County Surface Water
Joel Freudenthal Yakima County Surface Water
Khalid Marcus Yakima County Surface Water
Andreas Kammereck Golder Associates, Consultants
Steering Committee meetings were held on an as needed basis throughout the course of the
planning process. Eleven Steering Committee meetings were held between November lst,
2004 and July 27th 2006. See Table 2-2.
CHAPTER 2 — PUBLIC INVOLVEMENT 13
TABLE 2-2 Steering Committee Meetings, 2004-2006
Date
Topic
1
Nov. 1st, 2004
Setting for the planning process, role of committees
2
Dec. 16th, 2004
Public outreach- public meetings held
3
Mar. 7th, 2005
Formation of Committee
4
Mar. 28th, 2005
Committee, Outreach- postcard mailings
5
May 23rd, 2007
Committee meetings and membership, Technical
Memos by Golder Associates
6
Jul. 25th, 2005
Progress of background chapters as deliverable to DOE
7
Sept. 26th, 2005
Goals and Objectives, Finalizing memos for deliverable
to DOE
8
Nov. 28th, 2005
Review Goals and Objectives with both committees
9
Dec 15th, 2005
Goals and Objectives (Draft 12)
10
Jan. 30th, 2006
Finalize Goals and Objectives (Draft 12) , begin
Alternatives discussion
11
Mar. 27th, 2006
Golder Budget Revision, Plans on how to proceed with
Alternatives discussion
12
Jul. 27th, 2006
Combining Steering and Committees for Alternatives
discussion.
Advisory Committee
The Committee formed the heart of public involvement in the flood planning process. The
Committee includes members of the general public, the development community, the
business community, irrigation districts, the Department of Ecology, the Department of Fish
and Wildlife, the Yakama Nation, transportation agencies, and citizen environmental and
historic preservation groups. The role of Committee members and aspects of participation
are summarized below:
• Provide input into the planning process
• Provide information about flooding problems, and issues relating to flooding, in the
Ahtanum, Wide Hollow, and Spring (Chambers) Creek (Union Gap) watersheds
• Learn about flood hazard management
• Help develop goals and alternatives for flood hazard management in the Ahtanum-
Wide Hollow area
• Be kept informed about the regulations and policies surrounding flood planning
• Help educate the community about flood issues
• Support implementation of the plan by the County, the Yakama Nation, and the cities of
Yakima and Union Gap; and adoption by the County and cities
4 1 Ahtanum-Wide Hollow CFHMP
• Review and provide input on draft FEMA restudy maps
Committee members were selected through several different methods. A list of potential
Committee representatives was created representing diverse groups with an interest in
flooding issues. The list was discussed and approved by the Steering Committee. Categories
were as follows:
• Irrigation Districts
• Department of Ecology
• Environmental/Historical Preservation Groups
• Schools
• Development Community
• Engineering/Surveying
• Fish and Wildlife
• Business Community
• Transportation Agencies
• North Yakima Conservation District
• General Public
Members of the public who had expressed interest in participating at public meetings were
contacted, based on geographic location.
Urban areas were underrepresented in the public meetings, so a postcard inviting residents
and business owners to join the Committee was sent to residents near the floodplain within
the urban areas of Yakima and Union Gap. This generated considerable interest, and several
business owners joined the Committee. Agency representatives and other representatives of
groups identified on the list were contacted by phone.
CHAPTER 2 — PUBLIC INVOLVEMENT 15
Table 2-3
AHTANUM-WIDE HOLLOW ADVISORY COMMITTEE
Committee Member
Representing
Bill Goggin
Bill Koreski
Brandon Rogers
Bruce Johnson
Buck Taylor & Mike Redmond
Chuck Steele
Dale Murphy
David Taylor
Ed Campbell
Eric Bartrand
Frank Glaspey
Joel Freudenthal
LaRayne Case-Malner
Lee Hacket
Leslie Wahl
Mark Herke
Mathew Barnett
Merle Warehime
Richard Visser
Robert Smoot
Ron Anderson
Steve Simon
Steve Strosahl
Tim Critchlow
Engineering - Private
Business - Union Gap
Yakama Nation — Fisheries
Public — West Valley
Yakima Air Terminal
Department of Ecology
Public - Wide Hollow
Ahtanum Irrigation District
Ahtanum Mission
WDFW
Business - Union Gap
Yakima County
Public- Emma Lane
Business - Union Gap
Audubon Society
Business - Ahtanum
Business - Union Gap
Yakima Association of Realtors
WDFW
Yakima Valley Canal Company
Yakima Association of Realtors
Public - Union Gap
Development Community
West Valley School District
Forty-eight Committee meetings were held between April 14th, 2005 and February 18th, 2010.
The Advisory Committee and Steering Committee were combined as of July 27th, 2006. See
Table 2-4 Committee Meetings.
TABLE 2-4 Advisory & Combined Committee Meetings, 2005-2010
Date
Topic
1
April 14, 2005
Introduction
2
April 28, 2005
Flood Information/Issues
3
May 17, 2005
Flood Issues
4
June 7, 2005
Membership/Goals and Objectives
6 1 Ahtanum-Wide Hollow CFHMP
TABLE 2-4 Advisory & Combined Committee Meetings, 2005-2010
Date
Topic
5
July 21, 2005
Goals and Objectives
6
Oct. 20, 2005
Goals and Objectives
7
Nov. 17, 2005
Goals and Objectives
8
Jan. 19, 2006
Goals and Objectives/Floodplains 101
9
Feb. 16, 2006
Goals and Objectives Finalized/Floodplains 101
10
May 18, 2006
Flooding Processes in Ahtanum
11
July 20, 2006
Introduction to Alternatives
12
Sept. 21, 2006
Process for Generating Alternatives (Steering Committee and
Committee Combined)
13
Oct. 19, 2006
Ahtanum Mission / North Fork Bridges
14
Nov. 16, 2006
Emma Lane / General Inundation Issues
15
Jan. 4, 2007
Irrigation Infrastructure
16
Jan. 25, 2007
Spring Creek / Shaw Creek
17
Feb. 18, 2007
Shaw Creek / Vegetation / Fish and Wildlife
18
March 8, 2007
Fish and Wildlife/Emergency Response / Union Gap
19
Apr. 5, 2007
Infrastructure
20
April 26, 2007
Infrastructure
21
May 17, 2007
Land Use
22
June 14, 2007
Regulatory Issues
23
June 28, 2007
Channel Issues
24
July 26, 2007
Channel Issues
25
Sept. 27, 2007
Close Alternative brain -storming, next steps
26
Oct. 18, 2007
Consider evaluation methods
27
Nov. 8, 2007
Review Alternative ranking worksheet
28
Jan. 24, 2008
Introduce Alternatives Summary Tables, review Ahtanum Mission,
Emma Lane, Union Gap
29
Feb. 26, 2008
Review channel issues, Shaw Creek, Wide Hollow
30
March 25, 2008
Review bridges & roads, and irrigation
31
April 7, 2008
Review land use and dropped alternatives
32
May 5, 2008
Review development standards, flood response,
information/outreach, and more on Shaw Creek
33
Sept. 4, 2008
Mapping update, edits to background chapters
34
Dec. 8, 2008
Alternatives tracking and edits
35
Jan. 21, 2009
Alternatives tracking and edits
36
Feb. 17, 2009
Alternative tracking and edits
37
March 16, 2009
Select Recommendations from alternatives
38
April 20, 2009
Select Recommendations from alternatives
39
May 18, 2009
Select Recommendations from alternatives
40
June 15, 2009
Select Recommendations from alternatives
CHAPTER 2 - PUBLIC INVOLVEMENT 17
TABLE 2-4 Advisory & Combined Committee Meetings, 2005-2010
Date
Topic
41
July 30, 2009
Chapter 9 to committee, review draft work maps, review potential
gaps in alternatives
42
Sept. 21, 2009
Review potential gaps in alternatives, 100 -year bridge
recommendations
43
Dec. 10, 2009
Tighter language for select recommendations
44
Jan. 21, 2010
Union Gap mill site, review Wide Hollow draft work maps
45
Feb. 18, 2010
Review Wide Hollow FEMA final draft work maps and last
suggested edits to draft recommendations
46
April 19, 2010
Prioritize recommendations, discuss funding for plan
implementation and economic costs of development in floodplains
47
Sept. 14, 2010
Discussion - additions from information developed during process
including: FEMA draft maps, hydraulics at existing bridges, smaller
flood events, and role of land use, maintenance, and management
48
Oct. 18, 2010
Integration of planning suggestions in chapter 8, review of bridge
analysis, stream clean-out demonstration project, and 25 -year flood
mapping. Last committee meeting.
PUBLIC MEETINGS, OPEN HOUSES, ADVERTISEMENTS, INTERVIEWS
Neighborhood Meetings
A wealth of information was gathered at neighborhood meetings about flood problem areas.
This information was entered into a master database, with corresponding points included
on a map of the two basins. This map and database serve as a baseline for identifying
problem "hot spots". The workshops were advertised on the radio, and there was some
newspaper and television coverage.
Four public workshops, facilitated by Yakima County and Golder staff, were held at the
following locations:
Table 2-5 Public Workshops, 2005
Date
Location
1.
Jan. 25, 2005
Ahtanum Valley Elementary School 3006 S. Wiley Rd., Yakima Co.
2.
Jan. 26, 2005
Wide Hollow Elementary School 1000 S. 72nd Ave., Yakima Co.
3.
Jan. 27, 2005
Ahtanum Youth Park 1000 Ahtanum Rd. Union Gap
4.
Feb. 1, 2005
Yakima Valley Restitution Center 2403 S. 18th St. Union Gap
The purpose of these workshops was to gather flood information from residents within the
Ahtanum and Wide Hollow watersheds, corresponding to the CFHMP project area.
8 1 Ahtanum-Wide Hollow CFHMP
Information gathered at the public meetings included personal statements, photographs,
and videos of flood events.
At each public workshop, attendees placed adhesive dots on laminated maps next to known
flood problems, while workshop facilitators wrote descriptions of each problem. Yakima
County GIS Department staff developed the maps, which correspond to six defined extents
within the Ahtanum and Wide Hollow watersheds, including:
• Ahtanum;
• West Valley -North;
• West Valley -South;
• West Yakima;
• Southwest Yakima; and,
• Yakima and Union Gap.
At the end of each workshop, the collected information was entered into an Excel database.
Upon completion of all four public workshops, the Yakima County GIS Department
translated the collected information into a GIS database that associates flood problems with
their locations. Reported information from the workshops was not verified at that time. The
maps provided background reports which were utilized when examining flooding
problems in the basin, rather than a final product.
Workshops Summary
The first public workshop was held on January 25, 2005 at the Ahtanum Valley Elementary
School located at 3006 South Wiley Road. There were approximately 38 attendees, which
was the greatest number of people to attend any of the workshops. This workshop spurred
many discussions about problems and issues throughout the region, particularly in the
upper Ahtanum area.
The second public workshop was held on January 26, 2005 at the Wide Hollow Elementary
School located at 1000 South 72nd Avenue. There were 8 attendees. Most comments and
problems brought to attention at this meeting regarded Wide Hollow Creek.
The third public workshop was held on January 27, 2005 at the Ahtanum Youth Park located
at 1000 Ahtanum Road. There were 13 attendees. Most comments and problems brought to
attention at this meeting pertained to the Southwest Yakima geographic extent.
The fourth public workshop was held on February 4, 2005 at the Yakima Valley Restitution
Center located at 2403 South 18th Street. There were 3 attendees.
Interviews of Agency/City/Tribal Representatives
Interviews were conducted with Dennis Henne, Public Works Director for the City of Union
Gap, Augie Martinez, County Roads Maintenance Supervisor, Ken McNamee, Department
CHAPTER 2 — PUBLIC INVOLVEMENT 19
of Natural Resources, and Virgil James, Yakama Nation Zoning Official. Regulatory
information and flood problem location information were gathered during these interviews.
Broader issues, such as land use and emergency management, were also discussed and
recorded for reference in the plan. More information about these interviews and field visits
is included in Chapter land Appendix E.
Additional Outreach and Results
Considerable information was gathered at the four public workshops and in stakeholder
interviews. Summaries of this information by watershed area are located in Appendix F.
The meetings established positive relationships with residents, which facilitated continued
field work and organization of the Committee. Several residents in the rural portions of the
two basins were active in providing information about past flooding, and participating in
the Committee.
Newsletters describing progress of the planning effort were mailed to everyone on the
contact list (over 100 people) between April 2005 and August 2006. This period saw creation
of the goals and objectives, a critical phase that would guide the rest of the process.
Maps, shown as Figures 2-1 through 2-6, were created by Yakima County GIS by combining
the information gathered through public meetings and interviews. A corresponding
database, which included comments gathered at public meetings, was also created
(Appendix C). These maps were passed out to committee members and referred to
throughout the process of identifying problems and determining plan alternatives. The
maps and databases are further explored in the following chapters and appendices.
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This map was derived from several
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CHAPTER 2 - PUBLIC INVOLVEMENT 115
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CHAPTER 2 - PUBLIC INVOLVEMENT 115
16 1 Ahtanum-Wide Hollow CFHMP
N This page intentionally left blank N
CHAPTER 3
FLOOD RELATED STUDIES
Although the area has experienced regular flooding there have been few formal flood
studies until more recently. There are a number of water quality studies in the basins.
UPPER YAKIMA RIVER COMPREHENSIVE FLOOD HAZARD
MANAGEMENT PLAN, 2007
The Upper Yakima River CFHMP was adopted by the County Commissioners in 1998. The
plan's purpose was to gain an understanding of flood hazard characteristics and
management alternatives in the more urbanized area along the Yakima River and Lower
Naches between Union Gap and the northern County line located in Yakima Canyon in
order to develop a flood hazard management program. Alternatives implemented after
adoption of the 1998 CFHMP included changes to policies, programs and regulations
through -out the county that will have a significant impact on flooding. Since the plan's
adoption, zoning changes have been made to reduce development density in frequently
flooded areas and a Floodplain Overlay District was added to the Yakima Urban Areas
zoning code.
The Upper Yakima River CFHMP was updated in 2007 to incorporate infrastructure
changes and new information available from a variety of studies. Since the land use
recommendations were largely implemented within the cities and county, including
ordinances in the interim, the updated plan focuses on reducing flood risks to - and caused
by - the existing infrastructure: levees, bridges and highways.
The Upper Yakima River CFHMP 2007 Update includes some information about Spring
(Chambers) Creek East.
CHANNEL MIGRATION ZONE
Yakima County Planning Division provided a Channel Migration Zone (CMZ) for Ahtanum
Creek in 2005, which is one of the requirements for the Shoreline Master Program update.
The County adopted the CMZ in April 2008. It is anticipated the City of Union Gap will also
adopt this CMZ delineation.
In 2007 this CFHMP provided a review of stream channel characteristics to help determine
the need for a more detailed CMZ study beyond the 2005 reconnaissance level. The review
by Golder Associates, located in Appendix D, indicates that channel migration over-all is a
minimal risk, so a more extensive study is not warranted.
2 1 Ahtanum-Wide Hollow CFHMP
FLOOD INSURANCE STUDIES
The National Flood Insurance Program (NFIP) is a federal program established in 1968 and
administered by the Federal Emergency Management Agency (FEMA), which allows
property owners to purchase flood insurance. Participating communities receive damage
coverage in exchange for implementation of floodplain management measures to reduce
flood risks. As part of NFIP, Flood Insurance Studies (FIS) develop Flood Insurance Rate
Maps (FIRMs) mapping flood risk in a region that are used to establish flood insurance rates
and to regulate development. An FIS typically provides descriptions of the topology,
geography, and hydrology of a region, summarizes principle flood problems, flood hazard
factors and flood protection measures, and determines flood insurance zones.
Existing Flood Insurance Rate Maps and Floodway Maps
The Federal Emergency Management Agency (FEMA) uses the results of the FIS to prepare
Flood Insurance Rate Maps (FIRMs) identifying special flood hazard area (areas subject to
inundation by the 100 -year flood). FEMA has adopted the 100 -year flood as the minimum
base flood for floodplain management purposes and the 500 -year flood as an additional area
of lower flood risk.
Flood insurance studies for portions of Yakima County, the City of Yakima, and the City of
Union Gap are based on information collected in the 1970s. The 1984 FIS study area includes
Spring (Chambers) Creek East (labeled as Spring Creek 2 on FEMA flood maps), and Wide
Hollow and Ahtanum Creek watersheds. A revision to the Yakima River maps was made in
1998 resulting from construction and certification of the levees along the Yakima River.
Most 1998 revisions for the FIS study area reflected changes to corporate limits; new
hydrologic and hydraulic analysis of a portion of the Yakima River; and reanalysis of
floodplains for Spring (Chambers) Creek East, needed due to the installation of a flood gate
and permanent blockage of a flapper gate downstream.
Three FIS reports cover these waterways, namely the City of Yakima FIS, the City of Union
Gap FIS, and the Yakima County FIS. Each FIS includes a portion of the Yakima River in its
study region and therefore provides the same general flood history summary for this area.
Spring (Chambers) Creek East is discussed in both the Union Gap FIS and County FIS
because it currently flows from the Yakima River in Union Gap to Wide Hollow Creek just
upstream of its confluence with Ahtanum Creek, which was in County jurisdiction.
Much of the Ahtanum and Wide Hollow watersheds area, such as the North Fork of the
Ahtanum and Cottonwood Creek, have not gone through a detailed FIS study, and
therefore have no mapped floodways. This will change in the FIRM restudy for Ahtanum
and Wide Hollow Creeks underway now and scheduled for completion in 2011. Because of
Spring (Chambers) Creek East's close connection with the Yakima River and its revision to
Zone X due to the floodgate mentioned above, the current restudy will not review the
mapping for this stream. Review of the floodplain for Spring (Chambers) Creek East will
occur with the next restudy of this section of the Yakima River.
CHAPTER 3 — RELATED FLOOD STUDIES 13
The following sections focus on some details of the FIS for each of these regions.
City of Yakima
The City joined the NFIP in the program on December 15, 1981. The Yakima area
experiences frequent flooding. Certified levees and highways that function as levees along
the Yakima River have decreased the city's risk from mainstem river flooding from a 100 -
year event. Various recurrence interval flood elevations at numerous cross sections on the
Yakima River, and Wide Hollow, Spring Creek West (labeled Spring Creek 1 on FEMA
maps) and Bachelor Creeks are available in the City of Yakima FIS.
City of Union Gap
The City of Union Gap joined the NFIP program on May 2, 1983. Union Gap is
approximately 5 miles south of the City of Yakima and is the location of the original Yakima
town site. "The site of Yakima City was too swampy and too constrained by the nearby
ridges for easy development. Thus, over the protests of the Yakima City residents, the
Northern Pacific established its station several miles north where there was more
developable land." Flooding caused by the Yakima River, Ahtanum Creek, Wide Hollow
Creek, and Spring (Chambers) Creek East are included in the FIS (labeled Spring Creek 2 in
the County FIS).
Yakima River floodwaters directly affect a portion of the City of Union Gap: floodwater
backwaters through the Wide Hollow Creek culvert under I-82. The current maps account
for this backwater, but show all other portions of I-82 as having sufficient freeboard to
contain the 100 year flood on the Yakima. The 1996 flood, which was just over a 100 year
flood as defined in the FIS, overtopped I-82 just south of the City of Union Gap, in the
project area of this CFHMP. The Upper Yakima CFHMP recommends remapping of the
floodplain in this area to account for changes in the channel that have occurred since the
original mapping in 1974.
Yakima County
The Yakima County FIS includes the unincorporated areas of Yakima County. The Yakama
Nation, which occupies almost half of the land in the county, is excluded from this FIS,
except the Yakima River and Ahtanum Creek floodplains that lie within the Yakama Nation
reservation boundary. Some outlying areas were not studied due to lack of development or
development potential in the near future. Yakima County entered the program of the NFIP
on June 5, 1985.
The FIRMs show different types of flood hazard areas, or zones, based on the location of the
100 -year floodplain and the type of analysis used to predict water surface elevations. Flood
hazard zones are used to determine insurance rates.
The FIRM shows the floodway, as determined by FEMA. The floodway usually includes the
main channel of the stream and the land along its sides that must be reserved in an
unobstructed condition in order to convey the 100 -year flood without increasing flood levels
4 1 Ahtanum-Wide Hollow CFHMP
by more than 1 foot (or less if specified in local ordinances). FEMA requires communities to
designate the floodway to avoid significantly increasing upstream flood elevations.
To maintain insurance coverage, communities must prohibit development within the
designated floodway that would cause any increase in the 100 -year flood elevation. The
state has additional restrictions beyond FEMA's in floodways (RCW 86.16.041) for
residential development.
2009 Map Modernization and Digital Flood Insurance Rate Maps
As part of the Federal Map Modernization program all Yakima County FIRMs were
updated in 2009 to digital versions, known as DFIRMs using updated and higher resolution
ground data, where it exists, including the Ahtanum and Wide Hollow basins.
2011 DFIRM Restudy
Map restudies for the Ahtanum Creek and Wide Hollow Creek watersheds were started in
2005 as part of FEMA's Map Modernization program using updated hydrology, higher
resolution 2 foot contour LiDAR ground data and detailed surveys at bridges. This new
data, along with historic flood path and elevation data from the 1996 flood (approximately
an 80 -year event) was incorporated in modern hydraulic models to increase floodplain and
floodway resolution as the basis for the new preliminary FIRMs to be released in 2011.
YAKIMA COUNTY HAZARD MITIGATION GRANT PROGRAM
APPLICATIONS
In September 1997, Yakima County Public Works submitted two applications to the
Washington State Military Department, Emergency Management Division, Hazard
Mitigation Grant Program. Both applications requested funding to alleviate flood risk in the
Ahtanum valley on Rutherford Road (affected by Hatton Creek) and near the intersection of
S 42nd Ave and Emma Lane (affected by Ahtanum and Bachelor Creeks). Yakima County
was not awarded funding for either project proposed in 1997.
The 1997 Rutherford Road application proposed building overtopping structures at the
beginning of Rutherford Road to stop flood waters from gaining uncontrolled access to the
roadside ditches. It also proposed that additional control structures be placed along
roadside ditches to control water velocity. The second 1997 application proposed
development of a second channel on Ahtanum Creek west of S 42nd Ave near Emma Lane
that is in closer alignment with what is believed to be the natural channel of creek. This
second application was successfully resubmitted in 2007 and will lead to structural
measures to minimize flood damage. A third HMGP application was made in 2007 for Shaw
Creek overflows (documented in 2001 and identified in this CFHMP). This application was
unsuccessful and was resubmitted in 2010 as a Pre Disaster Mitigation grant.
CHAPTER 3 — RELATED FLOOD STUDIES 15
The most recent HMGP application FEMA identified repetitive loss properties - to purchase
or elevate the buildings in 2009 has successfully made it through the state review process
and has been awarded by FEMA in 2010.
Yakima County Flood Control Assistance Account Program Grant Applications
As described in Chapter 1 the Flood Control Assistance Account Program (FCAAP)
provided grant support to produce this CFHMP. FCAAP also provides grant assistance for
flood mitigation projects. Yakima County applied for several mitigation grants pertaining to
this area beginning in 2003. Unsuccessful applications included proposals for a Flood
Response Plan and Emma Lane area mitigation. Successful applications include: Wide
Hollow Creek and North and South Fork Ahtanum Creek map restudies; and a grant for
repetitive loss property buy-outs. The map FIS restudy will be finalized in 2011 and one
house on Wide Hollow Creek has been purchased. This house had several flood insurance
claims and is a FEMA identified repetitive loss property.
AHTANUM WATERSHED ASSESSMENT & PROGRAMMATIC EIS
The "Ahtanum Creek Watershed Assessment" was released by Ecology in February 2004.
The assessment included analysis of additional water storage in a new Pine Hollow
Reservoir and associated water rights modifications between Ahtanum Irrigation District
(AID) and Wapato Irrigation District (WIP), habitat rehabilitation opportunities, and flood
hazard reduction opportunities in the basin, including the limited role of the proposed
reservoir in management of flood flows. The assessment included major stakeholders
concerned with irrigation and water use in the Ahtanum watershed including: Department
of Ecology, Department of Fish and Wildlife, AID, WIP, Yakama Nation and Yakima
County.
Flooding issues were considered in the analysis and recommendations of the assessment. As
currently proposed, the off -channel storage possibility will not provide a decrease in flood
flows due to the design and cost increase that would be required for the project.
The "Draft Programmatic Environmental Impact Statement for the Ahtanum Creek
Watershed Restoration Program" (EIS) was released in February 2005. Implementation of
the major component of the EIS, the proposed Pine Hollow Reservoir, will require
development of agreements between the Yakama Nation, other (both on- and off -
Reservation) water rights holders, and the Washington State Department of Ecology.
Negotiation and development of these agreements has not occurred since the EIS was
finalized. The ongoing Storage Study for the Yakima Basin EIS by the Bureau of
Reclamation, Ecology, the Yakama Nation and the County will include reference to Pine
Hollow as a storage alternative; this basin -wide process may result in some movement
forward on the Pine Hollow Reservoir.
6 1 Ahtanum-Wide Hollow CFHMP
NATIONAL WATER QUALITY ASSESSMENT
The National Water -Quality Assessment (NAWQA) Program is a study undertaken by the
USGS to describe the status and trends in the quality of the nation's groundwater and
surface -water resources and to provide a sound understanding of the natural and human
factors that affect the quality of these resources. Agricultural lands are one focus of these
studies.
At the end of the first of two planned stages, which included sampling in the Yakima basin
in 1987, the Yakima basin was selected as one of several nationwide watershed pilot studies
for intensive data collection and analysis of water, sediment and aquatic biota, in order to
direct and complete parameters gathered across the nation in the second phase. The USGS
conducted additional Yakima basin sampling between 1999 and 2000 to assess trends in
water quality. The assessment focused exclusively on agricultural impacts to surface water
quality. The follow-up study identified fecal coliform, arsenic, sediment, phosphorus and
insecticides above water quality standards, although at lower levels than previously found
due to improved sediment control in agricultural return drains.
The studies are contained in the following USGS publications: Circular 1237, Water Quality
in the Yakima River Basin, Washington, 1999-2000, Water Resources Investigations Report
02-4054, Fecal -Indicator Bacteria in the Yakima River Basin, Washington — An Examination
of 1999 and 2000 Synoptic Sampling Data and their Relation to Historical Data, and Water
Resources Investigations Report 02-4177, Occurrence and Distribution of Dissolved Trace
Elements in the Surface Waters of the Yakima River Basin, Washington.
A stream condition index, consisting of four water quality measures and four habitat
measures, showed "good" overall stream condition at two of three sample locations on
Ahtanum Creek, the remaining location was ranked "intermediate" condition. Fecal
coliform bacteria remained elevated at 3 of 4 sample locations on Ahtanum and Wide
Hollow Creeks.
TOTAL MAXIMUM DAILY LOAD
Section 303(d) of the Federal Clean Water Act requires states and the EPA to biannually list
all surface waters for which beneficial uses — such as drinking, recreation, aquatic habitat,
and industrial use — are impaired by pollutants. Waters placed on the 303(d) list require the
preparation of Total Maximum Daily Loads (TMDLs) to identify the maximum amount of a
pollutant to be discharged into a waterbody so as not to impair uses of the water, and
allocate that amount among various sources. Once listed, Ecology prioritizes 303(d) water
bodies for TMDLs.
Wide Hollow Creek is on the current 303(d) list for fecal coliform and temperature. The
proposed 303(d) list, pending acceptance from EPA, has Wide Hollow Creek impaired by
dissolved oxygen; pH; endosulfan; dieldrin; DDT; 4,4' -DDE and 4,4' -DDT. Wide Hollow
Creek has been included with an existing TMDL for toxics in the Lower Yakima watershed
CHAPTER 3 — RELATED FLOOD STUDIES 17
to address the listed pesticides. In addition, Wide Hollow Creek has been combined with
Moxee Drain and Cowiche Creek in an "Urban Creeks" TMDL for temperature and fecal
coliform based on data in 2001.
There are Drainage Improvement District (DID) pipes and City storm sewers that carry
urban runoff and drain to Wide Hollow. Additional information about DIDs is located in
Chapter 4.
Ahtanum Creek is proposed for the 303(d) listing for temperature and fecal coliform.
8 1 Ahtanum-Wide Hollow CFHMP
N This page intentionally left blank N
CHAPTER 4
WATERSHED AND FLOODPLAIN CHARACTERISTICS
GEOGRAPHIC SETTING
The Ahtanum and Wide Hollow watersheds are within Yakima County, which lies east of
the Cascade Range, between Mount Adams, Mt. Rainier and the Columbia River, in the
south-central region of Washington State (see Figure 1-1). The watersheds stretch east from
headwaters in the Cascade Mountains downstream through the cities of Yakima and Union
Gap to the confluence with the Yakima River. The Ahtanum basin does not extend quite
fully west to the Cascade divide. The Wide Hollow basin lies to the north and adjacent to
the Ahtanum basin and its headwaters do not extend as far west into the Cascade Mountain
range. The northern boundary of the basins is formed by Cowiche Mountain, and the
southern boundary by Ahtanum Ridge.
Elevations range from over 6,500 feet in the mountainous portion of the watershed area to
1,000 feet in Union Gap. There are three general types of topography represented in the
Ahtanum and Wide Hollow basins - mountains in the west, foothills and a dissected plateau
with hollows (small valleys formed by geologic folding) in the middle sections of the
watersheds, and a broad, flat expanse of floodplain /and Missoula Flood Deposits in, and
adjacent to, the urban areas and the Yakima River.
The headwaters of Ahtanum Creek are high in the Cascade Mountains, and are significantly
affected by the rain shadow effect of the Cascade Divide Crest, which lies 10 miles further
west than the headwaters. The North Fork and South Fork of Ahtanum originate in the
Cascades and meet downstream from the settlement of Tampico, to form Ahtanum Creek.
Ahtanum Creek and its two distributaries - Bachelor and Hatton Creeks - flow through the
middle portions the Ahtanum Valley and rejoin the creek upstream of the City of Union
Gap. Ahtanum Creek enters the Yakima River just near Union Gap, upstream of the Wapato
Dam. Drainage area of the watershed is approximately 173 square miles.
Wide Hollow Creek begins in the hills west of Yakima, and flows through the southwestern
portion of the City of Yakima. Two tributaries, Cottonwood Creek to the south and Shaw
Creek to the north, flow into Wide Hollow Creek. Wide Hollow Creek enters the Yakima
River in the City of Union Gap. Drainage area of Wide Hollow Creek is approximately 78
square miles.
Spring (Chambers) Creek East is a tributary to Wide Hollow near its confluence with the
Yakima River and flows through the eastern edge of the City of Union Gap. Originally a
side offshoot channel of the Yakima River, Spring (Chambers) Creek East has been cut off
from the Yakima by a closed floodgate under Interstate 82. Currently, Spring (Chambers)
Creek East flows are derived from springs and from stormwater drainage.
2 1 Ahtanum-Wide Hollow CFHMP
Irrigation diversions and channel relocations to assist farming practices have had a
significant effect on the channel forms and hydrology of Ahtanum and Wide Hollow Creeks
since the latter part of the nineteenth century.
The watersheds are subject to frequent flooding due a combination of hydrology, alterations
to hydrology through diversions, some from and to other watersheds, topography, man-
made land form and channel alterations, and naturally occurring floodplain characteristics.
Both creeks flow into the Yakima River in Union Gap.
GEOLOGY
Structural Geologic Units
The Ahtanum-Wide Hollow watershed area lies within the Columbia Basin
physiogeographic province, and is adjacent to the Cascades province. Two geologic
formations dominate the topography in the watershed area: the Columbia River Basalt
Group, and Consolidated and Unconsolidated Non -Marine Sedimentary Rocks (Figure 4-1).
The Columbia River Basalt Group is a cumulative series of layers that covers 63,208 square
miles in the states of Washington, Oregon, and Idaho (WA Department of Natural
Resources, 2005). These basalt flows originated in a series of events from fissures in
southeast Washington beginning about 15 million years ago (WA Department of Natural
Resources, 2005). Geologic and volcanic activity associated with the rise of the Cascade
Range resulted in large amounts of sands and gravels being deposited on top of these layers
and eventual cementing of the gravel layers due to pressure and dissolved minerals,
primarily caliche, to form the Ellensburg formation.
Additionally, the Columbia River Basalt group has been squeezed in a north -south
direction, folding the Columbia River Basalts and the Ellensburg formation (weakly
consolidated gravels) that overlies them into a series of ridges and valleys that extend along
the entire Cascade Range from the Fraser River in Canada to the Columbia River. In the
project area, the valley created by these dual processes of uplift and folding is called the
Moxee Valley, which is drained by Ahtanum and Wide Hollow Creeks on its western
extent, and also contains the Yakima River, and Moxee Creek or drain in its western extent.
Ahtanum Creek has downcut through these consolidated and unconsolidated layers to form
the Ahtanum Valley, which is bounded on the north by a large plateau of this Ellensburg
formation, and on the south by a much less extensive area of this formation that overlays
exposed basalts.
Wide Hollow Creek and its tributaries drain the foothills of the Cascade Range and flow
across the Ellensburg formation plateau which lies north of Ahtanum Creek. The streams
have cut wide valleys through these formations, with the Ellensburg formation forming the
valley walls. These are the characteristic "Hollows" from which Wide Hollow Creek gets its
name. Several of these "Hollows" also drain toward Ahtanum Creek, or its tributary,
Bachelor Creek.
YAKIMA COUNTY
GEOGRAPHIC INFOKMAI ION SLNVIC. S
Figure 4-1
Ahtanum-Wide Hollow
CFHMP
Geologic Formations
Stree:s
Streams
Project Area
Geology
LITHOLOGY
Basalt Flows
Continental Sedimentary
Alluvi.am, Alluvial Fan Deposits
Loess
- Landslide deposits
Other
Parcel Lot lines are for visual display
only. Do not use for legal purposes.
Miles
0 05 1 2 3 4
1 inch equals 2.88 miles
N
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County car not accept responskul tyfor any emrse
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Dater September 7, 2007
4 Ahtanum-Wide Hollow CFHMP
These processes of folding and uplift are continuing to the present day, with the northern
faces of fold ridges rising faster than the southern faces, and tilting of the valley bottom
between. This fold uplift also tends to warp the valley floors, contributing to the complexity
of flood plains and flooding patterns.
At the Narrows on Ahtanum Creek, (shown as cross-section 1 on Figure 4-2) , soils
information indicates that periodic movement of the northern and southern folds has
resulted in repeated formation of a lake upstream of the Narrows through which Ahtanum
Creek has repeatedly downcut (Kinneson and Sceva, 1964), even in relatively modern times.
Cross sections of the entire Ahtanum Valley, based on LiDAR Flights, reveal the ongoing
warping of the valley floor. Upstream of the Narrows, the floodplain is tilted toward the
South. The floodplain is level at the Narrows (x -section #1), tilts downward toward the
north below the Narrows (x -section #1) until the vicinity of Emma Lane, (x -section #3) where
it begins to tilt back toward the south, then levels out, and then is tilted to the south again as
it approaches the Yakima River (x -section #4). These changes in valley side -slope have a
dominating influence on flow paths in the valley. Ahtanum Creek is not in the low point in
the floodplain, overbank flows can travel long distances, and in some cases never return to
Ahtanum Creek. (Figure 4-2)
Figure 4-2
ISO
760
Bachelor Creek Ahtanum Creek
0 MO 400 600 11110 1000 UM 1403 1600 1303 1000
IMO
1330
1160
1.
CM1er Flow
&Canal
H2
ehtanurn Creek
Hatton Creek / Canal
kachelor creek
2000 4000 6000 MOB 10000 1.0
1300
IMO
ISO
ISO
1130
ISO
1130
1080
3
Spring Creek Bachelor creek Ahtanum Cree
Spring Creek 2
200 COO MO SW HMO MO
1018
'6 Bachelor Creek Ahtanum Creek
I /
#4
1011
00
ISM
11006
1004
. HOB 1. 2000 2500 30M 3500 4000
Chapter 4 — Watershed and Floodplain Characteristics 15
SURFICIAL GEOLOGY
Most of the watershed is overlain by thin to relatively thick layers of material that have been
transported by wind or water.
Beginning approximately 13,500 years ago, a series of catastrophic floods — the Missoula or
Bretz Floods — repeatedly deposited sediments in the lower elevations of the Moxee Valley,
generally below 1200 feet in elevation. These sediments are fine-grained silts and sands that
were eroded from the "channeled scablands" (Bretz, 1923) of eastern Washington, as water
from glacial Lake Missoula was released by collapse of the glacial ice dams that formed the
lake. Wallula Gap, near the confluence of the Walla Walla River and the Columbia River,
acted as a constriction on the large volume of water released by the flood, and formed a
temporary lake — Lake Lewis — which extended across much of what is now central
Washington and parts of Oregon. These events effected the current valley in two ways: 1)
leaving large areas of undulating sediment deposits that effect the routing of floodwaters
across the valley floors, and 2) providing a source of silt that was transported by wind to
adjacent slopes (Ritzville series), some of which in turn was carried into stream channels
and deposited on the floodplain as the Logy or Track soil series.
The soil series that are related to Missoula Flood Deposits are generally alkaline to highly
alkaline soils, with a well developed, cemented caliche (generally a white layer composed of
calcium carbonate salts) layer. This alkalinity limits the productivity of these soils for
orchard crops. In many locations in the lower watershed, water tables are near the surface,
which has lead to the development of wetland soils (increased amounts of organic matter
and weathered clays) the intermixture of low areas and slightly higher "ridge" has resulted
in large areas of mosaics of wetland and non -wetland soils in the lower Wide Hollow and
Ahtanum watersheds (Figures 4-3 & 4-4).
Wind—deposited loess covers much of the watershed. This loess was deposited during
glacial periods and also after the Missoula floods noted above. Deep deposits of loess and
soils derived from transported loess are found on the foothills and the plateau drained by
Wide Hollow Creek. Especially deep and productive soils are found in the "hollows" in this
area, as well as a large silt fan that Wide Hollow Creek has formed downstream from the
plateau, and in adjacent areas of the Ahtanum Valley. These relatively deep silt soils have a
large water storage capacity, and can absorb large amounts (up to 7 inches) of precipitation
in the upper soil layers. When these types of soils are wetted and then frozen however, they
become relatively impervious to rainfall and snowmelt. Due to the soils in the lower
watershed, major flood events follow a similar weather pattern — rain or snow, followed by
sub freezing (usually sub -zero) temperatures, followed by snow, and turn followed by a
rapid snowmelt event at all elevations in the watershed. In the upper watersheds, the layers
of loess are thin or absent, and most soils there are the result of weathering in place of the
native basalts, and in forested areas, volcanic ash from repeated eruptions of Cascade
volcanoes, of which Mount St. Helens in 1980 is the most recent.
Figure 4-3
YAKIMA COUNTY
GEOGRAPHIC INFORMATION SERVICES
Ahtanum-Wide Hollow CFHMP
(West Half)
Stream Typing and Geologic Hazards
Al Roads
Stream Types:
NOne
NTwo
NThree
NNFour
Five
Geologic Hazards
11 Alluvial Fan Intermediate Risk
Alluvial Fan High Risk
Avalanche Intermediate Risk
Avalanche High Risk
Earthquake Intermediate Risk
Earthquake High Risk
Landslide Intermediate Risk
I- ] Landslide High Risk
Oversteepened Slopes Intermediate Risk
Oversteepened Slopes High Risk
Stream Undercutting Intermediate Risk
Stream Undercutting High Risk
P1 Suspected Hazard
Unknown Hazard
OStudy Area Boundary
0 05 1 15 2 25 3 Miles
1"=
t3 miles
t4
Yakiinap4im
copyrght (c) 2006 vakma County
This map was derived from several databases. The
County cannot accept responsibility for any errors.
Therefore,there are no warranties forthis product.
6 1 Ahtanum-Wide Hollow CFHMP
Figure 4-4
GEOGRAPHIC INFORMATION SERVICES
Ahtanum-Wide Hollow CFHMP
(East Half)
Stream Typing and Geologic Hazards
A/ V Roads
Stream Types:
NOne
NTwo
AtThreeFour
NFve
Geologic Hazards
Alluvial Fan Intermediate Risk
Alluvial Fan High Risk
Avalanche Intermediate Risk
Avalanche High Risk
- Earthquake Intermediae Risk
Earthquake. High Risk
Landslide Intermediate Risk
Landslide High Risk
Oversteepened Slopes Intermediate Risk
.Oversteepened Slopes High Risk
Stream Undercutting Intermediate Risk
Stream Undercutting High Risk
- Suspected Hazard
Unknown Hazard
Cities
Study Area Boundary
0 05 1 1.5 2 2.5 3 Mlles
1=1 3 miles
YYlslmap-ilmo
Capynght(C) 2006 Yakima County
This map was denied from several databases. The
County cannot accept responsibility for any errors.
Therefare,there are no warranties fortnis product.
Plot Date July 7, 2006, Map3 3b
8 Ahtanum-Wide Hollow CFHMP
DRAINAGE IMPROVEMENT DISTRICTS
The high water table and the presence of caliche layers in all of these soils led to the
construction of numerous artificial drainage networks leading to creeks to lower the water
table, increase agricultural productivity, and allow high rates of application of irrigation
water to "flush" alkalinity out of the soil profile. These systems were for the most part were
constructed in the first half of the 20th century, when this area was dominated by
agricultural land uses. With the expansion of the urban areas, many of these systems,
especially those supported by taxing districts and known as Drainage Improvement
Districts (DIDs), are now located in the cities and serve dual purpose of lowering
groundwater tables and providing urban stormwater conveyance to the creeks. This has
been accomplished by direct connection of storm water discharge to the DIDs. Recent
investigations show that ninety-five percent of the connections are from storm water and the
function is one of storm water, as farmland irrigation has effectively ceased with urban
expansion. Currently there are six DIDs within the basin that discharge into Ahtanum and
Wide Hollow Creeks. See Figure 4-5.
In addition, installation of buried infrastructure in these areas — such as water, sewer, or
power lines - often requires the installation of permanent or temporary drainage systems, or
results in the disruption or destruction of existing drainage systems.
CLIMATE
The climate in the Ahtanum area varies from desert conditions in the southern lowlands
with average rainfalls of 6 inches to moist alpine conditions in the mountain headwater
region. This area, like the surrounding Yakima Valley region, is shielded from winter cold -
air masses moving southward from Canada by the Rocky Mountains to the east and north,
and shielded from moist Pacific Ocean marine air moving eastward by the Cascade
Mountain barrier to the east. This produces relatively mild winters, and warm and dry
summers. Average temperatures and mean monthly precipitation is shown in Table 4-1,
Figure 4-6 and Figure 4-7.
Figure 4-5
Drainage Improvement
Districts
Boundaries
Drains
Streams
10 Ahtanum-Wide Hollow CFHMP
While winters are generally mild, in most winters several weeks to months of temperature
inversions occur. These inversions keep colder, dry, dense air in the lower elevations of the
watershed below approximately 3,000 feet. These conditions can effect flooding in a in the
watershed in two ways. Prolonged cold temperatures generate anchor ice formation,
especially in the steeper canyons which do not receive direct sunlight in the winter. In
severe episodes, the entire channel may freeze, routing water flowing water onto the
floodplain. If weather conditions change rapidly, breakup of this anchor ice may occur, ice
jams can them form on infrastructure or natural debris. Inversions can also cause freezing of
the soil profile to a considerable depth, making lower elevation soils impermeable to
snowmelt or runoff. If a weather change is accompanied by snowmelt, localized severe
flooding can result in specific areas of the watershed; if the change in weather is
accompanied by rain -on -snow or rapid snowmelt at higher elevations, generalized flooding
can be expected throughout the watershed, as was the case in the 1974 flood, which is the
flood of record for this basin.
The dominant climatological factor is that both watersheds lie in the rainshadow of the
Cascade Mountains. Storm systems generally move west to east across the watershed, the
Cascade Crest forces these storms to rise as they come over the mountains, causing
increased precipitation on the western slopes. This increased precipitation is continued for a
distance of 8-10 miles on the east side of the crest as storms are still rising and losing water
after the crest. Past this high precipitation band, snow and rainfall decrease rapidly. The
Ahtanum and Wide Hollow watersheds are bounded on the south, west and north by
another series of mountain ranges, and lie in the rain shadow of those mountains as well.
The upper Ahtanum Creek watershed, which is several miles closer to the Cascade crest, can
accumulate significant snowfall on the broad the ridge crests that surround the valley,
particularly to the west, while Wide Hollow Creek's watershed has only limited areas that
can accumulate snowfall due to the very small area in the watershed that lies at high
elevation, and its relative distance further east of the Cascade crest. See Figure 4-6.
Figure 4-6
YAKIMA COUNTY
GEOGRAPHIC INFORMATION SERVICES
Parcel Lot !res are for visual display
only. Do not use for legal purposes.
0 1 2 4
toes
1 in[II = 21250 feet
III NORTH
Chapter 4 - Watershed and Floodplain Characteristics 111
TABLE 4-1
CLIMATE DATA FOR THE YAKIMA AREA
Temperature
Precipitation
Snowfall
Month
Avg Daily
Max
(°F)
Dail
y
MFS
Monthly
Avg
(in)
Max on
Record
(in)
Min on
Record
(in)
Monthly
Avg
(in)
Max on
Record
(in)
Min
on Record
(in)
January
37
20
1.23
3.66
0.09
8.21
24.20
0.20
February
46
26
0.75
2.46
0.00
3.34
16.50
0.00
March
55
30
0.69
2.63
0.01
1.56
11.50
0.00
April
64
35
0.49
1.62
0.00
0.00
0.20
0.00
May
73
42
0.50
2.76
0.03
0.00
0.00
0.00
June
80
49
0.73
2.53
0.01
0.00
0.00
0.00
July
87
53
0.16
0.71
0.00
0.00
0.00
0.00
August
86
52
0.34
2.10
0.00
0.00
0.00
0.00
September
78
44
0.38
2.07
0.00
0.00
0.00
0.00
October
64
35
0.55
2.22
0.00
0.16
2.90
0.00
November
48
28
1.04
2.83
0.00
2.46
21.20
0.00
December
38
22
1.24
4.19
0.07
8.76
50.00
0.00
Annual
63
36
8.07
13.22
4.18
23.59
56.10
1.50
SOURCE: EarthInfo 1994 (National Weather Station 9465 for period 1946-1993).
12 Ahtanum-Wide Hollow CFHMP
Yakima County
UPPER YAKIMA RIVER CFHMP
KCM
i
10
9
8
7
6
5
4
3
2
1
0
Month
E
0
O
O
E
0
0
z
E
0
Q
SOURCE: Earth info 1994
FIGURE 4-7
MEAN MONTHLY PRECIPITATION IN YAKIMA
Figure 4-7. Mean Monthly Precipitation in Yakima (Source: Naches CFHMP)
Annual Flow Patterns in the Ahtanum and Wide Hollow Watershed
Ahtanum Basin
Streamflows in the upper watershed respond typically to variations in snowpack and
rainfall (see Figure 4-7). Long-term and seasonal hydrograph responses from the upper
watershed do not suggest that significant hydrologic changes have occurred since
streamflow data became available in 1913. Flows from the upper watershed in the range of
350 to 400 cfs (see figure 4-8) have been identified as "channel forming" (i.e. a 2 year flow).
Natural low flows typically range from 20 to 25 cfs, but are further reduced by irrigation
diversion.
• Mean Monthly Precipitation. (in.)
Average Annual = 8.07 inches
o Mean Monthly Snowfall (in.)
Average Annual = 23.59 inches
I■
I.
I I I. III I � . 1 1
1 1
Month
E
0
O
O
E
0
0
z
E
0
Q
SOURCE: Earth info 1994
FIGURE 4-7
MEAN MONTHLY PRECIPITATION IN YAKIMA
Figure 4-7. Mean Monthly Precipitation in Yakima (Source: Naches CFHMP)
Annual Flow Patterns in the Ahtanum and Wide Hollow Watershed
Ahtanum Basin
Streamflows in the upper watershed respond typically to variations in snowpack and
rainfall (see Figure 4-7). Long-term and seasonal hydrograph responses from the upper
watershed do not suggest that significant hydrologic changes have occurred since
streamflow data became available in 1913. Flows from the upper watershed in the range of
350 to 400 cfs (see figure 4-8) have been identified as "channel forming" (i.e. a 2 year flow).
Natural low flows typically range from 20 to 25 cfs, but are further reduced by irrigation
diversion.
0
35c
s2F
2`L+
150
1:G
Chapter 4 — Watershed and Floodplain Characteristics 113
CCT
ticv DEC JAN
::F. ASF MAY JUK AIL AUGSEP
Figure 4-8 — Combined Wet, Average and Dry Year Streamflows for Ahtanum Creek North and
South Forks (without irrigation diversion). Source: Ahtanum Creek Watershed Restoration Program
EIS, Ecology, 2005
Streamflow data in the middle portion of the watershed is very limited. There has never
been a continuous record of streamflows over a full hydrologic year in this portion of the
watershed. With the exception of intermittent spot measurements, historical flow conditions
are largely unknown. Routine streamflow measurements have been initiated at various gage
sites monitored by the Yakama Nation since 2001. The most complete record is at Carson
Road and at American Fruit Road, below both the Ahtanum Irrigation District and upper
WIP diversions. The effect of diversions from the AID and WIP canals is clearly shown in
the hydrograph at Carson Road.
In the lower watershed, this pattern of lower summer flows in continued, but is somewhat
modified by the regional water table of the Moxee Valley. From its confluence with the
Yakima River to a point approximately five miles upstream (between 42nd and 62nd Avenues)
the river and water table are affected by the flow patterns of the Yakima River. The flow
patterns of the Yakima River have been modified by the irrigation storage dams, and flows
remain high throughout the summer. As Ahtanum Creek approaches the Yakima River,
summer flows in the Ahtanum (and Bachelor) generally increase, due to influence from the
water table of the Yakima River and also tributary inputs from Spring and Bachelor Creeks,
both of which are also fed by the local water table.
Irrigation influences on the hydrology of Ahtanum Creek.
The first stream diversion for irrigation in the Yakima Valley was constructed by Yakama
Chief Kamiakin in the mid -1800s, near what is now Slavin Road, upstream of the St.
Joseph's Mission. After the establishment of the Mission in 1852, the Catholic priests also
constructed an irrigation system for their garden ("Saint Joseph's Mission at Ahtanum Creek
is founded in the Yakima Valley on April 3, 1852." historylink.org).
Currently, there are two diversions near the Ahtanum Mission property. The Upper Wapato
Irrigation Project (WIP) diversion diverts water into the WIP canal, which is managed by the
M.
."
hi t' r.. R FZw 4A•
„lite FM k'Y a%r'�
Mem MeMity FM (Dry Ter -WY 1M;;
.... NORTH FORK: -
SOUTH FORK
., ..
AbE F
'A'":
Y'3....2E��.,2„:EG,,�.F
- - - ✓.�
_
CCT
ticv DEC JAN
::F. ASF MAY JUK AIL AUGSEP
Figure 4-8 — Combined Wet, Average and Dry Year Streamflows for Ahtanum Creek North and
South Forks (without irrigation diversion). Source: Ahtanum Creek Watershed Restoration Program
EIS, Ecology, 2005
Streamflow data in the middle portion of the watershed is very limited. There has never
been a continuous record of streamflows over a full hydrologic year in this portion of the
watershed. With the exception of intermittent spot measurements, historical flow conditions
are largely unknown. Routine streamflow measurements have been initiated at various gage
sites monitored by the Yakama Nation since 2001. The most complete record is at Carson
Road and at American Fruit Road, below both the Ahtanum Irrigation District and upper
WIP diversions. The effect of diversions from the AID and WIP canals is clearly shown in
the hydrograph at Carson Road.
In the lower watershed, this pattern of lower summer flows in continued, but is somewhat
modified by the regional water table of the Moxee Valley. From its confluence with the
Yakima River to a point approximately five miles upstream (between 42nd and 62nd Avenues)
the river and water table are affected by the flow patterns of the Yakima River. The flow
patterns of the Yakima River have been modified by the irrigation storage dams, and flows
remain high throughout the summer. As Ahtanum Creek approaches the Yakima River,
summer flows in the Ahtanum (and Bachelor) generally increase, due to influence from the
water table of the Yakima River and also tributary inputs from Spring and Bachelor Creeks,
both of which are also fed by the local water table.
Irrigation influences on the hydrology of Ahtanum Creek.
The first stream diversion for irrigation in the Yakima Valley was constructed by Yakama
Chief Kamiakin in the mid -1800s, near what is now Slavin Road, upstream of the St.
Joseph's Mission. After the establishment of the Mission in 1852, the Catholic priests also
constructed an irrigation system for their garden ("Saint Joseph's Mission at Ahtanum Creek
is founded in the Yakima Valley on April 3, 1852." historylink.org).
Currently, there are two diversions near the Ahtanum Mission property. The Upper Wapato
Irrigation Project (WIP) diversion diverts water into the WIP canal, which is managed by the
14 Ahtanum-Wide Hollow CFHMP
Yakama Nation/Bureau of Indian Affairs. The WIP canal follows the contours of Ahtanum
ridge, and supplies water to farms on the south side of Ahtanum Creek on the Yakama
Reservation. The Bachelor Creek diversion, managed by the Ahtanum Irrigation District
(AID), diverts water into Bachelor Creek which supplies water to farms north of Ahtanum
Creek. Just downstream from the Bachelor diversion, Hatton Creek separates from the
mainstem of Ahtanum Creek. Thus, Ahtanum, Bachelor, and Hatton continue downstream
in three branches. During flood events, these creeks become active flood channels of
Ahtanum Creek. Hatton Creek rejoins Ahtanum Creek at 62nd Avenue eight miles
downstream from the Mission. Bachelor Creek returns near Goodman Road, fourteen miles
downstream and only 2 miles from the Yakima River. Bachelor Creek also has a
considerable watershed of its own which on the North Side of the Ahtanum Valley and a
portion of the foothills. The stream changes in location since 1911 can be seen on Figure 4-9.
Prior to the 1960s the AID diverted water year-round, for irrigation during the spring,
summer and fall, and stockwater in the winter. Anecdotal evidence indicates that Ahtanum
Creek routinely was dry below the diversions during the summer. After 1964, pursuant to a
lawsuit filed by the United States on behalf of the Yakama Indian Nation, and referred to as
the Pope decree, AID was required to cease diversion after July 10 in any given year, and
resumes diversion in late October. All irrigation diversions after July 10 are reserved for the
Wapato Irrigation Project for use on the Reservation; prior to July 10th 25% of the available
flow is reserved for use by the WIP. Low flows are still prevalent in the early summer, but
recent changes in diversion amounts by the WIP have improved summer streamflow after
July 10. Since 2001, a continuous flowing reach has been established below the diversions
after July 10, with flows on the order of 8 to 10 cfs (Ahtanum Assessment Executive
Summary, 2004).
Bachelor and Hatton Creeks are used as irrigation conveyance by the AID and other water
users. Flow in these creeks is reduced or eliminated after July 10 as described above.
Beginning in October in most years, irrigation delivery resumes in these systems, and
continues throughout the winter. This lowers the flows in Ahtanum Creek for much of the
year, and also results in "charging" of the surficial aquifer in the Ahtanum Valley via
leakage from these conveyances. Flooding patterns are likely altered by this practice since in
most years very little available water storage capacity is available in the soil profile of the
lower valley, and during inversions, the lower valley soil profile can freeze to a significant
depth, increasing runoff generated by rain or rain -on -snow events. Spring Creek West, near
the Yakima Airport, is a stream fed by natural spring water, and poses a flood risk to areas
around the Yakima Air Terminal. The 1911 USGS mapping shows that the headwaters of
Spring Creek West previously contained an intermittent channel, which has been removed
through farming practices.
Figure 4-9
Historic Stream & Canal Locations VS Current Stream & Channel Locations
LEGEND
1911* streams- perennial intermittent
1911* canals
2011 streams - perennial intermittent
2011 canals
Contours 100' intervals *source USGS Map
N
16 Ahtanum-Wide Hollow CFHMP
Irrigation influences on the hydrology of Wide Hollow Basin
The natural hydrograph of Wide Hollow Creek was likely very flashy above 48th Avenue
(almost the midpoint of the watershed) and stable below that point to its confluence with
the Yakima. The upper watershed hydrology is driven by snowmelt runoff, and usually a
peak runoff occurs in early May most years, lasting a week or less. Natural flow continues in
the upper watershed until June or early July in most years, and discontinues after that. In
the lower watershed, a series of natural springs and high water tables drain cool clear water
to the creek, exhibiting very little variation in flow (approximately 7 cfs) through the winter,
based on limited flow sampling by Yakima County Surface Water Division.
Except for the headwaters of the creek that drain the foothills, the natural hydrograph has
been dramatically altered. Wide Hollow Creek is used as a conveyance for irrigation water
and receives a relatively large amount of irrigation "spill" during the irrigation season. This
additional flow results in an "inverted" hydrologic cycle. This means that during times of
year when the flow would naturally be low, such as in the summer, it is actually high. This
is most severe below the Congdon Ditch input, which is currently located upstream of 96th
Avenue, but most of the tributary streams to Wide Hollow also exhibit inverted
hydrographs.
The introduction of the Congdon Ditch in 1906 was a dramatic alteration to the basin
drainage in that it brought Naches River flows to the upper watershed and preceded major
channel realignments within the basin. This ditch was reworked several times between then
and 1918. The 1911 USGS map of the basin shown in Figure 4-10, shows the initial alignment
that tailed out into the Shaw Creek and Wide Hollow Creek confluence located
approximately mid -way between the future alignments of Wide Hollow and Tieton Roads.
The map also shows the current stream locations and the significant realignments of the
Wide Hollow and Shaw Creek channels made to enhance agricultural benefits. Figure 4-11
shows the irrigation ditches in place in 1947 after Shaw Creek and Wide Hollow creeks had
been moved. The early map shows many cases where channels have disappeared or been
moved to valley walls, such as Shaw Creek at the former confluence with Wide Hollow and
Wide Hollow Creek just upstream of the airport. Spring Creek upstream of the Airport has
been filled in and presumably replaced by field tiles. Although this facilitates flood
irrigation it creates significant flood hazard for existing and future urbanization.
The Yakima-Tieton Irrigation District, the Yakima Valley Canal Company (Congdon Ditch)
and various other small districts supply irrigation water to residents in the Wide Hollow
Watershed. The Yakima-Tieton serves the upper portions of the watershed. Prior to the
1980's, all of the upper tributary streams in the Wide Hollow drainage were used as
irrigation conveyance by the Yakima-Tieton, now they only carry relatively small volumes
of stock water to specific parcels. With the almost total conversion of the Naches-Tieton to a
piped delivery system in the early 1980s, these tributaries are no longer major components
of the irrigation delivery system. However, these streams were altered when they were
integral to irrigation delivery,
Chapter 4 — Watershed and Floodplain Characteristics 117
Figure 4-10
Historic Stream & Canal Locations VS Current Stream & Canal Locations
LEGEND
911" stream location
1911' canal location —
2011 stream location
2011 canal location
(Contours
sou ce USGS Ma
174
Figure 4-11
1947 Stream & Irrigation Ditch Locations
Ditch Stream
18 1 Ahtanum-Wide Hollow CFHMP
and they have not been restored to their former channel shape, location or function.
Currently many of these streams are "perched" in their floodplains (i.e. on the highest spot
in the valley floor) to allow more efficient delivery of irrigation water, even though these
channels are no longer used for irrigation delivery. These perched channels can pose
significant flood hazard during flood events due to their position on the floodplain and the
loss of natural channel form and processes combined with cessation of channel maintenance
for irrigation conveyance.
An example of these altered tributary systems is Cottonwood Creek, a tributary to Wide
Hollow Creek, which follows a canyon to its confluence with Wide Hollow Creek. Much of
Cottonwood Creek is aligned along the south side of the valley and slightly perched to
allow farming and delivery of irrigation water to the canyon floodplain. Also Shaw Creek is
a small stream, which has been altered into a roadside ditch as it approaches Wide Hollow
Creek, near West Valley Park. Shaw creek is prone to sheet flooding from snow melt events.
Sheet flooding also occurs in upper Wide Hollow Creek itself, above its confluence with
Cottonwood Canyon Creek.
Spring (Chambers) Creek East, in Union Gap, is a side channel of the Yakima River, which
has been cut off from the Yakima River by I-82. Water from Spring (Chambers) Creek is
used for irrigation. Water still enters the creek through springs, drainage systems and
stormwater runoff. It is also prone to backwater flooding effects from the Yakima River. The
current configuration is fed by groundwater drains and has extremely stable flow pattern
throughout the year.
STREAM CHANNEL AND FLOODPLAIN MORPHOLOGY
The interaction of hydrology and climate over time with geologic processes and surficial
geology determines the dynamic riverine topographic features in an ongoing process
referred to as fluvial geomorphology. This interaction, along with agricultural interventions,
defines the present- day features and flow tendencies during floods in the Ahtanum and
Wide Hollow basins. These geomorphic processes can be locally altered by human actions,
which may change flooding patterns. The natural and human -caused stream and floodplain
geomorphic processes drive flood conditions (depth, velocity, duration) of floods.
Ahtanum Creek
North and South Fork Ahtanum Creek — These stream channels are generally in narrow
canyons which follow geologic fault lines in the Columbia Basin Basalts. Stream gradients
are fairly steep, most in excess of 2.5% gradient. The majority of the streams are very
confined in their channels, but small areas of forested floodplain do exist, and are
increasingly being subdivided and used for vacation or retirement homes. The combination
of steep gradients, confined valleys, and naturally high rates of sediment supply result in
stream channels that have high availability of coarse and fine sediments, and high levels of
energy to transport sediments, woody debris, and erode banks. The channels themselves
generally maintain a single thread with limited side channel development. Channel pattern
Chapter 4 — Watershed and Floodplain Characteristics 119
is generally sinuous, migration of the channel does occur in the forested floodplains, but
rapid channel migration is relatively rare.
Alluvial Fans and Ahtanum above the Narrows — Where both the North Fork and South
Fork Ahtanum leave the confined mountain valleys and enter the larger Moxee Valley, they
have created large alluvial fans. Both streams are naturally unstable in the upper portions of
these areas due to the large amounts of coarse sediments that are deposited in this location.
Farther along the fans, there are several old relict channels which have been occupied by
these streams in relatively recent times. Downstream of the fans, Ahtanum Creek lies on a
broad floodplain with a gradient of approximately 1.8%. The channels, floodplain, and the
fans above them are mostly composed of boulders and gravels. The channels on the
floodplain and on the fans are subject to periodic episodes of rapid channel migration.
The Narrows on Ahtanum Creek — The Narrows is formed by the close proximity of two
"folds" of Columbia Basalts that lie exposed at the surface, which form a geologic "nick
point" between the upper Ahtanum Valley and the remainder of the Valley. Typical of these
nick points, the stream on the upper end has developed side channels and a water table near
the surface. In the narrowest portion of the valley, channel and floodplain gradients are
steep, and the stream has high energy for erosion, but a relatively low coarse sediment load,
channel migration can be expected to be rapid under these conditions.
The Ahtanum Mission — Below the Narrows, the floodplain broadens, and this area is a
major depositional zone for finer silts transported from the upper watershed. The channel is
generally sinuous and single thread, and somewhat incised in the floodplain. The two
distributaries of Ahtanum Creek exit from the channel in this location. Bachelor Creek is
currently used as an irrigation conveyance, and is fed by the Ahtanum Irrigation District
diversion located just upstream from the Mission. Bachelor Creek flows along the northern
valley wall, Ahtanum Creek the southern wall. Based on the types of soils and the stream
landforms in the area, and reports of the early settlement of the mission, Bachelor Creek was
probably a natural side channel of Ahtanum Creek. See Figure 4-12
Hatton Creek, which formerly was fed by a diversion directly from Ahtanum Creek, was
probably also a natural side channel and its "natural" exit from Ahtanum lies in the low
point of the floodplain between Bachelor and Ahtanum Creeks. Given the generally level
topography in the floodplain, the potential for avulsion or other rapid channel movement at
this location is high. Records do not indicate that such avulsions have occurred since
establishment of the Mission in 1853, and for much of that time irrigation diversions and
control structures have been in place. The man made works and their maintenance at this
location have likely effected the likelihood of avulsion, although recent avulsion threats
have increased and required intervention.
20 Ahtanum-Wide Hollow CFHMP
Figure 4-12 The Ahtanum Mission Flow Diversion
N
ti
Bachelor & Hatton
Irrigation Diversion
Ahtanum Mission
Major Flood
Flow Path
Major Flood
& Avulsion
Path
KEY
Floodway 100yr Floodplain 500yr Floodplain
Ahtanum from the Mission to the confluence with Yakima River — Below the Mission the
creek flows through stream deposited sediments for several miles, then through Missoula
flood deposits. The channel itself is similar in both areas — slightly incised, sinuous and
fairly stable, with the exception of the Emma Lane / 42nd Avenue area, where the channel is
perched to the north within its floodplain. The upper portion, above Wiley Road typically
has a wider floodplain and numerous relict channels are present. In the Missoula flood
deposits, the floodplain is much narrower and the channel even more stable, probably as a
result of the strong caliche layer which makes these sediment deposits somewhat resistant
to lateral erosion. Near the confluence with the Yakima River, upstream to the vicinity of
Fulbright Park, the geomorphic floodplain of Ahtanum Creek meets the geomorphic
floodplain of the Yakima River, and widens dramatically. With the construction of Interstate
82 in the early 1970s the mouth of Ahtanum Creek altered, and now enters the Yakima River
approximately 1/2 mile downstream of its "natural" confluence.
Wide Hollow Creek
The upper reaches of Wide Hollow Creek occur on the slopes of Pine and Cowiche
Mountains. There is very little forest cover on the upper watershed, but there are large areas
of medium elevation that can be prone to rain on snow events. In most years, there is some
snowpack in the watershed that usually drains off in less than a week during early to mid-
May.
Chapter 4 — Watershed and Floodplain Characteristics 121
Below the foothills, the watershed is composed of a dissected plateau of the Ellensburg and
Thorp formations, which are weakly cemented gravels. The streams have cut valleys into
this material. Generally these valleys have a relatively broad floodplain for the small stream
size (floodplain width of 25 times channel width), or in many cases, a floodplain has been
formed where there is little to no evidence of a current stream channel. These valleys are
locally termed "hollows", from which Wide Hollow Creek gets its name. Side slopes on
these "hollows" are generally somewhat steep, 30 to 50% or more. The stream channels in
this area are generally low gradient, have low banks, and are composed of large gravels
derived from the Ellensburg formation, adjacent floodplains are shallow silts over these
same gravels. Flood flows during rain -on -snow events, especially when the soil profile is
frozen, often occupy the entire floodplain, even in areas without a defined channel.
Downstream of the Plateau, the creek enters the broad bottom of the Moxee valley. From
approximately 80th Avenue until 40th Avenue, the stream crosses a large alluvial fan
composed of stream deposited silts; these soils are some of the most productive agricultural
soils in the valley, but are now mostly being converted to residential and other urban uses.
The many channels changes made to accommodate agricultural practices and irrigations
were mentioned above and noted on Figure 4-8. The stream channel is fairly stable in this
reach, has moderate sinuosity and is slightly incised.
Beginning at 48th Avenue, Wide Hollow Creek changes dramatically. At this location the
creek receives groundwater input from springs, and also several Drainage Improvement
District Drains that discharge directly to the Creek. Also at this location, the creek enters
Missoula Flood Deposits. The stream channel (where it has not been straightened) is
sinuous, slightly incised, with excellent vegetation on the bank. In several locations in this
reach, the channel has been straightened and or armored. Straightening and armoring of the
channel was usually done to increase agricultural land area, or align the creek on property
lines. Straightening of the channel will usually result in channel downcutting and bank
erosion (hence the armoring) during flood events. Straightened channel generally will tend
to attempt to reform to a meandering channel, and therefore must be maintained over time.
Once maintenance ceases (such as when an agricultural field is converted to residential or
commercial use) these types of channels can change dramatically during flood events. As
the creek crosses the airport it is severely incised with eroding and unstable banks, and
again along Pioneer Lane in Union Gap it has been armored. Downstream there is yet
another straightened reach through the Ahtanum Business Park.
Below Bay Street in Union Gap, there is a small reach of natural channel, and then below
that the creek has been straightened through Union Gap until its confluence with the
Yakima River. There is some debate whether the current creak is near its natural location, or
used to flow into Ahtanum Creek. A reference showing Wide Hollow Creek flowing into
Ahtanum Creek is a U.S. Department of Agriculture soils map from 1901 (Figure 4-13). One
of the original purposes of the straightening of the creek was to serve a grist mill currently
located on Main Street in Union Gap. As the creek approaches the Yakima River, it crosses
several terraces, the Mill is located on the edge of the highest terrace and the fall generated
22 Ahtanum-Wide Hollow CFHMP
at this location ran the water wheel. Original surveys show the presence of a creek below the
terrace at this location, but no mention is made of Wide Hollow creek in any of the original
surveys (1860s through 1890s) in this location. Due to the presence of a dam at the location
of the mill, these straightened channels are artificially "perched" and lack flood conveyance
capacity, resulting in repeated flood damage to adjacent businesses and homes.
Figure 4-13 1901 U.S. Department of Soils Map
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FISHERIES AND WILDLIFE
According to the Ahtanum Creek Watershed Assessment, Ahtanum Creek provides
potentially important habitat for Endangered Species Act (ESA) -listed summer steelhead
(Oncorhynchus mykiss) and bull trout (Salvelinus confluentus) as well as coho (Oncorhynchus
kisutch), spring chinook (Oncorhynchus tschawytscha) and a number of resident fish species.
Bull Trout, Coho, and steelhead spawn and rear in Ahtanum Creek and spring chinook use
the lower portion for rearing (Ahtanum Creek Watershed Assessment, 2004).
The 2004 Yakima Subbasin Plan identified four focal fish species as bearing ecological
significance. These include spring chinook, fall chinook, steelhead / rainbow trout, and bull
trout.
A significant portion of Wide Hollow Creek is fed by groundwater, which could provide
good to excellent water quality for salmonids spawning and rearing. At the grist mill, near
the mouth of Wide Hollow Creek, the dam that provides head to turn the mill wheel has
been fitted with an Alaska Steep Pass fishway, which theoretically provides passage for
adult salmonids, but not for juvenile or small resident fish. Passage at this facility by adults
Chapter 4 — Watershed and Floodplain Characteristics 123
can be problematic as well as the ladder only operates efficiently at a relatively narrow
range of flows or water surface elevations. Consequently, the use of Wide Hollow Creek for
spawning and rearing by native anadromous or migratory species, such as steelhead or bull
trout, is limited.
Spring Chinook
Spring chinooks are listed as threatened under the Endangered Species Act (ESA). Spring
chinook return to the watershed in the spring at the average age of four, and spawn in late
summer or fall. They are known to have historically spawned in Ahtanum Creek. Changes
in flow regime since the 1940s have reduced summer flows needed for this species to hold
(wait over the summer) prior to spawning in the fall. Current use of Ahtanum Creek is
limited to rearing and migration in the lower portion of Ahtanum Creek (Yakima Subbasin
Summary, 2001).
Steelhead/Rainbow Trout
Steelhead/Rainbow trout are listed as threatened under the ESA. Steelhead are anadromous,
while rainbow remain in fresh water for their lifespan. However, the two interbreed, and
offspring can be either anadromous or resident (Yakima Subbasin Plan, 2004). Historically,
steelhead spawned in Ahtanum and Bachelor Creeks. Currently, steelhead are known to
spawn in Ahtanum Creek, and their presence has been documented in Ahtanum, Bachelor,
and Wide Hollow Creeks. Surveys conducted by the Yakama Nation between 1999 and 2003
suggest that steelhead spawning is increasing in Ahtanum Creek (Yakima Subbasin Plan,
2004).
According to the Ahtanum Assessment (2004), "Most fisheries overview studies, such as the
Washington Conservation Commission Limiting Factors Analysis (Haring, 2001), have
indicated that Ahtanum Creek would be a significant steelhead producer if habitat
conditions and passage barriers (including barriers resulting from diversion of streamflows)
were improved" (Ahtanum Assessment, 2004).
Bull Trout
Bull trout are listed as threatened under the ESA. The species is known for variability and
adaptability to local conditions. They can be either migratory or resident (Yakima Subbasin
Plan, 2004). Historic data for bull trout is sparse. The Washington State Salmonid Stock
Inventory (1998) identified Rimrock Lake as having the only stable population of bull trout
in the Yakima Subbasin. However, bull trout adults and spawning have been documented
in Ahtanum Creek, in both the North and South Forks (Yakima Subbasin Plan, 2004).
Other Salmon Species
Fall chinooks are not listed under the ESA, and are not known to have spawned in the
Ahtanum or Wide Hollow watersheds.
Coho salmon reproduce in the Yakima and Naches Rivers, largely as a result of
reintroduction program for this species sponsored by the Yakama Nation. Ahtanum Creek
does support spawning and rearing habitat for coho salmon, especially in the lower reaches.
24 Ahtanum-Wide Hollow CFHMP
Wide Hollow Creek also supports some coho spawning where the creek is accessible. Wide
Hollow Creek could provide nearly ideal habitat conditions if fish passage near the mouth
of the creek and at several irrigation diversions could be improved.
VEGETATION
Natural vegetative conditions can be inferred from soil maps and early surveys of the area.
Large areas of the lower Ahtanum and Wide Hollow drainages (i.e. below 40th Avenue)
were composed of greasewood, saltgrass and Basin Wild Rye communities, with riparian
plant communities dominated by Black Cottonwood and Coyote Willow. Fingers of these
plant communities followed all of the current streams and distributaries (Bachelor, Hatton,
Spring Creek West, Wide Hollow) upstream. At approximately 48th Avenue on Wide
Hollow, and Wiley City in the Ahtanum, soils become much less alkaline and plant
communities likely changed to Basin Big Sage and Bluebunch Wheatgrass in the majority of
the watershed, with Cottonwood, willows, Red Osier Dogwood, wild roses, etc. composing
the riparian zone. It should be noted that Wide Hollow channels or vegetative communities
are not mapped on the original surveys, although there is mention of a brook 3 links (2.33
feet) wide at the current location of upper Cottonwood Canyon Creek — the brook is not
noted on the other section line a mile downstream. It is possible that there were no, or only
intermittent areas of riparian vegetation in the Wide Hollow watershed upstream of the
springs which begin at 48th Avenue and keep the stream perennial from that point
downstream. The earliest air photos available of Wide Hollow Creek generally show this
pattern. Ahtanum Creek is mapped in its entirety on the old surveys as it forms the
boundary of the Yakama Indian Reservation, riparian vegetation extended for the entire
length of Ahtanum Creek from its mouth to the forested areas upstream.
Currently, most of the mainstem Ahtanum Creek has a similar type of riparian vegetation to
that which existed historically. Several areas of Ahtanum Creek in its lower portion, totaling
over 2 miles, have had the riparian zone totally or mostly removed, these areas of lack of
riparian vegetation are usually associated with channel straitening or incision which
occurred prior to the 1947 air photos, likely in the 1890s. Based on the air photo record,
riparian plant communities retaining native vegetation on the Ahtanum are currently less
robust and extensive than natural historic conditions due to decrease in streamflows in
Ahtanum Creek in all seasons of the year.
The lower 6 miles of Ahtanum Creek, the entirety of Hatton and Bachelor Creeks, and all
areas of Wide Hollow Creek used for irrigation conveyance or spill exhibit a mix of native
and invasive species in the riparian zone. While some remnants of native Cottonwood
remain, the majority of these channels are dominated by stands of non-native and/or
hybridized willows, with understory vegetation comprised of Reed Canarygrass (Phlaris
aurundacia). These willows are likely White Willow (Salix alba) and Crack Willow (Salix
fragilis), both of which have been described as existing in Washington State, with White
Willow described in numerous locations in the Yakima Basin. Both are known to hybridize
with Pacific Willow (Salix lucida ssp lasiandra). In Australia, (where there are no native
willows) all 3 species are known to hybridize and colonize native habitats, especially in
Chapter 4 — Watershed and Floodplain Characteristics 125
areas which exhibit altered stream hydrographs. The extent of willow invasion in Australia
is severe enough that these willows have been listed as "Weeds of National Significance"
and Noxious Weeds, Crack Willow is also listed as an invasive plant by the USDA Forest
Service and is considered an invasive species by the states of Colorado, Illinois,
Massachusetts, Michigan, Minnesota, Nevada, New York and Utah.
While there are acknowledged beneficial impacts of willow invasions (shade, variation in
the landscape, suppression of other non-native species) the negative effects of willow
invasion in Australia are documented as:
1. The aggressive growth habit of willows and their ability to colonize river and
stream beds by vegetative and sexual reproduction has been shown to cause
significant problems on the riparian and aquatic health of streams, and on the
morphology of the bed and banks. Detrimental impacts include:
• modification of stream morphology, hydrology and stability causing
blockages/diversions, avulsion, increased bank erosion and decreased
flood capacity;
• accumulation of fine silt in the bed around root masses, including
smothering of cobble and gravel bars, riffles and pools which may reduce
habitat availability for aquatic bugs and fish;
• increased water use where willow growth habit results in significant
infestations in the stream bed. Preliminary studies on transpiration rates
between willows on the stream bed compared to willows and native trees
on stream banks indicated a large difference in water uptake (maximum
daily transpiration 15.2 mm recorded for willows in the permanently
inundated stream bed compared to only 2.3 mm for willows and 1.6 mm
for river red gums on banks) (Doody et al 2006);
• damage to infrastructure where willow debris obstructs stream channels
during floods (for example, loss of bridges);
2. Alterations to ecological processes, including:
• changes to nutrient cycling due to their deciduous nature;
• water temperature modifications, particularly impacting on shading on
fish and bugs during summer
• changes in water quality by anoxic conditions (dissolved oxygen
demand) produced during breakdown of massed autumn leaf fall;
• suppression of native vegetation by intense shading, including exclusion
of understory;
• reduction in amenity values, for example reduced access for canoeists and
swimming holes along infested reaches; and
• loss of biodiversity when willows invade and displace native vegetation
in riparian areas.
Many of these conditions are found in the Ahtanum and Wide Hollow watersheds,
primarily in areas where channels have been maintained as irrigation or drainage ditches
without riparian zones, or in the case of the lower Ahtanum, where riparian zones along the
26 1 Ahtanum-Wide Hollow CFHMP
creek had been eliminated, and non-native species subsequently invaded. The willow trees
achieve unusually large size (over 60 feet) and produce large amounts of both litter in the
form of leaves and seeds, and also large quantities of small, medium and large pieces of
stems and trunks. The large amounts of litter tend to be cohesive and coat the bottom of the
channel in layers of muck as they break down, and the woody debris greatly increases
channel roughness. Spread of these willow populations within a drainage is primarily
through sprouting of the large amount of small and large woody debris generated by these
trees. Hybrid trees also remain fertile and can produce large amounts of airborne seeds
which can travel up to 15 miles to colonize other habitats. The negative effects of Reed
Canarygrass and to a lesser extent, yellow -flag iris, are similar in terms of changes in bank
form and sediment accumulation, increased water use, loss of native species, changes in DO
concentration during the leaf / stem die -off etc.
Figure 4-14 Effects to channels due to hybrid willows.
These non-native plant communities can have a dramatic impact on channel shape and
function over time — reducing flood conveyance, changing the nature of the channel
substrate (more fines material and organics) and increasing channel roughness so that
overbank flooding increases in frequency. This is a special concern in this watershed since it
is composed of flat or undulating floodplains which can route shallow floodwaters across
relatively large areas of the floodplain. The alteration of the basin since 1947 can be seen on
Figure 4-16. The impact on channel roughness thereby increasing flood levels can be seen
from Figure 4-17, which was assembled to support the FEMA flood mapping restudy.
Example of channel constriction is shown in Figure 4-14. Effect on structure in Figure 4-15.
Chapter 4 — Watershed and Floodplain Characteristics 127
Figure 4-15 Effects to structures due to hybrid willows.
Wide Hollow Creek Vegetation
An example of the progression of willows.
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34 1 Ahtanum-Wide Hollow CFHMP
WATER QUALITY
Human development including both agricultural and urban, has modified water quality in
the watersheds. The basin has been the subject of recent and ongoing studies to document
such impacts (Chapters 3 and 8).
Both watersheds will be the subject of water quality improvement programs known as the
setting of Total Maximum Daily Loads (TMDL). This process seeks to limit the amount of
pollutants or sources of pollution (i.e. lack of shade) which reduce water quality. TMDL
strategies may include setting permit limits and recommending best management practices
(BMPs) such as fencing, planting trees, and ensuring buffers next to streams to limit non -
point source contributions. These control actions are developed through a public
involvement process, and TMDL progress is monitored to determine the effectiveness of the
control actions. Change in management of the watershed as a result of the TMDL process
should be may result in changes to vegetation, irrigation and other agricultural practices,
which in turn may change flood patterns and flood hazard.
STREAM STRUCTURES
While formal flood facilities are uncommon in this CFHMP area there are a few flood
facilities, as well as permitted and unpermitted berms of various ages and maintenance
levels. Many of these have been abandoned. Most of these structures are of concern as they
redirect flood water toward neighbors. Some structures were identified through personal
interviews with residents, Yakima County and other agency staff, as well as Yakama Nation
staff. Also, one week of field reconnaissance included additional personal interviews,
verification of existing facilities, and verification of undocumented structures (i.e. levees and
dikes) identified using LiDAR (Light Detection and Ranging) data. The following sub-
sections outline additional interviews conducted and list additional facilities that were
identified through interviews or field reconnaissance.
Compilation of Existing Information
The Yakima County GIS staff provided GIS layers of existing facilities and other information
(boundaries, etc.) to be used as a basis for the facilities inventory. Table 4-2 summarizes
information provided by the GIS Department.
Chapter 4 - Watershed and Floodplain Characteristics 135
Table 4-2. Existing Structural Information Utilized
Existing Facilities
Extent
Bridges, bridge photos
CFHMP area
Culverts
CFHMP area
Streets
CFHMP area
Streams
CFHMP area
Beaver Dams
Ahtanum, Bachelor and Wide Hollow Creeks
Bridges
Ahtanum, Bachelor, Wide Hollow, Cottonwood and Shaw Creeks
Diversions
Ahtanum, Bachelor and Wide Hollow Creeks
Outfalls
Ahtanum, Bachelor, Cottonwood, Wide Hollow Creeks
Reference points
Ahtanum, Shaw and Wide Hollow Creeks
Other information provided by Yakima County included aerial photos, various political and
land use boundaries, and extents of various noxious weeds. This additional information was
used for background review.
Private Levees
Yakima County and Golder Associates staff reviewed LiDAR data for unmapped hydraulic
structures (i.e. private levees and dikes). This information was subsequently used as part of
field verification and was incorporated into the GIS database. The review process identified
38 levees within the project area.
Personal Interviews
Yakima County staff interviewed the following people to gain additional information about
existing facilities. The following people were interviewed:
George Marshall, Ahtanum Irrigation District (field work);
Washington Department of Natural Resources staff;
Joel Freudenthal, Yakima County wildlife biologist;
Ed Campbell, caretaker of the Ahtanum Mission;
Wapato Irrigation Project (WIP) staff;
Steve Simon, Spring (Chambers) Creek East area resident;
Yakama Nation staff;
City of Union Gap staff; and,
Other Yakima County staff.
A list of initial information identified through these interviews is provided in Appendix E.
Any comments pertaining to proposed causes or solutions to issues were provided by the
interviewees and public input and were not verified. Additional interviews were also
conducted during field reconnaissance and are also included in Appendix E.
Field Reconnaissance
During the reconnaissance, County and Golder staff met with: Yakama Nation staff; Wapato
Irrigation District staff (WIP); George Marshall from AID; Ed Campbell, caretaker of the
Ahtanum Mission; Spring (Chambers) Creek area resident, Steve Simon; and others. Flood
control and in -stream structures identified through interpretation of LiDAR data and other
36 1 Ahtanum-Wide Hollow CFHMP
available GIS information was also inspected during this reconnaissance. A list of
information gathered through field work is provided in Appendix E.
Inventory of Existing Facilities and Hydraulic Structures
The summary of inventoried information is presented in a series of GIS based maps (see
Figures 4-18 thru 4-23). The maps cover the six geographic extents within the project area as
follows: Ahtanum, West Valley -North, West Valley -South, Southwest Yakima, West
Yakima, and Yakima/Union Gap. Within the project area there are 38 private levees;
identified through review of LiDAR images. Additionally, there are 303 public and private
bridges and culverts conveying water under roads in the Ahtanum and Wide Hollow
drainages. This number only includes the bridges and culverts that were large enough to be
included in the new flood map modeling. There are also numerous small private bridges
and culverts that are below this threshold size. Yakima County has also identified 40 beaver
dams, 69 diversions, and 56 outfalls.
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Copyright(C) 2010 Yakima County
This map was derived from several
databases. The county cannot
accept responsibility for any errors.
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Chapter 4 — Watershed and Floodplain Characteristics 143
Lower Wide Hollow Flood Control Structure
A flood control structure was reported on Wide Hollow Creek just west of downtown
Union Gap at a weir near the Burlington Northern Railroad Bridge. Further discussion with
Union Gap and field investigation demonstrated there is no flood control structure in this
area.
Wide Hollow Flood Gate at the Mill
The Mill at the south end of Main Street in Union Gap used Wide Hollow Creek to power a
grist mill from the early 1900s to 1990s. Additional information about the mill is discussed in
the recommendation to relocate the mouth of Wide Hollow Creek in Chapter 9. The south
end of Main Street is also the beginning of U.S. Highway 97. In 1932 WSDOT initiated a
project which constructed a bridge over Wide Hollow Creek at this location. They also
constructed flood gates after 1940 to divert flows into concrete culverts during flood events.
Current understanding is the flood structure is owned and maintained by the property
owner of the mill. No agreement with WSDOT regarding this structure has been located to
date.
In addition to the flood facility, WDFW constructed an Alaska Steep Pass in 1989 to provide
fish passage around the diversion for the mill. At that time they also shored -up the flume
for the mill owner and repaired the WSDOT flood facility. WDFW's policy is that property
owners are responsible for operation and maintenance of fish passage structures. Staff from
the WDFW fish screen shop removes the control boards directing flows into the fish ladder
on an intermittent basis. A recommendation in this plan encourages the relevant parties to
formalize the operations and maintenance of the flood facility and fish ladder to ensure
effective operations during flood events.
Spring (Chambers) Creek East Flood Gate
Prior to 1985, Spring (Chambers) Creek East flowed westerly from the Yakima River
through a culvert under Interstate 82, and then southerly through the eastern portion of
Union Gap. A floodgate installed in March 1985 near the Valley Mall Boulevard interchange
now prevents floods smaller than or equal to the 100 -year flood from entering Spring
(Chambers) Creek. However, the 500 -year flood overtops Interstate 82 and flows into Spring
(Chambers) Creek.
Previously at River Mile 0.5, the majority of Spring (Chambers) Creek flow continued south
to its confluence with Wide Hollow Creek, but a small portion of the flow ran easterly to
rejoin the Yakima River through a culvert with a flapper gate under Interstate 82. The
flapper gate downstream of the floodgate was permanently plugged in 1985 in order to
prevent Yakima floodwater from entering Spring (Chambers) Creek and diverting all flow
to Wide Hollow Creek. The plugged culvert prevents backwater flooding from floods
smaller than or equal to the 100 -year flood, but does not prevent the 500 -year flood from
causing backwater into Wide Hollow Creek and Spring (Chambers) Creek. Spring
(Chambers) Creek is now affected only by the 500 -year flood from the Yakima River.
During the 1995 November -December flood events, various crews inspected water control
facilities along the Yakima River, including the upper floodgate at Spring (Chambers)
Creek. This gate was routinely inspected and then closed on November 30, 1995. The gate
was also closed during the February 1996 flood. The screw flood gate installed in 1985 is
owned and managed by Yakima County. Refer to Figure 4-17 for locations of floodgates.
44 1 Ahtanum-Wide Hollow CFHMP
N This page intentionally left blank N
CHAPTER 5
DEVELOPMENT IN BASIN FLOODPLAINS
CURRENT DEVELOPMENT
Much of the Ahtanum and Wide Hollow watersheds are rural in character and devoted to
agricultural uses. Currently, the land use and economic activity within the area is rapidly
changing through conversion from agriculture to urban use as the cities of Yakima and
Union Gap expand west into these watersheds. Industrial development is also occurring in
the floodplain west of Union Gap and near the airport. Flooding concerns about loss of use
of agricultural land and crop damage are being replaced by concerns of damage to homes
and businesses, plus loss of access during floods. In addition, agricultural diversions still in
place create entry paths for flood waters to unexpected areas.
Figure 5-1 shows lands that have shallow groundwater within three feet of the surface. This
is another physical feature that limits or adds to the expense of development in the valley
west of Union Gap and Yakima. Shallow ground water increases the probability of soil
saturation during storm events, increases costs related to subsurface and infrastructure
construction, and degrades sewer system performance.
Figure 5-1 Shallow Groundwater Areas
Legend
Depth of Ground Water
Depth Table
` 0.3-2.7ft
— 2.8-4.3ft
Perennial Stream
— Canal or Ditch
streets
�
.. I City Boundary
---- Urban Growth Boundary
2 Ahtanum-Wide Hollow CFHMP
Urbanization of CFHMP Area
Urbanization in the basin has occurred through subdivision of lands in the unincorporated
county and by annexation. Current urban zoning regulations add pressure to increase
development density and infrastructure in floodplains. The towns of Ahtanum and Wiley
City have existed since the 1880s, and currently exhibit many urban characteristics such as
businesses and business zoning, high residential density and small lot size. Both these
communities lack other urban services such as water and sewer utilities, which have in the
past created public health concerns and efforts to provide these services to those
communities.
Union Gap is located in lower flatter land at the confluence of these two creeks with the
Yakima River and has always dealt with constraints from flooding and a water table near
the surface. The City of Yakima, which is protected by levees from the Yakima River built
after World War II, and contains a large area west of 16th Avenue located on high ground
and has only more recently expanded into flood prone areas due to annexations westward.
A high proportion of the remaining developable land is located in or near floodplains.
Figure 5-2 shows the elevation contours and floodplains versus the recent and expected
future city expansions.
Figure 5-2 Urban Growth 1970-2011
1970 City Limits
2011 City Limits
2011 Urban Growth Area
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Lands west of urban Yakima and Union Gap have undergone annexations in response to
urban growth demand, removing lands previously devoted to agriculture or its supporting
activities. The majority of the annexations have been to the City of Yakima. Figure 5-3 shows
the annexation history of the two areas from 1940 to 2010.
CHAPTER 5 — DEVELOPMENT IN BASIN FLOODPLAINS 3
Figure 5-3 City of Yakima & City of Union Gap Annexation History
City of Yakima & Union Gap Annexations
5.1„,, 1975 55 1917 1999 ,"1935
8]1�•
1964 _ 0 1845
▪ 1976 1976
Streets
•—•— Urban Growth Boundary
▪ FioodwaNFIood Plain
V... City Limits
Annexations
By Year
1886
188]-1900
1901-1930
1931-1950
- 1951-1970
- 1971-1990
- 1991-2010
Date mnvzom
The largest annexations of floodplains in the CFHMP area occurred when the airport and
the surrounding area was annexed in the 1950's, and since 2000. These annexations
substantially increased the urban land proportion into flood prone areas, as shown by the
red hatched areas in Figure 5-3. The accelerated trend of expansions has been accompanied
by increased road, sewer and infrastructure construction in the floodplain.
The potential dangers from overdevelopment in flood prone locations is currently being
experienced in Kent, Auburn and Renton on the Green River, as they face huge economic
costs and development restraints from aging flood protection measures that could not be
sustained over the long term.
Addressing land use through zoning is an important aspect of minimizing future flood
damage in both rural and urbanizing areas. A means of preventing or reducing intense
development in high-risk flooding areas, or committing to mitigating measures is desirable.
Prevention of intense development in high-risk areas is one of the most effective methods to
minimize flood risks and is further discussed in the Alternatives and Recommendations
Chapters.
SOCIOECONOMIC CHARACTERISTICS
The Ahtanum-Wide Hollow area includes portions of the cities of Yakima and Union Gap,
as well as suburban and rural areas west of the cities. The top three employment sectors in
4 1 Ahtanum-Wide Hollow CFHMP
Yakima County are "Educational, health and social services," "Manufacturing," and
"Agriculture, forestry, fishing and hunting, and mining" (U.S. Census 2000). In the rural
portions of the Ahtanum Creek cattle ranching is common, as well as various types of
agriculture.
LAND USE
For the purposes of this CFHMP, Yakima County GIS combined the City of Yakima's 2004
land use survey with Yakima County's 1996 land use information, creating a combined map
and spreadsheet (current land use for Union Gap was not available).
Land use patterns show that most of the floodplains in the Ahtanum-Wide Hollow CFHMP
area (67.2%) were in agricultural use at the time of the surveys. Forage crops, such as hay,
are most common, but fruit production is increasing (Ahtanum Assessment Executive
Summary, 2004). The Pope Decree (Ch. X, page y) limits the types of agriculture that can
occur within the Ahtanum Irrigation District to hay and forage crops unless supplemental
irrigation (from groundwater) is available.
Single Unit housing is the second most common land use type in the floodplain (16.1%).
Vacant land makes up 6.5% of the floodplain, followed by land used for Wholesale/Industry
(5.5%). See Figure 5-4 below.
Figure 5-4 Land Use, Yakima County and Yakima Combined
Top Five, Floodplain Only
1 7%
❑ Agriculture
O Single Unit
o Vacant
o Other Residential
• Wholesale\Industry
ZONING
Since Ahtanum and Wide Hollow Creeks flow through three local jurisdictions, it is
necessary to analyze zoning patterns in each jurisdiction (Yakima County, the City of
Yakima, and the City of Union Gap) separately. Zoning data from 2005 was used for the
analysis of the cities and county. The unincorporated section of the CFHMP area in Yakima
County is predominantly zoned for rural and limited use. The largest percentage of land in
the floodplain is zoned as Valley Rural. This zoning designation "is intended to protect and
maintain the openness and rural character of outlying areas of the county in the lower
Wenas, and the valley floors of the lower Ahtanum, Naches and Yakima Valleys" (Yakima
County Code, 2005). While this zoning designation will greatly reduce the potential for
creation of new lots in the floodplain, along the North Fork Ahtanum, there are a significant
CHAPTER 5 - DEVELOPMENT IN BASIN FLOODPLAINS 5
number of small lots that were created prior to zoning, and which would result in high
development density and flood hazard if they are developed to their full potential.
Agriculture is the second most common zoning designation in the floodplain (24%),
followed by Single Family Residence (18%). Other zoning designations that are represented
in the floodplain include Federal/Tribal Trust, Forest Management, and Rural Transitional,
which are not shown on the County Zoning map west of the Valley Rural zoning on N. F.
Ahtanum Creek. See Figure 5-5 for County zoning, Figure 5-6 for City of Yakima and Union
Gap and Figure 5-7 for Yakama Nation zoning maps.
The zoning map for the Yakama Nation is broken into large categories that aren't applicable
to the type of floodplain zoning review analyzed for the cities and county. For the Yakama
Nation, most of the lower Ahtanum is zoned Rural Area; the next area upstream is zoned
Open Only During Hunting and Fishing Seasons; with the remainder of the Ahtanum and
South Fork Ahtanum zoned Closed Area.
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Figure 5-5
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CHAPTER 5 — DEVELOPMENT IN BASIN FLOODPLAINS 9
Pie charts for percent of specific zoning in the floodplain are in Figure 5-8 through 5-10
below. The analysis was based on 2005 zoning data for all jurisdictions. See Appendix A for
more detailed land use and zoning tables.
Land within the floodplain of Ahtanum and Wide Hollow creeks in the City of Yakima
reflect the urban character of the city, and show that for many years the floodplains now in
the city were not developed for residential uses. Light industrial zones, primarily associated
with the Yakima Regional Airport, dominate the floodplain zoning districts within the City
of Yakima, and much of this land has recently been developed for this purpose. A smaller
area of residential zones is located on Wide Hollow creek, upstream of 40th avenue. Much of
this land is still in agricultural use on the former Condon Orchard property, but will see
conversion to actual residential use in the future. The City of Yakima does not have actual
open space or agricultural zoning designations which would provide greater protection of
floodplains from development than their lowest density zone, which is currently R1, which
when it's used in the flood overlay zone, would allow development on one acre or larger
lots.
Significant areas of floodplain in Union Gap are zoned as Parks/Open Space or Planned
Recreational. These zoning districts occur in the combined floodplains of lower Ahtanum
and Wide Hollow Creeks, near their confluence with the Yakima River, an area of relatively
high flood frequency. Upstream, land within the floodplain is zoned as Light Industrial
which allows for some commercial development, such as Costco, as well. These areas do
not see as frequent flood events, but careful site planning is still necessary due to areas of
high groundwater during most of the year. Single Family Residential 1 and Single Family
Residential 2 make up most of the remainder of Union Gap's land in the floodplain. Most of
this land is fully developed, and Wide Hollow creek has been severely confined (along
Pioneer Ave) or wholly modified (lower Wide Hollow). Both areas have seen significant
flood damage during major flood events. Other classifications represented include the
Public Buildings District along Ahtanum Road adjacent to Wide Hollow which is the
proposed new location for Union Gap's City Hall and currently undeveloped. A small area
is zoned Central Business District in the area where Wide Hollow crosses under Main Street.
Due to the confined nature of the creek and low gradient, businesses in this area have seen
repeated flood damage.
10 Ahtanum-Wide Hollow CFHMP
Figure 5-8 Yakima County Zoning in the Floodplain
27%
9%
9%
24%
APPirl
7%
6%
❑ Agriculture
• Forest Management
❑ Single Family
• Rural Transitional
❑ Federal Land \Tribal
Trust
• Valley Rural
• Others Combined
Figure 5-9
City of Yakima Zoning in the Floodplain
• Professional Business
• Local Business
❑ Central Business District
Support
❑ Light Industrial
❑ Single Family Residential
❑ Multi -Family Residential
❑ Suburban Residential
• Other
Figure 5-10
City of Union Gap Zoning in the Floodplain
3% 7% 3%
6%
9%
20%
24%
24%
4%
• Central Business District
❑ Light Industrial District
❑ Public Buildings District
❑ Planned Recreational
• Parks/Open Space
❑ Single Family Residential 1
❑ Single Family Residential 2
❑ Wholesale/Warehouse
• Other
The pie charts above, for the 3 non -tribal jurisdictions in the CFHMP area illustrate that
there are not common zoning districts. As urban growth areas expand, land is transferred
from County jurisdiction, to joint jurisdiction (urban growth area expansion) and eventually
into city jurisdiction. Zoning designations will accompany each of these moves, or can
occur every other year during Comprehensive Plan updates. For the most part in the
Ahtanum and Wide Hollow watersheds this transition should occur with minimal or no
increase in flood hazard.
There are locations adjacent to the Urban Growth Areas (UGA's) that could, if incorporated
into the UGA and eventually one of the cities, present a significant increase in flood hazard.
As shown in the pie chart above, there are areas of floodplain in the County jurisdiction that
are zoned either Valley Rural or Agriculture, which require the retention of relatively large
parcels, and the zoning was intended to protect floodplains as well when allowed land
CHAPTER 5 — DEVELOPMENT IN BASIN FLOODPLAINS 11
divisions occur. Several floodplain areas with these zoning designations abut the City of
Yakima or Union Gap UGAs, mainly along Ahtanum Creek.
Without an open space designation expansion of the UGA into these floodplains will
increase residential or other lot density from 5 acre (Valley Rural) or 20 (Ag) acre to an
average of an acre or less depending on the new urban zoning designations and associated
subdivision regulations in floodplains Increases in flood hazards can be avoided by the
cities through either Ag, Open space, or other zoning designations that maintain large lots
and floodplain function in the floodplain and adjacent areas. Where no such low density
zoning designations exist in a city's zoning code, development density and flood hazard
will increase unless other tools, such as flood or habitat preservation easements are
employed. Additional specifics about the Urban Area Zoning Ordinance are located in
Chapter 6.
ECONOMICS OF FLOODPLAIN DEVELOPMENT
The Ahtanum and Wide Hollow basins are flood -prone and are being converted from
agricultural to urban usage, as indicated by the zoning and annexations, described above.
Development in these floodplains has been subject to relatively frequent flood damage and
access issues for floods more frequent than the FEMA 100 -year flood threshold.
Economic loss due to loss of access, loss of function and emergency response impacts
businesses, homeowners and the community at large. Losses in Yakima County from the
1996 flood alone were estimated at $18 million. Yakima County carried $5 million in claims
that required federal reimbursement and resulted in County cash flow issues for several
years. Insurance policies, limit damages to homeowners and businesses to the amounts
insured, which have upper limits (i.e. $250,000 for a residence through NFIP). The average
NFIP claim is $25,000. Disaster relief funds are only available for federally declared
disasters, which has threshold criteria not easily attained, and are when obtained are usually
on a loan basis. Disaster claims average $2,500.
Currently, thirty percent of FEMA nationwide flood insurance claims are from outside the
FEMA 100 -year floodplains indicating that floods can exceed the mapped 100 year flood
level areas and inundate unexpected locations.
Due to the exorbitant costs of disaster relief in the past, FEMA regulations restrict
development in the floodplains. To reduce disaster and flood insurance claims, FEMA
provides minimum regulations for development in floodplains that are coupled with the
National Flood Insurance Rate Maps adopted by the community. New residences and
businesses are allowed in the flood fringe with attendant restrictions, but are not allowed in
the floodway. To reduce the public burden of disaster relief funding, flood insurance is
required for these structures, should any part of the mortgaging be supported by federal
funds. Flood insurance rates are high since the odds of flooding are high. There is a 26%
chance of flooding during a 30 -year mortgage for properties in the 100 -year floodplain. Due
to the high risk associated with floods, private underwriters are reluctant to offer flood
12 1 Ahtanum-Wide Hollow CFHMP
insurance and most flood insurance is underwritten by the National Flood Insurance
Program (NFIP). Due to the National Flood Insurance cap for businesses of $500,000 for the
building and another $500,000 cap for contents, larger businesses must purchase insurance
through private underwriters. Flood insurance at significantly higher rates than from NFIP
can be attained through underwriters like Lloyds of London.
Many homes in most communities, particularly those without mortgages, do not have flood
insurance, or do not have insurance that covers their current value.
The impact of new development cannot raise the flood elevation, also known as the Base
Flood Elevation (BFE), by more than one foot and buildings must be built at or above the
BFE. This rule allows new development to raise flood levels to inundate older developments
built at BFE by up to one foot. Consequently, FEMA has provided a model ordinance more
stringent than their regulations which recommends a number of items, including raising
residential structures requirement one foot or more above the BFE. The Yakima
communities are still using the BFE level requirement.
Although federal insurance costs are representative of community damages within flood
plains, they currently subsidize existing development in floodplains prior to current
insurance standards. Flood hazard planning through building elevation and building siting
above minimum standards will reduce insurance costs that are subsidies and will keep
insurance subsidizing dollars within the community.
Communities benefit financially from slightly higher standards for flood insurance
premiums, even without considering the reduced impacts and loss from floods. The chances
of inundation and loss are substantially reduced by providing more accurate flood mapping
and raising the minimum floor elevation above the BFE. Not only is the chance of damages,
flooding and hardships reduced, so are the insurance premiums paid by the owner, which
are largely lost to the community. Raising the minimum floor elevation one foot would
reduce the chance of inundation during a 30 year mortgage from 26 percent to around 5
percent and reduce the annual insurance premium per hundred thousand dollars of
insurance from $816 to $451, a 45% savings.
The cost of raising a home one foot at the time of construction is well under five thousand
dollars if a wall is used, and less if regarding or fill is used, and would pay for itself during
the first six years or less of the mortgage. At this time the International Residential Code
used by Yakima jurisdictions, requires elevation of the structural members and insulation to
approximately one foot, so that the base floor sits at one foot above BFE. The jurisdictions
would realize the insurance fee savings by formally adopting the current practice, which is
effectively one foot above BFE. Raising the minimum floor elevation another foot to two feet
would reduce the insurance to $276 for a total of 66% savings.
Local communities and the state can adopt higher standards than the FEMA minimum in
order to minimize community losses and exposure. For example, in response to frequent
damage and loss in floodplains, neighboring Pierce County has chosen to expand their
definition of the floodway, where new development is highly restricted, to include the
channel migration zone and areas of deep and fast flows. This has almost doubled the area
CHAPTER 5 — DEVELOPMENT IN BASIN FLOODPLAINS 13
of their floodways within their floodplains, moved more people out of harm's way, and
reduced hazard and economic exposure.
With the conversion in Ahtanum and Wide Hollow basins from extremely low density
farmland, where flooding was permissible, and in some cases desirable, to high density
development of homes and businesses, the level of suffering and the cost of future damages
in new development will being undertaken by the new owners and the community through
damages and insurance fees.
Protection of these lands by levees is not practical in this watershed for reasons noted
earlier, and even if so, would require further public expenditure. Experience elsewhere in
the County indicates that levees also increase flood exposure through encouraging further
development in a vulnerable location. This is a major concern in King and Pierce Counties.
ECONOMICS OF FLOOD PLAIN ZONING AND FLOODPROOFING
Land use zoning and infrastructure protection should recognize the economic impact of
flood plain development. Two methods to reduce damages and insurance premiums for
development in floodplains are raising structures and flood proofing. As the costs differ by
land use, land use zoning is an important tool to reduce flood damage costs.
The following extract from the 1991 Department of Ecology, "Comprehensive Planning for
Flood Hazard Management Guidebook", indicates the practicality and relative costs by land
use.
"Flood proofing might be defined, generally, as the construction or remodeling of physical
structures such that during floods they can either be closed or their occupancy can be
modified so that inundation, siltation, or velocity damage can be minimized. While it may
be rather expensive and impractical to completely flood proof all developments, this method
together with land use regulation (italics added), is useful in reducing flood damages."
The feasibility of such activity depends considerably on the use of flood plains. Existing
activity may be flood proofed but, in general, this would probably be more difficult and
costly than designing flood proofing into new developments. In urban areas where
development proceeds at a rather rapid pace, flood proofing techniques for different types
of development are briefly outlined as follows.
14 1 Ahtanum-Wide Hollow CFHMP
Light Industry
Typical flood proofing measures might include elevating all processing operations and
storage facilities of materials, especially hazardous materials, subject to damage above the
flood plain elevation.
Commercial Enterprise
Firms selling products and/or services for human consumption may find flood proofing
relatively more difficult and costly than in the case of industry. Nevertheless, it may be
entirely feasible in this instance, to develop customer parking and receiving and delivery
areas directly on the flood plain. Suitable access could then be provided to upper level trade
areas (perhaps only one-half of the normal flood height above existing grade). Inundation
would thus occur only to areas which could be evacuated. As an alternative, flood doors
and other partitions with sealing mechanisms could be provided so that areas could be
closed with advancing flood threat.
Residential Occupation
Flood proofing here would appear to be the least practical of the three examples cited.
Physically, the difficulty would not be insurmountable, but in terms of relative cost
requirements, the benefit -cost ratio may be very low for existing structures. However, it
may be entirely feasible and possible (if the terrain of the flood plain so allows) to construct
new residences on existing "backgrounds" or on built-up areas. Yards, parks, school
playfields, and public recreation could then be placed on lower levels of the flood plain. The
NFIP standards (see below) require that the first floor of all new residential buildings be at
or above the 100 -year flood level.
Utilities
Any development on the flood plain will require that certain utilities (e.g., lights, heat, and
water) be available to them. Placement of utilities on the flood plain should be designed to
withstand sedimentation, erosion and other forms of damage. This is particularly important
if activity is to continue on the flood plain under flood conditions.
The real key to a successful flood proofing program is to coordinate activity with land use controls
and structural flood hazard management measures so that the most cost effective approach is taken for
a given situation (italics added). For example, in some undeveloped sections of a watershed,
flood proofing may be much more cost effective than dikes or levees. To achieve this
coordination, the flood hazard management planning process must bring together those in
charge of building permit review, land use regulations and public construction (italics added).
Usually, this requires the often difficult task of framing a common strategy among the local
departments of planning, building and public works.
Ecology does not require that local flood plain management ordinances exceed the NFIP
standards. However, in many cases it may be advisable for local governments to set higher
standards than those imposed by the NFIP. For example, the NFIP requires that the first
floor of new residential construction be at or above the 100 -year flood level. A local
CHAPTER 5 — DEVELOPMENT IN BASIN FLOODPLAINS 15
community may wisely elect to set the minimum elevation at 2 feet above the 100 -year flood elevation
to allow a greater margin of safety for several reasons (italics added), including:
• Projection of higher flooding levels due to changing conditions in the watershed.
• Lack of data in hydrological modeling.
• Special conditions that could exacerbate flood conditions.
The preferred land use in floodplains to minimize community costs would be, in order,
open space, parks, golf courses, agriculture, light industry, commercial and low density
residential. In order to reduce costs these land use preferences should be fully considered in
future floodplain planning and zoning decisions
PLANNING FOR FUTURE FLOODPLAIN DEVELOPMENT
Table 1-1 identifies hazard reduction goals for land use, which include:
• mitigate increased hazard risk created by development,
• minimize residential structures in "harm's way",
• evaluate lands prone to repetitive flooding in relation to open space uses,
• minimize residences located in designated areas and
• ensure that all development can be adequately provided with life safety services.
The City of Yakima, Yakima County, and FCZD staffs have reviewed proposed changes to
the Yakima Urban Area Zoning Ordinance, which was prompted by adoption of the
updated Yakima Urban Area Comprehensive Plan 2025 in December 2006. Bringing this
ordinance in line with the Plan 2025 policies will help recognize the land use and density
limitations of lands in flood -prone areas. The Yakima Urban Area Comprehensive Plan 2025
replaces the 1997 Yakima Urban Area Comprehensive Plan.
The goals and policies established in Yakima Urban Area Comprehensive Plan 2025 apply to
the entire Yakima Urban Growth Area, including the West Valley Neighborhood Planning
Area. In addition, Plan 2015 (the Yakima County Comprehensive Plan) is a regional plan
that establishes the County's perspective on urban policy and the transitioning of land from
rural and resource uses to urban uses.
The 1997 Yakima Urban Area Comprehensive Plan did not include detailed planning for the
west and southwest portion of the Yakima UGA, an area now known as the West Valley
Neighborhood Planning Areal. The Planning Area consists of West Valley lands that were
not included in the "Yakima Urban Area" designated in the mid-1970s in conjunction with
the planning for the regional wastewater system. As such, the West Valley Planning Area
1 The 1997 Yakima Urban Area Comprehensive Plan referred to the West Valley Neighborhood Planning Area
as the "Urban Reserve." However, in December 2006 the Board of Yakima County Commissioners and the
Yakima City Council adopted an updated plan for the Yakima UGA entitled Yakima Urban Area
Comprehensive Plan 2025. Because the update eliminated all references to the "Urban Reserve," the West
Valley Neighborhood Plan will refer to this area as the "West Valley Neighborhood Planning Area" or simply,
the "Planning Area."
16 1 Ahtanum-Wide Hollow CFHMP
represents additional West Valley lands designated after 1997 for future urban growth2. The
1997 Yakima Urban Area Comprehensive Plan contemplated that a neighborhood plan would
be developed for this Planning Area at a later date through a joint process involving Yakima
County, the cities of Yakima and Union Gap, and West Valley residents.
The West Valley Neighborhood Plan (WVNP) is the fulfillment of that intention. Figure 5-11
shows the initial West Valley Neighborhood Planning Area (for final the planning area
boundary, refer to the WVNP). In 2006, approximately 74% of the Planning Area was vacant
or undeveloped, but urban development is rapidly occurring.
In early 2005, the West Valley Neighborhood sub -area planning process was reactivated
with a new emphasis on mobility, housing and parks & open space. With these three areas
of emphasis in mind, work went forward to provide a framework that would guide a
renewed effort with adoption of the Plan in 2010. The WVNP plan would provide guidance
for locating housing of various densities, commercial uses, and industrial uses. The WVNP
is to guide urban service planning in the West Valley Urban Area. Flood related topics were
incorporated into the WVNP by the County planning department.
The WVNP, including the area -wide rezone, was adopted by both the City of Yakima and
Yakima County to provide a common vision for the future physical development of this
portion of the Yakima urban area. They became effective on February 28, 2010 in the
unincorporated area, and on March 20, 2011 inside the Yakima City limits. The WVNP
covers a narrow north -south strip of the CFHMP area immediately west of City of Yakima
boundary. Additional information and zoning maps are available in the WVNP.
2 The Board of County Commissioners expanded the Yakima UGA in 2003 by adding the "Apple Tree" area,
and again in 2007 by adding the "Dazet" and "Scenic" areas, which are now included in the WVNP Planning
Area.
Figure 5-11
West Valley
Neighborhood
Plan
City Limits
Neighborhood
Limits
Streams
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SNIIV'Id00013 NISVd NI 1N1YSJdO11A30 - S ?II.LdVHJ
18 1 Ahtanum-Wide Hollow CFHMP
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CHAPTER 6
PLANNING AND REGULATORY SETTING
A critical component of effective flood hazard management is a system of regulations that
can support the recommendations proposed by a CFHMP. As well as regulatory
recommendations affecting land use, shoreline management, resource management, and
floodplain management, the CFHMP recommendations may include engineered projects to
protect existing developments. An understanding of existing flood regulations can prevent
the waste of time and money on projects that will never be permitted. More significantly,
the need for engineered projects to prevent or mitigate flood hazards can often be
eliminated if complementary and future hazard orientated regulatory programs are initiated
before extensive development occurs.
This chapter provides an overview of existing federal, state, and local regulatory and
permitting requirements that relate to flood hazard management. This also includes surface
water management, land use, water quality, environmental and wetlands protection
regulations.
SUMMARY OF EXISTING REGULATIONS
The laws that directly or indirectly address flood hazard management are enacted at the
federal, state, and local levels. Table 6-1 lists these laws in the categories of flood hazard
management, endangered species, planning policy, sensitive areas, stormwater
management, environmental and water quality; Table 6-2 provides further details on each of
the laws cited.
Many federal laws are implemented at the state and local levels. For example, the Federal
Clean Water Act regulates stormwater discharge, but the EPA has delegated the
responsibility of administering the program for non-federal lands to the Department of
Ecology within the State of Washington, which in turn requires local jurisdictions and
industry to obtain permits. The Endangered Species Act may be implemented by states, as
was the case with the protection of Bald Eagles in the State of Washington, but the majority
of the regulatory programs, especially for salmonids, remains at the federal level. The
National Flood Insurance Program, which offers affordable flood insurance to private
property owners, remains a national program administered by FEMA, but requires cities
and counties to adopt floodplain ordinances to restrain floodplain development and impose
minimum building standards. The NFIP also restrains federal lending institutions, such as
mortgage lenders.
Apart from NFIP, the laws most relevant to flood hazard management originate at the state
level. Most of these begin with state legislation that enables local governments to adopt
regulations promoting public health, safety, and general welfare. Environmental laws that
affect flood hazard management through habitat, shoreline, and other critical -area
protection measures also exist at the state level, but enforcement is increasingly becoming
1
2 1 Ahtanum-Wide Hollow CFHMP
the responsibility of local governments. State growth management requirements through
the Growth Management Act contain additional recommendations regarding land use and
development near wetlands and in frequently flooded areas, with regulatory
implementation largely in the hands of local jurisdictions.
Local governments are also responsible for implementation of State flood regulations that
are more stringent than the federal requirements. An important example of this is
Washington State RCW 86.16.041 which prohibits residential development in floodways.
Because this regulation also limits substantial improvements or repairs, the net effect is that
a substantially damaged house (regardless the cause) cannot be rebuilt or repaired in the
floodway. There are exemptions for existing farmhouses and for properties that have local
jurisdiction approval and can meet depth, velocity and erosion risk requirements.
TABLE 6-1.
SURFACE WATER MANAGEMENT POLICIES & REGULATIONS IN YAKIMA COUNTY
Category
Federal
State
Yakima County
Land Use
• National Flood Insurance
Act
• Flood Disaster Protection
Act
• Executive Order 11988
• Endangered Species Act
• Floodplain Management
Program (RCW 86.12,
86.16, 86.26)
• Shoreline Management
Act (SMA)
• Growth Management Act
(GMA)
• Comprehensive Plan
• Shoreline Master Program
• Critical Areas Ordinance
• Zoning Ordinance
Infrastructure
• Hydraulic Code (HPA)
• Building Code
Planning and Policy
• Endangered Species Act
• Growth Management Act
(GMA)
• Shoreline Management
Act (SMA)
• Flood Control by Counties
• Comprehensive Plan
• Shoreline Master Program
• Critical Areas Ordinance
Facilities
• Endangered Species Act
• Hydraulic Code (HPA)
• Comprehensive Plan
• Zoning Ordinances
Water Quality
• Clean Water Act, Sections
401 and 402
• Water Pollution Control
Act (WQ Cert or Mod)
• Statero ram for NPDES
P g
(cities < 100,000)
• Stormwater Ordinance
• Comprehensive Plan
• Shoreline Master Program
• Critical Areas Ordinance
Fisheries and
Wildlife Habitat
• Hydraulic Code
• Comprehensive Plan
• Critical Areas Ordinance
General
Environmental
• National Environmental
Policy Act (NEPA)
• State Environmental
Policy Act (SEPA)
• SEPA Ordinance
• Comprehensive Plan
Stream Corridors
• Clean Water Act, Sec. 404
• River and Harbor Act
• Endangered Species Act
• Shoreline Management
Act
• Hydraulic Code (HPA)
• Comprehensive Plan
• Shoreline Master Program
• Critical Areas Ordinance
Wetlands
• Clean Water Act, Section
404 (dredge and fill)
• Executive Order 11990
• River and Harbor Act
• Shoreline Management
Act
• Executive Order 90-04
• Critical Areas Ordinance
• Shoreline Master Program
CHAPTER 6 — PLANNING AND REGULATORY 13
TABLE 6-2.
OVERVIEW OF MAJOR FEDERAL, STATE, AND LOCAL SURFACE WATER MANAGEMENT
REGULATIONS
Regulation
Implementing
Agency
Purpose
Jurisdiction
Required
Approval, Permit,
or Plan
Applicability to Flood
Hazard Management
FEDERAL
National Flood
Insurance Act
FEMA
Offers affordable flood
insurance to communi-Floodplains
ties that adopt approves
floodplain managementfrom
regulations
of the
U.S.
Flood Insurance Study
nd approval letter
FEMA
Participation in NFIP
requires minimum
floodplain management
regulations
Flood Disaster
Protection Act
FEMA
Provides incentive to
communities to join the
NFIP by increasing
amounts of flood
insurance available and
providing penalties for
communities and
individuals that do not
join the NFIP and are
subsequently flooded
Floodplains of the
U.S.
Approval by FEMA
Requires purchase of flood
insurance for funding by
federally backed lending
institutions for purchase of
property in floodplains
Clean Water Act,
Section 401
State agencies
empowered by
EPA (i.e., Ecology)
Ensures that federally
permitted activities
comply with the Clean
Water Act, state water
quality laws, discharge
limitations, and other
state regulations
Waters of the U.S.
Water Quality
Certification or
Modification
Structural measures
affecting surface water will
require Water Quality
Certification or Modification
Clean Water Act,
Section 402
State agencies
empowered by
EPA (i.e., Ecology)
Establishes permit
requirements for
stormwater discharges
under National PollutionGeneral
Discharge Elimination
System)
Program
Discharges
associated with
industrial and
construction
activities and
municipal (county
and cities) storm
sewer systems
Permits
MS4s and construction
activities disturbing more
than 1 acre of soil with
direct discharge to
receiving waters or to storm
drainage system
Clean Water Act,
Section 404
USACE
Regulates the
discharge of dredged
or fill material or
excavation in rivers,
streams, and wetlands
Waters of the U.S.,
including wetlands
Individual or
Nationwide Permits
Dredging or filling in
wetlands or rivers will
require permit
River and Harbor
Act, Section 10
USACE
Preserves the
navigability of the
nation's waterways
U.S. navigable
waters.
Section 10 permit
Regulates activities within
the Ordinary High Water
Mark (OHWM) on
navigable waters
ESA, Section 7
USFWS, NOAA
Ensures that federally
permitted or funded
projects provide
protection for species
listed as threatened or
endangered
All of United States
and Territories
Biological Evaluation
(BE) or Biological
Assessment (BA) with
formal consultation and
possibly EIS
Activities and work in river
channel or adjacent
wetlands, or that may affect
those habitats, requires
review of impacts and
identification of mitigative
measures
4 Ahtanum-Wide Hollow CFHMP
TABLE 6-2.
OVERVIEW OF MAJOR FEDERAL, STATE, AND LOCAL SURFACE WATER MANAGEMENT
REGULATIONS
Regulation
Implementing
Agency
Purpose
Jurisdiction
Required
Approval, Permit,
or Plan
Applicability to Flood
Hazard Management
ESA, Section 9
USFWS, NOAA
Broad protection to
prevent "take" of listed
species
All of United States
and Territories
Biological Evaluation
(BE) or Biological
Assessment (BA) with
formal consultation and
possibly EIS
Activities and work in river
channel or adjacent
wetlands, or that may
affect those habitats,
requires review of impacts
and identification of
mitigative measures
National
Environmental
Policy Act
Varies (usually the
federal agency
issuing the permit
or the action)
Requires full disclosure
of potential impacts
associated with
proposed actions and
mitigative measures
All federal actions
Environmental
Assessment or EIS
Applies to any action which
may adversely impact the
environment
Executive Order
11988
Federal Agencies
Protects floodplains
from development by
federal agencies
Federal projects
None
Enhances existing
floodplain management
regulations
Executive
Order 11990
Federal Agencies
Protects wetlands and
evaluates impacts of
proposed actions on
wetlands
Federal projects,
federally funded
activities, or other
activities licensed
or regulated by fed
agencies
None
Enhances existing wetland
protection regulations
STATE
Senate Bill 5411
(ESSB 5411);
Flood Control by
Counties (RCW
86.12)
Counties
RCW 86.12 gives
county governments
the power to levy
taxes, exercise
eminent domain, and
take action to
control/prevent flood
damage. ESSB 5411
provides a greatly
expanded role for
counties in formulating
and adopting drainage
basin plans to address
flooding and land use
regs
All drainage basins
located wholly or
CoUinly within the
Comprehensive Flood
Hazard Management
Plan
Allows for development of
CFHMPs
Floodplain
Management
Program
(RCW 86.16)
Ecology
Reduces flood damage:
and protects human
health and safety.
Department oversees
local implementation of
floodplain regulations
required for participation
in the NFIP, as well as
additional regs for
residential development
in floodways.
All floodplains with-
in the state
State approval of
floodplain
management programs
and regulations
Provides eligibility for
national flood insurance
and for state matching
funds to construct flood
control facilities
CHAPTER 6 — PLANNING AND REGULATORY 15
TABLE 6-2.
OVERVIEW OF MAJOR FEDERAL, STATE, AND LOCAL SURFACE WATER MANAGEMENT
REGULATIONS
Regulation
Implementing
Agency
Purpose
Jurisdiction
Required
Approval, Permit,
or Plan
Applicability to Flood
Hazard Management
STATE (cont)
State Participation
in Flood Control
Maintenance
(RCW 86.26)
Ecology
Assists local
jurisdictions in
comprehensive planninc
and flood control •
maintenance efforts
All flood hazard
management
activities of local
.
jurisdictions as
approved by
Ecology
FCAAP grant
application, approved
CFHMP for
maintenance grants
FCAAP funds available for
preparation of CFHMPs,
flood control maintenance
projects, and emergency
flood control projects
Floodplain
management
ordinances and
amendments...
(RCW 86.16.041)
Ecology
Review of local
ordinances and flood
way regulations
All flood hazard
management
activities of local
jurisdictions as
approved by
Ecology
Approval of local
ordinances
Assures ordinances
implementing NFIP and
Washington State
floodplain and floodway
regulations
GMA
(RCW 36.70A)
Washington State
Department of
Commerce
Requires comprehend -
sive plans to include
surface water
considerations and
facilities (quantityand
quality)
Requires designation
and regulation of critical
areas, including wet-
lands and frequently
flooded areas
Selected high-
growth counties
(includingYakimacomprehensive
County) and their
cities
All Washington
counties and cities.
Comprehensive Plan
Critical areas and
resource lands
designation
Requires adoption of
development regulations
and plans
Requires adoption of
q p
ordinances regulating
development in designated
areas
Executive Order
90 04, Protection
of Wetlands /
Model Wetlands
Protection
Ordinance
Ecology
Provides guidance to
local governments to
achieve no net Toss of
wetland functions and
values
State wetlands
buffers
None
Provides voluntary techni-
cal assistance to the local
jurisdiction to regulate
activities that affect
wetlands
Shoreline
Management Act
(RCW 90.58)
Ecology; local
jurisdictions when
state approved
Manages uses of the
shorelines of the state
for protection of public
interests and natural
environment
All shorelines of
the state (including
all marine waters,
lakes > 20 acres
reservoirs, streams
and rivers >20 cfs
mean annual flow,
and associated
wetlands)
State or state
approved local
shoreline permit
Applies to new
developments and uses
within Shoreline
Jurisdiction.
Water Pollution
Control Act
Ecology
Empowers the state to
develop, maintain, and
administer the federal
statutes and programs
required by the federal
Clean Water Act
All receiving waters
of the state
Water Quality
Certification or
Modification
Regulates activities that
violate state water quality
standards as per the Clean
Water Act
6 Ahtanum-Wide Hollow CFHMP
TABLE 6-2.
OVERVIEW OF MAJOR FEDERAL, STATE, AND LOCAL SURFACE WATER MANAGEMENT
REGULATIONS
Regulation
Implementing
Agency
Purpose
Jurisdiction
Required
Approval, Permit,
or Plan
Applicability to Flood
Hazard Management
STATE (cont)
Forest Practice Act
(RCW 76.09)
Department of
Natural Resources
and Forest
Practices Board
Regulates forest
practices on state and
private lands to
minimize damage to
public resources
Riparian and
wetland areas
located within
designated
Riparian & Wet-
land Management
Zones
Notification or
application based on
practices classification
Ensure that watersheds are
managed responsibly to
limit their contribution to
increased flooding
SEPA
(RCW 43.210)
Varies (usually the
local agency issu
ing the permit);
circulation to state
and federal
agencies for review
Requires
of the I kelyll significant
adverse impacts
associated with a
proposed action and
identification of mitiga-
tive measures
All proposed
actions that require
permits
Environmental
Checklist or EIS
Requires environmental
review of any project with
potential adverse
environmental impacts
LOCAL — Yakima
Co.
Building and
Construction
(Title 13)
Yakima County
Building & Fire
Safety
The purpose of this title is
to provide minimum
standards to safeguard life
or limb, health, property,
and general public welfare
Unincorporated
Yakima County
Building Permits
Establishes minimum flood
hazard area construction
standards
Subdivisions (Title
14)
Yakima County
Planning Division
Regulates the sub-
division of land
Unincorporated
Yakima County
Plat approval
Requires note on face of
plat for short plats within
flood hazard areas
Yakima Urban
Area Zoning
Ordinance (Title
15A)
Yakima County
Planning Division
Implements the growth
management policies of
the Comp Plan by
prescribing use and
density requirements fol
land development
Unincorporated
portions of Yakima
County within the
urban area
Land Use
approval/zoning review
Flood hazard overlay
district reinforces flood
regulations
Zoning Ordinance ty
(Title 15)
Yakima County
Planning Division
Implements the growth
management policies ofYakima
the Comp Plan by
prescribing use and
density requirements
for land development
Unincorporated
p
portions of the
Yakima CountCoy,
not in the urban
area
Land use permits/
zoning review
Establishes allowable uses
in floodplains
Critical Areas
Ordinance (Title
16C & 16A)
Yakima County
Planning Division
Enacts provisions of
GMA for preserving
critical areas at local
level. (Integrates
provisions to protect
specialof
flood hazard
areas identified by the
Federal Emergency
Management Agency.)
Designated critical
areas of the state
within un-
incorporated
Yakima County.
Critical Area standard
development
authorization
Regulates development in
critical areas, including
floodplains. May be more
restrictive than requirement
the National Flood
Insurance Program (NFIP)
if development lies within
an identified critical area.
CHAPTER 6 — PLANNING AND REGULATORY 17
TABLE 6-2.
OVERVIEW OF MAJOR FEDERAL, STATE, AND LOCAL SURFACE WATER MANAGEMENT
REGULATIONS
Regulation
Implementing
Agency
Purpose
Jurisdiction
Required
Approval, Permit,
or Plan
Applicability to Flood
Hazard Management
LOCAL — Yakima
Co.
(cont)
Shoreline Master
Program (Title
16D)
Yakima County
Planning Division
Regulates development
and land use in near
Shorelines. (Integrates
provisions to protect
special flood hazard
areas identified by the
Federal Emergency
Management Agency.)
All areas within the
Shoreline
jurisdictional limits
of the SMP
Shoreline Approval
(Substantial
Development Permit,
Conditional Use
Permit, Shoreline
Variance)
Regulates development in
shoreline floodplains, The
extent of shoreline
jurisdiction is based on the
location of FEMA
floodplains/floodways.
Stormwater
Ordinance (Title
12)
Yakima County
Surface Water
Division
Provide for the health,
safety, and welfare of
the citizens of Yakima
County through the
regulation of discharges
to county stormwater
control facilities and
underground injection
control
Yakima County
Unincorporated
Stormwater project
review — requirements
vary depending on
whether inside or
outside Stormwater
Utility boundary
Promotes preservation of
natural drainage corridors
and requires that
stormwater be retained on
site for certain storm
frequencies
Comprehensive
Plan (Plan 2015)
Yakima County
Planning Division
Guides orderly future
growth and develop-
ment of county land use
circulation, and other
elements of interest to
the community
Yakima County
unincorporated
areas
None
Promotes preservation of
natural drainage corridors,
cost-effective measures to
control flooding, and limits
floodway developments
LOCAL — Cities
Floodplain
Development
Permits —
regulations
contained in
Critical Areas
and/or separate
Floodplain Code
and/or Building
Codes
Cities
Maintain Cities
compliance with NFIP,
regulate development it
floodplains to meet or
exceed NFIP standards
for reduction of flood
hazard to structures an(
maintenance of flood
conveyance and flood
water storage.
The mapped 100 -
year floodplains
within each local
jurisdiction, and
best available local
information
regarding
frequently flooded
areas.
Although in code, a
separate flood hazard
permit is not issued
and these items are to
be covered within other
permits such as
building, grading,
critical areas. They are
to be issued to
maintain compliance
with standards in NFIP
or higher local
standards.
Proposed projects are
reviewed for compliance
with flood hazard items
within local ordinances.
Union Gap has ability to
condition development
permits in floodplains,
including reduction in
scope or density.
LOCAL — Cities
Zoning Ordinances
Cities
Implements the growth
management policies of
the local government's
Comprehensive Plan by
prescribing use and
density requirements fol
land development
Applicable to all
land uses within
the city limits of
each jurisdiction
Most permits reviewed
for consistency with
Code. Specific permits
(conditional uses or
rezones) may require a
more extensive review
process including
public notice, SEPA,
etc.
May be used to regulate
development density in
floodplains or other areas
of flood hazard.
8 Ahtanum-Wide Hollow CFHMP
TABLE 6-2.
OVERVIEW OF MAJOR FEDERAL, STATE, AND LOCAL SURFACE WATER MANAGEMENT
REGULATIONS
Regulation
Implementing
Agency
Purpose
Jurisdiction
Required
Approval, Permit,
or Plan
Applicability to Flood
Hazard Management
Critical Areas
Ordinance /
Regulations
Cities
Enact provisions of
GMA for regulating
development in critical
areas, including
frequently flooded
areas.
Designated critical
areas of the state
within each local
jurisdiction
Critical areas
development permit
Imposes development regs
in frequently flooded areas,
streams and geologic
hazard area that preclude
land uses or development
that are incompatible
w/critical areas function or
public safety.
National Flood Insurance Program (NFIP)
The NFIP determines floodplain boundaries, floodways, and flood hazard areas associated
with the 100 -year flood through a Flood Insurance Study (FIS) and Flood Insurance Rate
Map (FIRM). The NFIP provides federally -subsidized flood insurance and availability of
federal disaster funds to all property owners in participating communities in exchange for
the community's adoption of a local flood hazard ordinance that meets minimum standards.
Yakima County and the cities are currently enrolled in the NFIP; Table 8-3 displays dates of
entry into the NFIP. The Yakama Nation does not participate in the NFIP so flood insurance
through the NFIP is not available for trust or fee land within the open portion of the
Yakama Nation Reservation.
The FIRMs produced by FEMA are also used for floodplain delineation purposes in state
regulations. Washington State utilizes the FIRMs to help establish regulatory boundaries for
state Critical Areas and Shorelines environments. The cities and county are required to
implement minimum NFIP, Critical Areas and Shorelines regulations, but each jurisdiction
may choose the best approach for their community. Yakima County and the City of Yakima
have both included NFIP compliance in their Critical Areas and Shorelines Regulations.
Union Gap also utilizes a Floodplain Development permit separate from other building and
environmental permits. NFIP compliance through the International Building Code is
discussed below.
TABLE 6-3
YAKIMA COUNTY INVOLVEMENT IN THE NATIONAL FLOOD INSURANCE PROGRAM
Community
Community
Number
Initial FIRM
Identified
Date of Current FIRM
Yakima County
530217
June 5, 1985
November 18, 2009
Union Gap
530229
May 2, 1983
November 18, 2009
Yakima
530311
December 15, 1981
November 18, 2009
CHAPTER 6 — PLANNING AND REGULATORY 19
NFIP PLANNING AND COMMUNITY DEVELOPMENT CONSIDERATIONS
The NFIP requires the 20,000 communities within the program to consider additional
measures which are found in 44 CFR 60.22, Planning Considerations for Flood -prone Areas,
which are summarized in Table 6-4.
Table 6-4: NFIP Planning Considerations (44 CFR 60.2)
(a) The floodplain management regulations adopted by a community for flood -prone areas should:
(1) Permit only that development of flood -prone areas which
(i) is appropriate in light of the probability of flood damage
(ii) is an acceptable social and economic use of the land in relation to the hazards involved
(iii) does not increase the danger to human life
(2) Prohibit nonessential or improper installation of public utilities and public facilities.
(b) In formulating community development goals after a flood, each community shall consider:
(1) Preservation of the flood -prone areas for open space purposes
(2) Relocation of occupants away from flood -prone areas
(3) Acquisition of land or land development rights for public purposes
(4) Acquisition of frequently flood -damaged structures.
(c) In formulating community development goals and in adopting floodplain management
regulations, each community shall consider at least the following factors:
(1) Human safety
(2) Diversion of development to areas safe from flooding
(3) Full disclosure to all prospective and interested parties
(4) Adverse effects of floodplain development on existing development
(5) Encouragement of floodproofing to reduce flood damage
(6) Flood warning and emergency preparedness plans
(7) Provision for alternative vehicular access and escape routes
(8) Minimum retrofitting requirements for critical facilities
(9) Improvement of local drainage to control increased runoff
(10)Coordination of plans with neighboring community's floodplain management programs
(11 )Requirements for new construction in areas subject to subsidence
(12)Requiring subdividers to furnish delineations for floodways
(13)Prohibition of any alteration or relocation of a watercourse
(14)Requirement of setbacks for new construction within V Zones
(15)Freeboard requirements
(16)Requirement of consistency between state, regional
(1 7)Requirement of pilings or columns rather than fill to maintain storage capacity and local
comprehensive plans
(18)Prohibition of manufacturing plants or facilities with hazardous substances
(19)Requirements for evacuation plans
10 1 Ahtanum-Wide Hollow CFHMP
International Building Code and NFIP
Local officials administer building codes for their community. These codes regulate the
items most commonly audited for compliance with the NFIP - elevation certificates, flood
hazard development permits, and floodway encroachments. Land use, Critical Areas and
subdivision regulations also apply to development in floodplains. Some jurisdictions have
included all or portions of their building codes pertaining to floodplains into their Critical
Areas code. More details about Critical Areas ordinances are found in that section of this
chapter. The remainder of this section describes the building codes and engineering
standards adopted by jurisdictions in our area.
Cooperative work between FEMA, SEI (Structural Engineering Institute) and ASCE
(American Society of Civil Engineers) beginning in 1991 was the origin of the flood resistant
provisions for the International Codes, which apply to buildings. These flood loads became
part of ASCE 7 in 1995 and were amended and expanded to become the current edition,
ASCE/SEI 7-02. These cooperative efforts continued with ASCE 24-98 which has been
updated to the current version, ASCE/SEI 24-05. These ASCE standards are incorporated or
referenced in the I -Codes (International Codes).
The IBC (International Building Code) was adopted by Washington State (RCW 19.27) in
2003 and became effective in 2004. The IRC (International Residential Code) is adopted by
reference unless a community specifically excludes it. None of the jurisdictions in the
CFHMP area excluded the IRC when they adopted the state required codes. The Yakama
Nation has an automatic code adoption process that updates their regulations to the most
recent edition of all the International Codes, including the IBC and IRC. Additional
International Codes for specific categories have also been adopted by the State of
Washington, including the International Mechanical Code and International Fire Code. For
Plumbing regulations, Washington adopted the Uniform Plumbing Code. The current state -
adopted version for these codes is the 2009 edition for each.
In addition to flood resistant codes in the IBC and IRC, the IBC also contains two optional
appendices that are relevant for floodplain management: Appendix G Flood Resistant
Construction, and Appendix J Grading. Both appendices were adopted by Yakima County
and the City of Yakima. Union Gap has not adopted either appendix.
Appendix J contains two sections that apply directly to flooding. The first states the
requirements in this appendix do not apply to designated floodways unless analysis has
been performed to show there will be no increase in the base flood elevation. The second
section applicable to floodplain management is a drainage requirement that drainage across
property lines shall not be greater than existed before the grading.
The overarching purpose of Appendix G (of the IBC) is to provide comprehensive
floodplain management regulations that cover all floodplain development since the IBC and
IRC pertain specifically to building construction. Appendix G requirements include that no
ground disturbing activity is allowed in floodways unless it is demonstrated there is no rise
in the flood elevation. Appendix G includes:
CHAPTER 6 - PLANNING AND REGULATORY 111
G102.1 General
This appendix, in conjunction with the International Building Code, provides
minimum requirements for development located in flood hazard areas, including the
subdivision of land; installation of utilities; placement and replacement of
manufactured homes; new construction and repair, reconstruction, rehabilitation or
additions to new construction; substantial improvement of existing buildings and
structures, including restoration after damage; and certain building work exempt
from permit under Section 105.2."
G103.2 Other Permits
It shall be the responsibility of the building official to assure that approval of a
proposed development shall not be given until proof that necessary permits have
been granted by federal or state agencies having jurisdiction over such development.
Note that this is the responsibility of the building official, this is duplicative of other
portions in the CAO that have the same requirements of the Planning Administrator
or designee.
G103.5.1 Floodway Revisions
A floodway encroachment that increases the level of the base flood is authorized if
the applicant has applied for a conditional Flood Insurance Rate Map (FIRM)
revision and has received the approval of the Federal Emergency Management
Agency (FEMA).
G301.1 General.
Any subdivision proposal, including proposals for manufactured home parks and
subdivisions, or other proposed new development in a flood hazard area shall be
reviewed to assure that:
• 1. All such proposals are consistent with the need to minimize flood damage;
• 2. All public utilities and facilities, such as sewer, gas, electric and water systems
are located and constructed to minimize or eliminate flood damage; and
• 3. Adequate drainage is provided to reduce exposure to flood hazards.
G301.2 Subdivision Requirements
The following requirements shall apply in the case of any proposed subdivision,
including proposals for manufactured home parks and subdivisions, any portion of
which lies within a flood hazard area:
• 1. The flood hazard area, including floodways and areas subject to high velocity
wave action, as appropriate, shall be delineated on tentative and final
subdivision plats;
• 2. Design flood elevations shall be shown on tentative and final subdivision
plats;
• 3. Residential building lots shall be provided with adequate buildable area
outside the floodway; and
12 1 Ahtanum-Wide Hollow CFHMP
• 4. The design criteria for utilities and facilities set forth in this appendix and
appropriate International Codes shall be met.
These requirements may duplicate or conflict with, or exceed (delineation of floodplain and
floodway on the final plat) applicable code enforcement and permit process codes in the
local jurisdictions.
Appendix G also contains permitting process requirements, timing, permit suspension,
appeals and records retention. Sections are included for sewers, water supply, storm water,
streets, sidewalks, manufactured homes, recreational vehicles, tanks, accessory structures,
fences, sidewalks and driveways. Some of the requirements refer back to other codes or
standards in ASCE/SEI 24-05 or the IBC.
ASCE/SEI 24-05 is referenced in this appendix primarily for engineering standards for
buildings and utilities in flood hazard areas. The non -building elements listed in Appendix
G are mentioned in Reducing Flood Losses through the International Codes, 2008:
Because Appendix G covers some development activities other than buildings and
structures, it may be most appropriately administered by a planning or zoning
office.
ASCE/SEI 24-05 provides standards for Flood Resistant Design and Construction and is
referenced in several sections of the IBC (such as 1612.4) and Appendix G, but is not
reference in the IRC. These engineering standards apply to all new and substantial
improvement in floodplains for buildings and utilities. This document classifies structures
by type of occupancy and then provides standards for elements including building
elevation, fill, and foundation and footing requirements. Specifics for materials, connectors,
flood proofing, building utilities and building access are also identified. The "Miscellaneous
Construction" section includes decks, garages, chimneys, pools and storage tanks.
In ASCE/SEI 24-05 most structures fall into Category II or III and are required to be elevated
at or above the BFE (Base Flood Elevation) + 1 foot. However, residential buildings only
need to be elevated at or above the BFE since the IRC does not refer to the ASCE/SEI 24-05
for flood elevations. If a community chose to rely on the I -Codes for compliance with the
NFIP they would need to adopt all of the I -Codes including Appendix G.).
Where non -building and non-utility elements are included in Appendix G, specific
standards are frequently not identified. For example, G401.6 requires that street and
sidewalk designs minimize the potential to increase or aggravate flood levels, but there are
no standards or thresholds listed. The identification of specific requirements or
methodology to determine compliance for these items falls back to the community to
determine.
There is no connective piece to guide how the jurisdictions integrate land use and non -
building requirements of Appendix G into their permitting processes. How the multiple
standards and permit requirements are setup and administered, and coordination between
CHAPTER 6 — PLANNING AND REGULATORY 113
different administrators, will determine whether gaps arise and how easily the permitting
process is tracked and how easily violations are identified and addressed.
Biological Opinion & NFIP
FEMA was successfully sued for NFIP non-compliance with the Endangered Species Act
(ESA) consultation process regarding floodplain development in Puget Sound communities.
The requirements were clarified in the Biological Opinion issued by the National Marine
Fisheries Service on September 22, 2008. Any actions that could affect the habitat of listed
species, or result in a "take" of a listed species is regulated by the ESA. The ESA requires
"consultation" for federal projects, which include projects which receive federal funding, or
are regulated by federal programs such as the Corps of Engineers regulatory program or
Clean Water Act programs. This requirement also applies to NFIP communities in Puget
Sound.
FEMA has developed a response to the lawsuit that includes three options that communities
may use to demonstrate ESA compliance to FEMA: adoption of a model ordinance;
enforcing the same requirements in other ordinances; or documenting compliance on a
permit by permit basis. FEMA has indicated these regulations will eventually apply to all
communities in Washington State that have applicable ESA listed species. The listed species
in Yakima County which have the greatest potential effect are Mid -Columbia Steelhead and
Bull Trout.
While the requirement to demonstrate ESA compliance for projects in or along rivers is
nothing new, the need to provide this documentation for all projects in the regulatory
floodplain is a substantial change. FEMA Procedure Memorandum 64 (August 18, 2010)
clarifying the nation-wide requirement to demonstrate ESA compliance for CLOMCs
(Conditional Letters of Map Change) is likely only the first sign of ESA -related requirements
in our area.
Washington State Floodway Regulations and the NFIP
Washington State Floodplain Management Law (RCW 86.16) has contained a prohibition of
residences in FEMA floodways since 1969 for major rivers. This was expanded to all FEMA
floodways within the State in 1989. In 1999 a Farmhouse exception was added to allow
certain substantially damaged residences in the FEMA floodway to be repaired. The State
floodway regulation prohibits residential construction and substantial improvements or
repairs that exceed 50% of market value or that increase the ground floor area, requirements
that are more stringent than NFIP minimum requirements.
The 1999 Farmhouse exception allows repairs and reconstruction if the house is located on
agricultural lands of long-term significance (RCW 36.70A.170), does not exceed total square
footage of encroachment, repairs or replaces farmhouse on same site, and must be elevated
1 foot above BFE.
There is also a non -farmhouse exception that applies only to substantially damaged
residences. The exception is triggered if a local government requests Ecology perform a
floodway assessment of a residence. The assessment is based on thresholds for flood depths,
14 1 Ahtanum-Wide Hollow CFHMP
velocities and erosion hazard. The assessment is provided to the local government which
then decides whether or not to allow rebuilding. If construction is allowed there must be no
potential site outside floodway, replacement must be of equivalent size and use, and lowest
floor must be 1 foot above BFE.
WASHINGTON STATE GROWTH MANAGEMENT ACT
The Growth Management Act (GMA) was first passed by the Washington State Legislature
in 1990, and has been amended several times. GMA has largely superseded the voluntary
preparation of Comprehensive Plans by jurisdictions under the Planning Enabling Act
(RCW 36.70) which was adopted in 1963. In the Ahtanum and Wide Hollow basins the
County and both Cities had a long history of oftentimes collaborative planning since the late
1960s, and many of the elements and initiatives in the pre-GMA comprehensive plans are
similar to current comprehensive plans.
The rationale for development of the GMA was stated as "The legislature finds that
uncoordinated and unplanned growth, together with a lack of common goals expressing the
public's interest in the conservation and the wise use of our lands, pose a threat to the
environment, sustainable economic development, and the health, safety, and high quality of
life enjoyed by residents of this state." Many elements of GMA have a strong relationship to
flood hazard reduction. GMA requires periodic assessment and update of all GMA
components, usually on a frequency of every 7-10 years, or as expressly required by the
legislature.
County -Wide Planning Policies and Urban Growth Areas
GMA prescribes a process for counties and cities to develop comprehensive plans and
regulations to implement those plans. The first step in the planning process (whether
initially developing a plan or updating a comprehensive plan) is the development of
County -wide Planning Policies. These policies are jointly agreed to by the cities and county
and improve consistency between city and county Comprehensive Plans. The central
element of these Planning policies is agreement among the jurisdictions for expansion of
Cities and the urban services they provide into what GMA terms "Urban Growth Areas"
(UGAs). The intent of UGAs is to allow the orderly development of areas adjacent to
existing cities. In relation to future flood hazard reduction the manner in which UGA's are
defined, expanded and converted to urban land uses is arguably the single most important
element of the GMA.
In recognition of this strong relationship of economic losses encountered in floodplains
GMA recently prohibited the expansion of UGAs into designated floodplains in Counties
west of the Cascade Crest, unless certain conditions are met. These conditions may be
applied in future to Yakima County and only allow expansion of the UGA into floodplains
only where:
1. Urban growth areas are fully contained within a floodplain and lack adjacent
buildable areas outside the floodplain; or
CHAPTER 6 - PLANNING AND REGULATORY 115
2. Urban growth areas where expansions are precluded outside floodplains because:
(A) Urban governmental services cannot be physically provided to serve areas
outside the floodplain; or
(B) Expansions outside the floodplain would require a river or estuary crossing to
access the expansion; or
3. Urban growth area expansions where:
(A) Public facilities already exist within the floodplain and the expansion of an
existing public facility is only possible on the land to be included in the urban growth
area and located within the floodplain; or
(B) Urban development already exists within a floodplain as of July 26, 2009, and is
adjacent to, but outside of, the urban growth area, and the expansion of the urban
growth area is necessary to include such urban development within the urban growth
area; or
(C) The land is owned by a jurisdiction planning under this chapter or the rights to
the development of the land have been permanently extinguished, and the following
criteria are met:
(I) The permissible use of the land is limited to one of the following: Outdoor
recreation; environmentally beneficial projects, including but not limited to habitat
enhancement or environmental restoration; storm water facilities; flood control
facilities; or underground conveyances; and
(II) The development and use of such facilities or projects will not decrease flood
storage, increase storm water runoff, discharge pollutants to fresh or salt waters
during normal operations or floods, or increase hazards to people and property.
Yakima County is the most flood -prone County east of the Cascades and may eventually be
subject to this ruling, although such potential losses should be considered in current
planning.
The Yakima County Planning Policies do not contain similar language or standards for
UGA expansion in floodplains. UGA expansion in floodplains may indeed be necessary in
some cases, usually where a city lies adjacent to a river and has limited options for
expansions outside the floodplain.
If UGA expansion into a floodplain was not allowed, "islands" of county jurisdiction would
develop which would preclude provisions of urban services, most notably police and fire
protection by a city, in those "islands". As discussed in the end of Chapter 5, expansions of
a UGA, or annexations of designated floodplains can increase flood hazard (increased
development density or uses incompatible with floodplains) if the city does not have
Comprehensive Plan land use designations or zoning districts that will retain low density
development in these floodplain areas.
Development of Comprehensive Plans
GMA Comprehensive Land Use Management Plans for Cities and Counties must contain
the following elements: land use, housing, capital facilities, utilities, rural element,
transportation, economic development, and a park and recreation element. Jurisdictions
16 1 Ahtanum-Wide Hollow CFHMP
may include additional optional elements, items or studies dealing with other subjects
related to physical development within the jurisdiction.
The land use element lays out the location of the broad categories of urban, rural and
resources (agriculture, forestry and mining) lands and compatible uses. This element also
recognizes areas of urban density that preceded the passage of GMA. In the Ahtanum and
Wide Hollow watersheds these areas include the towns of Ahtanum and Wiley City which
lie in Yakima County jurisdiction. The housing element seeks to provide appropriate mixes
of residential types (low income, multi -family, single-family, etc). The capital facilities,
utilities, and transportation elements forecast needed schools, utilities and utility corridors,
roads and highways, and other infrastructure, and the capital facilities element specifically
addresses the coordinated development and management of infrastructure over time to
meet the overall goals of the plan. The rural element guides the mix of uses and facilities
that allow economic development but maintain the rural character (i.e. low levels of urban
services and development density) of areas of the County. The Parks and Recreation
element examines the current levels of recreational facilities, the future demand for such
facilities, and recommends policies or actions to meet demand.
Each of these elements has a relationship to flood hazards. The strongest relationship to
flood hazard reduction is in the land use element which guides land use in floodplains. The
capital facilities elements which control development of public facilities that serve or more
often, cross floodplains have a large impact on access issues for public safety and on
infrastructure damages and income losses incurred during flood events. For example, road
closures during a flood event can cause large economic disruptions such as when Interstate
82 was damaged during the 1996 flood, causing an estimated $2.6 million daily impact on
the statewide economy for each day of reduced traffic flow. In the Ahtanum and Wide
Hollow watersheds, severe economic damage was inflicted in 1996 and 1974 due to road
closures during and after the flood, even though direct damage to economic facilities such
as factories, food processing facilities, government buildings was minor or negligible.
The Parks and Recreation element also has a strong relationship due to many recreational
facilities also serving as open space, flood water storage areas, or simply being located along
existing waterways. The Comprehensive Plan is essentially the implementing regulation for
the Parks and Recreation Element since there are no dedicated funding or implementation
sources for acquisition and management of open space or park lands. Private organizations
such as land trusts, trail and water recreation clubs or organizations can provide some
structure or capacity for open space and Parks acquisition, but the Comprehensive Plans of
both the City of Yakima and Yakima County recognize that acquiring and maintaining these
types of facilities or features on the landscape is has historically been very difficult and
remains so today.
An optional Natural Hazard Reduction element, as described by CFHMPs and by other
hazard identification plans, can be added as described in the "Optional Comprehensive Plan
Element for Natural Hazard Reduction", Washington State, June 1999. This is particularly
useful in hazardous or flood -prone areas, such as these two basins. Generic natural hazard
reduction goals from this report are provided in Table 1-1. None of the jurisdictions in the
CHAPTER 6 — PLANNING AND REGULATORY 117
Ahtanum and Wide Hollow watersheds currently include a Natural Hazard Reduction
element in their comprehensive plans, although this option is available.
The June 1999 Natural Hazard Reduction document also indicates further comprehensive
plan connections and opportunities:
• Page 3-19: [referring to CFHMPs] "The overlap and possible coordination of such a
document and the flood hazard portions of a Natural Hazards Reduction Element are
obvious. In addition, the community and property owners may reap benefits under the
community rating system. Typically local hazard mitigation plans contain more specific
language than the comprehensive plan, but the comprehensive plan is an excellent
vehicle for bridging the gap between general policies and the on -the -ground
implementation of the FCAAP plan. The flood hazard management plans may address
flood hazards through a variety of techniques, including:
o Non-structural flood damage reduction techniques, such as wetland restoration;
o Prioritized home acquisition and structural elevations; and
o Land use controls which prohibit or condition development in flood -prone
areas.
11
• Page 4-2: [referring to Chapter 4] "This chapter describes some methods that can be used
to examine and revise comprehensive plan policies, with a new focus on addressing
hazard concerns within the plan, while respecting its existing character."
Planning Considerations for NFIP communities are listed in Table 6-4. The City of Yakima's
Comprehensive Plan 2025 contains policy goals specific to flood hazard reduction and
floodplains. These include:
10.9.1 Protect natural drainage system associated with floodways and floodplains.
10.9.2 Ensure that new development will not affect the flood elevations in surrounding
areas.
10.9.3 Ensure adequate protection of life and property from flood events.
10.9.4 Limit development located within the 100 -year floodplain unless it is possible to
mitigate and restrict development within the floodway.
10.9.5 Emphasize non-structural methods in planning for flood prevention and damage
reduction.
10.9.6 Encourage compliance with stormwater regulations for onsite retention of
stormwater.
10.9.7 Preserve natural drainage courses.
10.9.8 Minimize adverse storm water impacts generated by the removal of vegetation and
alteration of landforms.
10.9.9 Minimize the extent of parking lots and impervious surfaces near or along river and
stream corridors.
10.9.10 Encourage new development to adopt best management practices such as reduction
of impervious surfaces and provisions for filtering pollutants.
10.9.11 Encourage and support the retention of natural open spaces or land uses that
maintain hydrologic function and are at low risk to property damage from
floodwaters within frequently flooded areas."
18 1 Ahtanum-Wide Hollow CFHMP
Washington State law RCW 86.12.200 establishes minimum requirements for a CFHMP and
also mentions an optional connection to county comprehensive plans: "When a county plans
under chapter 36.70A RCW, it may incorporate the portion of its comprehensive flood
control management plan relating to land use restrictions in its comprehensive plan and
development regulations adopted pursuant to chapter 36.70A RCW." None of the
jurisdictions in Yakima County with adopted CFHMPs have utilized this option to date.
Once a Comprehensive Plan is created or updated, implementing regulations for the plan
are formulated. Each jurisdiction will develop a:
• Zoning Code — these regulations define specific areas and land uses that are
preferred within them. Zoning has a strong influence on flood hazard through
controlling development density, levels of service for capital facilities, and in some
cases, special zones or overlay zones where floodplains exist in the jurisdiction. As
mentioned above, city zoning codes may or may not contain zoning districts which
are dedicated for low intensity uses such as open space or agriculture. Thus when
areas of floodplain are annexed they may receive a zoning designation that allows
for inappropriate amounts of development density or use in high hazard
floodplains.
• Subdivision Code — These regulations define standards (size, dimensions, road and
road access) for creation of new building lots in the jurisdiction. Some jurisdictions
have specific requirements for new lots in the floodplain relating to size, road access,
depiction of floodplains on the plat etc.
• Critical Areas Code — GMA requires that each jurisdiction develop regulations to
protect critical areas and the functions (habitat, clean water, open space) that critical
areas provide to the citizens of the state. Critical Areas include: fish and wildlife
habitats (streams, migration corridors and habitat for specific species); geologically
hazardous areas (steep slopes, landslide hazard, earthquake hazard, erosion hazard);
critical aquifer recharge areas; A goal of GMA is to have these regulations consistent
or concurrent with regulations developed under the Shoreline Management Act
(SMA), often jurisdictions will have a combined code that implements SMA and
GMA.
A significant issue in Ahtanum and Wide Hollow Creeks and in Yakima County in general,
is the management or regulation of the spectrum of channels that exist in the County and
Cities. These range from entirely man made irrigation and drainage systems with convey
only irrigation or drain water; to similar systems which convey some natural flow; to highly
modified natural channels that convey irrigation, drain water, and natural flow; to natural
channels which convey irrigation, irrigation return flows, drain water, and natural flows.
This mix of natural and artificial channels, and natural and artificial flows, results in
modified drainage characteristics which can increase or decrease the conveyance of flood
waters, route floodwaters to areas that would otherwise not receive flood waters, or in a few
cases, prevent floodwaters from being routed through the natural drainage system.
CHAPTER 6 - PLANNING AND REGULATORY 119
Many of these channels, especially Wide Hollow Creek, Bachelor and Hatton Creeks, were
maintained as irrigation systems for many decades, and with the advent of new
environmental laws, this maintenance has ceased. With the cessation of maintenance, these
channels have generally become less efficient in conveyance of floodwater than they were
when maintained or less efficient than natural drainage systems due to invasive weeds or
their relocation to high points on the landscape to facilitate irrigation of bottomlands. The
Critical Areas and State Hydraulic Code regulations discourage regular maintenance of
channels which support fish life, which is normally an appropriate approach for natural
channels. But where streams have been relocated or have flow patterns that facilitate the
establishment of non-native species, some type of long-term and thoughtful maintenance
program is probably appropriate, especially in circumstances where adjacent development
has fixed the location of the channel in place, or will in the near future. Development of a
program for management of these systems that is consistent with the goals of the Critical
Areas provisions and case law related to GMA and the Hydraulic Code is a significant
regulatory hurdle to cross.
Yakima Urban Area Comprehensive Plan
This regional planning effort pre -dated GMA regulations and applied to the urban Yakima
area, including some unincorporated county, and the cities of Yakima and Union Gap. The
plan was initiated to allow funding assistance for the Yakima Regional Wastewater
Treatment Facility. Though Union Gap provided a representative to participate in the
process, they did not adopt the final Comprehensive Plan.
One goal of the Yakima Urban Area Comprehensive Plan was to establish zoning in the
urbanizing portion of the unincorporated County that would be compatible with eventual
annexation into the cities. The Yakima UAZO (Urban Area Zoning Ordinance) was
developed which applies within the City of Yakima and unincorporated Yakima County
including the Terrace Heights Sewer District and other urban areas around Yakima and
Union Gap. Even though Union Gap does not participate in the Yakima Urban Area
Comprehensive Plan, a remnant of the Yakima UAZO exists in the Union Gap UGA since
the UAZO boundary was created when it was anticipated that Union Gap would also adopt
the Comprehensive Plan. Zoning within the City of Union Gap has no connection to the
UAZO.
In 2009 Yakima County withdrew from the Regional Planning Agreement with the City of
Yakima. The unincorporated Yakima County and City of Yakima UAZO's are both still in
effect at the time of this CFHMP, but they are being updated and modified independently
by each jurisdiction. It is currently unknown whether Yakima County will continue the
UAZO as a separate ordinance from the rest of the County's zoning into the future.
In the current post -Regional Planning Agreement setting, the urban emphasis for Yakima
County and the City of Yakima is to review and update the existing Interlocal Planning
Agreements through the Intergovernmental Committee. The Intergovernmental Committee
is composed of elected officials from both jurisdictions.
20 1 Ahtanum-Wide Hollow CFHMP
LOCAL FLOOD HAZARD REDUCTION ADMINISTRATION TOOLS
While the GMA process has a large influence on local development patterns and individual
developments, other laws that pre-existed GMA also have a large influence on land use and
on how local regulations are administered. The Planning Enabling Act was passed by the
legislature in 1963, which means that jurisdictions in this watershed already had a planning
department and planning commission prior to GMA. Beginning in the 1970s, these planning
departments also were charged with implementation of new environmental laws such as the
State Environmental Policy Act (SEPA) in 1971, the Shoreline Management Act (SMA) in
1973, both these laws required the designation of a responsible official, usually the planning
or development director. "Building permits" issued by cities or counties prior to the mid -
1970's were a means of tax assessments on new structures, ensuring conformance with local
nuisance laws, and ensuring that buildings were located on a legal lot. In the mid 1970s, all
the local jurisdictions began to participate in the National Flood Insurance Program and
developed a floodplain ordinance, and also had a formal zoning code, which also
necessitated the issuance of building permits pursuant to a Building Code. These laws also
required the designation of a responsible official, initially the County or City Engineer, or
later Building Official to implement the building codes.
The above four pre-GMA laws - SEPA, Shorelines, UAZO, Floodplain Code and Building
Code - still have a strong influence on flood hazard reduction. In Yakima County and the
City of Yakima, SEPA, Shorelines, UAZO, Floodplain and Building Code were implemented
by the Planning Departments prior to GMA, and Building Code and Floodplain Code were
administered by Building Departments. In Union Gap, due to its relatively small size, all of
these regulations were and remain administered by a single department. The UAZO
described above is administered by Planning Departments in the City of Yakima and
Yakima County.
SEPA - The State Environmental Policy Act requires the state and each local government to:
• "Utilize a systematic, interdisciplinary approach which will insure the integrated use
of the natural and social sciences and the environmental design arts in planning and
in decision making which may have an impact on man's environment;" and
• Ensure that "...environmental amenities and values will be given appropriate
consideration in decision making along with economic and technical
considerations...."
The environmental review process in SEPA is designed to work with other regulations to
provide a comprehensive review of a proposal. Most regulations focus on particular aspects
of a proposal, while SEPA requires the identification and evaluation of probable impacts for
all elements of the environment. Flooding and flood hazard is an environmental element
that can be examined in the SEPA process, especially where conditions of a site or region are
unique or specific, such as the unusual topography and flood paths that occur in the
Ahtanum and Wide Hollow Basins. Each jurisdiction has its own SEPA ordinance and
CHAPTER 6 — PLANNING AND REGULATORY 121
policy, and similar to Shoreline Management above, the state and local jurisdictions have
endeavored to integrate SEPA and GMA regulatory environment.
Local Administration of Flood Hazard Reduction
Prior to GMA, the Floodplain Codes of the jurisdictions were designed to set standards for
building construction in the floodplain and include planning considerations listed in table 6-
4 to meet standards for inclusion in NFIP. Over time, the Building codes were updated and
became increasingly specific in regards to the actual materials, standards, and engineering
data needed to meet the minimum requirements of the National Flood Insurance Program,
not only for the construction of buildings but also for site design to insure that there would
be limited off site flood impacts. When GMA was enacted, the Act required regulations for
the protection of Frequently Flooded Areas. These regulations largely replaced prior
floodplain codes, but often these codes did not fit the structure of separate planning and
building departments which had developed prior to GMA. In many cases, the responsible
official for floodplain management shifted from the building official to the designated
planning official, or as is the case in Yakima and Yakima County, the frequently flooded
area regulations are the only portion of GMA regulations where the Building Official is the
responsible official for the majority of the regulations. This segregation of responsibility
between differing officials and departments can lead to inconsistencies in the processing of
floodplain development permits. For smaller jurisdictions such as Union Gap, there is no
segregation of responsibility, and administration of the various floodplain codes should be
more straightforward.
Each jurisdiction also has a separate permit process code, which are applicable to planning
permits (rezones, conditional use, subdivisions, etc.) that also include Critical Area -related
permits. Critical Area Permits, in turn, normally include standards for frequently flooded
areas and reference building codes, which have their own permit processing requirements
within the adopted Building Codes. This creates a conflict in processing and responsible
decision makers, appeal processes, notice, etc. For example, a developer may propose a
land division within the floodplain to the planning department, the planning department
reviews the land division for consistency with zoning, subdivision, and Critical Areas
regulations, which can be approved in most cases without detailed engineering drawings
for quantities of fill, road elevations, building envelopes or building standards, especially
for small developments. Then either the developer or subsequent purchaser goes to build
access roads, bridges or buildings on the property and the standards for these features in
either Appendix G or Appendix J are applied to the subject property or properties by the
Building Official through the International Codes, which may alter or prevent the layout of
infrastructure or buildings as shown in the original plat. This then would require
amendment or alteration of the plat, and associated delays and costs.
Jurisdictions may choose in their permit administration codes or other codes to raise the
level of administrative review — requiring greater levels of public and agency notice,
removing exemptions from SEPA or Critical Areas Ordinances, requiring a higher level
decision maker to finalize a development proposal — in an effort to better coordinate these
multiple development standards in the jurisdictions own ordinances and other relevant
22 1 Ahtanum-Wide Hollow CFHMP
regulations such as the Washington State Hydraulic Code or Department of Ecology
regulations.
Jurisdictions may also choose among several options for enforcement of their codes which
relate to development in floodplains or stormwater management. Ordinances specific to
enforcement can be found within a standalone floodplain development ordinance; or a
separate enforcement ordinance for all ordinances in the jurisdiction; in the critical areas
code; or in the building code ordinance.
Flood Hazard Management Regulatory Tools Administered by Yakima County
The County has developed a Comprehensive Plan, Plan 2015, which implements many
surface water related goals and policies primarily through the administration of the County
Codes including the Critical Areas Ordinance (CAO) (YCC Title 16C and 16A), the Shoreline
Master Program (SMP) ( YCC Title 16D), the Zoning Ordinances (YCC Titles 15 and 15A)
and Subdivision Code (YCC Title 14). The CAO was updated in 2009 and the SMP was
updated in 2010. Regulations and programs affecting flood hazard management,
requirements for participation in the NFIP, are integrated into both the Critical Areas
Ordinance and the Shoreline Master Program. These minimum standards and regulations
for development in Flood Hazard Areas are administered by the Building Official, while
stream corridors, along with their associated floodplains and floodways are regulated as
critical areas by the same ordinances, and are administered by the Planning Official.
• Section 16C.03.12 table 3-1 requires a Flood Hazard Permit for activities
within floodplains "It is different in that it has special administrative
provisions, and may include many of the specific permit types noted above
within it, which are described in Chapters 16C.05.20 through 16C.05.72. It is
focused mainly on construction methods, but may include site design to
minimize impacts to adjacent properties or resources, or to locate the
proposed development in areas where depth and velocity of floodwaters
during the base flood do not exceed the current standards for construction of
human occupied structures or safe access." At this it is the specific permit
types noted above are used instead of a flood hazard permit.
• Yakima County Building Code—is currently using the International
Building and Residential Building Codes and Appendices G and J plus
related ASCE standards. County ordinances do not currently contain a
requirement for residential elevations above the minimum established by the
NFIP and State of Washington, of at or above the BFE. However, the County
interpretation of this minimum level is the support level for the floor joist in
order to match requirements in the I -code for services required, so that it
effectively results in the floor surface location at approximately one foot
above BFE.
• Yakima County Critical Areas Ordinance—Relevant portions of the CAO to
flood hazard reduction are — "Structures within 100 feet of the floodway, or
the ordinary high water mark if no floodway has been established, shall be
elevated to a height equal to or greater than the base flood elevation using
zero -rise methods such as piers, posts, columns, or other methods, unless it
CHAPTER 6 - PLANNING AND REGULATORY 123
can be demonstrated that nonzero -rise construction methods will not impede
the movement of floodwater or displace a significant volume of water." In
addition, portions of the Frequently Flooded Areas regulations require
location of utilities, roadways and other structures outside of the "zone of
maximum channel migration". These standards exceed the minimum NFIP
standards and can significantly reduce flood hazards. Regarding
subdivisions, the most recent CAO update applies a one acre minimum lot
size for subdivisions entirely within the floodplain. The update also requires
new lots partially within the floodplain provide a usable building envelope
outside the floodplain.
• Yakima County Shoreline Master Program— Implements the policies of the
Washington's Shoreline Management Act at the local level, regulating land
use and development of shorelines. The Yakima County SMP includes
policies and a regulation based on state laws and rules, but is tailored to
Yakima County's unique landscape. "Shorelines" are the larger rivers and
lakes along with their associated shorelands, wetlands, and floodplains. The
extent of shoreline jurisdiction in Yakima County is intrinsically tied to
FEMA's established floodway and floodplain. The County's Shoreline Master
Program has also been adopted by the Cities. A major component of the
Master Program is the designation of Shoreline Environments (Urban, Rural,
Conservancy, Natural) and a Floodway/Channel Migration Zone
Environment. The Floodway/Channel Migration Zone regulates uses to
maintain floodplain function in this zone.
• Yakima County Zoning Ordinance—Both the Yakima County Urban Areas
Zoning Ordinance (UAZO) and the Yakima County Zoning Ordinance
implement land use recommendations from the comprehensive plan for
areas within the unincorporated County. The zoning ordinances establish
allowable uses in different zones. The UAZO contains a floodplain overlay
zone that reinforces floodplain development requirements and requires a
minimum Type 2 review. Since this overlay zone is limited to the urban area,
it means Type 2 reviews are not automatic outside the UAZO. Type 2 reviews
include greater public and affected agency notice, and increase the ability of
the Planning Department to condition development on the site to address
concerns. The requirement for one acre minimum lot size for residential
subdivisions in the UAZO was incorporated into the most recent CAO
update; however the CAO applies to all zones.
• County Open Space Tax Program—Defines floodplains as a high-priority
open space resource. The Tax Program reclassifies land as open space through
the approval of the Planning Commission and County Commission. Once
reclassified, assessed value of the property usually falls, based on realistic use
and results in reduced property taxes to the landowner.
24 1 Ahtanum-Wide Hollow CFHMP
Code Enforcement
Yakima County has a code enforcement officer under the Building Official. This officer has
authority over a broad range of ordinances for both the building and planning department.
Ordinances to vest this authority under the Building Official are found in the Building Code
Amendments, the Zoning Code, and Critical Areas Code.
Currently, each of the cities in the planning area has its own environmental regulations.
These environmental regulations are briefly outlined below.
Flood Hazard Management Regulatory Tools Administered by City of Yakima
The City of Yakima has floodplain development and protection standards in the Zoning
Code, which also contains the Critical Areas Code, in their adopted Building Codes, and in
their Building Code Ordinance which has a chapter on Flood Damage Prevention.
Yakima Urban Area Zoning Ordinance
Section 15.27.309 table 27.3-1 of the requires a Flood Hazard Permit for activities
within floodplains "It may include many of the specific permit types noted above,
which are described in Part Four, YMC 15.27.400 through 15.27.436. It is focused
mainly on construction methods, but may include site design to minimize impacts to
adjacent properties or resources, or to locate the proposed development in areas
where depth and velocity of floodwaters during the base flood do not exceed the
current standards for construction of human -occupied structures or safe access." At
present the Flood Hazard permit is issued through the Critical Area Code, which is a
chapter of the zoning ordinance.
• The UAZO contains a floodplain overlay district that reinforces floodplain
development requirements and requires a minimum Type 2 review.
• Minimum lot size in the Floodplain overlay zone -where the underlying zone
is residential -is one acre, unless there is buildable area on the lot outside the
floodplain. A similar requirement was incorporated into the most recent CAO
update, see below.
• UAZO does not contain an open space, Ag, or other low intensity non-
residential zoning designation.
Critical Areas Ordinance
Chapter 15.17 of the City of Yakima Code describes the City's Critical Areas Ordinance. This
ordinance is similar to Yakima County's above and contains the standards for the City of
Yakima's Compliance with the NFIP. The most recent CAO update applies a one acre
minimum lot size for subdivisions entirely within the floodplain. The update also requires
new lots partially within the floodplain provide a usable building envelope outside the
floodplain. Both of these updates apply to all zones.
CHAPTER 6 - PLANNING AND REGULATORY 125
Building Code
The building Code is separate from both the Critical Areas and Zoning Codes.
The City of Yakima has adopted the IBC and Appendices G and J, as well as the IRC.
The City of Yakima required elevation of residential structures at or above the BFE + 1 foot
in both their building and Critical Areas Code, until their Critical Areas ordinance was
updated in 2008. At that time Yakima reduced the elevation requirement in their Critical
Areas Code for residences to at or above the BFE, but did not modify the standard in their
building codes, which still apply.
Code Enforcement
The City of Yakima has a code compliance division under the Building Official. This
division has authority over a broad range of ordinances for both the building and planning
department. Ordinances to vest this authority under the Code Compliance Division are
found in the Building Code and the Zoning Code (which includes the Critical Areas Code).
Flood Hazard Management Regulatory Tools Administered by City of Union Gap
Section 14.28.080 requires a development permit before construction or development
begins within any area of special flood hazard. This is not a specific flood hazard
permit. This permit is a Type I level review, the lowest level of review.
Critical Areas Ordinance and Zoning Code
The Union Gap critical areas development regulations provide limitations on the
development of: geologically hazardous areas, wetlands, and stream corridors (UGC 17.19).
In the Critical Areas Regulations and the Zoning Code for Union Gap the decision maker
(Development Administrator or Hearing Examiner For major projects) has a specific
authority to condition project by reducing their scope, scale or intensity where they impact
critical areas such as frequently flooded areas. Union Gap is the only jurisdiction which
provides this type of conditioning authority.
The Union Gap Zoning Code and Comprehensive Plan do have open space zoning
designations, and significant areas of Union Gap along stream corridors are zoned as
Parks/open space.
Building Code
The City of Union Gap has adopted the IBC as well as the IRC but has not adopted
Appendices G (floodplain construction standards) or J (grading). The current floodplain
ordinance has not been modified to reflect the requirement for non-residential structures of
a minimum floor elevation one foot above the BFE, as required by the IBC.
Code Enforcement
Union Gap has a code enforcement officer under the Planning and Building Administrator.
This Administrator has authority over all building and planning department regulations.
26 1 Ahtanum-Wide Hollow CFHMP
Ordinances to vest this authority under the Building Official are found in the Union Gap
Building Code.
Yakama Nation
Bureau of Indian Affairs oversight for Trust Lands
Tribal lands are owned by the Yakama Nation, but held in trust by the United States on
behalf of the Nation. When projects need to be done on tribal lands, the Yakama Nation
regulates water quality and hydraulic approval, and the arrangement for any easements
needed would be under responsibility of the Bureau of Indian Affairs (BIA).
Flood Hazard Management Regulatory Tools Administered by Yakama Nation
The Yakama Nation has adopted zoning regulations in order to "encourage the most
appropriate use of the land; to protect the social and economic stability of residential,
agricultural, commercial, industrial, forest, reserved, and other areas within the
reservation, and to assure orderly development of such areas, and; to obviate the
menace to public safety resulting from the improper location of buildings and the uses
with existing and proposed traffic movement on said highways; and to otherwise
promote public health, safety, morals and general welfare..." (Amended Zoning
Regulations of the Yakama Nation). These regulations help to reduce flood hazard by
controlling where and how land can be developed.
The Nation does not have a Flood Hazard ordinance at this time. As noted above the
Nation has adopted the International Building Codes and Appendices, with an
automatic update. The Yakama Nation requires residential floor elevations at or above
the BFE, as per the IRC code.
Implementation of the Yakama Nation zoning regulations is done through their Zoning
Administration Department.
Yakama Nation Hydraulic Code/Water Code
Implementation of the Yakama Nation hydraulic and water codes is through their office of
Water Code Administration.
SUMMARY
Regulations that impact or control development in floodplains and other areas of
flood hazard are found in many different sections of state and local codes. For local
jurisdictions, the structure of development regulations may be different in each
jurisdiction due to the different size, development patterns and types, and history of
those governmental units. As a result of this diversity of permits, regulations,
application and administrators the level of review varies by jurisdiction.
Ensuring that all regulations are applied in a consistent manner within and across
jurisdictions, and improving or reducing permit decision timelines is a difficult task
which will require changes to both the codes themselves and the mechanisms for
code administration.
CHAPTER 6 — PLANNING AND REGULATORY 127
Consolidation of all the requirements for development in the floodplain into a single
floodplain development permit checklist of separate floodplain permit - as opposed to
issuance of a (building, zoning, shorelines, etc.) permit(s) or decision, or application form
could greatly increase the consistency of the application of all relevant and necessary
floodplain development standards, and also reduce permit time and duplication of effort.
The current method in adopted Yakima County CFHMPs for implementing regulatory
recommendations has been to coordinate recommendations with required updates of
comprehensive plans, ordinances, or CAO -SMP requirements. Requested changes to
regulations may also be submitted or requested outside the required update schedule. The
anticipated process for recommended changes is:
1. jurisdiction initiates -or FCZD proposes -one or more regulatory recommendation be
considered;
2. jurisdiction considers recommendation(s); and,
3. jurisdiction decides to implement the recommendation(s); or,
4. jurisdiction decides to implement the amended recommendation(s); or
5. jurisdiction decides not to implement the recommendation(s).
Process numbers 4 and 5 should require adequate documentation of the consideration
process, results and rationale for any modification or rejection of the recommendation(s).
Yakima County recently changed the comprehensive plan amendment schedule to accept
applications biannually rather than yearly. The next required GMA compliance review and
revision (if needed) of Yakima County Comprehensive Plan 2015 is on or before December
1, 2016, and thereafter every seven years (Yakima County cities have the same schedule for
the required updates). The schedule for County GMA component updates is:
• Urban Area Boundary amendments will be considered every five years (maximum is
every ten years); and,
• CAO and SMP regulations must be updated every seven years (next is 12-1-13).
NPDES Phase II Municipal Stormwater Permits
Clean Water Act and National Pollution Discharge Elimination System
In Washington State, the Department of Ecology has been delegated by EPA to determine
appropriate water quality standards. The surface water quality standards are intended to
protect the beneficial uses of waters of the state, such as swimming, fishing, aquatic life
habitat, and agricultural, industrial, municipal and domestic water supplies using numeric
criteria. State standards must be at least as protective of beneficial uses as federal standards.
The standards specify how criteria are to be implemented and contain policies to protect
degradation of high quality waters
As part of the Clean Water Act in 1972, Congress enacted the National Pollutant Discharge
Elimination System (NPDES). The NPDES requires a permit for all discharges into the water
via a discrete conveyance called a point source. The act also permitted the states to
administer this act which was begun by the Department of Ecology in 1973. The permit
28 1 Ahtanum-Wide Hollow CFHMP
describes what the discharger must do to protect the receiving water, what types of
monitoring and reporting the discharger must perform, and limits the pollutants that can be
discharged. Point sources originally included wastewater treatment plants and industrial
process waters, but have expanded through time to include stormwater runoff from
construction sites, municipal storm sewers, and industrial sites.
In March of 2003, the County and the cities of Yakima, Union Gap, each individually
submitted a notice of intent to apply for federal coverage under the NPDES Phase II
municipal stormwater permit. The final permit was issued by Ecology in 2007. These
permits may add additional Best Management Practices (BMPs) or maintenance
requirements above current standards. The County and the cities of Yakima, Union Gap,
and Sunnyside are co -permittees under a regional stormwater NPDES permit. The permit
requires development of ordinances for illicit discharge, construction stormwater and post
construction stormwater controls. The communities have adopted Stormwater ordinances
compliant with Federal and State regulations on February 16, 2010.
Project Permitting Requirements
The permit requirements for the regulatory programs summarized in Tables 6-1 and 6-2
depend on project nature and location. In many cases more than one permit is required.
Table 6-5 shows permits required for projects of various types and in various locations in
the County.
Permit requirements for locations in the cities would include similar items for their
jurisdiction. The Yakama Nation includes compliance with their hydraulic and water codes.
At least five permits are typically required for in -stream, shoreline, floodplain, and river
engineering projects. The table also indicates that State Environmental Policy Act (SEPA)
review is generally required for all the listed types of projects. SEPA review may consist of
completing a checklist or an environmental impact statement (EIS) if the project is expected
to have significant impact.
Many permit requirements depend on the project location in relation to the stream,
shoreline jurisdiction, and floodplain boundary. Only work in and adjacent to the streams
would require a COE 404 permit.
Figure 6-6 illustrates permit timing relationships. Some permits are issued following
acquisition of other permits. The WSDOT right-of-way permit process, required whenever
work is proposed within a state right-of-way, is listed first because it can have the longest
processing time. The COE and Shorelines permit processes require procurement of most
other required permits and approvals before issuance. SEPA compliance may be
accomplished by preparing an environmental checklist, but if an EIS is found to be
necessary, this can substantially delay procurement of all permits that require completion of
the SEPA process.
The Hydraulic Project Approval (HPA) application can be submitted before the SEPA
process is finished, but it will not be issued until SEPA review has been completed. Ecology
will not issue the Water Quality Modification/Certification until the HPA has been issued.
CHAPTER 6 — PLANNING AND REGULATORY 129
The grading and filling permit requires SEPA compliance prior to issuance. Individual
processing times may require up to two months for these permits.
30 1 Ahtanum-Wide Hollow CFHMP
TABLE 6-5.
COUNTY PERMIT REQUIREMENTS FOR FLOOD CONTROL WORK
Project Location
Type of Work
In-
Stream
Work
Shoreline
Work
Floodplain
Work
Outside
Floodplain
Structural
Flood
Control
Nonstructural
Using
Existing
Regulation
Nonstructural
Using
Modified
Regulations
DOT ROW Permit (for
work in State right-of-
way)
Washington Department
of Transportation
X
X
X
COE 404/10 and ESA
consultation
U.S. Army Corps of
Engineers
X
X
X
X
X
Shoreline Substantial
Development
Yakima County
X
X
X
X
Hydraulic Project
Approval (HPA)
Washington Department
of Wildlife
X
X
X
X
SEPA Review
Yakima County
X
X
X
X
X
X
X
Water Quality
Modification/
Certification
Washington Department
of Ecology
X
X
X
X
COE 401 (Water Quality
Certification)
Washington Department
of Ecology
X
X
X
X
Critical Areas Standard
Development
Yakima County
X
X
X
X
X
CHAPTER 6 — PLANNING AND REGULATORY 131
Months
Permits/Approvals
1 2 3 4 5
6
7
DOT Right -of -Way Permit
Washington Department of
Transportation
Up to 18,
months
Corps 404110*
U.S. Army COE
,
Shoreline Substantial Development*
111111111'County
Hydraulic Project Approval
Washington Department of
Wildlife
11111110, Issued up to 30 days following
SEPA compliance
SEPA Review
Checklist SEPA EIS
County
(If EIS is required, SEPA Compliance
Compliance would be delayed accordingly)
F
Water Quality Mod./Cert.
Issued up to
30 days
Washington Department of Ecology
g p gY
following HPA
Compliance
Grading & Filling
County
Prior SEPA compliance
, required before approval
*These are "umbrella" permit processes that require procurement of all other permits before they can be issued.
Yakima County
AHTANUM-WIDE HOLLOW WATERSHED CFHMP
FIGURE 6-6
TYPICAL PERMIT TIMING REQUIREMENTS
32 1 Ahtanum-Wide Hollow CFHMP
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CHAPTER 7
BASIN FLOODING CHARACTERISTICS
INTRODUCTION
Historical flood -related information was gathered for this section on flood generating
mechanisms and routing of floods within the basin.
FLOOD PEAKS
The flooding characteristics of Ahtanum and Wide Hollow basins are a function of the
topography of the basin as a whole, meteorologic characteristics (rainfall and temperature),
and characteristics of the channels and floodplains in the watershed. With the relative
absence of Wide Hollow peak gage data it's runoff peaks are inferred from similarities and
differences from the Ahtanum basin characteristics, including vegetation, plus resident
anecdotes. The Wide Hollow reports indicate less frequent floods than Ahtanum with
slightly different timing, as discussed below.
Investigation of longer term gages on the Yakima, Naches and Ahtanum rivers in Figure 7-1
reveals that the eleven largest recorded floods in Yakima Basin were, in order of magnitude:
1933, 1906, 1996, 1917, 1896, 1974, 1948, 1904, 1977, 1980, and 1990. Except for 1948, these
floods were winter rain on snow storms. The peak floods of record on the Ahtanum basin,
namely 1974, 1996, 1977, 1995, 1910, 1948 and 1933, were also experienced on the Yakima
basin, even though the Ahtanum basin is small in comparison. A more extensive recorded
peaks comparison is prevented by gaps in the Ahtanum gage data record.
In addition, the time to peak in the Ahtanum basin is in the order of several days and occurs
about the same time as the Naches river gages which have very large drainage areas, so the
gage data indicates a snowmelt dominated hydrograph on Ahtanum Creek for peak events.
The runoff hydrographs for the small size Ahtanum basin show similar long drawn out
peaks and this is attributed to the basin shape and presence of snow in the higher rainfall
western end.
Of particular interest is that most of the top ten floods on the upstream North Fork gage are
snowmelt flood events in the late spring months, which differs from all the other Yakima
basin gages listed in Figure 7-1, even though they come from larger contributing areas. This
infers less penetration of rain into the Ahtanum basin. This is significant in that the North
and South Forks of the Ahtanum contribute most of the Ahtanum peak flows.
Unfortunately, the gage near the mouth of Ahtanum was not in operation during the four
largest of these snowmelt events: 1948, 1951, 1956 and 1916.
1
2 Ahtanum-Wide Hollow CFHMP
Figure 7-1 Yakima Basin Peak Floods of Record
Yakima River at Kiona
Date of
Event
Flow
(cfs)
(USGS)
Area (sq mi)
5615
Dec -23-1933
67,000
Period of Re-
cord
1878-1914,
1933-2007
Nov -17-1906
66,000
Feb -11-1996
49,400
27,800
Jan -18-1974
39,700
27,200
Nov -18-1896
38,000
22,900
May -31-1948
37,900
22,800
Apr -17-1904
32,000
21,500
Nov -26-1909
30,600
Missing Flood Data
Dec -28-1980
27,600
1917 1921
Dec -4-1977
27,000
Yakima River at Umtanum
(USGS)
Date of
Event
Flow
(cfs)
Area (sq mi)
1594
Nov -14-1906
41,000
Period of Re-
Period of Re-
cord
Dec -23-1933
32,200
cord
1907-2007
May -29-1948
27,800
Neches River at Neches
Feb -9-1996
27,200
(BOR)
Nov -25-1909
22,900
Area (sq mi)
Nov -25-1990
22,800
16,434
Dec -2-1977
21,500
Dec -13-1921
Nov -23-1959
19,100
Missing Flood Data
Dec -26-1980
16,800
1904, 1906 _
Dec -3-1975
16,600
Neches River below Tieton
(USGS)
Date of
Event
Flow
(cfs)
Area (sq mi)
941
Dec -22-1933
32,200
Period of Re-
Period of Re-
cord
Feb -8-1996
20,924
cord
1909-1979
Nov -24-1909
19,400
Neches River at Neches
Dec -2-1977
18,000
(BOR)
Dec -30-1917
16,800
Area (sq mi)
941
Nov -20-1995
16,434
Period of Re-
Jun -18-1916
Dec -13-1921
14,500
cord
1979-2007
Dec -4-1975
14,100
May -20-1912
Jun -1-1956
13,300
Jun -10-1972
Jun -17-1974
12,800
Missing Flood Data
May -25-1948
12,600
1904, 1906
Jun -18-1916
11,700
North Fork Ahtanum near
Tampico (USGS)
Date of
Event
Flow
(cfs)
Area (sq mi)
78.9
Jan -15-1974
1,580
Period of Re-
cord
1908-1921,
1932-1979
Dec -2-1977
1,080
May -20-1956
823
North Fork Ahtanum near
May -27-1948
770
Tampico (AID)
Mar -1-1910
766
Area (sq mi)
78.9
Dec -22-1933
755
Period of Re-
Period of Re-
Jun -18-1916
728
cord
1997-2006
May -11-1951
655
Missing Flood Data
May -20-1912
629
1904, 1906, 1980, 1990, 1996
Jun -10-1972
593
Yakima River near Parker
(USGS)
Date of
Event
Flow
(cfs)
Area (sq mi)
3660
Dec -23-1933
65,000
Period of Re-
Period of Re-
Feb -9-1996
58,150
cord
1908-1977
Dec -30-1917
52,900
Yakima River near Parker
Dec -27-1980
47,337
(BOR)
May -29-1948
37,700
Area (sq mi)
3660
Nov -30-1995
36,504
Period of Re-
Nov -23-1959
Nov -26-1990
35,620
cord
1979-2007
Dec -13-1921
35,800
10,600
Dec -3-1977
35,090
10,100
Jan -8-2009
32,630
Jan -16-1974
28,800
Missing Flood Data
Nov -23-1959
27,400
1904, 1906
Dec -4-1975
26,500
Yakima River at Cie Ekim
(USGS)
Date of
Event
Flow
(cfs)
Area (sq mi)
502
Nov -14-1906
25,600
Period of Re-
1910-1914,
1960-2007
Dec -30-1917
19 900
cord
1907-1990
Dec -13-1921
19,500
1,530
Dec -2-1977
17,600
1,340
Dec -24-1909
17,300
1,240
May -29-1948
16,700
1,110
Nov -23-1959
14,000
1,020
Jun -3-1913
11,300
Missing Flood Data
Dec -13-1928
10,600
1904, 1906, 1990
May -30-1917
10,100
American River near Nile
(USGS)
Date of
Event
Flow
(cfs)
Area (sq mi)
78.9
Dec -26-1980
6,280
Period of Re-
1910-1914,
1960-2007
Dec -4-1975
4,860
cord
1940-2006
Jan -16-1974
4,310
1,530
Feb -9-1996
4,050
1,340
Jan -2-1968
3,440
1,240
May -27-1948
3,420
1,110
Nov -2-2006
3,130
1,020
Dec -21977
3,020
Missing Flood Data
May -20-1956
2,870
1904, 1906, 1909, 1917, 1921
Nov -27-1949
2,530
Ahtanum Creek at Union
Gap (USGS)
Date of
Event
Flow
(cfs)
Area (sq mi)
173
Jan -16-1974
3,100
Period of Re-
cord
1910-1914,
1960-2007
Feb -9-1996
2,660
Feb -2-1995
1,700
Mar -3-1910
1,530
Feb -5-1963
1,340
Mar -13-1983
1,240
Feb -21-1982
1,110
Missing Flood Data
Feb -29-1980
1,020
1904, 1906, 1909, 1916,1917,
Feb -1-2003
1,010
1921, 1933, 1948, 1951, 1956
Dec -3-1977
882
Largest Basin Floods in order: 1933, 1906, 1996 1917, 1974, 1896, 1948, 1977, 1904, 1980, 1990, 1909
Largest Spring Floods in order: 1948, 1904, 1956, 1974
The largest Ahtanum flood in mid January 1974 impacted the Ahtanum basin more severely
than the Yakima basin. The 1974 flood was not a major flood on the Yakima River, and did
not affect the Kittitas Valley or other portions of the Upper Yakima. The weather events that
Chapter 7 - Basin Flooding Characteristics 13
trigger major flooding in the Ahtanum and Wide Hollow Creeks are established below by
examining the 1974, 1996 and 1933 floods. Rain data for the floods are only available at
Yakima Airport.
The 1974 event was a snowmelt event associated with a chinook wind. As the Ahtanum
basin experienced relatively higher flood peaks than elsewhere it is suspected that a rain cell
may have stalled in the Cascades near the Ahtanum headwaters in 1974. Alternatively, there
were very high rates of snowmelt.
Weather conditions leading up to the 1974 flood (at the Yakima Airport Weather Station)
include an existing water equivalent snow depth of approximately 9 inches and 20 days of
below freezing weather, with most nightly low temperatures below zero. This was followed
by rapid warming, increased southern wind, and precipitation (at the Yakima Airport
Weather Station) totaling l an inch over 3 days. By the 14th of January — 2 days before the
flood peak — 7 inches of snow remained on the ground. The temperatures overnight
remained in the 50s, with 20 mile per hour winds and an additional 1/2 inch of rain; by the
end of the day all the low elevation snow had melted. Temperatures and wind remained
high that night and snowmelt must have also continued at a rapid rate at higher elevations
in the watershed. On the 16th of January, the South Fork Gage reported a peak of 1210 cfs
(currently estimated in excess of a 500 year flow) indicating rapid snowmelt at higher
elevations. The peak on the North Fork was 1580 cfs. The downstream peak flow of 3100 cfs
that occurred on that date at the Union Gap gage is currently estimated to exceed the 200
year flow. Even after the flood peak, weather remained warm and an additional lh an inch
of rain fell.
Given the lack of gage data for Wide Hollow Creek, we can only rely on news reports for
Wide Hollow plus resident anecdotes that indicate it behaved similarly to Ahtanum during
this event but peaked one to two days earlier and was the largest flood. The anecdotes
indicate a lesser severity on Wide Hollow.
The 1996 flood, the second largest event on Ahtanum Creek, was similar to both the 1974
and 1933 floods (large amounts of rainfall at higher elevations). In the Ahtanum basin, the
1996 flood, in comparison to the other two events, was preceded by longer duration freezing
weather, and a greater maximum snow depth, while the warming was less severe
(temperatures remained below freezing at night) and occurred over a much longer time
period (5 days) resulting in gradual snowmelt and at least some warming of the soil profile.
Like the 1974 flood, a l inch of rain fell on the day of the peak in Yakima (Yakima Airport),
but there was little or no snow on the ground at the airport when it fell. The peak flow of
2660 cfs is currently estimated as approximately a 70 year flow. Residents report that this
was not really as severe an event on Wide Hollow and could be considered the fourth or
fifth highest peak behind 1974, 1995, 1983 and 1985. Personal reports indicate peaks
occurring several days prior to the Ahtanum.
4 1 Ahtanum-Wide Hollow CFHMP
In 1995, County bridge damage on the much smaller Wide Hollow drainage was 125% of
that on the Ahtanum, and residents reported the most localized damage and flooding on
Wide Hollow, except for 1974.
The flood of record for most gage stations in the Yakima basin is the flood that occurred on
December 22, 1933. The combination of saturated soils, already high streamflows, lack of
storage capacity in the reservoirs, and a final rain on snow event resulted in the December
22nd flood. This flood was generated by a series of five Pacific Storms that moved through
the state in November and December; many precipitation records for those months were set
in western Washington in 1933, and have not been eclipsed since. Prior to the major flood on
December 22, two previous floods had occurred in the basin, and the reservoir system
(which had just been completed) was "as full as you would ever want to see it" (quote from
the BOR administrator) for that time of year. Subsequent to those floods, the next storm
event was colder, and deposited approximately 4 feet of relatively wet snow at higher
elevations. The storm that caused the flood was again warmer, and melted the snow that
had accumulated in the previous storm. It is important to note that this high precipitation
event, creating the largest peaks for most gages in the Yakima basin, was less than a ten year
event in the Ahtanum basin, according to recent FEMA studies.
The difference between the events on the Ahtanum versus Wide Hollow Creeks appears to
be the difference in their distance from the Cascade crest, their protection by mountainous
ridges, their orientation and their snow pack retention - the Wide Hollow receives
considerably less snow, is largely south facing, has open cover and loses its snowpack more
quickly and continually due to sun exposure. There is not a lot of snow falling in Wide
Hollow compared to Ahtanum due to its location further from the Cascade ridge. Rain on
snow, or rain on ice, are still the prime flood generators for both basins. Wide Hollow peaks
arrive within one day of peak rainfalls, while Ahtanum peaks are delayed three days.
In addition, as noted earlier, winter rain generated from Pacific air masses rising over the
Cascade crest (orographic rain), do not penetrate to Wide Hollow basin and are often
limited in the Ahtanum basin. The Ahtanum receives significant snowfall due to the flatter
trajectory of Cascade Crest induced snow. This is not so for the Wide Hollow basin. This is
evidenced by the high forest percent in the upper Ahtanum of 94 per cent versus zero per
cent in Wide Hollow. The Wide Hollow basin is probably the most sheltered basin in the
region, protected topographically to the west by the Cascade Crest and the mountainous
Upper Ahtanum basin, including Sedge Mountain, and to the north and south by Cowiche
Mountain and Ahtanum Ridge, respectively.
The 100 -year 24 hour rainfall for Wide Hollow is 2 inches. Summer rain storms are rare due
to the dry desert -like conditions and the basin orographic protection. The 1974 US Corps of
Engineers Wide Hollow hydrology study for FEMA recognized the basin sheltering and
used mean annual precipitation to reduce peak floods.
Chapter 7 - Basin Flooding Characteristics 15
FEMA HYDROLOGY
Below in tables 7-1 and 7-2 are the FEMA estimated flood peaks for selected return periods
for the two basins. The Ahtanum basin exhibits higher peak runoff.
Table 7-1. FEMA Ahtanum Flood Discharges.
Drainage Area Peak Discharges (cfs)
Flooding Source and Location (Square Miles) 10 -Year 50 -Year 100 -Year 500 -Year
Ahtanum Creek
Near Tampico
At Union Gap
North Fork Ahtanum Creek
Near Mouth
South Fork Ahtanum Creek
Near Mouth
119 950 1,750 2,250 4,100
173 1,100 2,200 2,850 5,200
68.9 790 1,140 1,290 1,680
24.8 440 710 840 1,180
Table 7-2. FEMA Flood Discharges for Wide Hollow Creek and Tributaries
Nlooding Source and Location
llralnage Area Peak Discharges (Cubic Neet per Second)
(Square Miles) 10 -Percent- 2 -Percent- 1 -Percent- 0.2-Percent-
Annual- Annual- Annual- Annual -
Chance Chance Chance Chance
Wide Hollow Creek
At mouth 70.5 362 665 817 1,262
Above confluence with Wide Hollow Tributary 3 62.7 343 631 775 1,198
Above confluence with Shaw Creek 41.2 283 521 642 993
Above confluence with Cottonwood Creek 24.6 223 412 509 789
Above confluence with Wide Hollow Tributary 2 14.3 174 322 398 619
Above confluence with Wide Hollow Tributary 1 4.9 106 198 246 384
Wide Hollow Tributary 2
At confluence with Wide Hollow Creek 7.9 132 246 305 475
Above confluence with Tributary to Wide Hollow Tributary 2 5.6 113 211 261 408
Tributary to Wide Hollow Tributary 2
At confluence with Wide Hollow Tributary 2 2.2 73 138 172 269
Wide Hollow Tributary 1
At confluence with Wide Hollow Creek
9.2 142 264 327 509
Shaw Creek
At confluence with Wide Hollow Creek 11.0 154 286 354 551
Above confluence with Shaw Creek Tributary 2.9 83 156 194 304
Shaw Creek Tributary
At confluence with Shaw Creek 6.4 120 224 278 433
Cottonwood Creek
At confluence with Wide Hollow Creek 15.3 179 332 411 638
Above confluence with Cottonwood Creek Tributary 2 11.8 159 295 365 568
Above confluence with Cottonwood Creek Tributary 1 7.5 129 240 298 464
6 1 Ahtanum-Wide Hollow CFHMP
CHANNEL ROUTING OF FLOOD WATERS
The upper portions of the Ahtanum Creek watershed (i.e. above "the narrows") are steep
and forested. The tributary and main channels of the upper watershed are generally steep,
have some large woody debris or other channel roughness, and naturally high levels of
sediment. In general, these channels can convey significant flows due to the high gradient,
and it is not unusual to have flood events where there is little evidence of out -of -bank
flooding in the upper watershed even though the creek is out -of -bank in the lower
watershed.
The high velocities of these channels can cause channel erosion, especially where riparian
vegetation has been removed, or where bridges or other constrictions cause a decrease in
slope. There are 120 public and private bridges and culverts on Ahtanum drainage streams
that were large enough to be included for new FEMA flood map models, and 183 crossings
on Wide Hollow drainage creeks. These structures are largely a result of development and
urbanization, which can contribute to flooding.
In the lower north fork Ahtanum, an area of relatively frequent out -of -bank flooding occurs
where the lower two bridges cross the creek. This area is where a natural change in slope
occurs from the steep mountain valley to the broader and gentler valley formation. The
bridges and irrigation diversion dam that are located there probably also contribute to the
high flood frequency at this location, but historical records indicate this location frequently
flooded and changed course prior to construction of these bridges. Flood waters from these
locations are can be routed over and along the NF Ahtanum Road, spreading water across
the upper portion of the alluvial fan. The recent FEMA flood mapping exercise showed that
without the flow diversions caused by these bridges, floodwaters would remain near the
current channel of Ahtanum Creek. With these flow diversions, water is routed across a
broad area of the alluvial fan, impacting residences and SF Ahtanum Road downstream.
Specific areas of high frequency flood occurrences are described below in the Flooding
Issues discussion, but the general channel conditions in Ahtanum Creek below the narrows
are low -gradient, naturally incised, have high sinuosity and good to excellent riparian
vegetative cover directly adjacent to the stream. This type of channel is very stable, and the
sinuosity of the channel also absorbs much of the stream energy of a flood. This creates an
"attenuation" of flood peaks — the flood peaks are reduced and lengthened.
For example in the 2003 flood, which peaked at approximately 900 cfs (a 5 year event) the
flood waters peaked on the North and South Forks of the Ahtanum on Thursday evening
(February 13) but did not peak at Emma Lane, 18 miles downstream, until Sunday morning
(February 16). In the North and South Fork the peak of the flood lasted no more than 2
hours, but the peak at Emma Lane lasted for 3 days and caused significant damage. Given
these types of channel conditions, areas such as Emma Lane, which regularly experience
overbank flooding, can expect high levels of damage during relatively minor flood events
due to the usually longer flood duration. Even large floods, such as 1996 have very long
durations in the Ahtanum system. The flood peak of the 1996 flood moved rapidly
Chapter 7 - Basin Flooding Characteristics
downstream (lower elevations were also contributing floodwaters due to rain and rapid
snowmelt) and remained at elevated flood levels for the next 3 weeks.
Channel conditions in the Wide Hollow drainage are more variable, and have had more
direct changes from human activities, as noted in Chapter 4. In its natural state, the upper
reaches of Wide Hollow were likely ephemeral streams with wide, coarse channels and
relatively sparse riparian vegetation. These channels (i.e. upstream of 96th Avenue) generally
retain these characteristics. Flooding in this portion of the basin results in relatively rapid
and numerous areas of overbank flooding, and high rates of channel migration where not
constrained by bridges, roads or levees. Where bridges or levees are present, gravel
accumulations and/or changes in the approach angles result in frequent overbank flood
events. Currently, many of channels in the upper portions of the watershed have been
straightened, lengthened farther up valley, or moved to a different location to allow for
conveyance of irrigation water. Where this has occurred the channels are generally sized
and maintained for irrigation conveyance, which can easily be exceed by flood flows,
resulting in overbank flooding.
In the middle portion of the watershed, Wide Hollow crosses a large silt fan. Below
approximately 40th Avenue the channel would have been, and remains in spots, similar to
the Ahtanum Creek channel — sinuous and slightly incised.
In the lower watershed, channels have been straightened and relocated to increase the
amount of farmable or developable land, or to act as drains, or, in the City of Union Gap, to
convey water used historically to turn a grist mill wheel. In most cases this has resulted in
channel incision and bank erosion, especially in urban areas. In the case of the channel in
Union Gap, frequent flooding can occur just upstream of the grist mill due to lack of
conveyance capacity at the mill itself.
The largest current influence on capacity within the channel and flooding characteristics in
the Wide Hollow watershed is the presence of stands of native willows, non-native Silver
Willow (Salix alba), and hybrids between the two, and the conveyance capacity at bridge
crossings where sediment and vegetation accumulates. These trees thrive in areas where the
streams hydrograph exhibits higher flows in the summer than in the winter. Most native
species are not adapted to these types of water level changes, consequently riparian stands
are converted to these Willows and associated non-native plants such as Reed Canary Grass
(Phlaris arundacea) and Russian Olive (Elaeagnus angustifolia).
The Willow trees achieve unusually large size (over 60 feet) and produce large amounts of
both litter in the form of leaves and seeds, and also large quantities of small, medium and
large pieces of stems and trunks. The large amounts of litter tend to be cohesive and coat the
bottom of the channel in layers of muck as they break down, and the woody debris greatly
increases channel roughness.
These combined effects often dramatically reduce channel capacity, especially in areas with
high concentrations of Reed Canary Grass which further reduces channel capacity. Over
7
8 1 Ahtanum-Wide Hollow CFHMP
time, these channels can become very wide and shallow, further increasing habitat for the
willows and other non-native species. This results in an increase in the frequency of
overbank flooding events in these areas, often several such events will occur annually.
Routing of Floods Across Floodplain
As mentioned in Chapter 4, these watersheds are in an active geologic region, and the valley
itself is warped with differential rates of rise in the ridges to the north and south of the
valley. This differential rise has a large influence on flooding patterns during major events
in the Ahtanum Valley, but little effect in Wide Hollow Creek.
The complexity of the Ahtanum Valley, combined with channel conditions, can result in
long duration floods where floodwaters extend several miles from the creek itself. Even
small changes in topography in this wide and complex valley can alter flood patterns from
decade to decade or year to year. The frequency with which such large scale, long duration
floods occur is generally low, occurring in 1910, 1974 and 1996, with a shorter duration
event in 1995. In general, the Ahtanum basin has a large area of floodplain for water storage,
consequently damages caused by high energy floodwaters to structures such as bridge or
homes is minor, as are dramatic changes in channel location in the lower watershed. The
impact of these events is severe in terms of low velocity damage to infrastructure (roads,
bridges, and irrigation), disruption of transportation systems, and damage to private
property.
The long floodplain of Ahtanum Creek which begins near Tampico and ends at the
confluence with the Yakima River is warped in different directions along its course. From
Tampico to the area upstream of the Mission, the valley tilts to the south and the stream and
flooding pattern are along the southern valley wall. Just upstream of the Mission the valley
flattens and large floods may occupy the entire valley floor. In large floods, much of the
floodwaters will not return to Ahtanum Creek, but flow down the Bachelor Creek Channel
on the north valley wall. For approximately 1/4 mile on the Mission property, near the
beginning of Hatton Creek, the valley tilts to the north. This location allows large amount of
floodwaters to be routed to the Middle and northern parts of the valley, and is the location
of a potential avulsion of Ahtanum Creek.
Further downstream the valley is again tilted to the South for several miles until the vicinity
of Wiley City. At that point Ahtanum Creek, on the south valley wall, is somewhat incised
in the valley floor and floodwaters remain in the south. Floodwaters that have already
exited Ahtanum Creek and are in Hatton and Bachelor creeks are routed farther to the
North, and can become essentially impounded in the vicinity of the town of Ahtanum and
areas to the east. These impounded floodwaters then slowly travel eastward in a variety of
swales where they enter the head of Spring Creek West, which flows into the Yakima
Regional Airport. As these floodwaters move northward, they can become diverted by
roads and routed down valley. Rutherford Road and Meadowbrook Roads in several places
act as interceptors, causing damage to the roadways, adjacent road ditches and private
driveways, and further increasing floodplain storage.
Chapter 7 - Basin Flooding Characteristics 19
The valley below Wiley City once again tilts toward the South and a portion of the
floodwaters from Hatton Creek return to Ahtanum at 72nd Avenue. For the next several
miles flooding is along the south valley wall from Ahtanum Creek, and the north valley
wall from Bachelor and Hatton Creeks. Near 52nd Avenue, the gradient of the valley as a
whole reduces, and the valley is once again level, spreading floodwaters across the valley as
a whole.
Near 42nd (Emma Lane) the valley tilts strongly toward the north, overbank flood waters
travel north from Ahtanum into floodplain swales and the already swollen Bachelor Creek.
All of these overland flow paths (overbank from Ahtanum, overbank and channel from
Bachelor, and overbank and channel from Spring Creek West) meet on and near the Airport,
and flow in a variety of paths, including some contribution to lower Wide Hollow Creek.
The valley then again tilts to the south, with most of the floodwaters from Bachelor and its
tributary Spring Creek, returning to Ahtanum at Goodman Road. At this point flooding is
confined once again to the southern valley wall. Near the confluence with the Yakima, the
gradient of the channel decreases and the floodplain is nearly level. This area is frequently
flooded but flood damage is minor as most of this area is managed as a Park (Fulbright) by
the City of Union Gap.
Arial photographs of the 1996 flood are shown in Figures 7-2 and 7-3
10 1 Ahtanum-Wide Hollow CFHMP
Figure 7-2
1996 Ahtanuin Flooding
Emma Lane & 42nd — looking Southeast
Rutherford Road — looking Northeast
Chapter 7 - Basin Flooding Characteristics 111
Figure 7-3
1996 Ahtanum Flooding
Community of Ahtanum- looking East
Wiley City — looking North
12 Ahtanum-Wide Hollow CFHMP
Wide Hollow Routing of Floods in Floodplain
Wide Hollow Creek has 3 major floodplain landforms — hollows, low gradient alluvial fans,
and Missoula flood Deposits, each has unique flood routing characteristics.
Hollows are relatively broad valleys with very flat valley floors. Infrequent flood events,
usually snowmelt over frozen soil, result in flows being routed across the width of the
valley floor. The flatness of the floor causes water to spread, so flood events in hollows are
generally shallow and of short duration. Changes to the valley floor due to roads, fences,
houses, etc can cause changes to routing of flood waters in the Hollows. More intense levels
of residential development in Hollows can cause dramatic changes in flood routing and
increase the duration of the flood due to the increased roughness of the floodplain and
increased impervious surfaces. Even though the valley floors of the Hollows are floodplains,
very few of them have been mapped as floodplains in the past, or are planned for mapping
in the future.
The low gradient alluvial fans of Wide Hollow Creek should tend to route shallow
floodwaters across a wide area, with areas of deeper flood waters against the valley walls.
This type of shallow flood should and does occur with greatest frequency near the upper
portions of the fans. The area of the confluence of Wide Hollow and Cottonwood Creeks is
the beginning of the first major fan, Shaw Creek is another fan that enters the valley just
downstream, and the fan landform extends downstream to approximately 48th Avenue.
Flooding in the vicinity of 96th Avenue for both Wide Hollow and Shaw Creeks exhibits this
shallow broad flooding behavior with historical floods known to cover the majority of the
fan. Where the Wide Hollow and Shaw Creek fans join, there is a broad swale that can route
floodwaters from either fan downstream, this swale is best depicted on the Wide Hollow
only flooding maps in the Shaw Creek area. This swale ends at the intersection of 80th and
Wide Hollow Road, an area of frequent shallow inundation. Downstream of 72nd, the Wide
Hollow Fan buts up against the Ahtanum Creek watershed. This forms another broad swale
that can route floodwaters from either Wide Hollow or Ahtanum watershed, this area
generally lies just to the North of Washington Avenue, and has numerous irrigation ditches,
drains and Spring Creek West, all of which can become active during flood events.
Spring Creek (Chambers) East flood Routing
Unlike the remainder of the watershed, Spring Creek (Chambers) East is a side channel of
the Yakima River. When the Yakima River is in flood, floodwaters travel upstream into
Lower Spring Creek (Chambers), Wide Hollow, and during large events, Ahtanum Creek.
LiDAR data and other information sources indicate that the bed of the Yakima River is
rising in this reach, which in turn, should cause flood levels in the river and in these
backwater areas, and the local groundwater table, to rise as well. Recent studies by WSDOT
for the Valley Mall Boulevard exit also indicate that flood levels have risen since the original
flood studies from the early 1970s. If the bed of the Yakima River continues to rise, the
potential exists for the freeway to be overtopped, which would bring a large area of the City
Chapter 7 - Basin Flooding Characteristics 113
of Union Gap into the floodplain, or at much higher flood risk than currently on the Flood
Insurance Rate Panels. See Figure 7-4.
Figure 7-4 1996 Flood Extent in Union Gap
Impacts of Roads and Bridges on Flood Routing
Both watersheds are prone to large areas of shallow flooding due to the characteristics of the
land forms — low gradient alluvial fans, Missoula flood deposits, warping of the valley
floors and farming practices taking advantage of these opportunities. A large common
factor in the development of flow paths and subsequent routing of floodwaters across the
floodplains of both watersheds is the effect of roadways, bridges and irrigation diversion
structures.
Historically, due to the flat floodplains bridges were built to span the active channel,
resulting in under -sizing of the bridges to pass flood flows and causing sediment
accumulations in the channels upstream of bridges. Private parties and public agencies
found it necessary to periodically "clean out" the bridge approaches to maintain conveyance
capacity for annual flood events. With the increasing regulation of activities in stream
channels, this maintenance activity has decreased for both public and private bridges. This
14 1 Ahtanum-Wide Hollow CFHMP
in turn results in more frequent out of bank flooding associated with bridge crossings,
especially the larger public bridges. In addition, the FEMA remapping has shown that the
improvement of arterial roads with large amounts of fill, when orientated east -west parallel
to the streams, has blocked the north south alignment of historic flow paths and redirected
flows onto previously unaffected land.
During large flood events, floodwaters can be distributed across a large area of the
floodplain. Construction of bridges to efficiently convey these floodwaters across the road,
or constructing the road and bridge to concentrate all of the flood flows at a single bridge
crossing is difficult at best, and not economically feasible in many locations due to the flat
configuration of the floodplain. Channeling all flood flows to one bridge location can have
the effect of raising the flood level upstream of the bridge with consequences to local private
properties and infrastructure. Maintaining a spread flow across the wide areas of floodplain
can make roads impassable or unsafe. Providing overflow culverts or other structures along
the roadway tends to concentrate flow into several streams, which can in turn change the
flooding characteristics — depth and velocity of floodwaters — downstream. Given the large
amounts of woody and other debris that is generated in large floods, these culverts can also
plug and lose their effectiveness, raising upstream flood elevations further, or causing
further changes in flooding characteristics downstream.
The large amount of vegetation, noted in Chapter 4, contributes to reduced channel
conveyance at the bridges and within their approaches further exacerbating the crossing
flood issue.
Figure 7-5 Example of a bridge constriction - Cottonwood Creek
Chapter 7 - Basin Flooding Characteristics 115
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CHAPTER 9
FLOOD ACTION ALTERNATIVES & PRIORITIES
Comprehensive flood hazard management emphasizes selecting a mix of approaches to
minimize flooding impacts and considers an adequate reach of river to capture impacts.
Options for addressing flooding concerns include engineered projects, channel conveyance
measures, public information programs, flood warning, planning measures, and floodplain
enhancement measures. This chapter presents the process that was used by the Combined
Committee to evaluate and select alternatives that were considered for recommendations in
Chapter 11.
TYPES OF FLOOD HAZARD SOLUTIONS
Flood hazard management measures are commonly classified as structural or nonstructural.
Structural measures involve physical activities in or near the stream, such as excavation,
placement of bank protection materials, and other engineering and construction activities,
these measures pertain primarily to existing flood prone development. Nonstructural
measures include stormwater and land use regulations, flood preparedness programs, public
awareness programs, floodproofing, and maintenance programs, which are intended to
minimize flood impacts on future development and redevelopment. Nonstructural methods
are also expected to minimize the possible affect of future development upon existing
development.
Due to rising damage costs from over -reliance on structural approaches prior to the 1960's,
the federal government began to encourage the use of cost-effective, long-term
nonstructural alternatives instead. A very effective federal example of the movement
towards non-structural approaches was the provision of Federal Flood Insurance in 1968
through the National Flood Insurance Program. Summaries of typical structural and
nonstructural solutions are provided Tables 9-1 and 9-2, respectively.
1
2
Ahtanum-Wide Hollow CFHMP
TABLE 9-1
TYPICAL STRUCTURAL FLOOD HAZARD MANAGEMENT SOLUTIONS
Measure
Description
Typical Activities
Alignment
Control
Bank
Protection
Conveyance
Capacity
Floodplain
Protection
Measures designed to accommodate
discharge along a course that allows
the channel to develop without
eroding adjacent property
Measures designed to produce a
stable, durable streambank that can
withstand floodwaters up to the
predicted 100 -year flood
Increasing channel bed slope or cross-
sectional area or decreasing channel
roughness in order to increase the
amount of flow that a stream can carry
before water spills over the bank;
increasing off -channel storage or
floodplain storage
Measures that reduce flood hazards
for property, structures, and occupants
in the 100 -year floodplain; protection
from inundation, floating debris,
sediments, and the force of water
flowing in the floodplain
• Barbs (spur dikes)
• Flow realignment
• Reestablishing riparian vegetation
(bioengineering)
• Reducing bank slope
• Constructing standard trench fill revetment
(riprap)
............................................................................................................................................................................................................................
• Constructing overflow/secondary channels
• Widening or deepening the channel
• Increasing floodplain storage by removing
levees or moving roads
• Replacing multi -span bridges with single
span bridges (no interior piers)
• Installing culverts through embankments to
minimize obstructions to flow.
• Constructing setback levees
• Constructing ring levees
• Elevating roads
• Redesigning and replacing bridges
• Constructing/expanding storage reservoirs
• Changing the configuration/alignment of
headgate structures at diversions
CHAPTER 9 - ALTERNATIVES 3
TABLE 9-2
TYPICAL NONSTRUCTURAL FLOOD HAZARD MANAGEMENT SOLUTIONS
Measure
Description
Typical Activities
Open Space
Maintain and increase open space in
floodplains to provide conveyance,
storage capacity and minimize flood
hazards to structures
• Provide incentives for developers
• Provide incentives for agricultural lands
• Land acquisition
• Purchase of flood easements
• Encourage parks and trails in floodplains
• Meet Growth Management requirements for
open space & shoreline/habitat protection
Public
Information
Public information activities to advise
people of the risks associated with
flood hazards and about flood
insurance and ways to reduce flood
damage
.....................................................................................................................................................................................................................................................................................................................................................................................................................................
Regulatory and mapping measures to
provide protection for existing
structures and new development
through land use regulation and the
collection of accurate floodplain
information
• Map determinations/technical assistance
• Public outreach projects
• A flood protection library
• Flood preparedness programs
• Hazard disclosure
• Elevation certificates
• Higher regulatory standards
• Low-density zoning
• Open -space preservation
• Ordinance consistency
• Interagency agreements
• Accurate floodplain and floodway mapping,
and migration hazard mapping
Regulation
and Mapping
Planning,
Evaluation &
Data
Collection
Activities to develop accurate
floodplain information and flood data,
analyze alternative feasibility, and
increase the understanding of the
river's flood characteristics
Measures addressing flood damage to
existing structures (buildings, roads,
bridges, levees, canals, ditches etc.)
.....................................................................................................................................................................................................................................................................................................................................................................................................................................
Actions to minimize the effects of
on people, property, and the
contents of buildings
Activities to maintain stream
conveyance
• Flood data maintenance (GIS, databases)
• Floodplain audits
p
• Flood gage installation/improvements
• Engineering studies & mapping products
• Provide FEMA hydraulic models to project
proponents
Flood Damage
Reduction
• Acquiring, elevating or relocating flood -
prone structures
• Wet or dry floodproofing
• Developing repetitive loss plans
• Management of interconnected irrigation
and natural drainage systems
• Localized action and access plans
• Comprehensive response planning
• • Flood warning systems
• Flood facility maintenance programs
Floodflooding
Preparedness
p
Maintenance
• Removing vegetation and debris
• Controlling growth of vegetation in the
channel
4
Ahtanum-Wide Hollow CFHMP
FLOOD MITIGATION APPROACH ANALYSIS
Table 9-3 provides guidance on how well common alternatives address a particular type of
flooding problem and their likely environmental impacts. These considerations along with
the goals and objectives for this plan were utilized to select and prioritize recommendations
TABLE 9-3.
PROBLEM ADDRESSED AND ENVIRONMENTAL IMPACT
ASSOCIATED WITH FLOOD HAZARD MANAGEMENT MEASURES
Problem Solve da
Impactb
O O
.a a O
a U o '-a 0
a •- m by -
U be 'd O
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Alternative .° ) ° 2 0 o
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W ° E be ti (23'-1
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C
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0
ca
U
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Nonstructural
+
+
+
—
+
0
0
+
—
+
+
0
—
+
—
+
0
—
+ +
0 0
+ +
— —
+ +
0 0
0 0
0 0
— —
+ +
+ +
0 0
— —
0 to + 0
— 0
+ +
0 — to 0
— — to 0
+
+
+
—
+
0
0
+
—
+
+
0
+
0
— to 0
+
—
— to 0
+
+
+
0
+
0
0
0
—
0
0
0
0
0
0
0
0
+
+
0
+
— to
+
0
0
0
—
0
0
0
0
0
— to
+
0
0 to
0
0
+
Open space + + + + 0 0 +
Public Information Program 0 0 0 + 0 + +
Regulatory Measures + 0 + + 0 0 +
Vegetation & Debris Removal 0 — 0 0 — or + 0 —
Flood Damage Reduction for 0 0 0 + 0 0 +
Existing Structures
Floodproofing of Structures 0 0 0 + 0 0 +
Flood Preparedness/ Emergency 0 0 0 + 0 + —
Management
Structural
Barbs (Spur Dikes) + + — + — 0 —
Flow Realignment + + — + — 0 —
Bioengineering + + 0 + 0 0 +
Cabling Trees + + — + 0 0 0
Reducing Bank Slope + + + 0 0 0 0
Standard Riprap + + — + 0 0 —
Overflow Channels + + + + 0 0 —
Channel Widening or Deepening + + + + + 0 —
Setback Levees + 0 — + 0 0 —
Ring Levees + — — + — 0 —
Storage Reservoirs + + 0 + 0 0 —
a. + = problem solved; 0 = problem not addressed; — = problem aggravated
b. + = positive impact; 0 = no impact; — = negative impact
in Chapter 11.
ALTERNATIVE GENERATION
Based on problems identified in Chapter 8, Flooding Issues, input and discussions at
committee meetings, the primary flood issues identified included:
• accurate mapping of flood hazards and overflow paths,
• agricultural modifications to channels and floodplains,
• irrigation infrastructure and "ditched" stream channels,
• bridge capacity and road alignment/elevation impacts,
• reduced channel capacity due to sediment,
• abnormal growth of hybrid willows and other riparian vegetation,
CHAPTER 9 - ALTERNATIVES 15
• wildlife management of beavers;
• flood risk awareness; and
• future development pressure in the floodplain.
Brainstorming Exercise
Flood problems were grouped in Table 9-4 based on their nature, cause or geographic
location. The Committee then developed alternatives using these group numbers as
identifiers.
TABLE 9-4 FLOOD PROBLEMS
1.
Instream Debris
2.
St. Joseph's Mission at Ahtanum
3.
Emma Lane
4.
Inundation
5.
Irrigation Infrastructure
6.
Spring Creek East in Union Gap
7.
Vegetation
8.
Shaw Creek
9.
Fish and Wildlife
10.
Flood Fight - Flood Response
11.
Union Gap
12.
Transportation Infrastructure (Roads and Bridges)
Note: North Fork Ahtanum problems was merged into this
group before individual alternative numbers were assigned
13.
Land Use
14.
Regulatory Issues
15.
Channel Issues
Problem statements, shown in Table 9-5 below, were generated for each problem group in
Table 9-4 and sent to Committee members. The Committee then went through a
brainstorming process using Table 9-5, Tables 9-1 and 9-2, and site specific knowledge
obtained during the plan to generate Plan alternatives.
TABLE 9-5 PROBLEM / ALTERNATIVES WORKSHEETS
Process for Developing Alternatives:
1. Problem - What is the problem? (Problem Statement)
2. Causes - What is causing the problem?
3. Alternatives - What Alternative solutions will address the problem?
a. What has already been proposed to address the problem?
b. Are there any new solutions that have not already been proposed?
c. What still needs to be studied?
d. Do these proposals address the causes of the problem?
4. List Alternatives - Proposals that address the causes of the problem are listed as
Alternatives, as well as instances where further study is required.
6
Ahtanum-Wide Hollow CFHMP
The completed Problem Statements / Alternatives Worksheets generated during the
committee meetings are contained in Appendix F.
Nomenclature Key
Alternatives generated by the committee on the problem worksheets were assigned a
unique individual alternative number which was retained through -out the formation of this
plan. The numbering convention is based on the group numbers in Table 9-4 and follows a
number letter -number format, placed in parentheses (i.e. 8E-6). Some alternatives were not
assigned a letter (i.e. 15 or 4-7).
The "Alternatives Discussion" beginning on page 9-12 and summarized in the Alternatives
Summary Table 9-8, follow this parentheses format. These individual alternative numbers,
generated from the worksheets can be used to track a specific alternative through -out
Chapters 9 and 11, and Appendix G.
Alternative Analysis and Selection
Over 300 alternatives were generated in the Problem Worksheet meetings. The large
number of alternatives created difficulties in determining the best method to group or
eliminate alternatives, so that the committee would have a manageable number to consider.
An objective rating method was sought to reduce the number and facilitate the analysis of
the alternatives.
Accordingly, alternatives were initially evaluated and scored with regard to importance
(severity & benefits), feasibility (impacts, cost & acceptance) and their meeting multi -objectives
from the plans objectives in Table 1-2. This differentiation recognizes the need and degree of
expected success for alternatives.
It was found after several iterations on this approach using scoring methods that each
attempt retained too many alternatives of low priority and also dropped some important
alternatives. Staff then presented the results to the committee which dropped the
alternatives listed in Table 9-6.
Alternatives considered and not included
The Committee reduced alternatives by dropping several and consolidating some of the
remainder for review.
Pine Hollow Reservoir considerations
The potential for the proposed Pine Hollow Reservoir to reduce flood peaks was explored at
the beginning of the CFHMP committee process and this alternative did not receive an
alternative number. The Ahtanum Creek Watershed Assessment (Ecology, 2004)
investigated various options for increasing water storage and restoring natural habits in the
Ahtanum drainage, including the Pine Hollow Reservoir. The project consists of a diversion
to an off channel storage site.
In June 2005 Ecology released the Final Programmatic Environmental Impact Statement for
the Ahtanum Creek Watershed Restoration Program (Ecology Publication #05-06-016). The
CHAPTER 9 - ALTERNATIVES 17
use of the proposed Pine Hollow Reservoir to help mitigate flooding was addressed in
several locations in the EIS. In the discussion of Alternatives on page 6-10 the document
states, "None of the alternatives would significantly reduce flooding". Later in the Public
Services section (page 6-58) of the same chapter, additional flood information is provided:
"The proposed Pine Hollow Reservoir would provide storage for surface water to be
used for irrigation and augmentation of instream flows. The reservoir would not
provide a drinking water supply and would not generate hydroelectricity. The
reservoir would not provide significant flood control to the project area, but could
provide a small reduction of flood flows during non -peak events. The reservoir
would be an off -stream reservoir and would not be designed to provide storage of
flood waters. The diversion and enlarged John Cox Ditch would operate during
winter and spring high flows, and could divert up to 160 cfs. That could reduce flood
flows during non -peak events. Peak flows during major flood events have exceeded
1,000 cfs. The reservoir and smart diversion would have to be operated for flood
control in order to provide any such benefits."
A somewhat more detailed explanation is included in the EIS as a response to a letter
(Comment Letter No. 12) received during the public process. The first part of the EIS
response to the comment was:
"12-4 Flood control has not been included as a primary feature of the proposed
diversion and reservoir. As noted in the EIS, the ability of the proposed reservoir to
reduce flooding would be limited by the size of the diversion from the Ahtanum
Creek and maintenance of channel -forming flows. The proposed diversion would
have a capacity of 160 cfs. For comparison, the flood flows on the North Fork of
Ahtanum Creek are approximately 600 cfs (10 -year flood), and 860 cfs (100 -year
flood). Providing capacity to divert a significant portion of these flood flows to the
reservoir would require a much larger diversion and ditch."
Since the proposed Pine Hollow Reservoir project does not include flood control in its
design and estimated cost, it was not viewed as a viable alternative for this CFHMP.
The dropped alternatives listed in Table 9-6 were reviewed and discussed several times by
the Committee and staff. The discussion and basis for dropping the specific alternatives
follow Table 9-6.
Table 9-6.
Dropped alternatives identified during Alternative Tracking process
Alt. No.
Alternative Text
1A-4
Utilize heated irrigation gates to prevent ice buildup (most gates are closed in
the winter)
1B-6
Put standards or policies in Critical Areas Ordinance addressing fences across
streams
1C-1
Reconsider closing solid waste dumps near streams
1C-6
Jurisdictions should remain cognizant that they are liable to enforce laws
related to known public hazards
8
Ahtanum-Wide Hollow CFHMP
Table 9-6.
Dropped alternatives identified during Alternative Tracking process
Alt. No.
Alternative Text
1D-4
Utilize corrections crew for roadside cleanup
2A-4
Tribe is working with Herkes to do some stream restoration work- cooperation
with the Yakama Nation
2A-9
Define acceptable level of flooding relative to headcuts
2B-1
Construct levees along Hatton to redirect flow
3-4
Re -mapping of FEMA flood maps at Emma Lane
4-1
Adhere to rules of the National Flood Insurance Program
4-2
Adhere to rules under the Critical Areas Ordinance
4-5
Create more stringent subdivision standards in flood prone areas
4-14
Coordinate with City of Yakima on checking old regulations against
Comprehensive Plan updates
4-16
Engage in "Full Build -out Mapping" exercise
5A-3
Create hard structures in ditches and diversions, preserving natural drainages -
involves designating some channels as "artificial" and some as "natural"
5D-6
Develop a water conservation plan that includes designation of fish habitat and
other uses
6B-3
Coordinate with WDFW's Restoration Plan for Spring Creek (WDFW)
6D-1
Culverts under Hwy. 97 either need to be plugged and repaired or sealed.
WSDOT has plugged or repaired culverts in the past. Recent observations
indicate they are once again backwatering.
7B-1
Enforce regulations that protect or encourage restoration of riparian vegetation
(Critical Areas Code)
7D-1
Utilize riparian setbacks and buffers
7D-2
Respond to log jams in a site-specific manner
8A-1
Classify Shaw Creek (or parts of it) as a ditch or stream
8D-2
Model the Shaw Creek watershed at full build -out
9A-4
Beaver -proof culverts (don't normally function well during floods). And provide
alternatives for water passage through beaver dams.
9A-8
Consider establishing areas where beavers should not be allowed. (i.e. dense
urban areas, irrigation, artificial ditches).
9A-9
Identify protocols for beaver management. Who is responsible?
10C-6
Provide open contract for aerial observation during floods for event
documentation
11B-2
Limit extension of services to flood prone areas
12A/B 9
Limit/restrict/reduce the number of bridges and bridge crossings, especially
small private bridges and culverts.
12C-4
Study the level of service standard for designing roads in floodplains in flood -
prone watersheds
12D-4-9
Potential hole- contact with private landowners- driveways, culverts, etc.
12E-6
Build private driveways at grade, where culverts generate flooding.
12G-4
County utilize existing and amended floodplain and critical areas codes to reduce
flood hazard.
12H-1
Apply stormwater management standards for new and reconstructed roads
12H-5
For roads in floodplains in flood prone watersheds develop special standards by
road functional type and private road classification.
12H-9
County (and Cities) evaluate access needs on a case by case basis
12H-10
Use Unnumbered A -zones (Regulatory Parking Lot) on maps
13A-1
Rely on Existing zoning (status quo)
13A-2
Continue to implement NFIP standards (regulatory standards)
13A-6
Use Critical Areas update policies to establish open space
CHAPTER 9 - ALTERNATIVES 9
Table 9-6.
Dropped alternatives identified during Alternative Tracking process
Alt. No.
Alternative Text
13A-8
Focus lower -intensity development within the floodplain corridors, while
focusing higher intensity developments to the sides of the flood corridor. Lower
density for subdivisions in the floodplain. (repeat)
13A-12
Establish land use standards within flood hazard zones
13A-14
Establish policies for retrofitting and re -development of stormwater facilities and
flood water routing in existing urbanized areas
13B-1
As per Code new developments must meet development standards and go
through the planning process.
14A-1 (part)
Build road bed at grade? Implement standard for access, and Define "island" size
(other elements of alternative were retained)
14C-6
Create policies for areas of existing dense development within the floodplain
(such as Ahtanum and Wiley City) (From Land Use) (repeat)
14D-2
Provide incentives or bonuses for developers who actively protect flood hazard
areas. (10% density bonus). Specific development standards in zoning ordinance.
(From Land Use) (repeat)
14D-3
Focus lower -intensity development within the floodplain corridors, while
focusing higher intensity developments to the sides of the flood corridor. Lower
density for subdivisions in the floodplain. (Froin Land Use) (repeat)
14E-2
Use Critical Areas update policies to establish open space (Froin Land Use)
15
Open space taxation policies (repeat)
15C-5
Levees, armor, buffers, CMZ (channel migration zones) (repeat)
15C-6
"Softer" solutions for bank stabilization (plantings, etc.) (repeat)
15C-7
Buyouts/relocation/easements and flood -proofing for areas threatened by
meandering and erosion.
15C-8
Agricultural subsidies allowing flooding on some farmland. Depends on erosion
verses sheet flow. Compensation program for productive ag. land lost to erosion.
Linked to property loss protection program (?). (repeat)
15G-3
Model flood effects of build -out
17
Better system of checks and balances within local government for agencies to
buy in.
Shaw Creek Classification
Alternative 8A-1 "Classify Shaw Creek (or parts of it) as ditch or stream" received a great
deal of discussion at several committee meetings. This alternative arose due to difficulties
managing the channel as both a creek and as an artificial irrigation and drainage facility.
Shaw Creek is not unique in this respect; there are other stream reaches both within and
outside the Shaw Creek area that have similar classification issues.
While everyone in the committee acknowledged the difficult management issues regarding
Shaw Creek, agreement on this alternative was not obtained. The committee decided to
drop this classification alternative at the February 26, 2008 meeting since a consensus could
not be reached.
Several other alternatives were generated that address the overall issue of channels that
have some current or historic irrigation function. These alternatives will be discussed at the
beginning of the Channel Issues/River Function section.
10
Ahtanum-Wide Hollow CFHMP
Miscellaneous Dropped Alternatives
Six alternatives were dropped early in the process when the committee reviewed
alternatives for Bridges and Roads.
Alternative 1D-4 is not directly related to flooding and at best would only help reduce risks
for the smallest flood events. Alternative 12D-4-9 was not required since it was created to
cover a perceived "hole" in the alternatives that did not exist.
Alternatives 12G-4, 12H-1, and 13B-1 are either already being implemented or don't indicate
a specific action that could be implemented. All six of the above alternatives were reviewed
at several committee meetings and also received detailed review by the staff before being
dropped. Alternative 12E-6 relates to private development and would probably not
significantly reduce flooding in the few locations where it might apply. For new road access
in the unincorporated county, the required driveway culvert is sized according to the depth
of the pre-existing ditch that is part of the road system.
Seven Alternatives were duplicates of other alternatives, so they were dropped: 13A-8, 14C-
6, 14D-2, 14D-3, 15, 15C-5, 15C-6, 15C-7, and 15C-8. One alternative, 2B-1, though not an
exact duplicate was determined to be redundant since other alternatives adequately cover
preventing an avulsion of Ahtanum Creek into Hatton Creek. Another redundant
alternative is 9A-9 since responsibility for management of beavers lies with the Washington
State Department of Fish and Wildlife. During recommendation review alternative 10C-6
was determined to be included within 15D-5, so 10C-6 was dropped as redundant.
During the alternative tracking process additional Alternatives were identified that were not
included in earlier alternative review discussions. Approximately half of these were either
"status quo" alternatives, are already being done, were too general, or did not have a clearly
identified action that could be implemented: 1C-6, 2A-4, 3-4, 4-1, 4-2, 4-14, 7B-1, 7D-1, 7D-2,
12H-10, 13A-1, 13A-2, 13-A-6, 13A-12, 14E-2 and 17. During the recommendation review
process one alternative (4-5) was dropped due to lack of specificity and because other
recommendations already address subdivision standards.
Three Alternatives (4-16, 8D-2, and 15G-3) proposed modeling "full build -out" conditions in
specific locations or the entire FEMA study area. FEMA refers to this type of mapping as
"Future -Conditions Hydrology". When this type of mapping is requested by a community,
FEMA will identify the future -conditions floodplains on the official maps in addition to the
usual floodways and floodplains, but it is up to the community to enact an ordinance to
regulate to this higher standard. Since the likely outcome (wider floodplains) of
implementing these alternatives was not thoroughly discussed and analyzed by the
committee, these alternatives were dropped.
Several alternatives did not receive support from the committee and were dropped.
Alternative 1B-6 for regulation of fences through Critical Areas Ordinances was felt to be
unwanted regulation of something that is not believed to be a widespread problem. The
committee suggested it was more appropriate to include the issue of fences in floodplains in
public outreach to property owners. The next alternative in this group, 11B-2, proposed
CHAPTER 9 - ALTERNATIVES 111
limiting extension of services. The committee decided this was not the proper method to
reduce density in floodplains and dropped this alternative. During this discussion the
committee also decided to reinstate the floodplain overlay alternative which had previously
been dropped (13B-3).
For Alternative 14A-1 the committee decided to drop two elements related to "islands" of
non -floodplain areas surrounded by overland floodplain. The remaining elements of this
alternative were retained.
One dropped alternative, 5A-3, was similar to the classification of Shaw Creek as a ditch or
stream (8A-1). Though 5A-3 does not identify a specific stream to be reclassified, the
committee expressed no interest in addressing this topic. Eight dropped alternatives
appeared to be impractical, unlikely to produce flood reduction benefits, or are not
identified as a serious problem in the CFHMP area, 1A-4, 1C-1, 2A-9, 6D-1, 9A-4, and 9A-8.
Two dropped alternatives were beyond the scope of this plan or funding has been removed
for the project, 5D-6 and 6B-3. One alternative, 13A-14, was dropped because the flood
concerns were adequately covered in other alternatives and it also had considerable overlap
with the new stormwater program.
Four alternatives (12H-5, 12H-9, 12A/B-9, 12C-4) grouped together were dropped by the
committee at the end of the alternative review process. These alternatives were grouped
together since they all involve consideration of new roads and bridges in the floodplain, and
determining the appropriate standards for roads in floodplains. The committee felt these
alternatives were redundant since they are already included in other alternatives or in
current regulations.
Alternative Consolidation
Staff deleted alternatives common to more than one worksheet and combined like
alternatives as noted above. As part of this process the flood problem groups (Table 9-4) were
also consolidated and renamed flood issue categories. A new category titled "Monitoring and
Inventories" was created for alternatives aimed primarily at data collection that is not site-
specific. The final flood issue categories are shown in Table 9-6.
TABLE 9-7 FLOOD ISSUE CATEGORIES
1.
Channel Issues / River Function
2.
Watershed
3.
Bridges and Roads
4.
Irrigation
5.
Land Use
6.
Development Standards / Enforcement
7.
Union Gap
8.
Information / Outreach
9.
Flood Response
10.
Shaw Creek
11.
St. Joseph's Mission at Ahtanum
12.
Emma Lane Area
13.
Monitoring / Studies / Inventories (added during alt. review process)
12
Ahtanum-Wide Hollow CFHMP
The approved alternatives table (Tale 9-8) includes all alternatives, which were not
prioritized at this stage of the process. The combined Committee felt the alternatives in this
list were worthy of further discussion before final recommendations were made.
ALTERNATIVES DISCUSSION BY FLOOD ISSUES CATEGORIES
The alternative descriptions in the section below are summarized in Table 9-8 and organized
based on the 13 flood issue categories in Table 9-7, not the 15 flood problem groups in Table
9-4. The original alternative numbering scheme, using the groups from Table 9-4, is
maintained in parentheses. For additional background regarding alternative generation, see
Chapter 4 Floodplain Characteristics, Chapter 5 Development in Basin Floodplains, Chapter
6 Planning and Regulatory Environment, Chapter 7 Basin Flooding Characteristics, and
Chapter 8 Flooding Issues.
Dropped alternatives from Table 9-6 are not carried forward into Table 9-8 or the discussion
below. However, alternatives that were dropped later in the process of developing
recommendations are retained in Table 9-8 and the discussion below. They are noted as
being dropped within Table 9-8.
The discussion of the alternatives below is brief if the alternative listing on the table is
largely self-explanatory or if the alternative is a minor component of other alternatives.
Greater discussion is reserved for alternatives that received a great deal of attention from
the committee or required additional explanation to address concerns generated during
committee meetings about their scope.
CHAPTER 9 - ALTERNATIVES 13
TABLE 9-8
Alternatives Summary by Flood Issue
1. CHANNEL ISSUES / RIVER FUNCTION
1. Stream Management - Natural vs. Irrigation Ditch or Urban Stream
A.
Separate irrigation conveyances from natural streams based on studies where it is shown this would
be effective as flood control. (15B-3, 5D-7)
• Reduce operational spill of irrigation water into streams (7A-2)
• As part of mitigation for piping of irrigation waters, create a more normative conveyance
schedule (7A-4)
Consideration- A non normative hydrograph results in overgrowth of species such as Pacific willow,
which contribute to flooding, particularly in the Wide Hollow basin. Lower Wide Hollow and Ahtanum
Creek are influenced by the water table of the Yakima River, which also has a non -normative
hydrograph.
B.
Establish work groups to clarify technical & regulatory measures and options for natural, artificial
and shared drainages effected by irrigation:
• Consideration- This may involve distinguishing between areas that should retain natural
functions and processes (e.g. Ahtanum Creek), as opposed to areas that should be managed
within the context of high intensity uses, such as irrigation conveyance or drainage ditches. (7B-
7, 15E-5, 15E-6, 5D-2, 5D-3, 5D-4, 5D-5, 5D-8, 5F-4, 15E-1, 2-2, 8A-3)
2. Riparian Protection / Restoration
A.
Utilize existing federal, state and local policies and programs to:
• Preserve/restore riparian areas- Acquisition/legal protection of riparian zones:
o Easements,
o Agreements, (Fee Simple, etc.).
o Consideration- This is most often done with multiple objectives -Fish and Wildlife habitat
protection, (Open Space, parks, trail and other)
• Protect riparian vegetation:
o Conservation Reserve Enhancement Program
o YTAHP (Yakima Tributary Access and Habitat Program)
o Open Space taxation incentives
• Limit rates of habitat loss:
o Endangered Species Act,
o Growth Management Act, Critical Areas Ordinance
o Hydraulic Code
• Maintain watershed and channel processes (i.e. Clean Water Act, In -stream flow rules (9C-1, 7B-
2, 7B-3)
B.
Coordinate/cooperate with currently in-place habitat protection and restoration programs (i.e.
Salmon Recovery Funding Board, Northwest Power and Conservation Council), as well as other
programs and funding sources that encourage habitat protection. (9C-2)
C.
Work with private habitat restoration organizations (e.g. Land trusts, Greenway, other non-profit
programs) to protect riparian areas. (9C-4)
3. Elk
A.
Move elk feeding stations to other areas away from streams. (9B-3)
B.
Apply similar management standards to elk confined feeding operations as livestock operations &
incorporate watershed management principles when managing elk. (9B-2, 9B-4)
C.
Develop a Coordinated Resource Management Group (e.g. Wenas working group). (9B-1)
14
Ahtanum-Wide Hollow CFHMP
4. Dumping and Pollution in Streams
A.
Investigate funding for enforcement and cleanup of illegal dumps on private ground. (1C-9, 1C-10)
FCZD would not be the lead
B.
Initiate/Encourage Stream cleanup programs (1C-2) Committee decision not to carry this forward as
a recommendation 3-16-09
5. Private Landowner Assistance
A.
Utilize fence designs that allow for prevention of floodwaters from backing up on fences, such as:
• Breakaway fence panels in locations that flood frequently.
• Suspension fences, which consist of steel pipe or cable hung high above the creek, and hanging
lighter materials down from the cable. This works as a fence, but is not lost during floods.
• Fence setbacks - hold fences back some distance from the creek (loss of traditional land usage)
(1B-1, 1B-2, 1B-3, 1B-4, 1B-5) (note: this is a problem in site specific locations & doesn't apply
to entire CFHMP area)
B.
Work with landowner assistance programs (i.e. Conservation Districts) for establishing or re-
establishing vegetation and information about flood resistant fencing (7B-4, 1B-7, 1B-8).
6. Vegetation
A.
Utilize natural solutions for in -stream flooding issues:
• In some locations, add wood to stream to "catch" wood debris- this accomplishes multiple
objectives- would benefit habitat as well as reduce the volume of woody debris that
accumulates on bridges, diversions, and other structures. (7D-4)
• Utilize plantings (such as Red osier dogwood, etc.) solutions for bank stabilization (15C-2).
B.
Control or Replace Undesirable Plant Communities (e.g. hybrid willows)
• Utilize other types of vegetation that can be substituted for Pacific Willow over the long term -
may include non-native plant communities. Research appropriate plant communities for
denuded riparian areas (7A-5 & 7B-8, moved alt #'s to associate with correct alt, 5-19-10)
• Utilize regulations or region -wide permits for management of the undesirable riparian plant
communities (7A-3,) Committee decision not to carry this forward as a recommendation 3-16-09
• Create program for removal and long term management of hybrid Willow- (may be at different
scales- site specific or throughout the watershed, i.e. for some distance upstream and
downstream of bridges on Wide Hollow, have a more aggressive Willow control program). (7A-
1)
C.
Increase evergreen riparian vegetation at known ice jam locations to reduce the formation of anchor
ice (1A-5). First step is to inventory locations where this occurs. Committee decision not to carry this
forward as a recommendation 3-16-09
7. Channel Relocation/Reconfiguration
A.
Relocate modified streams away from high-intensity uses, or restore incised stream channels to
allow for natural riparian/flood function
• Channel reconfiguration and reconstruction at Emma Lane, Shaw Creek, lower Wide Hollow in
Union Gap, and the Mission (15A-1, 15B-1, 7B-6).
B.
Flood overflow channels/conveyances where channels are perched (15B-9)
CHAPTER 9 - ALTERNATIVES 15
8. Channel Maintenance
A.
Perform periodic channel maintenance (Stream clean out) (15A-2) at identified problem areas.
Consideration- more effective when done on a small scale (site specific near bridges and other
problem spots). Not as effective for large flood events
• Convene technical work group to assess gravel management options in upper Wide Hollow
watershed (Ellensburg formation geology)
• Develop coarse sediment budget through empirical monitoring or modeling.
• Implement options to increase channel stability based on information generated in
alternatives A & C above.
• (gravel/sediment alternatives added from 2-26-08 committee meeting, so no alt. #)
9. Beavers
A.
Establish regulatory measures (buffers, setbacks, etc.) to allow for localized flooding/changes in
water surface level or the channel (9A-5, 9A-7)
B.
Deal with beavers on a case by case basis- use discretion based on situation ("is the floodplain
function provided by the beaver a good thing or a bad thing?") (9A-1)
• Remove "problem" beaver dams, under permits from Department of Fish and Wildlife. (9A-3,
9A-6)
• Establish policies for lethal trapping or relocation of "problem beavers." (9A-2)
• Encourage beavers in areas where their presence could restore degraded watershed function.
(9C-5)
10. Flood Protection
A.
Natural changes in the channel become a problem when they threaten homes, businesses,
agricultural land, or infrastructure therefore the following alternatives may be considered, where
appropriate.
• Levees, armor, buffers, CMZ (channel migration zones) (15C-1)
• Structural flood control measures either by individuals or government (4-7)
• Utilize "softer" solutions for bank stabilization, bio -engineering (15C-2)
• Levees constructed along perched channels (i.e. Cottonwood Grove) (15B-2)
2. WATERSHED FLOOD ISSUES
1. Non-Stormwater Watershed Issues
A.
Alter DID management over the long term as land use changes (15E-4) Committee decision not to
carry this forward as a recommendation 3-16-09
B.
Consider environmental benefits in funding processes (i.e. Benefit -Cost Analysis). (9C-9) Committee
decision not to carry this forward as a recommendation 3-16-09
C.
Include habitat goals in disaster response and post disaster mitigation (9C-8.) Committee decided (6-
15-09) to keep this as an alternative but not carry it forward as a recommendation.
D.
Preserve natural drainage including draws that provide flood protection (new from 2-26-08, so no alt
code)
E.
Planning for the joint needs of fish and wildlife in floodplain development. (9C-6) Committee decision
not to carry this forward as a recommendation 3-16-09
F.
Design bridges and irrigation diversions to reduce potential for debris and bedload (sediment)
accumulation. (5B-1, 7D-3, 7D-5) (see also debris alternatives under irrigation and bridges/roads and
channel maintenance under channel issues)
2. Stormwater
A.
Utilize NPDES stormwater programs to retain site runoff and reduce overland flow for Yakima
urbanized area. (1D-5) Committee decision not to carry this forward as a recommendation 3-16-09
B.
Develop stormwater standards for detention and retention on site and regional; abide by and enforce
16
Ahtanum-Wide Hollow CFHMP
3. BRIDGES AND ROADS FLOOD ISSUES
1. Design
stormwater design standards; and incorporate flood issues into stormwater programs (4-4, 13C-4, 1D-
6, 14C-7, 15G-1, 13C-1)
C.
Establish a relationship between stormwater standards and development standards in floodplains with
regard to flooding (high water table and low gradient) (13C-3)
D.
Preserve natural drainage including draws that provide flood protection (new from 2-26-08, so no alt
code) (same as 1.D above)
E.
Size drainage facilities for future build -out and flood flows — including ability to pass upland drainage of
100 -yr flow (15E-2, 15F-1, 15G-2).
F.
Limit new connections to existing undersized drainage systems, ie. DIDs, storm drains, and resolve the
runoff issues presented by the Drainage Improvement Districts (DIDs) that may act as stormwater
drainage systems although designed for subsurface flows. (13C-2, 15E-3)
G.
Implement an effective Stormwater Management Program that reduces basin flooding (4-15)
3. BRIDGES AND ROADS FLOOD ISSUES
1. Design
A.
Adequate Bridge & Road Crossing Standards:
• Develop bridge design and freeboard standards to account for backup from ice and other debris.
• Develop new floodplain width and function standards and policies for bridges in the floodplain to
account for effect of the structure relative to floodplain function. Includes consideration of
upstream and downstream beyond usual right-of-way (This will require public involvement.)
• Consider additional flow capacity to account for additional habitat permit requirements for new
bridges beyond the State hydraulic code requirement of 100.
• For new structures, include in -stream actions to maintain conveyance as part of the design and
construction (such as grade control) where needed.
• Design new bridges to allow natural channel processes where they occur. Take into consideration
natural channel processes that have been lost or altered, or where natural processes are highly
unpredictable.
(1A-1, 12A/B-1, 12A/B-5, 12A/B-6, 12A/B-7, 12G-7)
B.
Improve bridge conveyance at 16th Ave. on Ahtanum Creek (3-13).
C.
Consider lowering existing roads where they act as dams and cause flooding (ponding) (12D-5).
D.
Provide armoring of roads which act as levees (Cottonwood Canyon Rd., etc.)(12D-1).
E
New and reconstructed roads should be evaluated. New roads that are not intended to be passable to
a certain standard (10, 25, or 100 year flood), should be built at grade (12F-6, 12H-8). *Coordinate
with 2A. (below)*
• Consider designing new roads at grade in FEMA identified overflow areas. (12D-4)
F.
Armor road ditches where road fill is going to contribute to excess bedload (new alternative) (12E-3).
G.
Provide better floodplain mapping and modeling to allow for better infrastructure design, including
current Ahtanum-Wide Hollow remapping. (12C-2, 12A/B-2).
H.
Modify drainage standards for roads in overflow areas (i.e. Emma Lane area) (3-12)
I.
Recognize the limitations of culverts as flood conveyance structures (12E-2)
2. Monitoring / Maintenance
A.
Decide upon, designate and maintain critical access routes at 10, 25 and 100 year events *Coordinate
with 1D and 1E above (12F-3, 12H-7).
B.
Actively monitor and manage channels adjacent to bridges to improve and maintain bridge capacity
(Armor or sediment removal in poorly functioning bridges, and management of vegetation debris).
Monitor channel and floodplain conditions post bridge construction. If significant unforeseen
problems develop, after the stabilization period, respond to them (12A/B-4, 12A/B-8).
• Institute a policy of more maintenance at known problem bridges (12F-2)
C.
Replace old culverts with higher capacity culverts based on level of risk (12E -7a).
CHAPTER 9 - ALTERNATIVES 17
D.
Investigate and recommend increased maintenance and debris cleanout of culverts and ditches on
public roads (coordinate with road maintenance crews to optimize ditch cleaning for flood purposes)
(1D -1,12D-2, 12E-1).
E.•
Assess the cumulative effect of new road policies and standards regarding roads acting as dams or
conveyances. (12C-3.)
Take larger scale affects to the watershed into account when designing new transportation
systems: Minimize number of roads- maximize efficiency. (12H -4a)
3. General Planning
A.
Inventory and rank problem bridges throughout the watershed and coordinate with Capital
Improvement Plans of local and state jurisdictions. (12A/B-3)
Considerations: [(County Roads currently has an inventory, Surface Water is currently working on as
part of FEMA re -mapping). The rate of replacement of infrastructure is limited by funding, and to
some extent standards in the funding programs.]
B.
Integrate existing or new funding programs into strategic program for addressing problem bridges
(12A/B-10).
C.
Explore ways to take better advantage of Federal and state funding programs to reduce or mitigate
the environmental effects (including flooding) of existing road systems (12G-6).
D
Work with landowners upstream and downstream of new infrastructure to design access to property
to mitigate flood impacts (12G-9).
E.
Replace flood damaged transportation infrastructure in a manner that reduces vulnerability to future
flood hazard (12G-5).
F.
Identify and map overflow paths and relationship to road crossings. (12G-3)
G.
Minimize negative flood effects of accessing major arterials esp. when adjacent to or across
floodplains (12H -4.c)
4. IRRIGATION FLOOD ISSUES
1. Conversion of Irrigation Systems
A.
Consolidate irrigation diversions to minimize stream impacts, consider upgrades like piping, and
consider converting irrigation systems to a pressure -based system, i.e. Pine Hollow (5C-1, 5C-2, 5D-1)
2. Infrastructure Maintenance and Inventory
A.
Develop a program of proactive debris removal and maintenance on irrigation structures (1D-2, 5B-4)
• Install temporary or sacrificial debris capture structures adapted to existing channel conditions to
reduce debris problems, esp. Wide Hollow. (5B-2)
B.
Conduct an inventory of existing irrigation infrastructure (working or abandoned) and flooding
impacts. Identify problem locations and old drainage and irrigation systems that are affecting flooding
in the irrigation system, ie. gate at Wiley City (2C-1, 5A-1, 5E-1)
• Install removable structures, such as irrigation pumps, weirs, gates, etc. (potential problem with
ice), e.g. JM Perry Tech. (5B-3)
C.
Identify sources of funding for removal of abandoned irrigation structures (5E-2)
D.
Investigate the possible use of flood gates or siphons to reduce flood flow routing by irrigation
infrastructure, if needed, identify locations of most benefit:
• Stationary or removable flood gates for use at diversions or in channel (5A-2, 5A-5)
• Install undershots in some locations- siphons through gulleys and depressions under the ditch
(5A-4)
18
Ahtanum-Wide Hollow CFHMP
5. LAND USE FLOOD ISSUES
1. Subdivisions / Housing Developments
A.
Minimize new homes/structures etc. in harms way (15C-11).
• Effectively integrate protection of floodplain functions/flood hazard reduction in individual
subdivision platting process. (See also regulatory) (8C-5.)
• Create more stringent develop standards in some flood prone areas and jurisdictions (4-5.)
• Work toward common development standards (added at 4-7-08 mtg, so no alt. code #)
B.
Work for consistency in zoning standards for developments and buildings within floodplains. Determine
gaps in the regulatory scheme.
• Recognize that in some places, the issues associated with larger scale proposed developments are not
adequately addressed by current standards. (13A-9) (13B-7).
C.
Establish or maintain standards for subdivision in the floodplain- at the minimum require a buildable area
outside of the floodplain. Standards for lot size and housing location. (14D-1)
2. Incentives / Taxation
A.
Provide special incentives- (clustering, density bonuses, Transfer of Development Rights) for retention
of floodplain function in development design (13B-4).
• Provide incentives or bonuses for developers who actively protect flood hazard areas. (i.e. 10%
density bonus). Specific development standards in zoning ordinance. (From Land Use)- could
probably be moved into Regulations category. (14C-2, 13A-7).
• Utilize landowner incentive programs (i.e. Conservation District, Cost- Shares, Open Space taxation
and other tax breaks) (9C-3).
(These programs can provide significant restrictions, which may discourage participation)
• Utilize existing agricultural subsidies or programs to allow for flooding on some farmland.
Consideration- Depends on water velocity- erosion verses sheet flow. Develop a compensation
program for productive ag land lost to flood induced erosion. Consideration- could be linked to
property loss protection program (15C-4)
3. Open Space / Parks
A.
Encourage the retention of open space in floodplains through:
• Open space taxation policies (specifically including these problem areas in the public benefit rating)
(13B-6)
• The development of walking paths / trail systems (12H -4d).
• Develop policies and standards for open space retention within expanding UGA's, and within
individual developments. (14E-3)
• Incorporate open space/floodplain retention into site plans (e.g. La Salle High School)(11A-3)
• Include flood hazard reduction goals in Open Space Planning (13C-5)
• Encourage local governments to establish specific comprehensive plan policies to use floodplains and
other critical areas to meet their GMA requirements for Parks and Open Space. This may substitute
for designating some blocks of private land as open space. (13A-5, 14E-4)
• Maintain open areas near the mouth of Ahtanum creek for inevitable flooding (i.e. Fulbright Park and
adjacent areas).(11A-2)
• Encourage parks (County and City) in frequently flooded areas (i.e. Fulbright Park) (13A-3).
CHAPTER 9 - ALTERNATIVES 19
4. Large Scale Retention of the Floodplain
A.
Reduce density in the floodplain through various methods -(14C-3).
• Preserve and restore natural floodplain in places that retain some of the floodplain function.
Prioritization- allow for flexibility while identifying critical locations, based on CFHMP and mapping (4-
12).
• Make changes to comprehensive planning and zoning documents and maps to focus lower intensity
development within floodplain corridors and focus higher intensity development outside floodplain
corridors (14C-4, 14C-5).
• In certain high risk locations, consider development moratoriums or high standards of proof in place
where development is outpacing knowledge or tools available to keep the public safe (i.e. the area
has not been mapped, or conditions have changed since the last mapping) (13A-15).
• New major arterials and new traffic -generating developments should be located outside of
floodplains (See also Bridges & Roads). (12H -4b)
B.
Incorporate principle of floodplain planning into infrastructure & similar facilities plans (8C-2, 12H-2)
5. Acquisitions / Easements / Incentives
A.
Acquisition/easements of land surrounding flood problem areas (4-13, 15B-4, 15D-4)
• Acquire land- fee simple or easement, for a variety of purposes consistent with floodplain function
(13B-5).
• Address maintenance of drainage easements -establish who is going to enforce maintenance (9C-12)
• Develop a program/policy guidelines for areas threatened by meandering and erosion, or frequent
inundation, including:
• Buyouts
• Relocation
• Easements
• Flood -proofing
(15C-3, 15C-7, 15C-9, 15C-10)
B.
Utilize tools such as floodplain easements to preserve off-site storage of water and sediment in farmland
(existing pastures, alfalfa), while preserving use as farmland. Consideration: This could accomplish two
goals: preservation of use of land for agriculture, and preservation of floodplain. (15B-5, 15B-8). Link to
Farmland preservation programs.
C.
Encourage organizations (neighborhoods, County/City/Yakama Nation or others) to purchase floodplain
areas (9C-10).
D.
Provide incentives for landowners and developers who provide floodplain storage (4-6).
6. Standards for Development in High -Risk Areas
A.
Establish Flood Overlay Zones in affected jurisdictions. These overlay zones would have legal status (i.e. in
a zoning code) and contain development standards, objectives, and review/process criteria for the broad
suite of land uses that occur in floodplains. (13B-3)
• Consideration- The Flood Overlay Zone exists within the Yakima Urban Area Zoning Ordinance.
B.
Develop policies for areas of existing dense development within the floodplain (such as Ahtanum and
Wiley City) (14A-4, 13A-13)
Design better drainage, especially in Wiley City and Ahtanum.
Consideration: In the past, overflow water used a ditch along the railroad, which has been filled in.
Resulting lack of drainage causes sheet flow (14A-4)
Establish areas such as Wiley City & Ahtanum as special study areas
C.
Establish policies in flood prone and flood hazard areas for directing preferred locations for the siting of
new infrastructure such as major and minor arterials, water and wastewater distribution mainlines,
regional stormwater facilities, parks and greenbelts. (13A-11)
20
Ahtanum-Wide Hollow CFHMP
7. Miscellaneous Policies
A.
Ensure flood policies in the Yakima Urban Area Comprehensive Plan are implemented through ordinances
and land use decisions. Planning for flooding is supported in Objective E7 (13A-4).
B.
Develop special land use and flood -proofing standards for industrial uses relating to hazardous materials,
storage, use, disposal (11B-1)
6. DEVELOPMENT STANDARDS/ENFORCEMENT FLOOD ISSUES
1. NFIP Related
A.
Consider increased elevation above BFE of new structures in the floodplain. 14A-2
B.
Require Flood -proofing
• Flood -proof utilities
• Flood proof structures- elevate, make existing structures less flood damage -prone (4-8)
2. Special Zones
A.
Based on flood risk studies, consider stricter ordinances for flood zones in Union Gap (6C-4, 14A-3).
B.
Consider use of the Zero or 0.1 foot rise practice from International Building Code (14C-8)
C.
Identify areas with floodplain "islands" and develop standards that:
1. Limit density to provide flood passage
2. Provide emergency access
3. Transportation networks in these areas (even if they are zoned as low density) should be planned
to take into account surrounding properties, rather than a standard site-specific approach (12H-
6).
3. Miscellaneous
A.
Enforcement- Adequately fund enforcement activities. More effective code enforcement, especially
for blatant disregard of the law.
(1C-4, 1C-3, 18)
B.
Coordinate between jurisdictional procedures in place for expedited permit issuance during and
period after a flood event under State and County regulations (10D-1).
7. UNION GAP FLOOD ISSUES
(No Sub -categories for Union Gap Issues)
A.
Modify Wapato Dam (4-11, 6C-7) to decrease flood risk (See Upper Yakima CFHMP)
B.
Sediment Transport on the Yakima River
• Studies:
• Study how changes on the Yakima River adjacent to Union Gap may affect water tables in
Union Gap (4-18). (6C-9).
• Causes and rates of channel aggradation in the Yakima River (4-17)
• Identify future flood impacts that may occur as a result of aggradation (6C-1, 6C-2, 6C-3, 6C-
8)
• Improve sediment transport along the Yakima River (Refer to the Upper Yakima CFHMP) (4-10).
(Wapato Dam and upstream reach)
C.
Relocation of Wide Hollow Creek below 3rd Ave. (6C-6, 11A-4)
• Construct floodgates on Wide Hollow culverts if Wide Hollow is diverted into Ahtanum Creek
(abandoned culverts at/near the mouth if creek relocated) (6C-5)
D.
Bypassing the Mill structures. (11A-5)
E.
The Spring Creek floodgate should generally be closed except for habitat or flow enhancement for a
limited time period (see alternative F below also) (6B-1)
F.
Install a remotely controllable floodgate that could be opened some times of year, closed at others
(on Spring Creek floodgate) (6B-2)
CHAPTER 9 - ALTERNATIVES 21
G.
Improve conveyance downstream of the culverts on the Spring Creek irrigation channel by increasing
grade — this would help in most flood events, possibly not in large-scale flooding. (6D-2)
H.
Retain overflow path along the railroad right of way. (11A-1)
8. INFORMATION / OUTREACH FLOOD ISSUES
1. Mapping
A.
Use improved flood mapping and modeling to assess risk to new and existing infrastructure and for
designing new infrastructure (12G-1).
B.•
Re -map the floodplain for NFIP rate maps, to allow for up-to-date accuracy and application of land
use regulations. (8D-1, 4-3, 15B-6)
• Consider the contribution of high ground water to flooding (4-9). (4-19).
Complete floodway mapping in the region (15D-1, 15C-13)
• Regularly scheduled updates (15D-2)
Consideration: the re -mapping process for Ahtanum-Wide Hollow is currently underway
C.
Map Channel Migration Zones (and other hazards) (15G-4 15D-3)
• Identify areas that are at risk for channel migration in addition to identified CMZ, ie. N.F.
Ahtanum, below the Narrows, at the Mission, Shaw Creek, etc. (15C-12).
D.
Supply Better/Different mapping products
• For example, identify where hollows overflow, upland flood channels are located and (aside from
the formal FEMA mapping process) disclose when purchasing or developing property. 1D-8. 15F-
2
Consideration - (would be difficult for the County to produce in some locations)
2. Landowner Assistance
A.
Provide public education about potential flood hazards and responses on individual properties
including keeping debris sources out of known flood channels (10B-2, 1D-3, 1D-7).
B.
Encourage residents who are at high risk for flooding to purchase flood insurance even if they are not
in a mapped floodplain (8D-3.)
C.
Create pamphlets for new landowners i.e. pamphlet put out for small landowners in Kittitas County
by the Kittitas Conservation District (fence debris) [responsible party] (1B-9.)
D.
Prepare a program to educate landowners about riparian function and health before and after a flood
event (9C-7.)
E.
Provide information about properties up -front in public services (no surprises) (13A-10, 14B-1)
F.
Public education about maintaining driveway culverts, and correct sizing and maintenance of
culverts. (12E-5)
3. General Public Outreach
A
Cooperate with others to support or develop public education programs, such as stream cleanup
programs and volunteer monitoring (9C-13).
B.
Encourage citizens to report dumping in streams (public outreach) (1C-5).
C.
Cooperate with others to engage in public education regarding the values and esthetic appeal of
riparian corridors/open space for purpose of preservation of floodplain corridors (7B-5).
D.
Public education about how riparian and flood hazard management goals complement each other.
Inform people about the importance of the functions of streams, rivers, and natural drainage ways.
(9C-11).
E.
Provide public education directed to residents, farms and businesses to increase individual
preparation for floods (10A-3).
4. Outreach/Information Related to Flood Projects
A.
Flood Control Zone District to provide technical assistance and comments regarding flood hazards
and infrastructure design (12G-2).
B.
Public notice/disclosure/consultation when flood projects are planned (19).
22
Ahtanum-Wide Hollow CFHMP
5. Realtor, Lender, etc. Outreach
A.
Provide information about flood history to realtors, lenders, etc. in proposed new developments
(15C-14) (15C-15)
B.
Put on workshops and other outreach for realtors (15C-16)
9. FLOOD RESPONSE FLOOD ISSUES
1. General Flood Response Planning
A.
Participate in and support Flood Response planning efforts (as part of the Emergency Response Plan)
(10A-1, 10A-2, 12F-5).
B.
Implement Emergency Response Plan (Get Ready- Set- Go- Recover) procedures, from the Emergency
Response Plan (10C-1).
2. Planning/Mapping
A.
Identify and map problem spots throughout the watershed so flood responders know where to look
first (5F-5).
B.
Designate emergency response access routes and incorporate into transportation planning (12F-4).
Designation of evacuation routes and notification of the public and first responders (10B-3).
C.
The Flood Control Zone District will develop databases of parcels affected by different level flood
events, corresponding to upcoming Ahtanum-Wide Hollow FEMA re -map (10C-5).
3. Coordination
A.
Provide infrastructure or technology for better communication between agencies (EOC) (10C-2)
B.
Coordination between Emergency Management and the Irrigation Districts such as AID and Yakima
Valley Canal, for management during floods. Include Irrigation Districts in communications with the
EOC (emergency operations center) and FCZD (5F-1, 5F-3, 2B-3).
C.
Interagency coordination of flood information and response, including WDFW, Irrigation Districts and
Yakama Nation Natural Resources, Fisheries and Engineering (10C-4, 10C-9).
D.
Flood responders concentrate patrol and response on known problem bridges and roads - (12F-1).
E.
Public and agencies coordinate flood fight and post flood actions with recommendations identified in
the Ahtanum-Wide Hollow CFHMP, since they require approval by WDFW and Ecology (so will be
consistent with regulations), and provide a good basis for deciding whether to take emergency
actions. (10D-2)
4. Outreach
A.
Recognition and dissemination of knowledge about potential flood hazards during a flood event in
coordination with the EOC (10C-3).
B
Develop warning systems including mass media (10B-1)
• Investigate reverse 911 system
C.
Encourage volunteer flood -watchers program to provide information (10C-8).
D.
Provide special flood phone line for public to call in and provide information about current flooding
(10C-7). (EOC & FCZD cooperate/coordinate)
5. Irrigation Gates
A.
Improve access to Bachelor diversion during floods without diverting flood waters or making flood
problems worse (2C-3).
B.
Coordinate opening gates for flood relief, based on flood forecasts, channel maintenance needs, and
impact to diversion facility (5F-6).
6. Monitoring/Documentation
A.
Install a North Fork gage including telemetry (5F-2).
CHAPTER 9 - ALTERNATIVES 23
B.
Provide open contract for aerial observation during floods for event documentation (10C-6).
7. Ice Jams
A.
Inventory of locations where ice jams are known to occur- identify them in the Flood Response Plan
(1A-7).
B.
Outline emergency response to ice jams in the Flood Response Plan (1A-3).
• Alert residences at risk. (added by staff so no alt #)
• Blast ice jams- (normally only done on very stable ice jams) (1A-6).
• Facilitate regulatory approval by Ecology and Fish and Wildlife and local jurisdictions.
8. Regulatory
A.
Facilitate involvement of permitting agencies as a component of the Emergency Management Plan,
and are present in the EOC during a declared emergency. General guidelines for taking action during
a declared or non -declared emergency are: A. permitting personnel do a site visit (10D-3, 10D -3a).
• choose minimum flood fight action, or action that will meet the intent of the regulations- i.e.
better protect/enhance the resources (10D -3b)
• follow up- 6 months after a declared disaster to come into compliance for flood fight actions
(10D -3c)
10. SHAW CREEK FLOOD ISSUES
1. Structural Response for Shaw Creek Flooding
A.
Relocate Shaw Creek to the low point in the drainage to allow for more natural stream and floodplain
function, and less maintenance. Consider a potential for a larger solution that includes concurrent
considerations on Wide Hollow Creek
• Nob Hollow Road possibly a problem, possibly remove two Wide Hollow bridges, which would
help with conveyance on Wide Hollow
• Shaw Creek overflow Bridge added as part of Nob Hollow construction.
• Move Wide Hollow Creek South of Wide Hollow Road (if Nob Hollow is not constructed).
• Investigate ways to keep certain properties undeveloped (for flood protection, and for possible
relocation of Shaw Creek channel). Address Zeigler's property
• School owns property, and may be amenable to relocation.
• Consider downstream impact of changing Shaw Creek's confluence with Wide Hollow west. (If all
creeks diverge on Wide Hollow during a major flood, it may cause problems at 80th and West
Valley Park.)
• Recommend quick actions which allow us to keep options open:
o Keep at -risk areas undeveloped and,
o Require drainage easements,
o Allow for high density development in areas that are not at risk
Consider purchase of property or property interest (i.e. option, easement, etc.) needed for
relocation soon before development prevents this alternative (new from 2-26-08, so no alt code)
(8B-1, 8E -1.a -e, 8E-4, 8E -6.b -d)
B.
Reconfigure Shaw Creek to function as floodplain and fish and wildlife habitat (8A-2).
C.
Expand diking along Shaw Creek to protect new and existing development (8B-2, 8E-2, 15B-2)
D.
Consider developing regional retention upstream ofTieton Drive (8C-6, 8E-3)
E.
Consider overflow channel — addition from FCZD so no alt # (8-20-08)
2. Information and Outreach
A.
Notify developers and prospective residents of flood hazard on the property (8E -6.a)
B.
Hold neighborhood meeting for residents living near Shaw Creek (public outreach). (8D-4, 8D-5).
24
Ahtanum-Wide Hollow CFHMP
3. Floodplain Designation
A.•
Change zoning code/amend the Comprehensive Plan to allow for restrictions on development in
flood -prone areas around Shaw Creek, and protection of floodplain function (8C-3).
Request an administrative designation of floodplain on Shaw Creek, based on historic flood
patterns in the Shaw Creek area, prior to updating of the FIRM maps. (8C-4, 8C-7, 8E-5).
B.
Protect natural floodplain functions in Shaw Creek's watershed, especially before it is mapped (8C-1).
11. ST. JOSEPH'S MISSION AHTANUM FLOOD ISSUES
1. Study
A.
Continue Surface Water's study, which is predicting flood flow patterns at Ahtanum Mission, based
on surveys and modeling. Modifications to infrastructure management may result in relation to
headcuts (2A-1).
B.
Determine the effects of flooding at the Mission on irrigation structures and of irrigation
infrastructure on flooding patterns (2C-6)
C.
Verify if there is room for Ahtanum Creek to occupy old floodplain channels on the tribal land
adjacent to Ahtanum Mission. Determine if the tribe/allotment owners may be amenable to that (2-
3).
D.
Define the sensitive historical and cultural issues at Ahtanum Mission site (2-1).
2. Hatton
A.
Recreate a flood overflow channel back to Ahtanum Creek from Hatton Creek (natural overflow
channel blocked in the 1930s) (2A-5. 2B-2)
B.
Modify the old Hatton ditch channel below the diversion. Intent would be to block/armor channel to
prevent opportunity for formation of headcuts (2A-7).
C.
Remove the old Hatton Diversion (Ahtanum Mission Headcuts) (2A-6).
3. Levees/Armor
A.
Armor stream channel to prevent migration of Ahtanum Creek to the North (Soft levees on North
side would not be sufficient- river would cut through) (2A-8).
B.
Utilize Ring dikes to protect St. Joseph's Mission property (2A-3).
C.
Major levee construction on Mission property to alleviate headcuts (2A-2).
4. Bachelor
A.
Modify the Bachelor Diversion to improve functionality and decrease flood hazard (e.g. upstream of
90- degree turn on Ahtanum Creek) (2C-2, 2C-4)
• During floods, close Bachelor diversion and create a new high flow diversion channel from
Ahtanum creek (2C-5)
B.
Identify potential future downstream impacts from any proposed changes in the Ahtanum Mission
area, and establish acceptable level of flooding along the entire reach (2B-4).
12. EMMA LANE AREA FLOOD ISSUES
1. Study
A.
Perform an Emma Lane flood study, and develop design guidance on acceptable flood protection
levels. (3-2)
• Address Ahtanum Creek flood conveyance downstream of 42nd and Ahtanum Rd. (3-18).
B.
Perform a Cost -Benefit analysis of stream relocation at Emma Lane (3-19).
CHAPTER 9 - ALTERNATIVES 25
2. Relocation
A.
Move Ahtanum creek to a lower point in the floodplain (requires cooperation with Yakama Nation,
acquisition of at least two homes, and a new bridge) (Emma Lane) (3-1).
• If Ahtanum Creek is relocated, consider a design that does not include filling in the old Ahtanum
Channel- looking at the existing channel as habitat (3-15).
• Examine Constructing a controlled side channel to bypass Emma Lane, rather than moving the
creek (3-14).
3. Development in Emma Lane Area
A.
Limit future development in the Emma Lane area (3-3).
• Place controls on building in the flood -prone areas in and around Emma Lane (3-17).
B.
Adopt and implement more strict building standards in Emma Lane area- flood -proofed homes,
buildings (3-11, 3-3).
4. Channel and Drainage Capacity
A.
Improve drainage throughout the entire Emma Lane area- culverts, roads, etc. (3-8).
• Reconfigure the Bachelor Creek Bridge on Ahtanum Road to increase capacity and reduce
backwater flooding (3-6).
• Alter drainage systems and easements, based on Emma Lane floodplain remap study (3-10).
• Eliminate the Shropshire ditch or other irrigation ditch remnants (i.e. remove irrigation ditch that
directs flow and inundates Emma Lane- area pastures and residents) (3-7).
• Improve stormwater system on Ahtanum Road to limit Emma Lane overflows into the airport
area, and downstream to 16th (which floods the intersection at Ahtanum Road) (3-9).
B.
Widen bridge at 42nd Ave. (3-5).
C.
Remove old fill on Ahtanum at the Yakama Nation land just south of Emma Lane (3-16).
13. MONITORING/STUDIES/INVENTORIES FLOOD ISSUES
By Alternative Number
1C-7, 1C-8, 1C-11
Investigate methods for the following:
• Research how other communities deal with dumping, particularly concrete, fill, etc.
• Research measures to deal with illegal/contaminated dumps (meth labs, etc.)
• Examine statewide laws relating to dumping and streams
12D-3
Inventory roads acting as levees. Design site-specific solutions based on the inventory and
current and future road classification; solutions may include armoring or changes to road
configuration, or elimination of the road and selection of alternate route. Incorporate
findings into transportation planning.
12C-1
Inventory channel process problems in relation to existing and proposed roads
12D-6
Inventory of private roads acting as levees
12E-4
Identify road ditches that serve as flood conveyance, thus placing them at a high priority
for maintenance (i.e. Rutherford Rd and Shaw Creek at 80th).
12E -7b
Continue private road culvert inventory
12G-8
Investigate funding sources or incentives for private drainage infrastructure
12H-3
Monitor the effects of urbanization and land use intensification to the characteristics
(runoff, time of concentration, water quality) of the watershed over time. Take action to
mitigate for negative watershed scale effects.
13B-8
Seek land use examples from other similar areas.
14E-1
Investigate standards associated with geologic hazard areas to see if they would be
applicable for flood risk causes such as channel migration zones and alluvial fans.
15A-3
Identify areas where man-made alterations are affecting flooding (i.e. upstream of 64th on
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Ahtanum-Wide Hollow CFHMP
1. CHANNEL ISSUES / RIVER FUNCTION FLOOD ISSUES
This category includes all general channel issues that are not specific to a particular location
and are not included in the bridges and roads or other categories. The first section of this
category relates to Stream Management and the unique problems presented by streams that
are/were used for irrigation conveyance, especially those areas experiencing conversion to
urban characteristics.
1. Stream Management - Natural versus Irrigation Ditch or Urban Stream
These alternatives were generated from the committee meetings on the flood problems
related to: Irrigation Infrastructure, Vegetation Issues, Ahtanum Mission, and Channel
Issues. Four alternatives (15B-3, 5D-7, 7A-2, 7A-4) were merged into the alternative, "A.
Separate irrigation conveyances from natural streams". The alternative refers to a physical
separation between irrigation conveyances and streams. This would alleviate the following
causes of flood problems: perched ditches that convey flood flows, unnatural vegetative
growth due to the artificial hydrograph, and management difficulties related to stream
versus ditch needs and regulations. When this alternative was discussed, it was not
expected that a wholesale separation of ditches and streams could be done or financed
through this CFHMP. If particular small problem spots are identified the stream and ditch
could be separated in coordination with the specific irrigation district involved. This could
also include coordination with irrigation districts to seek funding for reregulation ponds.
However, the greatest value of including this alternative in the plan may be to provide a
local vision for irrigation districts or others to seek funding to separate ditches and streams
in this watershed.
Some of the small streams that are used for irrigation conveyance may not contain flowing
water most of the year if irrigation flows are removed. Regulatory agencies, environmental
stakeholders, and some property owners would likely be concerned about loss of riparian
habitat and amenity values.
The second alternative, "B. Establish work groups to clarify regulatory measures and
options for natural, artificial and shared drainages effected by irrigation" merges six
alternatives - 15E-5, 15E-6, 5D-2, 15E-1, 2-2, 8A-3. This alternative generated a great deal of
discussion in several meetings. Originally the alternative sought re -definition of regulatory
measures for artificial drainages. This approach and wording was deemed too aggressive by
several committee members and included concerns about the ability to implement the
alternative. The wording in the final alternative to establish "work groups to clarify
regulations regarding these channels" was considered to be both needed and something that
could be implemented.
Hatton, Diversion #14, and The Narrows) to allow for cooperative projects.
15B-7
Identification of areas that are near perched channels (disclosure that the area is at risk for
flooding). Identify areas that are of particular concern.
• Identify other perched stream locations (15B-10)
15D-5
Documentation of floods (air photos, etc.) Open contract with flights.
15F-3 &
15F-4
Identify critical hollows through risk assessment and through flood benefit (for protection
measures)
• Identify special flood protection measures for hollows
1. CHANNEL ISSUES / RIVER FUNCTION FLOOD ISSUES
This category includes all general channel issues that are not specific to a particular location
and are not included in the bridges and roads or other categories. The first section of this
category relates to Stream Management and the unique problems presented by streams that
are/were used for irrigation conveyance, especially those areas experiencing conversion to
urban characteristics.
1. Stream Management - Natural versus Irrigation Ditch or Urban Stream
These alternatives were generated from the committee meetings on the flood problems
related to: Irrigation Infrastructure, Vegetation Issues, Ahtanum Mission, and Channel
Issues. Four alternatives (15B-3, 5D-7, 7A-2, 7A-4) were merged into the alternative, "A.
Separate irrigation conveyances from natural streams". The alternative refers to a physical
separation between irrigation conveyances and streams. This would alleviate the following
causes of flood problems: perched ditches that convey flood flows, unnatural vegetative
growth due to the artificial hydrograph, and management difficulties related to stream
versus ditch needs and regulations. When this alternative was discussed, it was not
expected that a wholesale separation of ditches and streams could be done or financed
through this CFHMP. If particular small problem spots are identified the stream and ditch
could be separated in coordination with the specific irrigation district involved. This could
also include coordination with irrigation districts to seek funding for reregulation ponds.
However, the greatest value of including this alternative in the plan may be to provide a
local vision for irrigation districts or others to seek funding to separate ditches and streams
in this watershed.
Some of the small streams that are used for irrigation conveyance may not contain flowing
water most of the year if irrigation flows are removed. Regulatory agencies, environmental
stakeholders, and some property owners would likely be concerned about loss of riparian
habitat and amenity values.
The second alternative, "B. Establish work groups to clarify regulatory measures and
options for natural, artificial and shared drainages effected by irrigation" merges six
alternatives - 15E-5, 15E-6, 5D-2, 15E-1, 2-2, 8A-3. This alternative generated a great deal of
discussion in several meetings. Originally the alternative sought re -definition of regulatory
measures for artificial drainages. This approach and wording was deemed too aggressive by
several committee members and included concerns about the ability to implement the
alternative. The wording in the final alternative to establish "work groups to clarify
regulations regarding these channels" was considered to be both needed and something that
could be implemented.
CHAPTER 9 - ALTERNATIVES 127
Membership in the work groups will be determined during formulation of the CFHMP
recommendations or the implementation phase, but are expected to include WDFW, FCZD,
effected property owners, applicable irrigation district, and CAO/SMP regulatory officials.
Streams that should be reviewed first include Bachelor Creek, Hatton Creek and Spring
Creek (west).
2. Riparian Protection / Restoration
The three alternatives in this section all encourage protection, rehabilitation and restoration
of riparian areas through utilization of existing regulatory and habitat restoration programs.
The first alternative is "A. Utilize existing federal, state and local policies and programs
to:" preserve, protect, limit habitat loss and maintain channel processes (9C-1, 7B-2, 7B-3).
Examples for this alternative are listed on the Alternatives Summary Table (9-8).
The other two alternatives encourage interactions and partnerships with conservation
programs and organizations: "B. Coordinate/cooperate with currently in-place habitat
protection and restoration programs (9C-2)"; and "C. Work with private habitat
restoration organizations (9C-4)". Examples of programs and organizations are included on
Table 9-8 for each of these alternatives.
3. Elk
Three alternatives were generated that apply to elk management in the headwaters of the
Wide Hollow drainage. Alternative "A. Move elk feeding stations to other areas away
from streams (9B-3)" refers to occurring or potential negative effects on streams when
concentrations of elk are fed at a feeding station during the winter. The second alternative,
"B. Apply similar management standards to elk confined feeding operations as livestock
operations & incorporate watershed management principles when managing elk (9B-2,
9B-4)" applies to the feeding stations and also any other range issues that could contribute
to increased erosion or run-off changes. The Washington Department of Fish and Wildlife
(WDFW) maintain a winter elk feeding station off Winchester Road, near the end of Tieton
Drive. WDFW submitted a letter when the alternatives were being reviewed that objected to
treating elk similarly to livestock. Additional discussion about this alternative did not occur
during subsequent committee meetings.
Alternative "C. Develop a Coordinated Resource Management Group (e.g. Wenas
working group) (9B-1)" was suggested based on positive results seen for several local CRM
groups (a grazing group in the Ahtanum area and one that was started in the Wenas).
Coordinated Resource Management (CRM) is a process that creates a voluntary group to
address complicated or controversial resource issues to develop collaborative solutions. A
Memorandum of Understanding (MOU) for the CRM process in Washington State includes
many agency stakeholders, including the Washington Association of Conservation Districts,
USDA Natural Resources Conservation Service, USDA Forest Service and the Washington
State Departments of Natural Resources, Fish and Wildlife, and Agriculture. To initiate a
CRM, a person or organization presents their request to one of the stakeholders (MOU
agencies). The group is frequently coordinated by the local Conservation District, in this
case it would be the North Yakima Conservation District.
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Ahtanum-Wide Hollow CFHMP
The WDFW management plan for elk (Yakima Herd, 2002) includes concerns voiced by the
USDA Forest Service, Washington State Department of Natural Resources, and the Yakama
Nation that there may be more elk in the Yakima Herd than the habitat can carry. The
WDFW draft 2009-2015 Game Management Plan includes objective #25 to evaluate and if
possible, reduce winter feeding based on data from a research project gathering data on the
Yakima herd. The Yakima herd is one of the largest in the state.
4. Dumping Pollution in Streams
The two alternatives for this section are, "A. Investigate funding for enforcement and
cleanup of illegal dumps on private ground. (1C-9)", and "B. Initiate/Encourage Stream
cleanup programs (1C-2)". Illegal dumps are not known to be a large problem in these
watersheds and clean-up programs typically deal with water quality not flooding. For these
reasons, the FCZD would not be the lead for implementing these alternatives.
5. Private Land Owner Assistance
The first alternative is, "A. Utilize fence designs that allow for prevention of floodwaters
from backing up on fences". There are examples listed on the table. This is primarily a site
or area specific problem and may not be wide -spread across the plan area. The second
alternative, "Work with landowner assistance programs for establishing or re-
establishing vegetation (7B-4)" could be coordinated with alternatives in the next section
relating to vegetation.
6. Vegetation
Abnormal growth patterns of native and introduced plant species have been widely
identified as causing flooding problems in the Ahtanum and Wide Hollow watersheds, as
discussed in the Channel Routing of Flood Waters section of Chapter 7 of this plan
(additional background - Vegetation section of Chapter 4). The Committee discussed a
wide variety of options but also recognized several potential difficulties. First was the
anticipated high cost of watershed -wide vegetation management by one or several
agencies. The second was the possibility that private land owners would remove necessary
riparian plants if vegetation management was implemented on an as -needed parcel by
parcel basis. The FCZD and the City of Yakima conducted a pilot project in the winter of
2009-2010 to increase channel conveyance. Additional information about this project is
located in Appendix I.
The first alternative, "A. Utilize natural solutions for in -stream flooding issues:" contains
two sub -alternatives. The first is to add wood to selected stream reaches between bridges so
it will catch woody debris to decrease the amount that gets hung up on the bridge and also
improve habitat diversity. Identifying locations where this would be beneficial while not
adding an unacceptable increase in out of bank flooding may be difficult. The second refers
to utilizing native plant species - esp. shrubs - for erosion control and bank stabilization.
Revegetation is already a mitigation component in permits for other bank stabilization
methods like rip rap, but is not widely promoted or used to increase bank stability by itself.
The second alternative, "B. Control or Replace Undesirable Plant Communities" contains
three sub -alternatives. The first includes researching plants and plant communities that can
CHAPTER 9 - ALTERNATIVES 129
be substituted for hybrid willow, including non-native species. This would require input
from -and coordination with -regulatory agencies such as state Fish and Wildlife Department
(WDFW) and local jurisdictions that regulate Shorelines and Critical Areas habitats. The
next sub -alternative refers to using regulations or regional permits to control undesirable
species. A regional permit would likely only be possible for WDFW hydraulic permits, but
policies added by amendment to the Comprehensive Plans of the jurisdictions may provide
a comparable function at the local level. The last sub -alternative proposes a program for
long-term management of hybrid willow. This would be fairly expensive and would need to
occur into the future. This may not be feasible without an agency stepping forward or a
long-term funding source.
After further investigation of the status of hybrid willows, the FCZD added a new
recommendation to "Petition State Noxious Weed Control Board to list hybrid willows as
invasive species as designated in other states". This would provide a clear regulatory
framework for vegetation management in problem locations of the CFHMP area. Because
this item was added when the recommendations were being developed, it will be on the
Recommendations table, but not the Alternatives tables (and does not have an alternative
number). The FCZD submitted an application to add three willow species to the state
noxious weed list (C class) in March 2011. The species submitted are either non-native
willows or hybrids derived from non-native species. The Washington State Noxious Weed
Control Board (Board) will decide whether to add the submitted species of willow to the
Noxious Weed List in September 2011. The entire list is then open for comment at a public
hearing. After consideration of any testimony the Board will make final decisions on the
new weed list which will become effective January 2012.
The third alternative, "C. Increase evergreen riparian vegetation at known ice jam
locations" was identified as a site specific problem. Locations known to have frequent
anchor ice build-up are also frequently deficient in riparian cover, esp. evergreens that
would provide microclimate effects even in the winter. The first need for this alternative
would be an inventory to identify locations where this kind of vegetation would reduce ice
formation.
7. Channel Relocation/Reconfiguration
This section includes two alternatives. The first, "A. Relocate modified streams away from
high-intensity uses, or restore incised stream channels to allow for natural riparian/flood
function", refers to streams that are highly modified and are usually closer to urban or
commercial/industrial areas. Several creeks are identified as examples on the alternative
summary table. One assumption included in this alternative is that channels perched above
their floodplain experience flooding that is less predictable than stream channels in the
lowest portion of their floodplain. The more predictable a flood is, the less likely it will be to
cause personal or property risks. Greater predictability also makes flood hazard mitigation
more straightforward to design and more effective.
Alternative "B. Flood overflow channels/conveyances where channels are perched" was
not included in further committee discussions after it was generated. This was due to a
preference to relocate streams to the bottom of their floodplain whenever possible.
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Ahtanum-Wide Hollow CFHMP
Relocation is generally preferred because flood response would be more predictable and
there would be no design or maintenance needed for a diversion structure. However, there
may situations where relocation is not possible, so overflow channels would provide some
reduction of flood risk.
8. Channel Maintenance
This section includes one alternative, "A. Perform periodic channel maintenance (Stream
clean out) at identified problem areas". This alternative refers to gravel accumulation in
stream channels, especially where this decreases bridge conveyance. This is especially a
concern in the upper Wide Hollow drainage. Separate components of this alternative
include a need to explore policy options, model sediment transport in the drainage and
selecting options that will increase longer-term stability in the channels. This topic will
require a solid scientific background to help form a consensus on possible solutions. The
FCZD began analysis of a sample number of bridges to investigate sediment deposition and
options for sediment removal in and near bridges. More information about this analysis is
located in Appendix G. The FCZD also began pilot channel sediment and vegetation
removal projects, one of which is provided in Appendix I.
9. Beavers
There are three alternatives regarding beavers that range from the flood problems they
cause to their benefits for watersheds. The first alternative, "A. Establish regulatory
measures (buffers, setbacks, etc.) to allow for localized flooding/changes in water surface
level or the channel", considers allowing beneficial beaver activities where possible. The
largest difficulty for this alternative will be identifying locations where this will not create
local or downstream flooding that is unacceptable. Once potential locations are identified,
policy and regulatory changes would need to be proposed and implemented.
Alternative B, "Deal with beavers on a case by case basis- use discretion based on
situation (is the floodplain function provided by the beaver a good thing or a bad
thing?)" includes the status quo permitting by WDFW and other regulatory authorities for
beavers causing local problems. It also includes developing policies for relocation and use of
beavers to help restore degraded stream reaches. Some of the policy portions of this
alternative will require knowledge gained from the last beaver alternative, "C. Who is
responsible? Identify protocols for beaver management". A necessary step for beaver
management is to determine all of the various regulatory and responsible agencies and
governments. Once all of the stakeholders and regulators are identified (and their
authorities), the first two alternatives can be addressed.
10. Flood Protection
The alternative tracking process -to account for every alternative -turned -up three
alternatives that didn't fit easily into the other categories, so the Flood Protection section
was created in the channel issues/river function category. The first of these alternatives, "A.
Natural changes in the channel become a problem when they threaten homes, businesses,
agricultural land, or infrastructure" refers to structural flood protection measures. The first
sub -alternative lists alternatives that have already been suggested when channels change:
levees, armor, buffers, channel migration zones (CMZ). The second also includes measures
CHAPTER 9 - ALTERNATIVES 131
already being done and suggested (structural measures). Comments raised when these
alternatives were generated included defining "threaten" and whether there is a threshold
level of risk. Discussion of the term "threaten" identified it with erosion and potential for
land and buildings lost. A risk threshold was not determined. While the possibilities
described above may not be the preferred method to address channel changes, it may be the
only alternative in some locations.
The second alternative, "B. Utilize "softer" solutions for bank stabilization, bio-
engineering", expresses a preference for using bio -engineering methods when possible. The
use of vegetation for bank stabilization is included in the vegetation section already
discussed. Other possibilities included in this alternative are use of large woody debris and
reconfiguring the slopes of the stream bank so they are more easily revegetated.
The last alternative in this section is, "C. Levees constructed along perched channels (i.e.
Cottonwood Grove)". This alternative applies to perched channels used in the past for
irrigation conveyance or other agricultural practices. If channel relocation or overflow
channels are not possible in a specific location, construction of a levee would help reduce
the flood risk for existing properties or infrastructure. Due to anticipated high maintenance
and construction costs, permitting difficulties and residual risk for properties behind the
levee, this is not likely to be a preferred alternative unless other options do not exist.
2. WATERSHED FLOOD ISSUES
This category is divided into stormwater related and non-stormwater sections. It includes
items that are broader than the channel issues and that are generally a factor in the entire
watershed.
1. Non-Stormwater Watershed Issues
There are six widely varied alternatives included in this section. The first, "A. Alter DID
management over the long term as land use changes", deals with issues related to
conversion of land from agricultural to urban use. DIDs (Drainage Improvement Districts)
were originally created by groups of farmers to drain high ground water and/or to remove
excess irrigation flows. Any DID that becomes inactive (does not elect boards of directors)
reverts to management by the County Engineer. There are currently seven DIDs within the
CFHMP area, all of which are managed by Yakima County. Due to annexation by the cities
over time, most of these DIDs are now within cities of Yakima and/or Union Gap. Yakima
County has recently begun studies to determine whether there is a current need for the
DIDs. This will include how they do - or could - play a role in stormwater management. For
purposes of this plan, any future plans for the DIDs should include a criterion that any
conversions not increase flooding. Considerations would include high ground water
influences on flooding, removing private connections, and the sizing of run-off facilities
(discussed later in stormwater section).
Alternative "B. Consider environmental benefits in funding processes" refers to including
environmental benefits in cost benefit analysis for projects and grant applications. While
determining and directly including these costs is relatively new and not well defined, the
inclusion of habitat mitigation costs are already included in projects. One method is to offset
32
Ahtanum-Wide Hollow CFHMP
mitigation with the actual benefits. The next alternative, "C. Develop pre and post -disaster
program for implementation of habitat goals in flood hazard reduction/recovery
projects/programs", proposes that habitat goals be included as a component of flood hazard
reduction activities. This would require development of the habitat goals, their
dissemination to jurisdictions or agencies who could implement them, a commitment to
implement them when possible, and perhaps a funding source separate from those funding
the flood reduction/recovery project. There are several recent plans that include relevant
habitat goals, the Yakima Sub -basin Plan, and the Yakima Basin Salmon Recovery Plan.
Grant funding is also available for projects that implement goals identified in these plans.
The next alternative, "D. Preserve natural drainage including draws that provide flood
protection" was added to this section and the next section (Stormwater) by the committee
during the alternative review meetings. It was added in recognition of the flooding role
played by draws and intermittent streams that are typically not included as FEMA
identified floodplains. Type 5 streams are no longer regulated as streams in the 2007 Yakima
County Critical Areas Ordinance (under appeal as of November 2008). These topographic
features may still fall under regulation through grading or development permits or as
floodplains or geographic hazards.
Alternative "E. Planning for the joint needs of fish and wildlife in floodplain
development", encourages a more proactive approach for habitat needs when floodplain
development is considered. How this would be implemented (for example, as a mitigation
for development) will need to be addressed when recommendations are formulated from
the alternatives. Alternative, "F. Design bridges and irrigation diversions to reduce
potential for debris and bedload (sediment) accumulation", is placed in this more general
category (Watershed) since it refers to planning for both infrastructure types and includes
sediment. Because accumulation of debris and sediment is such a problem in this
watershed, additional alternatives related to design, maintenance and monitoring were also
developed in more specific categories such as roads and bridges.
2. Stormwater
This section contains eight alternatives, many of which refer to recent (2007) initiation of a
regional stormwater program in response to federal EPA requirements (NPDES - National
Pollutant Discharge Elimination System). These requirements apply to both cities and the
unincorporated county within the urbanized area of the City of Yakima (Sunnyside and
Selah are also included, but are outside the plan area).
The first alternative, "A. Utilize NPDES stormwater programs to retain site runoff and
reduce overland flow for Yakima urbanized area", acknowledges the contribution of urban
runoff to flooding. The regional stormwater manual and ordinances for the jurisdictions are
currently being developed so the timing allows an ideal opportunity to provide input
regarding flooding. The adopted ordinances for these flood -prone basins require on site
detention of the 25 year event which also means no incremental peak increase for the 100
year flow. This is a significant change to peak runoff from urbanization for all future
development. The second alternative, "B. Develop stormwater standards for detention
and retention on site and regional; abide by and enforce stormwater design standards;
CHAPTER 9 - ALTERNATIVES 133
and incorporate flood issues into stormwater programs", will require implementation
through a variety of mechanisms ranging from the manual mentioned above to the overall
stormwater programs.
Alternative, "C. Establish a relationship between stormwater standards and development
standards in floodplains with regard to flooding (high water table and low gradient)",
refers more specifically to the connection between stormwater, development and flooding.
How this relationship is identified and then incorporated into stormwater and development
regulations has not been determined. Some of these considerations may be included
development of the Stormwater Manual and Ordinances referred to above. Alternative, "D.
Preserve natural drainage including draws that provide flood protection", is the same as
the alternative listed above. It was included in stormwater also since recognition of natural
drainage is a significant component of stormwater programs.
The next two alternatives deal with sizing of drainage facilities, "E. Size drainage facilities
for future build -out and flood flows - including ability to pass upland drainage of 100 -yr
flow", and, "F. Limit new connections to existing undersized drainage systems, i.e. DIDs,
storm drains, and resolve the runoff issues presented by the Drainage Improvement
Districts (DIDs) that may act as stormwater drainage systems although designed for
subsurface flows". The first alternative could be addressed by modeling future build -out
and then including the sizing requirements in stormwater standards and guidelines. The
second points out there will be increased runoff problems if developers and jurisdictions try
to incorporate existing DID systems that were not designed for stormwater purposes.
Yakima County currently evaluates every request by new developments or cities to connect
to the DIDs, but it's likely that additional inventory, modeling, and retrofitting would be
required for any significant increase in their use for stormwater. This alternative also
includes consideration of existing stormwater facilities that were constructed for smaller
design storms (10 -year), no upland pass-through conveyance, and less impervious surface.
Alternative "G. Implement an effective Stormwater Management Program that reduces
basin flooding", specifically identifies stormwater management as a method to reduce
flood in the CFHMP area. This alternative may be more appropriate as the main stormwater
alternative with the other alternatives included in this section as sub -alternatives within it.
Alternative "H. Establish policies for retrofitting and re -development of stormwater
facilities and flood water routing in existing urbanized areas", would create the policy
framework necessary to implement many of the other alternatives in this section. DIDs, the
county and cities would be involved in creation of the policies which would likely include
funding sources and responsibilities for construction, maintenance and management. This
alternative was found to be redundant and already included in stormwater programs so
committee decided to drop it.
3. BRIDGES AND ROADS FLOOD ISSUES
Bridges and roads was one of the most discussed categories for this flood plan. Primary
flood problems identified included: bridge conveyance and orientation; roads interaction
with flood flows; roads acting as dams; roads over -topped during flooding; and, roads in
"islands" surrounded by flooding. Most of the emergency response alternatives related to
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Ahtanum-Wide Hollow CFHMP
over -topped roads are located in Flood Response (Category 9). Topics in this category are
split between existing infrastructure and future infrastructure.
1. Design
Nine alternatives are included in this section. The first alternative, "A. Adequate Bridge &
Road Crossing Standards", includes five sub -alternatives. Many of these require increased
standards which would likely need additional funding, public participation and expanded
design parameters. The first sub -alternative requires additional free -board to convey debris
and ice. Free -board in this instance refers to additional clearance included in bridge design
to prevent ice and debris from catching on the bridge. The fourth sub -alternative also refers
to increased conveyance but achieves it by in -channel designs, such as orienting large rocks
in the channel in such a way as to maintain stream depth and velocity. The second sub -
alternative would allow transportation planners and designers more flexibility to include
floodplain effects or flood reduction designs, including extended review of upstream and
downstream areas. The first step needed would be to determine the function standards and
policies. Currently design considerations are limited to a standard right-of-way area around
a project. The third sub -alternative also requires an increase in conveyance, but in this case,
to account for habitat requirements such as the large woody debris frequently required for
mitigation. The last sub -alternative promotes conservative design where channels are
unpredictable or where natural channel processes have been lost.
A new recommendation was added to "A" in the Bridges and Roads category in the Design
section, "Design of bridges and bridge footings should incorporate long-term erosion and
scour conditions that do not impede flood conveyance". Because this item was added
when the recommendations were being developed, it will be on the Recommendations table,
but not the Alternatives tables (and does not have an alternative number). The need for this
recommendation became apparent as bridges were being cleaned on Wide Hollow Creek
and during review of the new draft flood maps. The purpose is to ensure bridge footings are
deep enough to prevent erosion problems and ensure the design will convey the flows
expected at the bridge site for up to 100 -yr flood events.
Alternative "B. Improve bridge conveyance at 16th Ave", refers to a specific bridge and was
originally generated during the Emma Lane area discussion. The next alternative, "C.
Consider lowering existing roads where they act as dams and cause flooding (ponding)",
would first require identification of these road segments. Review for whether they are
needed for emergency response (alternative E below) would also be required before
deciding to decrease the road elevation.
A new recommendation was added to the Bridges and Roads category in the Design section,
"Also investigate installing culverts in currently undrained artificially ponded areas if
this would help mitigate risks from smaller 5 - 25 year floods". Because this item was
added when the recommendations were being developed, it will be on the
Recommendations table, but not the Alternatives tables (and does not have an alternative
number). This was merged with recommendation "C" regarding roads acting as dams and
creating ponding. This was added to mitigate inundation with relatively minor structural
projects in locations where even smaller floods can cause damage and reduce access to
CHAPTER 9 - ALTERNATIVES 135
property. These locations would need to be identified first and coordinated with the other
recommendation proposing lowering road elevations in specific areas.
Alternatives "D. Provide armoring of roads which act as levees (Cottonwood Canyon Rd.,
etc.)" and "F. Armor road ditches where road fill is going to contribute to excess bedload"
acknowledge that ditches conveying flood flows and roads acting as levees need additional
protection to allow emergency access (see E below), reduce repairs, and prevent delivery of
road prism material to streams during floods. Also see Alternative #12D-3 in the Monitoring
/ Inventories category (last alternative category).
Alternative "E. New and reconstructed roads should be evaluated. New roads that are not
intended to be passable to a certain standard (10, 25, or 100 year flood), should be built at
grade" requires that access standards during floods be included in road design
requirements. While the preference is to build roads at grade to prevent damming or
redirecting flood flows, there is also a need for access as part of an emergency flood
response (such as evacuation). Alternative A in the next section contains the first step which
is to decide on and designate critical access routes. Input sources for making these
determinations would include first responders, county emergency management,
transportation, planners and flood control. These two alternatives would likely be combined
to generate the recommendation for this topic. (Also see alternative 2.B. in the Flood
Response category).
Alternative "G. Provide better floodplain mapping and modeling to allow for better
infrastructure design, including current Ahtanum-Wide Hollow remapping" refers to
current and anticipated future floodplain mapping products. In addition, models generated
for specific projects may have additional utility for other infrastructure projects in the area.
This alternative could include distribution of products and/or notification of product
availability to jurisdictions and engineering consultants with projects in the watershed. The
next alternative, "H. Modify drainage standards for roads in overflow areas (i.e. Emma
Lane area)", requires special consideration of drainage design in areas that have flood flows,
but no identified stream channel. Considerations could include designs that would be less
likely to add to flooding or prevent redirecting flows to unexpected locations. The last
alternative in this section, "I. Recognize the limitations of culverts as flood conveyance
structures", may primarily be relevant for jurisdictions considering private road and
driveway access proposals. The vast majority of culverts in the CFHMP area are for private
access, minor natural drainage channels or irrigation related conveyance.
2. Monitoring / Maintenance
Five alternatives are included in this section. A few similar topics are included in the
Monitoring / Inventories category (the last alternatives category).
The first alternative, "A. Decide upon, designate and maintain critical access routes at 10,
25 and 100 year events *Coordinate with 1D and 1E above", was already discussed in
Alternative E above. Alternative "B. Actively monitor and manage channels adjacent to
bridges to improve and maintain bridge capacity" is similar to conveyance alternatives at
the beginning of the previous section, but it deals with existing bridges rather than design.
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This could be described as an adaptive management approach that includes additional
targeting of problem bridges.
Alternative "C. Replace old culverts with higher capacity culverts based on level of risk"
is currently thought to be a relatively minor problem. Additional information may be
needed to see how extensive this problem is. Only two culverts are currently known to have
capacity problems in the public transportation system for this area. It's also possible this
was viewed as a problem due to blockage of culverts used to convey irrigation waters or
located on intermittent drainages. The next alternative is similar, "D. Investigate and
recommend increased maintenance and debris cleanout of culverts and ditches on public
roads (coordinate with road maintenance crews to optimize ditch cleaning for flood
purposes)". The first step would be to identify locations where this is a recurring problem.
Implementation of alternatives C and D are unlikely to reduce damage caused by large
floods.
The last alternative in this section, "E. Assess the cumulative effect of new road policies
and standards regarding roads acting as dams or conveyances" includes a similar sub -
alternative to include watershed flooding considerations when planning transportation
infrastructure. The overall approach would be to maximize transportation efficiency and
minimize roads in floodplains.
3. General Planning
Eight alternatives are included in this last section for Bridges and Roads. These alternatives
deal primarily with program level planning and funding considerations. Alternatives "A.
Inventory and rank problem bridges throughout the watershed and coordinate with
Capital Improvement Plans of local and state jurisdictions" and "B. Integrate existing or
new funding programs into strategic program for addressing problem bridges" both refer
to developing and seeking funding for problem bridges. One funding difficulty that has
been identified is the definition of a bridge. Short -span bridges are not considered to be
bridges for some common funding sources. Bridge information from the jurisdictions and
recent data collected for flood map restudies could provide initial information to start the
inventory. Alternative "G. Identify and map overflow paths and critical bridges" would
also include overflow paths in this inventory. The last funding alternative in this section
includes not just bridges but also road systems, "C. Explore ways to take better advantage
of Federal and state funding programs to reduce or mitigate the environmental effects
(including flooding) of existing road systems".
Alternatives D and H both limit roads in the floodplain: "D. Limit/restrict/reduce the
number of bridges and road crossings, especially small bridges and culverts", and "H.
Limit access to major arterials where they cross or are adjacent to floodplains". This can
be accomplished through road standards, combining existing access points or limiting
development density. Both of these alternatives were created to prevent additional road
related flooding problems, including loss of access.
Alternative "E. Work with landowners upstream and downstream of new infrastructure to
design access to property to mitigate flood impacts" is related to the right-of-way sub-
CHAPTER 9 - ALTERNATIVES 137
alternative in the Design Alternative A above. These two alternatives could be combined
when recommendations are created. The last alternative in this section is, "F. Replace flood
damaged transportation infrastructure in a manner that reduces vulnerability to future
flood hazard". A first step for this alternative would include investigating whether FEMA's
Public Assistance program would fund additional replacement costs if it was needed to
reduce future vulnerability.
4. IRRIGATION FLOOD ISSUES
1. Conversion of Irrigation Systems
The only alternative for this section is, "A. Consolidate irrigation diversions to minimize
stream impacts, consider upgrades like piping, and consider converting irrigation
systems to a pressure -based system, i.e. Pine Hollow". This alternative differs little from
those listed in first Channel Issues alternative above, and they may be combined in the
recommendations. The three combined alternatives here place the emphasis on conversion
of irrigation infrastructure primarily to reduce flood damage risks to the irrigation
structures. The alternatives in the Channel Issues section address flood problems caused by
the irrigation hydrographs and infrastructure.
2. Infrastructure Maintenance and Inventory
Three alternatives are included in this section. The first alternative, "A. Develop a program
of proactive debris removal and maintenance on irrigation structures", would probably be
most helpful to mitigate small to moderate sized flood events. The sub -alternative is a more
specific debris related alternative that suggests use of temporary or sacrificial structures to
catch debris or prevent it from damaging permanent irrigation structures. Further
discussion with the irrigation districts to identify and quantify the problem could be the first
step for these alternatives.
The next alternative is, "B. Conduct an inventory of existing irrigation infrastructure
(working or abandoned) and flooding impacts". The inventory would also provide
valuable information useful for other irrigation related alternatives. The sub -alternative
suggests removable irrigation structures such as large pump and pipe systems that may be
prone to icing problems. It is currently unknown if ice forming on this type of irrigation
structure contributes significantly to flooding. The other major component of this alternative
is identification of abandoned infrastructure that is adding to flood problems. This is a
known problem at some of the site specific locations identified in this plan (Emma Lane area
and the near the Mission) and is expected to contribute to flooding in other locations as well.
Once the inventory listed above is complete the next alternative would seek funding for
removal of the abandoned structures, "C. Identify sources of funding for removal of
abandoned irrigation structures". This would involve discussions with irrigation districts,
North Yakima Conservation District and other agencies that may have funding available.
Who would apply for funding and implement projects will depend in part on whether there
is still an active irrigation district with a connection to the structure.
The last irrigation alternative involves possible new infrastructure, "D. Investigate the
possible use of flood gates or siphons to reduce flood flow routing by irrigation
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Ahtanum-Wide Hollow CFHMP
infrastructure, if needed, identify locations of most benefit". The siphons (or undershots)
referred to are intended to pass upslope flows from natural drainages (gulleys or low spots)
under the canals. It is unknown whether, or how much, a lack of siphons contributes to
flooding. Some use of flood gates or boards is already occurring, such as the Yakima Valley
Canal Company inserting boards in one canal each fall to prevent ditch -conveyed flooding.
Additional discussions with irrigation districts in the area, especially in the Wide Hollow
basin, may identify additional locations for new siphons or flood gates.
5. LAND USE FLOOD ISSUES
Alternatives in this category focus on the decreasing amount of land available for flood
conveyance and storage. This decreasing flood capacity endangers current and future
development and makes flooding less predictable. For these reasons, most of the
alternatives generated involve the following: increasing areas available for flooding;
decreasing the density of new structures in the floodplain; decreasing the number of
existing structures in especially dangerous locations; and increasing the potential for public
use of areas with the multiple purposes of flood capacity, recreation and open space.
Chapter 6 includes information about broader planning frameworks, the Growth
Management Act, regulations from the federal to local, permitting and how it is expected to
fit together.
1. Subdivisions / Housing Developments
Three alternatives are included in this section with the first also providing some over-
arching policy guidance, "A. Minimize new homes/structures etc. in harm's way". The first
sub -alternative is to effectively integrate flood functions and risks into individual
subdivision platting processes. The second is creation of more stringent development
standards for some flood prone areas and jurisdictions (note - this alternative was dropped
during recommendation review since it was not specific about what was included). This
would require either criteria or an inventory to identify these potential flood prone
locations. The last sub -alternative is to work toward common development standards. This
was a frequently voiced concern through -out the flood plan process. A wide variety of
stakeholders stated that development projects would be quicker and easier to conceive and
implement if the development standards were more similar for all jurisdictions within the
CFHMP area.
The second alternative, "B. Work for consistency in zoning standards for developments
and buildings within floodplains. Determine gaps in the regulatory scheme", continues
the flood theme but addresses zoning standards. One gap noted in Chapter 8 is that not all
jurisdictions have a zone identified that allows a reduced development density or Open
Space. The last alternative in this section is, "C. Establish standards for subdivision in the
floodplain- at the minimum require a buildable area outside of the floodplain. Standards
for lot size and housing location." This alternative was proposed to decrease flood risk for
new structures by ensuring a building envelope outside the floodplain.
2. Incentives / Taxation
The four sub -alternatives were grouped into an overall alternative for this section, "A.
Provide special incentives- (clustering, density bonuses, Transfer of Development Rights)
CHAPTER 9 - ALTERNATIVES
for retention of floodplain function in development design (13B-4)". The first sub -
alternative provides bonuses for developers who protect flood hazard areas. These could
include allowing increased density which could be specified in zoning ordinances. The next
sub -alternative suggests utilizing property owner incentive programs for maintaining flood
capacity. One method would be to provide property owners with a central information
resource about these programs.
The last sub -alternative applies only to agricultural land. To take advantage of the open
nature of agricultural land the first part of the sub -alternative would utilize existing
programs to provide benefits for farmers allowing some flooding on their property. To
prevent erosion, this would be most applicable to land with traits that encourage sheet flow
type flooding. The last part of this sub -alternative would develop a compensation program
for loss of productive farm land from erosion. Either of these would require more
investigation to determine what options are possible and if there are already existing
programs that could be utilized.
A new recommendation "B" was added to the Land Use category in the Incentives/Taxation
section, "Encourage jurisdictions to join FEMA's Community Rating System (CRS) to
reduce property owners' flood insurance premiums". Because this item was added when
the recommendations were being developed, it will be on the Recommendations table, but
not the Alternatives tables (and does not have an alternative number). Unincorporated
Yakima County is the only community that is a member of the CRS program. Communities
in this program implement activities that earn points to reduce flood insurance rate
premiums for property owners. The County has a classification of 8 which reduces flood
insurance premiums by 10% for those inside and 5% for those outside the regulatory
floodplain. The Yakama Nation would need to join the NFIP (National Flood Insurance
Program) before they could join the CRS.
3. Open Space / Parks
This category includes one alternative that has eight sub -alternatives, "A. Encourage the
retention of open space in floodplains through:" One way to provide adequate flood
conveyance and storage and decreased risk is to ensure there are open areas in the
floodplain. Parks permit multiple uses of floodplains for flooding as well as recreation.
Several of the sub -alternatives refer to the requirements for parks and open space in long
range planning for the Growth Management Act (GMA). The jurisdictions could include
floodplains in their planning for these GMA elements with the added benefit of reducing
flood risk. The sub -alternatives also include adding floodplains or flood problem criteria to
existing programs and activities. This includes the Open Space taxation program and
developing policies and standards for open space retention as part of the Urban Area
expansion process.
One sub -alternative calls for inclusion of open space in site plans: "Incorporate open
space/floodplain retention into site plans". The UAZO (Urban Area Zoning Ordinance)
requires a class 2 or 3 review for all development permits containing floodplains. Provisions
are also listed for projects where the developer proposes - or the reviewing official requires -
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Ahtanum-Wide Hollow CFHMP
Common Open Space for the development. Union Gap also contains requirements related to
Common Open Space for class 2 or 3 developments, but does not utilize a floodplain
overlay zone trigger for higher than a class 1 review. Yakima County outside the UAZO is
subject to a regulation stating the board of county commissioners may require plats to
designate up to 5% of their land area as public or private parks or recreation areas. To date,
this option has rarely been successfully utilized. Yakima County outside the UAZO also
does not have a floodplain trigger that automatically moves a development in the floodplain
above a type 1 review (comparable to class 1). Further discussion of a floodplain overlay
zone alternative is included below in section 6, "Standards for Development in High -Risk
Areas".
A slightly different approach incorporates walking paths or trails into floodplain retention.
This alternative would require planning and funding over a larger area and would need to
address any adjacent property owners concerns. Several large area trail systems have been
implemented or proposed in recent years, so this alternative may be more possible now than
in prior years.
4. Large Scale Retention of the Floodplain
This section contains two alternatives; the first has four sub -alternatives that deal with
development density in floodplains, "A. Reduce density in the floodplain through various
methods" (14C-3). The first sub -alternative (4-12) provides flexibility when reviewing
proposed developments in the floodplain. This would place a higher priority on preserving
and restoring floodplains in areas where floodplain functions have not already been
significantly modified. For example, a lower priority would be placed on floodplain
preservation and restoration in areas with substantial diking or development of the
floodplain.
The second sub -alternative (14C-4, 14C-5) proposes changes to zoning and comprehensive
planning documents to permit lower intensity development in high risk areas. These
floodplain corridors will be identified in the flood map restudies currently under contract
(see the Information/Outreach category). Implementation of this alternative could be
coordinated with the proposed floodplain overlay zone discussed in section 6 below.
The third sub -alternative (13A-15) addresses the use of development moratoriums or high
standards of proof in high risk areas. No specific areas were identified by the committee.
This alternative is only intended to be used in circumstances such as, unmapped areas and
locations with known significant changes since it was last mapped. Since this would be an
exceptional action, it is anticipated it would be used rarely and only for limited lengths of
time with clear documentation of the flood risk.
The last sub -alternative (12H -4b) in this group specifies that new major arterials and traffic
generating developments should be located outside the floodplain. Other similar
alternatives such as those mentioned above in the Bridges and Roads category (12H-5, 12H-
9, 12A/B-9, 12C-4, 12H -4c) also address the potential increase in risk and development
density connected to road system development. Alternative 12H -4b, however, is the only
CHAPTER 9 - ALTERNATIVES 141
one that specifically states this type of development should be located outside of the
floodplain.
The next alternative in this section, "B. Incorporate principle of floodplain planning into
infrastructure & similar facilities plans (8C-2, 12H-2)", combines two alternatives to ensure
capital facilities improvements and expansion of the transportation network are consistent
with applicable CFHMPs. This includes integrating protection of floodplain function for a
range of projects from new roads such as the proposed "Nob -Hollow connector", to routine
bridge replacement, and to larger planning efforts like the proposed north -south connector
route. Incorporation of floodplain principals would be done through Growth Management
and Capital Facilities planning processes. This would ensure floodplain options and
constraints are incorporated into the planning process earlier, which will reduce overall
costs and produce a more flood resistant outcomes.
A new recommendation "F" was added to the Land Use category in the Large Scale
Retention of the Floodplain section, "When developing floodplain planning, zoning, and
development standards or use designations, the jurisdictions should consider increased
costs created by floodplain risk". Because this item was added when the recommendations
were being developed, it will be in the Recommendations table, but not the Alternatives
tables (and does not have an alternative number). These additional costs include future land
owner costs for flood damage, NFIP insurance costs, and construction costs for flood
prevention. To minimize these costs consider urban land use preferences in the following
order from most to least preferred: open space, trails, parks and recreation, light industrial,
commercial, low density R1 (one lot per acre), and clustered residential. The purpose of this
recommendation is to encourage communities to include secondary costs in their
consideration of floodplain development. Additional information is included in the
Economics of Floodplain Development section of Chapter 5.
5. Acquisitions / Easements / Incentives
This section includes four groups of alternatives that compensate property owners for
maintaining or increasing floodplain capacity and conveyance. Though the cities, county
and FCZD can legally acquire land to reduce flood risk through condemnation, acquiring
land or easements would likely require assistance by grant funding. Grants available for
these purposes require willing sellers, which may reduce the effectiveness of this approach
or greatly increase the length of time needed to implement a specific project.
The first alternative, "A. Acquisition/easements of land surrounding flood problem
areas", includes a total of eight merged sub -alternatives. The first group of three sub -
alternatives (4-13, 15B-4, 15D-4) refers to properties in areas at risk for inundation. Known
risk locations include the specific areas identified in this plan: Emma Lane, Shaw Creek, St.
Joseph's Mission at Ahtanum, and portions of Union Gap. The next sub -alternative (13B-5)
is somewhat more general and provides for fee simple or easement acquisition of land for a
variety of purposes consistent with floodplain functions. This alternative would be
applicable when floodplain function and inundation risk reduction was the driving motive.
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The next sub -alternative (9C-12) addresses maintenance of drainage easements and asks
who will enforce maintenance. This alternative touches on several issues: who pays for and
does maintenance; does maintenance include planting, irrigating and mowing vegetation;
what enforcement is necessary if property owner obstructs the easement; and, might
enforcement be needed if property owner removes more or different species of plant than is
called for. Easements that support riparian vegetation may require a vegetation
management plan to ensure the easement remains open for flood conveyance.
The last group of alternatives (15C-3, 15C-9, 15C-10) refer to buyouts, relocations,
easements, and flood -proofing, and differ from the previous alternatives in several ways.
They include risks from erosion; they were generated with natural channel changes in mind;
and are grouped to specifically address the policy and/or program guidelines necessary for
implementation. Also, alternative 15C-9 specifically includes buyouts for property lost due
to flooding (also see 15C-8 in Taxation/Incentives above). While the wording in the original
alternatives don't specifically address guidelines, any jurisdiction or agency trying to
implement them will need to have a program and/or policy basis allowing them to make
these types of purchases.
A new recommendation was added to "A" in the Land Use - Acquisitions / Easements /
Incentives section, "Make acquisition of FEMA identified Repetitive Loss properties a high
priority". Because this item was added when the recommendations were being developed, it
will be on the Recommendations table, but not the Alternatives tables (and does not have an
alternative number). The Ahtanum and Wide Hollow watersheds contains six of the nine
FEMA identified Repetitive Loss properties in the county. Five of these six are in either the
Emma Lane or Shaw Creek areas. One of these houses was mitigated by acquisition in 2010
through an FCAAP grant. One of the difficulties in mitigating these properties is that most
FEMA grant funding is only available if the property still carries a flood insurance policy.
FEMA's Repetitive Loss strategy targets insured property that experienced:
• Four or more paid flood losses of more than $1,000 each; or
• Two paid flood losses within a 10 -year period that, in the aggregate, equal or exceed
the current value of the insured property; or
• Three or more paid losses that, in the aggregate, equal or exceed the current value of
the insured property.
The second alternative, "B. Utilize tools such as floodplain easements to preserve off-site
storage of water and sediment in farmland (existing pastures, alfalfa), while preserving
use as farmland" merges two individual alternatives (15B-5, 15B-8) to take advantage of the
unique attributes of farm land occurring in floodplains. This includes encouraging
maintenance of existing farm use of floodplains including possible floodplain easements
and links to programs for preservation of farm land. Maintaining farm use can reduce flood
risk by providing additional flood storage and conveyance on open land where buildings
will not be at risk. It would also more be more effective to coordinate vegetation
management and other flood related activities with one property owner versus multiple
owners if the land converted to more urban uses.
CHAPTER 9 - ALTERNATIVES
The third alternative, "C. Encourage organizations (neighborhoods, County/City/Yakama
Nation or others) to purchase floodplain areas (9C-10)", is another land purchase method
aimed at increasing flood storage and conveyance. This could be considered the purchase
component of alternatives proposed above in the Open Space section. Encouragement could
be in the form of: providing draft policy guidance; connecting organizations to grant
opportunities; and forming partnerships for acquisition as opportunities arise.
The last alternative, "D. Provide incentives for landowners and developers who provide
floodplain storage (4-6)", originally included buyouts also which duplicates the other
buyout alternatives listed above in the "A. Acquisitions..." section. The remaining portion
of this alternative (incentives for storage) appears to be the same topic as alternative 9C-3 in
the Taxation/Incentives section above and may not be needed.
6. Standards for Development in High -Risk Areas
The first alternative for this section, "A. Establish Flood Overlay Zones in affected
jurisdictions. These overlay zones would have legal status (i.e. in a zoning code) and
contain development standards, objectives, and review/process criteria for the broad suite
of land uses that occur in floodplains. (13B-3)", was initially dropped and later added back
to the list of alternatives. The alternative was dropped at an April 2008 meeting when a
planner on the committee explained this alternative was unnecessary due to zoning changes
and CAO -SMP updates. In February 2009 when it became clear there was a regulatory gap
since zoning and CAO -SMP regulations vary a great deal between jurisdictions, this
alternative was reinstated. There was also a request to modify the original wording of the
alternative, so staff clarified the overlay zones' status and connection to ordinances.
Currently the only floodplain overlay zone exists in the City of Yakima and the Yakima
Urban Area Zone portion of unincorporated Yakima County. Several benefits may be
possible through a floodplain overlay zone. One is the greater potential consistency of
floodplain regulations between jurisdictions. Another benefit from this alternative could be
a regulatory requirement for jurisdictions to do at least a Type 2 review for any
development proposed in a floodplain overlay zone.
The next alternative group is, "B. Develop policies for areas of existing dense
development within the floodplain (such as Ahtanum and Wiley City)", also includes
drainage improvements. Though both sub -alternatives (13A-13, 14A-4) use Ahtanum and
Wiley City as examples, they are not limited to these geographic areas. The final sub -
alternative in this group does not have an alternative number since it was added during a
committee meeting (April 7, 2008) about Land Use. The proposal for this alternative to make
Ahtanum and Wiley City a special study area occurred when it became clear these are
unique areas with serious flooding problems. Details about the alternatives in this group (B)
were not identified.
The next alternative in this section is, "C. Establish policies in flood prone and flood
hazard areas for directing preferred locations for the siting of new infrastructure such as
major and minor arterials, water and wastewater distribution mainlines, regional
stormwater facilities, parks and greenbelts (13A-11)". This alternative proposes including
flood risks in long range planning done by the jurisdictions. There are several other
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Ahtanum-Wide Hollow CFHMP
alternatives that address specific aspects of this topic, but this is the most broad policy
statement that includes all long range infrastructure planning.
The last alternative in this section was added back into the alternatives during the tracking
process and was then moved from the Bridges and Roads category to Land Use. This
alternative groups a number of sub -alternatives created initially during work on
transportation infrastructure, "D. Limit/restrict/reduce the number of bridges and road
crossings, especially small bridges and culverts. [This can be accomplished through road
standards, combining existing access points or limiting development density] (12H-5,
12H-9,12AB-9,12C-4)". This group of alternatives triggered much discussion, in part
questions about whether this is already included in CAO, SMP and other regulations. The
Committee decided to keep this alternative in part to reinforce the importance of this topic
and also because this plan includes several jurisdictions.
7. Miscellaneous Policies
There are two alternatives in this section, with the first, "A. Ensure flood policies in the
Yakima Urban Area Comprehensive Plan are implemented through ordinances and land
use decisions (13A-4)", calling for implementation of policies in this plan by adopting
ordinances by the applicable jurisdictions. Planning for flooding is supported in Objective
E7 of the Urban Area Comprehensive Plan. The jurisdictions currently included in the urban
area plan that would need to adopt implementing ordinances are Yakima County and the
City of Yakima. This alternative does not address whether or not Union Gap's
Comprehensive Plan would also benefit from an implementation alternative such as this
one. At the time this alternative was discussed by the committee, there was uncertainty
about whether Union Gap is a party to the Urban Area plan. It is unknown if a comparable
planning document has been created by the Yakama Nation.
The next alternative in this section and this category is, "B. Develop special land use and
flood -proofing standards for industrial uses relating to hazardous materials, storage, use,
disposal (11B-1)". This alternative was originally proposed in relation to the conversion of
flood prone areas in Union Gap to higher intensity uses in recent years. Committee
members suggested that adoption of the IBC Appendix G (International Building Code)
would mitigate these concerns. More information about the International Codes is included
in Chapter 6.
In reference to hazardous materials, Appendix G of the IBC includes requirements for
underground and aboveground tanks; new and replacement sewer systems; and some site
work. The appendix references ASCE 24 (American Society of Civil Engineers) for
engineering standards including classifying structures according to the nature of their
occupancy. Structures containing sufficient quantities or types of hazardous materials
considered to be dangerous to the public if they are released are classified in category III or
IV. For these types of hazards there may be increased elevation or flood proofing required.
Beyond this, does not appear to be any specific requirements or standards regarding
hazardous materials, storage, use or disposal in Appendix G. Additional discussion with
each jurisdiction would be required to determine what additional land use or flood proofing
standards would be desired and what the appropriate regulatory tool would be.
CHAPTER 9 - ALTERNATIVES 145
A new recommendation "C" was added to the Land Use category in the Miscellaneous
Policies section, "Provide 10 and 25 year flood extent maps for two creeks to indicate
vulnerable economic areas to abate or prevent chronic "nuisance" flooding and to
provide a design guideline for maintenance and improvement of channel capacity,
vegetation management and guide the location of structural improvements in the
floodplain". Because this item was added when the recommendations were being
developed, it will be on the Recommendations table, but not the Alternatives tables (and
does not have an alternative number). The range of flood events is included since it is
unknown which flood level will provide the most benefit until maps are produced and
reviewed. The intent is to reduce nuisance flooding caused in large part by loss of
conveyance combined with unusual flow paths due to valley topography. This nuisance
flooding - 10 to 25 year recurrence interval floods that inundate relatively large areas - can
produce inordinate amounts of structural and economic damage due to inundation of crawl
spaces or foundations of buildings, and road closures or road damage. Additional
information is included at the end of Chapter 8, Flooding Issues.
6. DEVELOPMENT STANDARDS / ENFORCEMENT FLOOD ISSUES
This category contains three sections aimed specifically at code enforcement, compliance
with the NFIP (National Flood Insurance Program) and possibilities for special zones for
specific identified problems. Chapter 6 includes information about broader planning
frameworks, the Growth Management Act, regulations from the federal to local, permitting
and how it is expected to fit together.
1. NFIP Related
This section contains two alternatives that would decrease flood risk to structures by
requiring floodproofing or elevating the building above NFIP and Washington State
minimum regulations. For purposes of this chapter, floodproofing refers to minimizing
damage from flooding but does not include elevating the building.
The first alternative, "A. Consider increased elevation above BFE of new structures in the
floodplain (14A-2)", generated discussion when the committee was finalizing the
alternatives. Planning staff in attendance from the jurisdictions did not believe their elected
officials would be willing to increase building elevation requirements in their communities.
So as not to lose the alternative completely, the wording was changed to read "consider"
rather than the original "require". Currently Washington State require at least one foot of
freeboard above the BFE (Base Flood Elevation) through the IBC (see Chapter 6) for all non-
residential structures. The City of Yakima and Yakima County meet the minimum IBC
freeboard requirements for non-residential buildings, but Union Gap does not. This is not
the case for residential buildings which are only required to be constructed at or above the
BFE. None of the jurisdictions in the CFHMP area currently exceed these minimum NIFP
and state IRC requirements, although the City of Yakima required one foot above the BFE
for residential structures until their CAO ordinance was updated in 2008.
There are many reasons this alternative was proposed. The first is that FEMA flood maps
with floodways allow activities in the floodplain that can raise flood level up to one foot.
This means home owners could find themselves with flooding in their ductwork or above
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Ahtanum-Wide Hollow CFHMP
their properly elevated floor. Another reason for additional elevation above the BFE is
because flood elevations rise as a watershed is built -out. For this area, this occurs as land is
converted from agriculture to urban land uses. One of the most important reasons to require
additional elevation are studies by the Army Corps of Engineers demonstrating significant
damage occurs when flood flows are still one foot below the BFE. In addition, if people
choose to remain in their homes when flooding is occurring, additional elevation above the
BFE may keep them safer in floods up to the 1% annual chance flood (100 -yr flood). The
FCZD welcomes the opportunity to present research to the jurisdictions regarding
additional elevation requirements above the BFE for structures in floodplains.
The second alternative, "B. Require Floodproofing - Floodproof utilities and Floodproof
structures- elevate, make existing structures less flood damage -prone (4-8)", combines the
floodproofing language from alternative 14A-2 described above with alternative 4-8. NFIP
and Washington State regulations allow new non-residential structures to use floodproofing
instead of the elevation requirement for residential structures. No mechanism was discussed
for how to apply this requirement to existing structures. Since substantial improvements or
repairs would already require any flood mitigation measures not already included when the
structure was built, implementation of this would be more valuable if it were an incentive or
other program to assist retrofitting rather than a requirement.
A new recommendation "C" was added to the Development Standards/Enforcement - NFIP
Related section, "Utilize available flood data in accordance with FEMA's definition".
Because this item was added when the recommendations were being developed, it will be
on the Recommendations table, but not the Alternatives tables (and does not have an
alternative number). This recommendation was added for any jurisdiction where the CAO's
"Best Available Science" might not apply to the FEMA requirement to utilize available flood
data. The intent is to encourage jurisdictions to clarify whether flood map data -such as draft
and preliminary maps -will be used for NFIP regulations or CAO -SMP regulations or both.
2. Special Zones
The alternatives in this section deal with less common topics or situations that are specific to
these watersheds or particular types of locations. The first alternative, "A. Based on flood
risk studies, consider stricter ordinances for flood zones in Union Gap (6C-4, 14A-3)",
combined an alternative generated in the Spring (Chambers) Creek in Union Gap meeting
with one developed in the meetings regarding regulations. This alternative was placed in
this category since it is regulatory in nature (the draft Recommendations list moved it to the
Union Gap category).
The alternative addresses the reality of aggradation of the Yakima River and the potential
for deeper flooding than people expect. The aggradation increases the likelihood of flood
waters upwelling west of I-82, flood flows seeping around or through the flood gates, and
the decreased ability of flood flows from Wide Hollow and Spring (Chambers) Creeks to
empty out into the Yakima River. Potential ordinances that would help mitigate the
increased risk in this area include requiring increased elevation of 2 or 3 feet above BFE for
new construction. If recommendations such as changes to Wapato Dam are implemented
and effective, this alternative may no longer be needed.
CHAPTER 9 - ALTERNATIVES 147
The second alternative, "B. Consider use of the Zero or 0.1 foot rise practice from
International Building Code (14C-8)", required further definition by the committee and
was not carried forward as a recommendation since it is not clear what was desired. This
alternative was created in reference to using zoning and floodplain overlay zone regulations
to reduce flood risk. FCZD staff was asked to research connections of zero -rise or 0.1 ft rise
to the IBC. The zero rise requirements in the IBC apply only to development in floodways,
and are comparable to current FEMA regulations. The only other place this is referred to in
the IBC is for a floodplain designation that has not been used so far in Yakima County - a
floodplain that determines BFEs but does not identify a floodway. If the new flood maps
include any of this type of floodplain they will also fall under zero rise requirements. Again,
these IBC regulations are comparable to FEMA minimum requirements.
There is also zero rise language in the current County CAO regulations, so the committee
may have been suggesting similar language be included for the proposed floodplain overlay
zone. The County Code (16C.05.28.010(1)(c)) specifies using zero rise methods when
elevating structures that will be within 100 ft of the floodway or 100 ft of the ordinary high
water mark if no floodway is identified. This ordinance applies to new construction and
improvements outside the existing structure footprint. The no rise methods given as
examples include piers, posts, or columns. This is required unless it can be demonstrated
that other construction methods will not impede the movement of floodwater or displace a
significant volume of water. As mentioned above, the committee's desires need to be
clarified before this alternative could be successfully implemented. One option the
committee could consider is to drop the IBC language and pursue the recommendation as
the zero or 0.1 ft rise currently existing in the County CAO Code 16C.05.28.010(1)(c).
The next alternative, "C. Identify areas with floodplain "islands" and develop standards
(12H-6, 14A-1 (part was dropped), 14C-1)", merges several alternatives to improve safety in
locations that would become islands of dry ground in large floods. These "island" areas are
caused primarily by the unusual topography of the flatter portions of the valley, especially
in the Ahtanum drainage. The occurrence of interconnecting overflow paths between the
streams creates "island" areas that are surrounded by, but not include in the identified
floodplain.
The merged alternatives include limiting density to allow flood passage (limiting density
was added at the May 2008 meeting), ensuring transportation networks take into account
the surrounding area, and multiple possibilities related to putting roads at grade to reduce
flood impacts as well as considering emergency access. The over-riding concern expressed
by the committee is there needs to be a mechanism to allow inclusion of factors outside the
site specific project area when a project includes or influences one of these "island" areas.
3. Miscellaneous
This section contains two alternatives aimed at increased coordination and support of
enforcement activities. The first, "A. Enforcement - Adequately fund enforcement
activities. More effective code enforcement, especially for blatant disregard of the law
(1C-4, 1C-3, 18)", recognizes the key role enforcement plays in floodplain management.
These three merged alternatives include making enforcement more effective, providing
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needed resources for enforcement and ensuring that existing policies and regulations are
enforced. So while the merged title seems to focus on funding, this merged alternative is
broader. Discussion with jurisdiction building officials would likely point to additional
actions that would aid code enforcement.
The second alternative, "B. Coordinate between jurisdictional procedures in place for
expedited permit issuance during and the period after a flood event under State and
County regulations (10D-1)", highlights the need for rapid response during flood
emergencies. Additional coordination could include: annually updated state and local
permit contact lists for jurisdictions and fact sheets for emergency permitting for
jurisdictions and the public.
The last alternative described in this section is, "C. Ensure floodplains and floodways are
identified on final plat maps - included would be text identifying effective map date and
disclosure regarding fact that the maps will change over time. Also consider including
identification of riverine Critical Areas buffer on plats". Because this item was added
when the recommendations were being developed, it will be on the Recommendations table,
but not the Alternatives tables (and does not have an alternative number). Identifying
floodplains and floodways on construction maps is required through the International
Codes (Chapter 6) but is not consistently applied. Some jurisdictions allow delineation of a
building envelope outside the floodplain instead the floodplains themselves. The Critical
Areas buffer would be a new requirement for some or all jurisdictions. Some jurisdictions
require their delineation on new plat maps on a project by project basis. Requirements to
include floodways, floodplains and Critical Area riverine buffers on final plats would
reduce inconsistency and ensure these areas which have special regulatory requirements are
identified for future property owners.
7. UNION GAP FLOOD ISSUES
Discussions about flood risks specific to Union Gap focused on various ways to reduce
impacts from aggradation of the Yakima River and flooding from Wide Hollow Creek. A
review of flood risks related to Spring (Chambers) Creek was also included, especially as
they pertain to Yakima River aggregation and flood gate management. Some of these
alternatives may not be required if others are done and several of them are dependent upon
previous alternatives. All of the Union Gap alternatives are grouped into one section.
The first alternative, "A. Modify Wapato Dam (4-11, 6C-7) to decrease flood risk (See
Upper Yakima CFHMP)", refers to the dam's contribution to increased aggradation of the
Yakima River near Union Gap. A thorough discussion of this alternative begins in Chapter
8, on page 8-30 of the Upper Yakima River CFHMP, June 2007 Update, so it will not be
duplicated here. Since this alternative will likely be included in three different CFHMPs (the
Ahtanum-Wide Hollow, Upper Yakima River, and upcoming Lower Yakima River), it is
anticipated any requests for funding or studies will reference all of these documents. In
addition to studies and CFHMPs initiated by the FCZD, the Yakama Nation has conducted
studies and projects that include the dam. One Yakama Nation project has been completed
to reduce flood elevation and improve flood flow alignment at the dam.
CHAPTER 9 - ALTERNATIVES
The second alternative, "B. Sediment Transport on the Yakima River (4-10, 4-17, 4-18, 6C-1,
6C-2, 6C-3, 6C-8, 6C-9)" groups eight alternatives proposing studies and sediment transport
improvements. Studies already in process include geomorphic studies and a sediment
model for the Gap -to -Gap Levee Pull Back Study (an Upper Yakima River CFHMP project).
Additional studies currently in the planning stage for the lower Yakima River reach will
also add valuable information about the river conditions and trends at Union Gap. Results
from current and future studies will be used to determine methods and projects to improve
sediment transport in the Yakima River.
The next alternative, "C. Relocation of Wide Hollow Creek below 3rd Ave (6C-6, 11A-4)",
also includes a sub -alternative (6C-5) to add flood gates to Wide Hollow culverts if this
project is implemented. This alternative proposes to relocate Wide Hollow Creek so it
would empty into Ahtanum Creek somewhere east of S. 3rd Avenue. This would move the
flooding caused by Wide Hollow Creek out of the heavily developed urban portion of
Union Gap to currently undeveloped agricultural fields. Relocation would abandon the
current artificial 90 degree bends in the stream channel and the constriction at the former
grist mill. The sub -alternative would add a new culvert and flood gate where Wide Hollow
flows underneath either I-82 or the US 97 on ramp.
The pre -settlement location of the mouth of Wide Hollow Creek has been the subject of
some debate. What is known at this time is Wide Hollow Creek was straightened in several
locations in the mid to late 1800's for farming purposes and also to power a grist mill at the
southern end of Union Gap. The mill was established in 1869 and continued using water
power from the creek into the late 1900s. Original surveys show the presence of Spring
(Chambers) Creek in the mill location, but no mention is made of Wide Hollow Creek in the
original surveys of this area. A 1901 soils map shows Wide Hollow Creek emptying directly
into Ahtanum Creek, Figure 4-12 in Chapter 4. This map was produced by the U.S.
Department of Agriculture.
This alternative has received support from some resource staff at various agencies and the
Yakama Nation since it was initially proposed as part of a sports development in 2001. More
recent discussions in the committee brought up some reservations due to water quality
concerns in Wide Hollow Creek. Improvement of water quality in the creek and resolution
of any remaining fish habitat issues would increase the likelihood this alternative could be
implemented (also see Alternative H below).
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Ahtanum-Wide Hollow CFHMP
A new recommendation "D" was added to the Union Gap category, "Encourage the
appropriate parties to develop Operations and Maintenance agreements for the flood
gates and fish passage structures at the Mill to ensure coordinated and effective
management for flooding". Because this item was added when the recommendations were
being developed, it will be on the Recommendations table, but not the Alternatives tables
(and does not have an alternative number). This recommendation was added when it
became clear during the flood mapping project that there is some disconnect between land
ownership, flood gate designers and owners, and fish screen owners and managers. The
purpose of this recommendation is to clarify the various roles and responsibilities to
promote maintenance implementation and effective actions during flood events. The FCZD
could organize and coordinate these discussions, but any agreements would be up to the
relevant participants.
Alternative "E. Bypassing the Mill structures (11A-5)" addresses the constriction at the mill
diversion, the steep pass for fish passage and erosion occurring at the site. If alternative C is
implemented this alternative will not be needed. The fact that the mill no longer uses the
creek for power eliminates one possible complication for this alternative. Any bypass
located near the existing mill may run into a difficulty due to a lack of space. In addition to
the close proximity of the mill building, there is a house on the adjacent parcel that would
constrain the design of a bypass channel. Elimination of the structures would also improve
fish passage. If this project includes re -grading or down -cutting of the creek upstream of the
bypass location it would also increase channel capacity at the S. 1St Street Bridge and reduce
flooding west of S. 1St Street.
The next three alternatives involve Spring (Chambers) Creek and the flood gate for the creek
at Interstate Highway 82. The first, "E. The Spring (Chambers) Creek floodgate should
generally be closed except for habitat or flow enhancement for a limited time period (6B-
1)", identifies changes to management of the flood gate that have occurred as the Yakima
River has aggraded. Because of the river's proximity and elevation in relation to Spring
(Chambers) Creek, the flood gate was closed several years ago and has not been reopened.
Water right needs have been able to be met without opening the flood gate. The FCZD
through County Roads Maintenance Division is responsible for management of this flood
gate. As long as the configuration of the Yakima River in this location is not improved to
lower flood risks, the gate would only be open for limited amounts of time. These
circumstances could include allowing some flow for temporary scouring of the channel to
improve stream flow through this area.
The second Spring (Chambers) Creek alternative, "F. Install a remotely controllable
floodgate that could be opened some times of year, closed at others (on Spring
(Chambers) Creek floodgate) (6B-2)", would allow remote control of the gate. This
technology is used to control irrigation flows in some districts, but has not been used for
flood gates in the Yakima area. Improvement in Yakima River channel conditions or
specifically defined beneficial temporary flows mentioned in the previous alternative would
likely be needed to justify the expense of this alternative. The last Spring (Chambers) Creek
alternative addresses improved conveyance, "G. Improve conveyance downstream of the
culverts on the Spring (Chambers) Creek irrigation channel by increasing grade - this
CHAPTER 9 - ALTERNATIVES
would help in most flood events, possibly not in large-scale flooding (6D-2)". This
alternative would include work with the ditch owner to eliminate or decrease the height of
the irrigation diversion structure to increase the stream grade. Because flooding also occurs
in this area from surfacing ground water and flows from Wide Hollow Creek, this
alternative would likely only improve flooding for smaller events.
The last Union Gap alternative identifies the flood capacity along the railroad embankment,
"H. Retain overflow path along the railroad right of way (11A-1)". The committee did not
discuss how this would be done, but it could include purchase of a floodplain easement
(also see Alternative C above). The recent FEMA flood re -mapping project points out the
importance of this flood overflow path in reducing hazard to urban Union Gap.
Modifications to the railway embankments that constrain this path would require
significant changes to the proposed new flood maps.
A new recommendation "J" was added to the Union Gap category, "Coordinate with
agencies planning large infrastructure projects - such as WSDOT - to look for
opportunities to reduce flood hazards for Union Gap". Because this item was added when
the recommendations were being developed, it will be on the Recommendations table, but
not the Alternatives tables (and does not have an alternative number). This recommendation
was added to ensure that opportunities to reduce flood risk have a higher priority when
large infrastructure projects are planned and designed. Current identified projects include
two by WSDOT: I-82 - Valley Mall Blvd Interchange Rebuild (currently under construction);
and I-82 - South Union Gap Interchange Improvements (developing design alternatives).
Union Gap and the FCZD have already been involved in planning and design for these
projects, so this recommendation would continue that participation and elevate the goal of
reducing flood risks where opportunity allows.
8. INFORMATION / OUTREACH FLOOD ISSUES
1. Mapping
This section contains four grouped alternatives that pertain to keeping flood maps current
and creating additional map products. The first alternative, "A. Use improved flood
mapping and modeling to assess risk to new and existing infrastructure and for
designing new infrastructure (12G-1)", reinforces using the new flood maps and models to
improve design of new roads, bridges and other structures. For example, the new models
allow engineers to try various designs to evaluate a new structure's effects on flood flows
and susceptibility to damage.
Alternative "B. Re -map the floodplain for NFIP rate maps, to allow for up-to-date
accuracy and application of land use regulations (8D-1, 4-3, 15B-6)" groups several
alternatives and also includes three sub -alternatives. A majority of the mainstem of
Ahtanum Creek is currently under contract with FEMA for a flood map restudy and is
expected to be finished in 2012. The FCZD has contracted a restudy for the remaining
portions of Ahtanum Creek including both forks and all of the Wide Hollow drainage. This
restudy is also scheduled to be finished in 2012 and will include the first flood maps for
Shaw Creek. Additional sub -alternatives (15D-1, 15C-13, 15D-2) include mapping floodways
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Ahtanum-Wide Hollow CFHMP
and regularly updating the maps to keep them current. The restudies mentioned above
include identifying floodways in areas that are already densely developed or expected to be
in the near future. The last sub -alternative proposes identifying areas that produce flooding
due to high ground water (4-9, 4-19). After the restudies are completed the FCZD will check
to see if there are areas that are not classified as floodplains but still have flood problems
from high ground water ponding. The new FEMA RISK Map program may offer additional
flexibility to identify these kinds of risks.
The next alternative includes one sub -alternative, "C. Map Channel Migration Zones (and
other hazards) (15C-12, 15G-4 15D-3)", all of which relate to identification of CMZ locations
and other risk areas including avulsions. A CMZ was identified for Ahtanum Creek as part
of the Yakima County Shoreline Master Program update in 2007. This update has not been
approved (as of July 2009) by the Washington Department of Ecology and is not known to
have been adopted by Yakima or Union Gap. The communities in Yakima County are
required to update their SMPs (including the new CMZ requirement) by 2013. Avulsion or
other hazardous areas are not currently included on FEMA flood maps. It is possible they
could be included in the new FEMA map program mentioned above.
The last mapping alternative provides the opportunity to develop additional map products
to identify risks not currently included in FEMA flood maps, "D. Supply Better/Different
mapping products (1D-8, 15F-2)". Examples of possible maps include flooding in and from
hollows and flooding in flat terrain where small changes can redirect flows, such as debris
in channels, flood fight actions by neighbors, etc. The alternatives also refer to notification
about the risk to potential property purchasers and developers. An additional note from the
meetings indicates it would be difficult for the County (FCZD) to produce these types of
maps. To implement this alternative would first require determining which flood risks are
not currently adequately identified, then determining mapping methods, and finally
deciding on the funding priority. After the flood map restudies are completed there will be
a better indication whether some risks remain unidentified.
2. Land Owner Assistance
All of the alternatives in this section include active outreach to property owners especially
as pertains to risks on their property. Alternative "A. Provide public education about
potential flood hazards and responses on individual properties including keeping debris
sources out of known flood channels (10B-2, 1D-3, 1D-7)", could be included with
alternatives C and F in this section. The outreach could include brochures, posting on web
sites, presentation at community meetings, or fliers. The topics that would be valuable
include: maintenance of private culverts, possible flood fight responses on private property,
responsible parties for various flood related topics, and fence management in floodplains.
Related alternatives are, "C. Create pamphlets for new landowners- i.e. pamphlet put out
for small landowners in Kittitas County by the Kittitas Conservation District (1B-9)", and
"F. Public education about maintaining driveway culverts, and correct sizing and
maintenance of culverts (12E-5)". Another related alternative is described in the next
section (Alternative E).
Alternative "B. Encourage residents who are at high risk for flooding to purchase flood
CHAPTER 9 - ALTERNATIVES 153
insurance even if they are not in a mapped floodplain (8D-3)", was included in part
because of wide -spread misconceptions about flood insurance. This could be as simple as
providing a FEMA flood insurance or Frequently Asked Questions brochure to property
owners or key contact organizations, such as title companies and lending institutions.
Alternative "D. Prepare a program to educate landowners about riparian function and
health before and after a flood event (9C-7)", is pretty straight -forward. First step could be
a brief review to see if there is already a publically available presentation that could be used.
Whether produced locally or acquired outside the area, a presentation also be made
available through the county web site. Also see alternatives C and D in the next section
which contain similar alternatives.
The last alternative in this section is a more general proposal to inform property owners and
prospective buyers about flood risks, "E. Provide information about properties up -front in
public services (no surprises) (13A-10, 14B-1)". It appears the "public services" text was
accidentally added since the term only applies to a Yakima County Department. Discussions
about this alternative did not include specifics about methods to use to get this information
to current and prospective property owners.
3. General Public Outreach
Though there is some overlap with alternatives in the previous section, these alternatives
are more general and do not target current and prospective property owners specifically.
The first alternative, "A. Cooperate with others to support or develop public education
programs, such as stream cleanup programs and volunteer monitoring (9C-13)" focuses on
participating with others who are doing public outreach related to streams and flooding.
This alternative, especially as regards clean-up programs, is related to the next alternative,
"B. Encourage citizens to report dumping in streams (1C-5)". For example, both of these
efforts could be led by a non-profit stream stewardship organization or Ecology.
The next two alternatives have some possible overlap with alternative D in the previous
section, "C. Cooperate with others to engage in public education regarding the values and
esthetic appeal of riparian corridors/open space for purpose of preservation of floodplain
corridors (7B-5)", and "D. Public education about how riparian and flood hazard
management goals complement each other. Inform people about the importance of the
functions of streams, rivers, and natural drainage ways (9C-11)". Outreach regarding flood
storage, habitat values and the amenity value of riparian corridors could also be coordinated
with alternatives in the land use category urging jurisdictions to include floodplains when
planning for open space and parks. Floodplain and habitat values outreach materials for
riparian areas are available from other organizations and jurisdictions. Local amenity value
examples include increased property values for parcels in Suncadia in Kittitas County (Tom
Ring, Yakama Nation). The Smart Growth organization may also have examples available
(http://www.smartgrowth.org/default.asp).
The last alternative, "E. Provide public education directed to residents, farms and
businesses to increase individual preparation for floods (10A-3)", is more narrowly
focused on flood safety. The emphasis for this alternative is pre -flood actions people can
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Ahtanum-Wide Hollow CFHMP
take to reduce their risks. This alternative is similar to the flood preparation alternative
described in the previous section (Alternative A) and they could probably be combined.
4. Outreach / Information Related to Flood Projects
This section contains two alternatives. The first, "A. Flood Control Zone District to provide
technical assistance and comments regarding flood hazards and infrastructure design
(12G-2)" proposes utilizing technical expertise housed in the FCZD. Though the FCZD
already provides comments on infrastructure projects when notice arrives at the County,
not all of the jurisdictions seek this technical support early in the design process. Early
technical input can reduce design and construction costs by reducing revisions and contract
amendments, and prevent unnecessary difficulties for project permitting. Other government
agencies or districts such as the Bureau of Reclamation and irrigation districts have
generally not contacted the FCZD for technical expertise early in the design process for their
riverine infrastructure projects. Some agencies such as the WSDOT have periodically
contacted the FCZD early in the design process. The committee did not discuss specific
ways to implement this alternative.
The other alternative refers to outreach to the public and neighboring property owners for
flood risk reduction projects, "B. Public notice/disclosure/consultation when flood projects
are planned (19)". The committee did not discuss how much outreach should occur, or
specifics for notice vs. disclosure vs. consultation, or what timeframe, or by which methods.
5. Realtor, Lender, etc. Outreach
Two alternatives are proposed for this section. The first, "A. Provide information about
flood history to realtors, lenders, etc. in proposed new developments (15C-14, 15C-15)"
does not include suggestions for how this should occur. This information (when flood
history is known for a property) is likely already available by request from the jurisdictions,
so more details from the committee would be useful to define their intent with this
alternative. The second alternative "B. Put on workshops and other outreach for realtors
(15C-16)" is self-explanatory.
9. FLOOD RESPONSE FLOOD ISSUES
1. General Flood Response Planning
The two alternatives in this section refer to planning at a broad level that includes
implementation of the Flood Emergency Response Plan and coordination with the Yakima
Valley Office of Emergency Management. The two alternatives are, "A. Participate in and
support Flood Response planning efforts (as part of the Emergency Response Plan) (10A-
1, 10A-2, 12F-5)", and "B. Implement Emergency Response Plan (Get Ready- Set- Go -
Recover) procedures, from the Emergency Response Plan (10C-1)". The Flood Response
Plan was completed and incorporated into the county response plan in 2008. This included a
multi -jurisdiction Flood Exercise in December 2007. Because the flood plan is now
completed, the committee may prefer to edit these alternatives to incorporate all or part of
Purpose B.B. from the Flood Emergency Response Plan:
CHAPTER 9 - ALTERNATIVES 155
(8) Providing for a flood response planning team comprised of representatives from
jurisdictions as identified and utilized through this plan development for: continuing
review and revision of the plan; exercise planning and evaluation; reviewing and
offering recommendations on flood emergency management initiatives.
The last alternative was added, "C. Determine where large numbers of animals may be
kept during a flood event and distribute information to the public. Work with Emergency
Management and Red Cross to establish animal food and shelter contingencies -
discussions may include Central Washington State Fairgrounds, farm feed stores,
veterinarians, and animal rescue organizations." Because this item was added when the
recommendations were being developed, it will be on the Recommendations table, but not
the Alternatives tables (and does not have an alternative number). Though farmers and
ranchers with large acreages may be able to move animals to higher ground away from
flooding, people with pets and those with small acreage "hobby farms" may have fewer
options. It became clear during Hurricane Katrina that some people even in severe flooding
situations will resist evacuation if it means leaving their pets behind. Even if large animal
owners were more willing to evacuate without their livestock, it would be preferable to
avoid the loss, heartache and post flood clean-up. It is likely other communities have
developed contingencies for animals that could be used as a starting point for discussions in
our area.
2. Planning / Mapping
The three alternatives in this section propose increased mapping and other products to
assist first responders and emergency responses during a flood. The first alternative "A.
Identify and map problem spots throughout the watershed so flood responders know
where to look first (5F-5)", would utilize information gathered from jurisdictions and
people experienced with flood response in this drainage as well as identifying possible new
locations indicated changed conditions or by the new flood map models. This alternative
includes identifying draws that may be prone to flash flooding.
The next alternative combines two similar alternatives, "B. Designate emergency response
access routes and incorporate into transportation planning (12F-4) and Designation of
evacuation routes and notification of the public and first responders (10B-3)". The first
part of this alternative will require coordination and cooperation with transportation
planning organizations at both the jurisdictional and regional/metro levels. The second part
of the alternative would utilize data from flood models and interaction with first responders
to determine safe access routes. Notification to the public could be accomplished in a variety
of ways. (Also see alternatives 1.E. and others in the Roads and Bridges category).
The last alternative in this section is, "C. The Flood Control Zone District will develop
databases of parcels affected by different level flood events, corresponding to upcoming
Ahtanum-Wide Hollow FEMA re -map (10C-5)". The FCZD has already done this for the
Naches River flood restudy area and plans to provide this information for first responders
after each restudy is completed.
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Ahtanum-Wide Hollow CFHMP
3. Coordination
The first alternative has already received some work on implementation, "A. Provide
infrastructure or technology for better communication between agencies (EOC) (10C-2)".
As a result of the Flood Response exercise mentioned previously and the accompanying
after action report, several communication gaps were identified. The Yakima Valley Office
of Emergency Management (YVOEM) subsequently purchased communication equipment
and improved communication process. Discussion with the emergency management office
will be needed to determine whether this alternative has been implemented.
The next merged alternative addresses the importance of including irrigation districts
during flood emergencies, "B. Coordination between Emergency Management and the
Irrigation Districts such as AID and Yakima Valley Canal, for management during
floods. Include Irrigation Districts in communications with the EOC (emergency
operations center) and FCZD (5F-1, 5F-3, 2B-3)". Included in these alternatives (5F-2) is a
proposal for the FCZD to communicate potential flood risks to the irrigation districts.
Discussion with the irrigation districts and Emergency Management will be needed to
determine the most effective method to coordinate and communicate during floods. One
aspect of this alternative that may be valuable would be a listing of flood operations
currently used by the irrigation districts.
Alternative "C. Interagency coordination of flood information and response, including
WDFW, Irrigation Districts, and Yakama Nation Natural Resources, Fisheries and
Engineering (10C-4, 10C-9)" addresses the more broad coordination effort. The after action
plan for the 2007 Flood Exercise would again be a good place to start for implementation of
this alternative. The next alternative, "D. Flood responders concentrate patrol and response
on known problem bridges and roads - (12F-1)", is dependent on alternative A in the
previous section to first identify known potential problem areas.
The last alternative in this section stimulated a great deal of discussion in the committee, "E.
Public and agencies coordinate flood fight and post flood actions with recommendations
identified in the Ahtanum-Wide Hollow CFHMP, since they require approval by WDFW
and Ecology (so will be consistent with regulations), and provide a good basis for
deciding whether to take emergency actions (10D-2)". The intent of the alternative is to
reduce permitting difficulties, reduce post -flood costs, minimize resource damage, prevent
increased flood risk, and increase implementation of alternatives of this CFHMP. Since
CFHMPs must be approved by WDFW and Ecology at the state level, flood response actions
that are consistent with recommendations in the CFHMP will likely be more easily
permitted. This approach could also reduce costs since it would be costly for agencies,
jurisdictions, or property owners to have to remove or reconstruct projects in order to
receive permits after the flood emergency is past. It is most likely this alternative would be
implemented through coordination with public agencies during large flood events and
through post -flood permitting review for actions during smaller floods. The FCZD already
reviews floodplain developments in these watersheds though the inclusion of consideration
of the CFHMP recommendations for these drainages would be new.
CHAPTER 9 - ALTERNATIVES 157
4. Outreach
Alternative "A. Recognition and dissemination of knowledge about potential flood
hazards during a flood event in coordination with the EOC (10C-3)" did not develop
specific suggestions about how this should occur (Note: the EOC is the Emergency
Operations Center - coordinated by staff of the YVOEM). The second alternative in this
category is very specific, "B. Develop warning systems including mass media (10B-1) -
Investigate reverse 911 system". Implementation of this alternative would be coordinated
with or led by YVOEM. The specific suggestion to investigate a reverse 911 system was
added to this alternative after committee members heard about this being used during
recent emergencies to contact community members by phone. This software program is
used during emergencies to alert them to the danger and issue guidance. Other jurisdictions
in Washington State have used this product so information on the pros and cons from their
experiences could help determine if this is one of the mass notification methods that would
work for Yakima County.
The next alternative is more of a grass roots type of approach, "C. Encourage volunteer
flood -watchers program to provide information (10C-8)". No additional information about
this alternative was discussed by the committee. A national program called CERT
(Community Emergency Response Team) may provide a way to implement this alternative.
The last alternative in this section is self-explanatory, "D. Provide special flood phone line
for public to call in and provide information about current flooding (10C-7) (EOC &
FCZD cooperate/coordinate)".
5. Irrigation Gates
The first alternative, "A. Improve access to Bachelor diversion during floods without
diverting flood waters or making flood problems worse (2C-3)", addresses the problem of
access to the diversion being cut-off by flooding. This prevents irrigation district staff from
having safe access for removing debris that accumulates on the diversion during floods.
Any diversion access improvements implemented in the near-term would need to consider
potential changes to the channel alignment or flood routing alternatives in the Bachelor
section of the St. Joseph's Mission at Ahtanum category (11.4. below).
The last alternative in this section proposes possible flood relief assistance that may be
provided by irrigation systems, "B. Coordinate opening gates for flood relief, based on
flood forecasts, channel maintenance needs, and impact to diversion facility (5F-6)".
While this would not be likely to help reduce flooding during major flood events, it may be
valuable for more frequent smaller floods.
6. Monitoring / Documentation
The first alternative would increase stream monitoring capabilities, "A. Install a North Fork
gage including telemetry (5F-2)". The FCZD has been investigating cooperative
arrangements and grant opportunities for several years. Including this alternative as a
recommendation in the CFHMP will increase the odds of being able to install and maintain
this stream gage. During recommendation creation Wide Hollow was added to this
alternative due to the lack of gages in this drainage and because it has different hydrologic
characteristics than the Ahtanum.
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Ahtanum-Wide Hollow CFHMP
The other alternative in this section would be valuable for many purposes, "B. Provide open
contract for aerial observation during floods for event documentation (10C-6)". The
possible uses for this data include: validation for FEMA flood mapping efforts, public
outreach, and information for first responders during future flood events. The FCZD has
begun implementation of this alternative through discussions with WSDOT to do aerial
observations for floods exceeding a predefined flow. The aerial observations proposed in
this alternative are included in alternative 15D-5 (Monitoring / Inventory category) so
during recommendation review alternative 10C-6 was dropped and 15D-5 was retained to
reduce redundancy.
7. Ice Jams
The first alternative, "A. Inventory of locations where ice jams are known to occur -
identify them in the Flood Response Plan (1A-7)", is necessary in part to determine
whether icing problems are a widespread problem or are uncommon. In recent years the
FCZD has received calls related to minor ice problems in the lower reach of North Fork
Ahtanum Creek and west of Wiley City. The property owner on the N. F. Ahtanum reported
the ice jam was broken up in 2007 using a backhoe to break up the ice on the stream bank.
The second alternative also contains several sub -alternatives, "B. Outline emergency
response to ice jams in the Flood Response Plan (1A-3)". The first sub -alternative was
added by the FCZD (so there is no alternative number) and proposes alerting residences at
risk as part of a flood response. Specific methods to accomplish this were not discussed. The
next sub -alternative calls for blasting (1A-6) the ice jam. It's was also noted during
discussions that this method typically only works on very stable jams. Another comment
included in this group of alternatives was added at some point after the alternative
worksheets were completed so it does not have an alternative number, "Facilitate regulatory
approval by Ecology and Fish and Wildlife and local jurisdictions".
8. Regulatory
This section contains one alternative with several sub -alternatives, "A. Facilitate
involvement of permitting agencies as a component of the Emergency Management Plan,
and are present in the EOC during a declared emergency (10D-3)". This alternative is
similar to 10D-1 and 10D-2 contained in other alternative categories described above (6.3.B
and 9.3.E). All of these alternatives came under the broad title "Expedited actions taken
during a flood" when the alternatives were first generated. The primary rationale for this
group of alternatives is that coordination with permitting agencies during and immediately
following the flood fight will reduce difficulties securing permits for the actions and reduce
unnecessary resource damage. These concepts are contained in the sub -alternatives:
• permitting personnel do a site visit (10D -3a);
• choose minimum flood fight action, or action that will meet the intent of the
regulations- i.e. better protect/enhance the resources (10D -3b); and
• follow-up - 6 months after a declared disaster to come into compliance for flood
fight actions (10D -3c).
CHAPTER 9 - ALTERNATIVES 159
10. SHAW CREEK FLOOD ISSUES
Shaw Creek has been a source of concern and discussions since before this CFHMP was
initiated. It is the only flood prone basin in the CFHMP area that was not included in the
initial flood studies done for the unincorporated portion of Yakima County, so it has no
FEMA identified floodplains. Whether this was due to it being identified as a ditch in the
past or because the lands were largely rural with little development expected in the
immediate future doesn't change the fact that this drainage is rapidly converting to urban
land uses while having unidentified flood risks. Some of the alternatives listed below will be
unnecessary after FEMA floodplains are identified for Shaw Creek as part of the Wide
Hollow Creek flood map restudy which is currently underway. Yakima County has
submitted grant applications for relocating the creek or construction of a flood bypass
channel.
1. Structural Response for Shaw Creek Flooding
Many specific proposals are grouped under the first alternative, "A. Relocate Shaw Creek
to the low point in the drainage to allow for more natural stream and floodplain function,
and less maintenance. Consider a potential for a larger solution that includes concurrent
considerations on Wide Hollow Creek (8B-1)". Note: for flood overflow channel option see
Alternative E below. The most important sub -alternatives are those that require quick
actions so future mitigations are not eclipsed by current development patterns. The first of
these sub -alternatives was added by the committee to reinforce the urgency felt as more
agricultural lands were proposed for development (therefore, no alternative number),
"Consider purchase of property or property interest (i.e. option, easement, etc.) needed
for relocation soon before development prevents this alternative". Another sub -alternative
aimed at maintaining options for reducing flood risk as urbanization continues is,
"Investigate ways to keep certain properties undeveloped (for flood protection, and for
possible relocation of Shaw Creek channel) (8E-4)". Though this sub -alternative does not
contain the sense of urgency of the previous sub -alternative, there is enough overlap
between them to suggest they might be consolidated to create the recommendation for this
topic.
Another group of sub -alternatives include several land use approaches related to the
concern about rapid urbanization, "Recommend quick actions which allow us to keep
options open:
• Keep at -risk areas undeveloped (8E -6.c),
• Require drainage easements (8E -6.b),
• Allow for high density development in areas that are not at risk (8E -6.d)"
The FCZD has applied for a grant to provide a Shaw Creek overflow channel to Wide
Hollow Creek at this location. Once a grant is obtained, likely in late 2011, the necessary
public process on routes can be completed. When these sub -alternatives were proposed,
specific mechanisms that could be used to implement them had not been detailed.
As part of the discussions about land required for a channel relocation, two of the parcels
that have been proposed for a portion of the relocated channel were specifically named and
60
Ahtanum-Wide Hollow CFHMP
listed as sub -alternatives, "Address Zeigler's property (8E -1.d)" and "School owns
property, and may be amenable to relocation (8E -1.a)". The FCZD entered into discussions
with the West Valley School District and applied for the grant noted above.
The remaining sub -alternatives deal with design issues. "Consider downstream impact of
changing Shaw Creek's confluence with Wide Hollow west (if all creeks diverge on Wide
Hollow during a major flood, it may cause problems at 80th and West Valley Park) (8E -
1.c)". The FCZD contracted West Consultants to create hydraulic models for investigating
changes to flood patterns by either the stream relocation or an overflow channel project (see
Figure 9-1 in alternative E below). These models will be used to ensure that any changes to
flood patterns on Wide Hollow Creek are identified and mitigated.
The last three sub -alternatives all deal with various aspects of a proposed new section of
road and how it would affect the Shaw Creek channel relocation (note: these issues would
be similar or identical if an overflow channel is implemented instead of the relocation).
Yakima County transportation planning is calling the proposed road segment Nob -Hollow
since it would connect west Nob Hill Blvd. to Wide Hollow Road. Two items identify design
considerations related to current and future bridge placement, "Nob Hollow Road possibly
a problem, possibly remove two Wide Hollow bridges, which would help with
conveyance on Wide Hollow (8E -1.b)", and "Shaw Creek overflow Bridge added as part
of Nob Hollow construction". The overflow bridge was added to ensure road project
planning includes the potential need for a new bridge to allow the relocated Shaw Creek (or
overflow channel) to continue south to its new confluence with Wide Hollow Creek. The
FCZD has communicated information about the proposed Shaw Creek project to both
Yakima County Roads and the City of Yakima as planning proceeds. The proposed Nob -
Hollow road project will be modified by development and annexation.
The last sub -alternative proposes, "Move Wide Hollow Creek South of Wide Hollow Road
(if Nob Hollow is not constructed) (8E -1.e)". This proposal is aimed at reducing flooding at
two county bridges (recently annexed into City of Yakima) that are approximately 1000 ft
apart. If the Nob -Hollow Road project is implemented and the existing bridges are removed
or otherwise mitigated, this alternative will not be necessary. If Nob -Hollow is not
constructed this will still be considered.
The next alternative in this section, "B. Reconfigure Shaw Creek to function as floodplain
and fish and wildlife habitat (8A-2)", incorporates a draft CFHMP Goal # 3 Objective:
"Protect existing, or enhance where possible, fish and wildlife habitat". Though there is
some debate about whether Shaw Creek was a fish bearing creek in the recent past, the
riparian habitat would be of value to a number of aquatic and animal species. This
alternative would not be possible as intended if the flood mitigation alternative
implemented is the flood overflow channel rather than the stream relocation alternative.
Alternative "C. Expand diking along Shaw Creek to protect new and existing
development (8B-2, 8E-2, 15B-2)" would likely be more extensive than was originally
envisioned. Flood history and draft hydraulic models show most flood overflows leaving
the existing stream channel well west of the Cottonwood Grove development. Additional
CHAPTER 9 - ALTERNATIVES 161
diking in this area would confine high flows in the channel to the east of 87th Avenue which
could increase the need for diking to the east and perhaps along 80th Avenue where the
creek is ditched along the road. The hydraulic modeling will allow analysis of this
alternative to see if and where it would be most feasible.
The next alternative in this section deals with reducing flood flows, "D. Consider
developing regional retention upstream of Tieton Drive (8C-6, 8E-3)". The committee did
not provide any details about this alternative. The only similar proposal in the past involved
preliminary plans for stormwater detention ponds in the northwestern Shaw Creek
drainage when Summitview Avenue was widened (from Gene Soules, former Yakima
County Bridge Engineer). The stormwater ponds were not included in the Summitview
road improvement project.
The last alternative in this section was added by the FCZD when land conversion issues
called into question the possibility of being able to relocate Shaw Creek, "E. Consider
overflow channel (no alternative number)". Though overflow channels are included as a
possible mitigation for perched channels in the Channel Issues category (1.7.B), the FCZD
staff felt it should be specifically identified as a possibility for Shaw Creek. See Figure 9-1 for
reduction in floodplain extent if a bypass channel is implemented. Other analyses in the
"Shaw Creek High -Flow Bypass Channel" report (contracted by the FCZD) modeled
alternatives including one with both the bypass channel and Wide Hollow Creek mitigation
actions. This modeled alternative further predicted a reduction in floodplain extent. The
main benefits to an overflow channel as opposed to stream relocation are a reduced width of
land required; existing property owners would retain the amenity value of the creek in its
current location; and possible foot paths or trails along the overflow channel. The cons for
an overflow channel include: no improvement to habitat in and along the creek; operation
and maintenance of the diversion structure would be needed; and continued concerns about
widening 80th Avenue because of existing Shaw Creek critical area permitting. Alternative A
above discusses relocation of Shaw Creek.
62
Ahtanum-Wide Hollow CFHMP
lam* e1 trieea C,SNIMq
1l.yr Fbedplmle am 1MM Has,.
Limit el exiting Camdleemm
111 yr Fbndo * mm YNem Mpemr
WEST
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Figure A2. 100 -Year Floodplain for
High Flow Bypass Alternative #1
mew Creek
- V.0de Hollow Creek
100 -Year Floodplain
2. Information and Outreach
The first alternative is similar to one in the Public Outreach category, "A. Notify developers
and prospective residents of flood hazard on the property (8E -6.a)". Developers are
notified by the jurisdictions about flood hazards during the permitting process. Currently
there is no formal method identified to notify prospective residents about flood risks unless
it is identified on the Sellers Disclosure Statement.
The other alternative in this section is aimed at current property owners, "B. Hold
neighborhood meeting for residents living near Shaw Creek (8D-4, 8D-5)". The committee
did not provide specific for this alternative. As part of the public outreach process for a
FEMA grant application, the FCZD held two public meetings at West Valley Jr. High School
in June 2008. The meeting announcements were mailed to residents in the area and the
meetings were well attended. Further meetings will be held upon project conceptual
design.
3. Floodplain Designation
The first alternative, "A. Change zoning code/amend the Comprehensive Plan to allow for
restrictions on development in flood -prone areas around Shaw Creek, and protection of
floodplain function (8C-3)", also includes a sub -alternative. This alternative could be
considered in conjunction with the land use alternatives included in the first Shaw Creek
alternative section, "Structural Response for Shaw Creek Flooding". The sub -alternative
specifically addresses the situation before the FEMA maps are completed, "Request an
administrative designation of floodplain on Shaw Creek, based on historic flood patterns
in the Shaw Creek area, prior to updating of the FIRM maps (8C-4, 8C-7, 8E-5)". The
CHAPTER 9 - ALTERNATIVES 163
committee decided not to submit this as an emergency request to the jurisdictions during
discussions finalizing the alternatives.
The last alternative, "B. Protect natural floodplain functions in Shaw Creek's watershed,
especially before it is mapped (8C-1)", has some overlap with some alternatives in the first
Shaw Creek section, but its emphasis is on protection of natural functions rather than just
trying to keep flood mitigation options available.
11. ST. JOSEPH'S MISSION AT AHTANUM FLOOD ISSUES
The flood hazards at and downstream of this location include: head -cuts through fields at
the Mission that threaten to capture the flow of Ahtanum Creek; flood flows directed to the
communities of Ahtanum, Wiley City and other developments downstream; and, damage
or loss of irrigation infrastructure.
The head -cuts are primarily due to low banks and the stream's location on the alluvial fan
which contains three creeks/ditches proceeding downstream from this point in the valley.
For this reason, there is a high avulsion risk for Ahtanum Creek, which presents a particular
hazard for Hatton Creek. Flood flows that leave Ahtanum Creek at this point continue
downstream towards Wiley City and Ahtanum by way of creeks and irrigation and
roadside ditches. Existing bridges and culverts further direct flows to sometimes
unexpected locations. Flooding causes damage to these two communities and other
buildings and developments downstream.
Flood hazards both to and from irrigation infrastructures are also a concern. Due to the
agricultural basis of much of the Ahtanum valley, any damage to irrigation headgates,
ditches or other structures could affect the valley's economy. There are also a number of
abandoned diversions and other structures that may redirect flood flows or increase channel
changes such as erosion.
Due to the potential of Ahtanum Creek channel change and flow redirection northward into
irrigation passageways with limited capacity, this scenario is considered the largest single
threat to new flooding within the CFHMP area. If this were to occur, the new 100 -year
mapping would be significantly altered and produce more basin flooding.
1. Study
Alternative "A. Continue Surface Water's study, which is predicting flood flow patterns
at Ahtanum Mission, based on surveys and modeling. Modifications to infrastructure
management may result in relation to head -cuts (2A-1)", refers to the FCZD study of flood
flows at the Mission (the Surface Water Management Division of Yakima County Public
Services manages the FCZD). The completed FEMA models are now available. Studies are
scheduled for 2011 and 2012.
The second study alternative involves effects from existing structures, "B. Determine the
effects of flooding at the Mission on irrigation structures and of irrigation infrastructure
on flooding patterns (2C-6)". This area will be modeled in late 2011 to determine design
scenarios.
64
Ahtanum-Wide Hollow CFHMP
The next alternative, "C. Verify if there is room for Ahtanum Creek to occupy old
floodplain channels on the tribal land adjacent to Ahtanum Mission. Determine if the
tribe/allotment owners may be amenable to that (2-3)", will require information from
hydraulic modeling and communication with tribal property owners. Current
communications with Yakama Nation staff and allotment owners about the Emma Lane
project may provide a framework for future discussions about proposals for the Mission
reach of Ahtanum Creek.
The last alternative in this section identifies the rich cultural and historical background of
the Mission area, "D. Define the sensitive historical and cultural issues at Ahtanum
Mission site (2-1)". The committee did not propose additional details about this alternative.
2. Hatton Creek
The first Hatton Creek alternative, "A. Recreate a flood overflow channel back to Ahtanum
Creek from Hatton Creek (natural overflow channel blocked in the 1930s) (2A-5. 2B-2)",
would help mitigate flood risks two ways. This alternative restores some lost flood capacity
and would help reduce the risk of head -cuts from Hatton Creek capturing Ahtanum Creek.
Again the 2011 and 2012 studies should clarify options.
The next alternative, "B. Modify the old Hatton ditch channel below the diversion. Intent
would be to block/armor channel to prevent opportunity for formation of head -cuts (2A-
7)", may be used in addition to or instead of other alternatives to reduce the risk of head
cutting. The last alternative in this section deals with abandoned irrigation structures, "C.
Remove the old Hatton Diversion (2A-6)". Flood events the last several years resulted in
down -cutting of the main Ahtanum Creek channel in this area so the risk of head cuts
capturing the creek has been reduced but not eliminated. These recent channel changes may
be significant enough to have reduced the time pressure to remove this abandoned
diversion. This appears to be an outstanding requirement of the Hydraulic Approval Permit
to construct the new diversion.
3. Levees / Armor
The first alternative for this section, "A. Armor stream channel to prevent migration of
Ahtanum Creek to the North (Soft levees on North side would not be sufficient- river
would cut through) (2A-8)", describes the need for this structural alternative. In addition to
concerns that "soft" levees would not be resistant enough to erosion, is the question of how
and where to key -in the foot and ends of a levee so it would be resistant to erosion.
The next alternative is aimed at protection of existing structures, "B. Utilize Ring dikes to
protect St. Joseph's Mission property (2A-3)". During committee discussions there was
some skepticism about this alternative providing adequate protection during floods.
The third alternative in this section, "C. Major levee construction on Mission property to
alleviate head -cuts (2A-2)", appears similar to the alternatives listed above. It was not clear
during committee discussions whether there are additional locations where head cuts are a
concern or whether this is just a broader proposal for structural mitigation.
CHAPTER 9 - ALTERNATIVES 165
4. Bachelor Creek
The alternatives in this section were all generated under the heading, "Damage or loss of
irrigation infrastructure could affect the economy of the Ahtanum Valley". Though the
focus is on protecting the irrigation infrastructure, modifications based on these alternatives
will also reduce flood risks downstream. The first alternative concerns channel modification
near the diversion, "A. Modify the Bachelor Diversion to improve functionality and
decrease flood hazard (e.g. upstream of 90 degree turn on Ahtanum Creek) (2C-2, 2C-4)".
The 90 degree corners stack the flood stage and increase the chances of blow out and by-
pass for flood events. A small amount of debris caught on the diversion will also kick high
flows out of the channel. For larger floods the primary concern is damage to the structure.
Also recall the alternative in the Flood Response category regarding access to this diversion.
This alternative also contains a sub -alternative, "During floods, close Bachelor diversion
and create a new high flow diversion channel from Ahtanum creek (2C-5)". The hydraulic
models will provide more information to help determine the feasibility and possible location
of this alternative.
The last alternative, "B. Identify potential future downstream impacts from any proposed
changes in the Ahtanum Mission area, and establish acceptable level of flooding along
the entire reach (2B-4)", reinforces the need to broadly evaluate potential effects from any
project in this area. Regardless of which alternatives are implemented, the streams will
continue to require room for their floodplains. Identifying floodplain areas that will still be
available for flood conveyance and storage after any flood reduction projects will mitigate
undesirable potential effects from projects in this area on lands downstream.
12. EMMA LANE AREA FLOOD ISSUES
Recurrent flooding in the Emma Lane area was one of the "poster children" that prompted
the Board of Yakima County Commissioners to form the County -wide Flood Control Zone
District in 1998. This area is larger than just Emma Lane and at a minimum includes lands
from upstream of S. 42nd Ave. to the parcels east of S. 34th Ave. It includes the Ahtanum
Creek and Bachelor Creek floodplains and overflow paths in this area south of Ahtanum
Road, though alternatives in this category include mitigations that may also reduce flooding
on the south portion of the airport and east to S. 16th Ave. Yakima County received approval
for a FEMA hazard mitigation grant for the stream relocation project (section 2 below). In
winter of 2010-2011 the project was undergoing federal NEPA analysis as required for the
grant process.
1. Study
The first alternative, "A. Perform an Emma Lane flood study, and develop design
guidance on acceptable flood protection levels (3-2)", focuses on the need for additional
detailed information. The FCZD will use models created as part of the FEMA map restudy
to examine potential projects and any additional effects. The sub -alternative also discusses
information that will be available from the hydraulic models, "Address Ahtanum Creek
flood conveyance downstream of 42" and Ahtanum Rd. (3-18)". This would be done as
part of 3-2 and include all potential benefits.
66
Ahtanum-Wide Hollow CFHMP
The second alternative, "Perform a Cost -Benefit analysis of stream relocation at Emma
Lane (3-19)", was required as part of the FEMA grant award. A cost -benefit analysis is a
requirement for FEMA mitigation grants and was submitted and approved by FEMA for a
2007 HMGP (Hazard mitigation Grant Program) grant awarded to the FCZD. An additional
update about the grant is in the next section.
Relocation
The alternative, "A. Move Ahtanum creek to a lower point in the floodplain (requires
cooperation with Yakama Nation, acquisition of at least two homes, and a new bridge) (3-
1)" suggests one of the various means to reduce flooding at this location. Ahtanum Creek at
the 42nd road crossing was ditched to the north side of the valley wall between 1911 and
1948 based on surveys. The resulting channel perched almost seven feet and the resulting 90
degree corners permits high flows to leave the stream channel and head off in unexpected
directions, prior to reaching the bridge even during minor flood events. Channel relocation
was also proposed in a federal grant application by Yakima County in 1997 following the
extensive flooding at this location and downstream through flow redirection in 1996. In
2007 the FCZD obtained a federal Hazard Mitigation Grant for this location. Channel
relocation, among several other alternatives are being considered within the grant for flood
hazard mitigation. (See Figures 9-2 and 9-3).
Figure 9-2 Emma Lane - January 2010 Draft Options
Yakama Nation Boundary
Possible Dwer;l an
LOC -0101W
Passlbie Diversion -.
Locations
Ahtanum Creek
Relocation Project
F boa Plans
u ma nor
.Y
•
Yaidmaa-cam
CHAPTER 9 - ALTERNATIVES 167
Figure 9-3 Emma Lane - January 2010 Draft Options
Yakima County Roads Division has agreed to rebuild the bridge on 42nd Ave. in a new
location if that alternative is selected. This funding commitment was proposed as part of the
match for the HMGP grant awarded by FEMA for the project. The required federal
environmental review (NEPA) for this FEMA grant is currently in process awaiting input
from the Yakama Nation and allotment owners. FEMA discussed with the Yakama Nation
other concerns including the Yakima Reservation boundary line (which by treaty is
Ahtanum Creek) and any cultural or historical concerns. The alignment in Figure 9-2was
dropped by FEMA in 2011. Yakima County Right -of -Way staff has been in discussion with
the property owners of the likely parcels to be purchased for the stream relocation.
Implementation of this alternative is in process, but may not be completed should
irresolvable problems arise.
Two sub -alternatives for this alternative involve design possibilities. The first, "If Ahtanum
Creek is relocated, consider a design that does not include filling in the old Ahtanum
Channel- looking at the existing channel as habitat (3-15)", proposes converting the old
channel to a side channel. The hydraulic models will provide more information to
determine if this is feasible. The second sub -alternative proposes an overflow channel
approach, "Examine constructing a controlled side channel to bypass Emma Lane, rather
than moving the creek (3-14)". These aspects will be considered in the project.
3. Development in Emma Lane Area
This section contains two alternatives, the first "A. Limit future development in the Emma
Lane area (3-3)", also has one sub -alternative. The sub -alternative is similar, "Place controls
on building in the flood -prone areas in and around Emma Lane (3-17)". Few specific
methods were discussed beyond the examples listed of using zoning and utility hook-ups to
limit development density. The new FEMA flood map restudy may decrease the desire for
68
Ahtanum-Wide Hollow CFHMP
this alternative if more of the risk area is identified as 1% annual chance floodplain (a.k.a.
100 -year floodplain).
The second alternative, "B. Adopt and implement more strict building standards in Emma
Lane area- flood -proofed homes, buildings (3-11, 3-3)", did not include additional
suggestions besides those included in the alternative title. FEMA only allows elevation as a
method for flood -proofing residential structures (as far as receiving an insurance rate
reduction is concerned).
4. Channel and Drainage Capacity
This section contains three alternatives. The first alternative, "A. Improve drainage
throughout the entire Emma Lane area- culverts, roads, etc. (3-8)", provides the big picture
view with several sub -alternatives contributing the details. These sub -alternatives range
from improving existing infrastructure to improving stormwater management. The first,
"Reconfigure the Bachelor Creek Bridge on Ahtanum Road to increase capacity and
reduce backwater flooding (3-6)", includes improvements to alignment of the existing
bridge. Another sub -alternative that addresses infrastructure improvements is, "Eliminate
the Shropshire ditch or other irrigation ditch remnants (i.e. remove irrigation ditch that
directs flow and inundates Emma Lane- area pastures and residents) (3-7)". Until the
hydraulic analysis is completed it is unknown if this proposal would provide a benefit
primarily for smaller floods or would also be useful for larger floods.
The next two sub -alternatives deal with drainage mitigations a somewhat more urban focus.
The first is, "Alter drainage systems and easements, based on Emma Lane floodplain
remap study (3-10)". This area was developed before 1968 and is currently in the
unincorporated portion of Yakima County. All roads in the area are public county roads
with some roads having ditches and culverts for driveways and others allowing sheet flows
across the road. The major roads in the development are paved, with the loop and cul-de-
sac roads having a gravel surface. None of the roads have curb and gutter drainage. If the
flood map restudy indicates locations that could use improved drainage, easements would
be possible, but changes to the "drainage system" would require more effort.
The last sub -alternative, "Improve stormwater system on Ahtanum Road to limit Emma
Lane overflows into the airport area, and downstream to 16th (which floods the
intersection at Ahtanum Road) (3-9)" refers to run-off from the main Emma Lane area.
Widening to four lanes, curbs, gutters, and other improvements to this stretch of Ahtanum
Road is listed on the county 6 -year transportation improvement plan and is slated to begin
preliminary engineering in 2012. Coordination of the CFHMP recommendations with this
roads capital improvement project may solve some stormwater problems. The addition of
curbs and gutters to a short stretch of Ahtanum Road west of S. 16th Ave. received a
drainage test during a minor flood event in February of 2003. Flooding down Ahtanum
Road was captured by the drainage system and conveyed to the intersection at S. 16th Ave.
where it then flowed up and out of the man holes. The flooding in the intersection took
several days to dissipate and at least one of the property owners sandbagged around their
house. The intersection of Ahtanum and 16th Ave. is further complicated by being located at
the corner of three jurisdictions.
CHAPTER 9 - ALTERNATIVES
The next alternative, "B. Widen Bridge at 42nd Ave. (3-5), is somewhat in doubt. Several
committee members are skeptical that this alternative by itself would do much to reduce the
flooding problems in this area. When the hydraulic model is finished it can be used to try
this alternative to see if it would reduce flood problems.
The last alternative, "C. Remove old fill on Ahtanum at the Yakama Nation land just
south of Emma Lane (3-16)", regards removing illegally place fill. Information from local
residents states a person leasing Yakima Reservation land filled in a large area at the end of
S. 42nd Road. Removing this fill would increase floodplain capacity and the restored area
could possibly be used to enhance habitat.
MONITORING & INVENTORIES FLOOD ISSUES
Some studies, inventories and monitoring alternatives are located in specific categories
described above. This category typically contains activities that would be of value across the
CFHMP area, rather than for a specific geographic area or stream reach. These are listed by
their original alternative number; they were not grouped into sections and labeled by their
location on the table, in contrast to labeling for the previous alternatives.
From a risk standpoint, the alternatives (15B-7, 15B-10, 15F-3 and 15F-4) for identification of
perched stream channels and flood risks related to hollows stand out. The FEMA flood map
restudies for this area will provide valuable information about perched streams so
disclosure of the flood risk will be possible and quantifiable. While the identification of risk
for larger hollows may also be aided by the restudies, smaller hollows not evaluated for
flood maps will require additional risk assessment.
Five alternatives (12D-3, 12C-1, 12D-6, 12E-4 and 12E -7b) in this category involve gathering
information about public and private roads and bridges that may contribute to flood risks.
This is a good indicator of the level of concern about transportation infrastructure and
flooding, as well as confirming there is still a lot that is not known. The current FEMA flood
map restudies being conducted will provide valuable information that will be aid these
inventories, though additional work will need to be done. Alternative 12D-3 also includes a
future development aspect to utilize information that is gathered for transportation
planning.
Several alternatives (1C-7, 1C-8, 1C-11, 12G-8 and 13B-8) call for investigating specific
methods to reduce flood risks or seek potential funding sources. These range from illegal
dumping in floodplains to funds for incentives for private drainage infrastructure. If
suitable methods were found, these land use, code enforcement and funding alternatives
would require ordinance changes or, in the case of private drainage infrastructure, a
mechanism to connect the financial sources to applicants.
The remaining four alternatives cover a wide range from specific site identification to broad
monitoring activities. Beginning with the most specific is alternative 15A-3. It is anticipated
that identifying locations where streams have been changed in ways that increase flooding
will allow cooperative flood reduction projects. This alternative would capture any man-
made changes that are not already identified in inventories of transportation and irrigation
infrastructure. Another specific site alternative (15D-5) in this category involves
69
70
Ahtanum-Wide Hollow CFHMP
documentation of flooding using methods such as aerial photos and recording high water
marks. The greatest challenge for this alternative is determining the most efficient way to
have the needed contracting ready to go when significant flooding occurs. This alternative
includes the aerial observations also found in alternative 9.6.B in the Flood Response
category (10C-6). Because alternative 15D-5 is broader, it was retained and 10C-6 was
dropped.
The last two alternatives are much broader and will likely require some background
research to determine the best approach to use. The first (12H-3) calls for watershed
monitoring to track urbanization and land use intensification effects that add to flood
problems over time. Determining which parameters to track and setting thresholds for
negative effects would likely be the first step.
Alternative 14E-1 would investigate the possibility of using geologic hazard areas to
identify channel migration zones and alluvial fans. Though there is a FEMA map process
available for mapping certain types of alluvial fans, there is currently no established method
for including channel migration risks into FEMA flood maps. It is also anticipated that some
alluvial fan areas may be under the size requirement for FEMA mapped drainages. In
Washington State, geologic hazards are regulated through local Critical Areas Ordinances
and channel migration zones (for identified larger streams only, such as Ahtanum Creek)
are regulated through local Shorelines Programs.
COMMITTEE SELECTION OF ALTERNATIVES
As noted above the Committee finalized, through discussion, the Table 9-8 alternatives by
dropping and merging those alternatives. The revised alternatives selected for
implementation are contained in Table 9-9.
Prioritization
Committee members' top alternatives were selected as high priority at a meeting on April
19, 2010. Based on the plan goals and objectives the FCZD selected some additional high
priority actions to cover gaps and these were presented again to the Committee.
Alternatives were selected as medium priority if they had been chosen by any committee
member and were rated high by the FCZD when rated at an earlier step in the process. The
remaining alternatives were considered lower priority. Table 9-9 contains all the
recommended alternatives for implementation.
Table Notation Notes
As part of the merging of like alternatives, the original alternative numbering was retained.
This is the best way to obtain more detail and to track an alternative through the steps in
this CFHMP creation. The numbers reference directly to the alternatives in Chapter 9 and
the appendices.
CHAPTER 9 - ALTERNATIVES 71
TABLE 9-9 SELECTED FLOOD ALTERNATIVES AND PRIORITIES
Priority - High, Medium, Low
Crosswalk # - reference to Tables 11-1,11-2,11-3 in Chaster 11
1. CHANNEL ISSUES / RIVER FUNCTION
1. Stream Management - Natural vs. Irrigation Ditch or Urban
Priority Crosswalk #
Stream
A.
Separate irrigation conveyances from natural streams based on
studies where it is shown this would be effective as flood control.
(15B-3, 5D-7)
• Reduce operational spill of irrigation water into streams (7A-2)
• As part of mitigation for piping of irrigation waters, create a more
normative conveyance schedule (7A-4)
Consideration- A non normative hydrograph results in overgrowth of
species such as Pacific willow, which contribute to flooding, particularly in
the Wide Hollow basin. Lower Wide Hollow and Ahtanum Creek are
influenced by the water table of the Yakima River, which also has a non-
normative hydrograph
High
MM -9
B.
Establish work groups to clarify technical & regulatory measures
and flood routing and management options for natural, artificial and
shared drainages effected by irrigation:
• Consideration- This may involve distinguishing between areas that should
retain natural functions and processes (e.g. Ahtanum Creek), as opposed to
areas that should be managed within the context of high intensity uses,
such as irrigation conveyance or drainage ditches. (7B-7) (15E-5, 15E-6,
5D-2, 5D-3, 5D-4, 5D-5, 5D-8, 5F-4, 15E-1, 2-2, 8A-3)
High
PR 9
2. Riparian Protection / Restoration
A.riparian
Utilize existing federal, state and local policies and programs to
protect the natural function of the system to reduce flood hazard:
Preserve/restore riparian areas using acquisition/legal protection of
zones -
• Easements,
• Agreements, (Fee Simple, etc.).
Consideration- This is most often done with multiple objectives - Fish
and Wildlife habitat protection, Open Space, parks, trail and other
Protect riparian vegetation -
• Conservation Reserve Enhancement Program
• YTAHP (Yakima Tributary Access and Habitat Program)
• Open Space taxation incentives
• Limit rates of habitat loss:
• Endangered Species Ad,
• Growth Management Act, Critical Areas Ordinance
• Hydraulic Code
High
g
High
MM -4
PR -6
72
Ahtanum-Wide Hollow CFHMP
• Maintain watershed and channel processes (i.e. Clean Water Ad,
In -stream flow rules (9C-1, 7B-2, 7B-3)
B.
Coordinate/cooperate flood efforts with currently in-place habitat
protection and restoration programs (i.e. Salmon Recovery Funding
Board, Northwest Power and Conservation Council), as well as other
programs and funding sources that encourage riparian habitat
protection. (9C-2)
High
MM -4
C.
Work with private habitat restoration organizations (e.g. Land trusts,
Greenway, other non-profit programs) to protect riparian areas for
flood hazard reduction. (9C-4)
High
MM -4
3. Elk
A.
Relocate elk feeding stations to other areas away from stream
corridors to lessen compaction, erosion, and pollution impacts. (9B-
3)
High
MM -6
B.
Apply similar management standards to elk in confined feeding
operations as in livestock operations & incorporate watershed
management principles when managing elk. (9B-2, 9B-4)
High
MM -6
C.
Develop a Coordinated Resource Management Group to develop
joint priorities for resource management (e.g. Wenas working
group). (9B-1)
Low
IS -20
4. Dumping and Pollution in Streams
A
Investigate funding for enforcement and cleanup of illegal dumps on
private ground. (1C-9, 1C-10)
Low
MM -18
5. Private Landowner Assistance
A.
Utilize fence designs that prevent floodwaters from backing up on
fences, such as:
• Breakaway fence panels in locations that flood frequently.
• Suspension fences, which consist of steel pipe or cable hung high
above the creek, and hanging lighter materials down from the cable.
This works as a fence, but is not lost during floods.
• Fence setbacks - hold fences back some distance from the creek
(loss of traditional land usage) (1B-1, 1B-2, 1B-3, 1B-4, 1B-5).
Low
MM 21
B.
Work with landowner assistance programs (i.e. Conservation
Districts) to establish or re-establish vegetation and provide
information about flood resistant fencing (7B-4, 1B-7, 1B-8).
Medium
PO -6
6. Vegetation
A.
Utilize natural solutions for channel related flooding issues:
heading
• In some locations, add wood to stream to "catch" wood debris -
this accomplishes multiple objectives- would benefit habitat as well
as reduce the volume of woody debris that accumulates on bridges,
diversions, and other structures. (7D-4)
Low
ST 18
• Utilize plantings (such as Red osier dogwood, etc.) solutions for
bank stabilization (15C-2).
High
MM -1
B
Control or Replace Undesirable Plant Communities that can
contribute to flooding (e.g. hybrid Willows):
heading
CHAPTER 9 - ALTERNATIVES 73
• Utilize other types of vegetation that can be substituted for Pacific
or hybrid Willows over the long term- may include non-native plant
communities. Research appropriate plant communities for denuded
riparian areas (7A-5 & 7B-8)
High
MM -1
• Create program for removal and long term management of hybrid
Willow, may be at different scales: site specific or throughout the
watershed, e.g. for some distance upstream and downstream of
bridges on Wide Hollow (7A-1)
High
MM -1
• Petition State Noxious Weed Control Board to list hybrid willows
as invasive species as designated in other states (new)
High
PR -2
7. Channel Relocation / Reconfiguration
A.
Relocate modified streams away from high-intensity uses, or restore
incised stream channels to allow for natural riparian/flood function
• Channel reconfiguration and reconstruction at Emma Lane, Shaw
Creek, lower Wide Hollow in Union Gap, and the Mission (15A-1,
15B-1, 7B-6). Note: main title for 15B is, "Perched irrigation
conveyances are not compatible with natural flooding patterns and
development"
Medium
ST -14
B.
Create or maintain Flood overflow channels/conveyances where
channels are perched (15B-9)
Medium
ST -14
8. Channel Maintenance
A
Perform periodic channel maintenance (stream clean-out of
sediment, woody debris and invasive vegetation) at identified flood
hazard areas. (15A-2)
• Convene technical work group to assess gravel management
options in upper Wide Hollow watershed (Ellensburg formation
geology)
• Develop coarse sediment budget through empirical monitoring or
modeling.
• Implement options to increase channel stability based on
information generated in alternatives above.
High
g
IS -1
9. Beavers
A.
Deal with beavers on a case by case basis- use discretion based on
situation (determine "is the floodplain function provided by the
beaver a good thing or a bad thing?") (9A-1)
• Remove "problem" beaver dams, under permits from
Department of Fish and Wildlife. (9A-3, 9A-6)
• Establish policies for lethal trapping or relocation of "problem
beavers." (9A-2)
• Encourage beavers in areas where their presence could restore
degraded watershed function. (9C-5)
High
MM -2
B
Establish regulatory measures (buffers, setbacks, etc.) to allow for
localized flooding/changes in water surface level or the channel (9A-
5, 9A-7) Consideration — would first need to identify locations where this
would be appropriate or likely
High
g
MM -2
74
Ahtanum-Wide Hollow CFHMP
10. Flood Protection
A.•
The following structural alternatives can be considered where
changes in the channel threaten homes, businesses, agricultural
land, or infrastructure.
• Levees, armor, buffers, CMZ (channel migration zones) (15C-1)
Structural flood control measures either by individuals or
government (4-7)
• Utilize "softer" solutions for bank stabilization, bio -engineering.
(15C-2)
• Levees constructed along perched channels (i.e. Cottonwood
Grove) (15B-2)
Low
ST 16
2. WATERSHED
1. Non-Stormwater Watershed Issues
A
Review DID management in relation to flood hazard over the long
term as land use changes (15E-4)
Low
MM 17
B.
Preserve natural drainage including draws and hollows that
provide natural flood paths. (new, so no alternative number)
Medium
PR -24
C.
Design bridges and irrigation diversions to reduce potential for
localized debris and bedload (sediment) accumulation and from
creating un -natural overflow channels/paths (5B-1, 7D-3, 7D-5)
Medium
IS -16
2. Stormwater
A.
Utilize NPDES stormwater programs to retain site runoff and
reduce overland flow for the Yakima urbanized area (1D-5)
High
PR -14
B.
Develop stormwater standards across the basins for detention and
retention on site; abide by and enforce stormwater design standards;
and incorporate flood issues into stormwater programs (4-4, 13C-4,
1D-6, 14C-7, 15G-1, 13C-1)
Medium
PR -1
C.
Establish a relationship between stormwater standards and
development standards in floodplains with regard to flooding (high
water table and low gradient) (13C-3)
Medium
PR -1
D.
Size drainage facilities for future build -out and flood flows —
including ability to pass upland drainage of 100 -yr flow (15E-2, 15F-
1, 15G-2).
Medium
PR -1
E.
Limit new connections to existing undersized drainage systems, i.e.
DIDs, storm drains, and resolve the runoff issues presented by the
Drainage Improvement Districts (DIDs) that may act as stormwater
drainage systems although designed for subsurface flows. (13C-2,
15E-3)
Medium
IS -13
F.
Implement an effective Stormwater Management Program that
reduces basin flooding (4-15)
High
PR -14
G.
Modify drainage standards for roads in overflow areas to minimize
flood impacts (i.e. Emma Lane area) (3-12)
Medium
MM -13
CHAPTER 9 - ALTERNATIVES 75
3. BRIDGES AND ROADS
1. Design
A.
Adequate Bridge & Road Crossing Standards:
Build new bridges & roadways in agreement with the hydraulic
model to optimize flow passage in bridge/culvert design.
• Develop the following bridge design standards and policies for
implementation by the jurisdictions such as:
o freeboard to account for ice and debris (1A-1)
o include floodplain functions and natural channel
processes, including expanded up and downstream
right-of-way where needed to account for these
functions (12A/B-7 & 12A/B-6)
o include in -stream actions to maintain conveyance (such
as grade control) where needed to reduce erosion and
flooding (12A/B-1)
o place priority on infrastructure flooding issues at the
federal, state, tribal and local level (12G-7)
o design of bridges and bridge footings should
incorporate long-term erosion and scour conditions that
do not impede flood conveyance (new, so no alternative
number)
High
PR -15
IS -5
IS -5
IS -5
PR -3 OR 23
IS -5
B.
Improve bridge conveyance at S.16th Ave. at Ahtanum Creek (3-13).
High
ST -3
C.
Consider lowering existing roads where they ad as dams and cause
flooding (ponding) (12D-5).
Investigate installing culverts in currently artificially ponded areas if
this would help mitigate risks from 5 — 25 year floods. (new, so no
alternative number)
High
IS -3
D.
Armoring:
• Provide armoring of roads which ad as levees
(Ahtanum/Cottonwood Canyon Rd., etc.)(12D-1).
• Armor road ditches where road fill is going to contribute to
excess bedload and to protect road prism (12E-3).
Low
ST -19
E.
New and reconstructed roads should be evaluated; roads that are
not intended to be passable to a certain standard (10, 25, or 100 year
flood), should be built at grade (12F-6, 12H-8). Coordinate with 2A
(below)
• Consider designing new roads at grade in FEMA identified
overflow areas. (12D-4)
High
IS -12 & PR-
7
F.
Culverts:
• Recognize the limitations of culverts as flood conveyance
structures (12E-2)
• Replace old culverts with higher capacity culverts based on
flood risk (12E -7a).
Low
ST -20
76
Ahtanum-Wide Hollow CFHMP
2. Monitoring / Maintenance
A
Decide upon, designate and maintain critical access routes at 10, 25
and 100 year events. Coordinate with 1E above (12F-3, 12H-7).
High
IS -12 & PR-
7
B.
Actively monitor and manage channels adjacent to bridges to
improve and maintain bridge capacity (armor or sediment removal
in poorly functioning bridges, and management of vegetation
debris). Monitor channel and floodplain conditions post bridge
construction. If significant unforeseen problems develop, after the
stabilization period, respond to them (12A/B-4, 12A/B-8).
• Institute a policy of more maintenance at known problem bridges
(12F-2)
High
MM 3
D.cleanout
Investigate and recommend increased maintenance and debris
of culverts and ditches on public roads (coordinate with
road maintenance crews to optimize ditch cleaning for flood
purposes) (1D-1, 12D-2, 12E-1).
Low
IS 21
E.
Assess the cumulative effect of road policies and standards for new
roads that ad as dams or conveyances. (12C-3.)
• Take larger scale affects to the watershed into account when
designing new transportation systems: Minimize number of roads -
maximize efficiency. (12H -4a)
Low
PR -32
PR -31
3. General Planning
A.
Inventory and rank problem bridges throughout the watershed and
coordinate with Capital Improvement Plans of local and state
jurisdictions. (12A/B-3)
High
IS -3
B.
Integrate existing or new funding programs into strategic program
for addressing inventoried problem bridges (12A/B-10).
High
IS 3
C.
Explore ways to take better advantage of Federal and state funding
programs to reduce or mitigate the environmental effects (including
flooding) of existing road systems (12G-6).
Medium
MM -15
D.
Work with landowners upstream and downstream of new
infrastructure to design access to property to mitigate flood impacts
(12G-9).
High
PR -16
E.
4. IRRIGATION
Replace flood damaged transportation infrastructure in a manner
that reduces vulnerability to future flood hazard (12G-5).
Medium
MM -14
1. Conversion of Irrigation Systems
A
Consolidate irrigation diversions to minimize stream impacts,
consider upgrades like piping, and consider converting irrigation
systems to a pressure -based system, e.g. Pine Hollow (5C -1,5C -2,5D-
1)
High
g
MM 10
CHAPTER 9 - ALTERNATIVES 77
2. Infrastructure Maintenance and Inventory
A.
Develop a program of proactive debris removal and maintenance on
irrigation structures (1D-2, 5B-4)
• Install temporary or sacrificial debris capture structures adapted
to existing channel conditions to reduce debris problems, esp. Wide
Hollow. (5B-2)
High
MM -3
ST -18?
B
Conduct an inventory of existing irrigation infrastructure (working
or abandoned) and flooding impacts. Identify problem locations and
old drainage and irrigation systems that are affecting flooding in the
irrigation system, i.e. gate at Wiley City (2C-1, 5A-1, 5E-1)
• Install removable structures, such as irrigation pumps, weirs,
gates, etc. (potential problem with ice), e.g. JM Perry Tech. (5B-3)
High
g
IS -4
TBD
C
Identify sources of funding for removal of abandoned irrigation
structures (5E-2)
Low
ST -21
D.
Investigate the possible use of flood gates or siphons to reduce flood
flow routing by irrigation infrastructure, if needed, identify
locations of most benefit:
• Stationary or removable flood gates for use at diversions or in
channel (5A-2, 5A-5)
• Install undershots in some locations- siphons through gulleys and
Medium
MM -12
de.ressions under the ditch (5A-4)
5. LAND
USE
1. Subdivisions
/ Housing Developments
A.
Minimize new homes/structures etc. in harm's way (15C-11).
• Effectively integrate protection of floodplain functions/flood
hazard reduction in individual subdivision platting process. (See
also other regulatory recommendations) (8C-5.)
• Create more stringent subdivision standards in flood prone areas
(4-5.) Note: dropped due to lack of specifics during recommendation
review.
• Work toward common development standards. (new, so no
alternative number)
Medium
PR -28
PR -28
PR -27
B.
Work for consistency in zoning standards across jurisdictions for
developments and buildings within floodplains. Determine gaps in
the regulatory scheme. (13A-9)
• Recognize that in some places, the issues associated with larger
scale proposed developments are not adequately addressed by
current standards. (13B-2) Note: was moved to high in Chapter 11 &
added SEPA & Comp Plans text.
Medium
PR -27
PR -13
C.
Establish or maintain standards for subdivision in the floodplain- at
the minimum require a buildable area outside of the floodplain.
Standards for lot size and housing location. (14D-1)
Medium
PR -28
78
Ahtanum-Wide Hollow CFHMP
2. Incentives / Taxation
A.
Provide special incentives- (clustering, density bonuses, Transfer of
Development Rights) for retention of floodplain function in
development design (13B-4).
High
PR -6
• Provide incentives or bonuses for developers who actively protect
flood hazard areas. (i.e. 10% density bonus). Specific development
standards in zoning ordinance. (14C-2, 13A-7).
High
PR -6
• Utilize landowner incentive programs (i.e. Conservation District,
Cost- Shares, Open Space taxation and other tax breaks) (9C-3).
High
PR -6
• Utilize existing agricultural subsidies or programs to allow for
flooding on some farmland. Note: Will depend on water velocity -
erosion verses sheet flow. Develop a compensation program for
productive agricultural land lost to flood induced erosion. (15C-4)
High
PR -6
B.
Encourage jurisdictions to join FEMA's Community Rating System
to reduce property owners' flood insurance premiums. (new, so no
alternative number)
High
MM -11
3. Open Space / Parks
A.
Encourage the retention of open space in floodplains through:
heading
• Open space taxation policies (specifically including these problem
areas in the public benefit rating) (13B-6)
High
PR -5
• The development of walking paths / trail systems (12H -4d).
High
PR -5
• Develop policies and standards for open space retention within
expanding UGAs, and within individual developments. (14E-3)
High
PR -5
• Incorporate open space/floodplain retention into site plans (e.g. La
Salle High School)(11A-3)
High
PR -5
• Include flood hazard reduction goals in Open Space Planning
(13C-5)
High
PR -5
• Encourage local governments to establish specific comprehensive
plan policies to use floodplains and other critical areas to meet their
GMA requirements for Parks and Open Space. This may substitute
for designating some blocks of private land as open space. (13A-5,
14E-4)
High
PR -5
• Maintain open areas near the mouth of Ahtanum creek for
inevitable flooding (i.e. Fulbright Park and adjacent areas).(11A-2)
Medium
PR -26
• Encourage parks (County and City) in frequently flooded areas
(i.e. Fulbright Park) (13A-3).
High
PR -6
4. Large Scale Retention of the Floodplain
A.
Reduce density in the floodplain through various methods(14C-3):
High
PR -5
• Preserve and restore natural floodplain in places that retain some
of the floodplain function. Prioritization- allow for flexibility while
identifying critical locations, based on CFHMP and mapping (4-12).
Low
ST -22
• Make changes to comprehensive planning and zoning documents
and maps to focus lower intensity development within floodplain
High
PR -5
CHAPTER 9 - ALTERNATIVES 79
corridors and focus higher intensity development outside floodplain
corridors (14C-4, 14C-5).
• In certain high risk locations, consider development moratoriums
or high standards of proof in place where development is outpacing
knowledge or tools available to keep the public safe (i.e. the area has
not been mapped, or conditions have changed since the last
mapping) (13A-15).
Medium
PR -25
B.
New traffic -generating developments should be located outside of
floodplains (See also Bridges & Roads). (12H -4b)
Low
PR 36
C.
New major arterials should be located outside of floodplains where
possible. If in floodplain, design to minimize flood impacts. (12H-
4b)
High
PR -4
D.
Incorporate principle of floodplain planning into infrastructure &
similar facilities plans (8C-2, 12H-2)
Medium
PR -23
E.
Minimize negative flood effects of accessing major arterials esp.
when adjacent to or across floodplains (12H -4c)
High
PR 4
F.
When developing floodplain planning, zoning, and development
standards or use designations, the jurisdictions should consider:
• future land owner costs for flood damage,
• NFIP insurance costs
• construction costs for flood prevention.
• urban land use preference in the following order from most
to least preferred: open space, trails, parks and recreation,
light industrial, commercial, low density R1 (one lot per
acre), and clustered residential.
High
PR -3
5. Acquisitions / Easements / Incentives
A.
Acquisition/easements of land surrounding flood problem areas, i.e.
Emma, Shaw, Union Gap, Ahtanum Mission (4-13, 15B-4, 15D-4)
• Acquire land- fee simple or easement, for a variety of purposes
consistent with floodplain function (13B-5).
• Address maintenance of drainage easements -establish who is
going to enforce maintenance (9C-12)
• Develop a program/policy guidelines for areas threatened by
meandering and erosion, or frequent inundation, including
(15C-3, 15C-9, 15C-10):
Buyouts
Relocation
• Easements
Flood -Proofing
• Make acquisition of FEMA identified Repetitive Loss properties
a high priority (6 of the 8 properties with this FEMA designation
are in the CFHMP area). (new, so no alternative number)
High
MM -5
MM -5
MM -5
PR -5
ST -1
B
Utilize tools such as floodplain easements to preserve off-site
storage of water and sediment in farmland (existing pastures,
alfalfa), while preserving use as farmland. Consideration: This could
accomplish two goals: preservation of use of land for agriculture,
and preservation of floodplain. (15B-5, 15B-8). Link to Farmland
preservation programs.
High
g
PR -6
80
Ahtanum-Wide Hollow CFHMP
C.
Encourage organizations (neighborhoods, County/City/Yakama
Nation or others) to purchase floodplain areas (9C-10).
High
PR 5
D.
Provide incentives for landowners and developers who provide
floodplain storage (4-6).
High
PR 5
6. Standards for Development
A.
Establish Flood Overlay Zones in affected jurisdictions. These
overlay zones would have legal status (i.e. in a zoning code or other
ordinance) and contain development standards, objectives, and
review/process criteria for the broad suite of land uses that occur in
floodplains. (13B-3) Note: language substantially modified in final
review.
Medium
PR -8
B.
Develop flood abatement policies for areas of existing dense
development within the floodplain (such as Ahtanum and Wiley
City) (13A-13)
• Design better drainage, especially in Wiley City and Ahtanum. In
the past, overflow water used a ditch along the railroad, which has
been filled in. Resulting lack of drainage causes sheet flow (14A-4).
• Establish areas such as Wiley City & Ahtanum as special study
areas. (new)
Medium
PR -19
C.
Establish policies in flood prone and flood hazard areas for directing
preferred locations for the siting of new infrastructure such as major
and minor arterials, water and wastewater distribution mainlines,
regional stormwater facilities, parks and greenbelts. (13A-11)
High
PR 4
D.
Limit/restrict/reduce the number of bridges and road crossings,
especially small road capacity bridges and culverts for new
development through subdivision standards. Also offer incentives
for improvements or consolidation for existing crossings esp. post
disaster. (12H-5, 12H-9, 12A/B-9, 12C-4).
High
PR -16
E.
Seek land use examples from other similar areas. 13B-8
Medium
PR -21
7. Miscellaneous Policies
A.
Ensure flood policies in the Yakima Urban Area Comprehensive
Plan are implemented through ordinances and land use decisions.
Planning for flooding is supported in Objective E7 (13A-4).
Medium
PR -22
B.
Develop special land use and flood -proofing standards for
industrial uses relating to hazardous materials, storage, use,
disposal (11B-1). Jurisdictions should adopt Appendix G.
Medium
PR -29
C
Consider 25 -year flood as design and regulatory floodplain for
future development to minimize frequent damages (new, so no
alternative number). Note: language modified in final
recommendation review.
High
g
IS -7
6. DEVELOPMENT STANDARDS/ENFORCEMENT
1. NFIP Related
A.
Consider increased elevation above BFE of new structures in the
floodplain. 14A-2
High
PR 10
CHAPTER 9 - ALTERNATIVES 81
B.
Require Flood -proofing for non-residential structures:
• Flood -proof utilities
• Flood proof structures- elevate, make existing structures less
flood damage -prone (4-8).
Medium
PR -29
C.
Utilize available flood data in accordance with FEMA's definition;
this is may be valuable esp. for jurisdictions where NFIP compliance
regulations are not affected by CAO's "Best Available Science"
requirements. (new, so no alternative number)
High
PR 15
2. Special Zones
A.
Identify areas with floodplain "islands" and develop standards that:
1. Limit density to provide flood passage 2. Provide emergency
access 3. Transportation networks in these areas (even if they are
zoned as low density) should be planned to take into account
surrounding properties, rather than a standard site-specific
approach (12H-6).
Medium
PR -20
3. Miscellaneous
A.
Enforcement- Adequately fund enforcement activities. More
effective code enforcement, especially for blatant disregard of the
law.(1C-4, 1C-3, 18)
High
PR 11 &
PR 18
B.
Coordinate between jurisdictional procedures in place for expedited
permit issuance during and period after a flood event under State
and County regulations (10D-1).
Low
FR -13
C.
Ensure floodplains and floodways are identified on final plat maps
— included would be text identifying effective map date and
disclosure regarding fact that the maps will change over time. Also
consider including identification of riverine Critical Areas buffer on
Added
PR -17
slats (new) Added durin: final recommendations review
7. UNION
GAP
A.
Modify Wapato Dam (4-11, 6C-7) to decrease flood risk (See Upper
Yakima CFHMP)
High
IS 6
B
Identify future flood impacts that may occur as a result of
aggradation (6C-1, 6C-2, 6C-3, 6C-8).
Sediment Transport on the Yakima River Studies:
• Study how changes on the Yakima River adjacent to Union Gap
may affect water tables in Union Gap (4-18)
(cont.)
• Causes and rates of channel aggradation in the Yakima River (4-
17, 6C-9)
• Improve sediment transport along the Yakima River (Refer to the
Upper Yakima CFHMP) (4-10). (Wapato Dam and upstream reach)
High
g
IS -6
C.
Relocation of Wide Hollow Creek below 3rd Ave. (6C-6, 11A-4)
• Construct floodgates on Wide Hollow culverts if Wide Hollow is
diverted into Ahtanum Creek (abandoned culverts at/near the
mouth if creek relocated) (6C-5)
High
ST 6
82
Ahtanum-Wide Hollow CFHMP
D.
Encourage the appropriate parties to develop Operations and
Maintenance agreements for the flood gates and fish passage
structures at the Mill to ensure coordinated and effective
management for flooding. (new, so no alternative number)
Medium
ST -15
E
Bypassing or modifying the Mill structures on Wide Hollow Creek.
(11A-5)
High
g
ST -8
F.
The Spring Creek floodgate should generally be closed except for
habitat or flow enhancement for a limited time period (6B-1)
Low
MM 16
G
Install a remotely controllable floodgate that could be opened some
times of year, closed at others (on Spring Creek floodgate) (6B-2)
Low
ST 23
H.
Improve conveyance downstream of the culverts on the Spring
Creek irrigation channel by increasing grade — this would help in
most flood events, possibly not in large-scale flooding. (6D-2)
High
ST -7
I.
Retain Wide Hollow overflow path along the railroad right of way.
(11A-1)
Medium
ST -15
J.
Coordinate with agencies planning large infrastructure projects —
such as WSDOT — to look for opportunities to reduce flood hazards
High
ST -6
8. INFORMATION
for Union Ga.. (new, so no alternative number)
/ OUTREACH
1. Mapping
A
Provide and use improved flood mapping and modeling to assess
risk to new and existing infrastructure and for designing new
infrastructure, including current Ahtanum-Wide Hollow
remapping. (12G-1, 12A/B-2, 12C-2, 12G-3).
High
PR 15
B.
Re -map the floodplain for NFIP rate maps, to allow for up-to-date
accuracy and application of land use regulations. (8D-1, 4-3, 15B-6)
• Consider the contribution of high ground water to off channel
flooding (4-9). (4-19).
• Complete floodway mapping in the region (15D-1, 15C-13)
• Regularly scheduled updates (15D-2)
High
PR -11 &
PR -15
C
Map Channel Migration Zones (and other hazards) (15G-4 15D-3)
Identify areas that are at risk for channel migration in addition to
identified CMZ, i.e. N.F. Ahtanum, below the Narrows, at the
Mission, Shaw Creek, etc. (15C-12).
Low
IS 23
D.
Supply specific flood mapping products beyond NFIP.
• For example, identify where hollows overflow, upland flood
channels are located (aside from the formal FEMA mapping
process) and disclose when purchasing or developing property. 1D-
8. 15F-2
High
IS 11 & PR-
15
2. Landowner Assistance
A.
Provide public education about potential flood hazards and
responses on individual properties including keeping debris
sources out of known flood channels (10B-2, 1D-3, 1D-7).
High
PO -5
B.
Encourage residents who are at high risk for flooding to purchase
flood insurance even if they are not in a mapped floodplain (8D-
3.)
Medium
PO -8
CHAPTER 9 - ALTERNATIVES 83
C.
Create pamphlets for new landowners- i.e. pamphlet put out for
small landowners in Kittitas County by the Kittitas Conservation
District (fence debris) (1B-9.)
High
PO -5
D.
Prepare a program to educate landowners about riparian function
and health before and after a flood event (9C-7.)
High
PO 5
E.
Provide flood risk and regulatory constraints at beginning of
development process (no surprises) (13A-10, 14B-1)
High
PO 3
F.
Public education about maintaining driveway culverts, and correct
sizing and maintenance of culverts. (12E-5)
Medium
PO -10
3. General Public Outreach
A.
Cooperate with other agencies to support or develop public
education programs, such as stream cleanup programs and
volunteer monitoring (9C-13).
Low
PO -13
B
Encourage citizens to report dumping in streams (public outreach)
(1C-5).
Low
PO -14
C.
Cooperate with other agencies to engage in public education
regarding the values and esthetic appeal of riparian corridors/open
space for purpose of preservation of floodplain corridors (7B-5).
High
PO -5
D
Provide public education about how riparian and flood hazard
management goals complement each other. Inform people about the
importance of the functions of streams, rivers, and natural drainage
ways. (9C-11).
High
g
P0-5
E.Provide
public education directed to residents, farms and businesses
to increase individual preparation for floods (10A-3).
High
g
P0-5
4. Outreach/Information Related to Flood Projects
A.
Flood Control Zone District to provide technical assistance and
comments regarding flood hazards and infrastructure design (12G-
2).
Medium
PO -11
B
Public notice/disclosure/consultation when flood projects are
planned (19).
Medium
P0-9
5. Realtor, Lender, etc. Outreach
A'
Provide information about flood history to realtors, lenders, etc. in
proposed new developments (15C-14) (15C-15)
High
PO -4 & PO-
5
B.
Put on workshops and other outreach for realtors (15C-16)
High
P0-4 & PO -
5
9. Flood Response
1. General Flood Response Planning
A
Participate in and support Flood Response planning efforts (as part
of the Emergency Response Plan) (10A-1, 10A-2, 12F-5).
High
g
FR -2
B.
Implement Emergency Response Plan (Get Ready- Set- Go- Recover)
procedures, from the Emergency Response Plan (10C-1).
High
FR 2
C.
Determine where large numbers of animals may be kept during a
flood event and distribute information to the public. Work with
High
FR 4
84
Ahtanum-Wide Hollow CFHMP
Emergency Management and Red Cross to establish animal food
and shelter contingencies - discussions may include Central
Washington State Fairgrounds, farm feed stores, veterinarians, and
animal rescue organizations. (new)
2. Planning/Mapping
A.
Identify and map problem spots throughout the watershed so flood
responders know where to look first (5F-5).
Medium
FR -9
B.
Designate emergency response access routes and incorporate into
transportation planning (12F-4). Designation of evacuation routes
and notification of the public and first responders (10B-3).
High
IS 12 & PR
7
C.
The Flood Control Zone District will develop databases of parcels
affected by different level flood events, corresponding to upcoming
Ahtanum-Wide Hollow FEMA re -map (10C-5).
Medium
FR -9
3. Coordination
A.
Provide infrastructure or technology for better communication
between agencies (EOC) (10C-2)
Medium
FR -12
B.
Coordination between Emergency Management and the Irrigation
Districts such as AID and Yakima Valley Canal, for management
during floods. Include Irrigation Districts in communications with
the EOC (emergency operations center) and FCZD (5F-1, 5F-3, 2B-3).
High
FR -5
C.
Interagency coordination of flood information and response,
including WDFW, Irrigation Districts, and Yakama Nation Natural
Resources, Fisheries and Engineering (10C-4, 10C-9).
Medium
FR -12
D.
Flood responders concentrate patrol and response on known
problem bridges and roads (12F-1).
Medium
FR -9
E.
Public and agencies coordinate flood fight and post flood actions
with recommendations identified in the Ahtanum-Wide Hollow
CFHMP to provide a good basis for decision whether to take
emergency actions. (10D-2)
Medium
FR -6
4. Outreach
A.
Recognition and dissemination of knowledge about potential flood
hazards during a flood event in coordination with the EOC (10C-3).
Medium
FR -12
B
Develop warning systems including mass media (10B-1)
• Investigate reverse 911 system
Medium
FR -8
C.
Encourage volunteer flood -watchers program to provide
information (10C-8).
Medium
PO -12
D.
Provide special flood phone line for public to call in and provide
information about current flooding (10C-7).
Medium
FR -10
5. Irrigation Gates
A.
Improve access to Bachelor diversion during floods without
diverting flood waters or making flood problems worse (2C-3).
Medium
FR -11
B
Coordinate opening gates for flood relief, based on flood forecasts,
channel maintenance needs, and impact to diversion facility (5F-6).
High
g
MM -8
CHAPTER 9 - ALTERNATIVES 85
6. Monitoring/Documentation
A.
Install North Fork Ahtanum & Wide Hollow gages including
telemetry (5F-2).
Medium
FR -7
B.
Documentation of floods (air photos, etc.) Open contract with
flights. (15D-5) Note: this replaced 10C-6 since they were near
duplicates
Medium
IS -14
7. Ice Jams
A.
Inventory of locations where ice jams are known to occur- identify
them in the Flood Response Plan (1A-7).
Medium
FR -9
B.•
Outline emergency response to ice jams in the Flood Response Plan
(1A-3).
Alert residences at risk.
• Blast ice jams - (normally only done on very stable ice jams) (1A-6)
• Facilitate regulatory approval by Ecology and Fish & Wildlife and
local jurisdictions due to short time frame (new)
Low
FR 14
8. Regulatory
A.
Facilitate involvement of permitting agencies as a component of the
Emergency Management Plan, and are present in the EOC during a
declared emergency. General guidelines for taking action during a
declared or non -declared emergency are: A. permitting personnel
does a site visit (10D-3, 10D -3a).
• Choose minimum flood fight action or action that will meet the
intent of the regulations - i.e. better protect/enhance the resources
(10D -3b)
• Follow up - 6 months after a declared disaster to come into
High
FR 3
com.liance for flood fi:ht actions (10D -3c)
10. Shaw
Creek & Wide Hollow/80th Ave. Area
1. Structural
Response
A
Relocate Shaw Creek to the low point in the drainage to allow for
more natural stream and floodplain function, and less maintenance.
Consider a potential for a larger solution that includes concurrent
considerations on Wide Hollow Creek.
• Recommend quick actions which allow us to keep options open:
• Keep at -risk areas undeveloped
• Require drainage easements
Allow for high-density development in areas that are not at
risk.
• Consider purchase of property or property interest (i.e. option,
easement, etc.) needed for relocation soon, before development
prevents this alternative (new, so no alternative number)
• Investigate ways to keep certain properties undeveloped (for
flood protection and for possible relocation of Shaw Creek
channel). Address Zeigler's property.
• School owns property and may be amenable to relocation.
High
g
ST -5
86
Ahtanum-Wide Hollow CFHMP
• Proposed Nob Hollow Road possibly a problem, possibly
remove two Wide Hollow bridges, which would help with the
conveyance on Wide Hollow
• Shaw Creek overflow bridge added as part of Nob Hollow
construction.
• Move Wide Hollow Creek south of Wide Hollow Rd (if Nob
Hollow is not constructed)
• Consider downstream impact of changing Shaw Creek's
confluence with Wide Hollow west.
(8B-1, 8E -1.a through e, 8E-4, 8E -6.b through d)
B.
Consider overflow channel (new)
High
ST -5
C.
Reconfigure Shaw Creek to function as floodplain and fish and
wildlife habitat (8A-2).
Medium
ST -14
D
Expand diking along Shaw Creek to protect new and existing
development (8B-2, 8E-2, 15B-2)
Low
ST -17
E
Consider developing regional retention upstream of Tieton Drive
(8C-6, 8E-3)
High
g
ST -4
F.Protect
natural floodplain functions in Shaw Creek's watershed,
especially before it is mapped (8C-1).
Low
ST 24
2. Information and Outreach
A
Notify developers and prospective residents of flood hazard on the
property (8E -6.a)
Medium
PO -7
B.
Hold neighborhood meeting for residents living near Shaw Creek.
(8D-4, 8D-5).
Medium
PO -7
11. St.
Joseph's Mission at Ahtanum
1. Study
A
Initiate hydraulic study to predict flood flow patterns at Ahtanum
Mission, based on surveys and modeling. Modifications to
infrastructure management may result in relation to head -cuts (2A-
1).
High
g
IS -9
B.
Determine the effects of flooding at the Mission on irrigation
structures and of irrigation infrastructure on flooding patterns (2C-
6)
High
IS -9
C.
Verify if there is room for Ahtanum Creek to occupy old floodplain
channels on the tribal land adjacent to Ahtanum Mission to reduce
uncontrolled flow down Bachelor Creek and damage to AID
diversion. Determine if the tribe/allotment owners may be amenable
to that (2-3).
High
IS -9
D.Define
the sensitive historical and cultural issues at Ahtanum
Mission site (2-1).
High
g
IS -9
E.
Identify potential future downstream impacts from any proposed
changes in the Ahtanum Mission area, and establish acceptable level
of flooding along the entire reach (2B-4).
High
IS -9
CHAPTER 9 - ALTERNATIVES 87
2. Hatton
A.
Recreate a flood overflow channel back to Ahtanum Creek from
Hatton Creek due to lack of flood capacity on Hatton and risk of
avulsion from current flood routing/channel configuration (natural
overflow channel blocked in the 1930s). (2A-5. 2B-2)
High
ST 9
B.
Modify the old Hatton ditch channel below the diversion. Intent
would be to block/armor channel to prevent opportunity for
formation of head -cuts (2A-7).
High
ST -9
C.
Remove the old Hatton Diversion to reduce flood stage at Mission
and avulsion potential into Hatton Creek (Ahtanum Mission head-
cuts) (2A-6).
High
ST -9
3. Levees/Armor
A.
Armor stream channel to prevent migration of Ahtanum Creek to
the North (Soft levees on North side would not be sufficient- river
would cut through) (2A-8).
High
ST -9
B.
Utilize Ring dikes to protect St. Joseph's Mission property (2A-3).
Low
IS -17
C.
Consider major levee construction on Mission property to alleviate
head -cuts, this would not be needed if Recommendations A & B in
Hatton section are successfully implemented. (2A-2).
Low
IS -18
4. Bachelor
A
Modify the Bachelor Diversion to improve functionality and
decrease flood hazard (e.g. upstream of 90- degree turn on Ahtanum
Creek) (2C-2, 2C-4)
(cont.)
• During floods, close Bachelor diversion and create a new high
flow diversion channel from Ahtanum creek (2C-5)
High
g
ST -9
12. Emma Lane Area
1. Study
A
Perform an Emma Lane flood study, and develop design guidance
on acceptable flood protection levels. (3-2) • Address Ahtanum
Creek flood conveyance downstream of 42nd and Ahtanum Rd. (3-
18).
Low
IS -19
B.
Perform a Cost -Benefit analysis of stream relocation at Emma Lane
(3-19).
Medium
ST -13
2. Relocation
A.
Move Ahtanum creek to a lower point in the floodplain (requires
cooperation with Yakama Nation, acquisition of at least two homes,
and a new bridge) (Emma Lane) (3-1).
High
ST -2
• If Ahtanum Creek is relocated, consider a design that does not
include filling in the old Ahtanum Channel- looking at the existing
Medium
ST -12
88
Ahtanum-Wide Hollow CFHMP
channel as habitat (3-15).
• Examine constructing a controlled side channel to bypass Emma
Lane, rather than moving the creek (3-14).
Medium
ST 14
3. Development in Emma Lane Area
A.
Limit future development in the Emma Lane area (3-3).
- Place controls on building in the flood -prone areas in and around
Emma Lane (3-17) (e.g. using zoning, utility hook-ups, etc.)
Low
PR -32 &
PR -33
B.
Adopt and implement more strict building standards in Emma Lane
area- flood -proofed homes, buildings (3-11, 3-3).
Low
PR 35
4. Channel and Drainage Capacity
A
Improve drainage throughout the entire Emma Lane area- culverts,
roads, etc. (3-8).
Low
PR -37
• Reconfigure the Bachelor Creek bridge on Ahtanum Road to
increase capacity and reduce backwater flooding (3-6).
High
ST -3
• Alter drainage systems and easements, based on Emma Lane
floodplain remap study (3-10).
Low
IS 24
• Eliminate the Shropshire ditch or other irrigation ditch remnants
(i.e. remove irrigation ditch that directs flow and inundates Emma
Lane- area pastures and residents) (3-7).
Medium
ST -11
• Improve stormwater system on Ahtanum Road to limit Emma
Lane overflows into the airport area, and downstream to 16th
(which floods the intersection at Ahtanum Road) (3-9).
Low
MM -19
B.
Widen bridge at 42nd Ave. to reduce localized flooding and
overflows (3-5).
Medium
ST -11
C
MONITORING
1C 7, 1C
1C-11
Remove
at the
8,
old fill that restricts floodplain capacity on Ahtanum Creek
Yakama Nation land just south of Emma Lane (3-16).
- INVENTORIES (By Alternative Number)
Investigate methods for the following:
• Research how other communities deal with dumping in
floodplains, particularly concrete, fill, etc.
. Research measures to deal with illegal/contaminated dumps
(meth labs, etc.)
• Examine statewide laws relating to dumping and streams to
establish authorities
Medium
Low
ST 11
MM -20
12D 3
Inventory roads acting as levees. Design site-specific solutions
based on the inventory and current and future road
classification; solutions may include armoring or changes to
road configuration, or elimination of the road and selection of
alternate route. Incorporate findings into transportation
planning.
High
g
IS -3 & PR -4
12C 1
Inventory channel process problems in relation to existing and
proposed roads
Medium
IS 15
12D-6
Inventory of private roads acting as levees
Low
IS -25
12E-4
Identify road ditches that serve as flood conveyance, thus
placing them at a high priority for maintenance (i.e.
Rutherford Rd and Shaw Creek at 80th).
High
CHAPTER 9 - ALTERNATIVES 89
12E -7b
Private road culvert inventory
Low
IS -26
12G 8
Investigate funding sources or incentives for private drainage
infrastructure
Low
IS -27
12H-3
Monitor the effects of urbanization and land use
intensification to the characteristics (runoff, time of
concentration, water quality) of the watershed over time. Take
action to mitigate for negative watershed scale effects.
Low
IS -22
Investigate geologic hazard areas standards for applicability
14E-1
to high flood risk hazard categories such as channel migration
zones and alluvial fans to address potential regulatory gaps.
Low
PR -36
Identify areas where man-made alterations are affecting
15A-3
flooding (i.e. upstream of 64th on Hatton, Diversion #14, and
Medium
IS -15
The Narrows) to allow for cooperative projects.
Identification of flood prone or high risk areas that are near
15B-7
perched channels (disclosure that the area is at risk for
flooding).(15B-10)
Medium
IS -15
15F-3 &
Identify critical hollows through risk assessment and through
flood benefit (for protection measures)
High
IS -11
15F-4
• Identify special flood protection measures for hollows
90
Ahtanum-Wide Hollow CFHMP
N This page intentionally left blank N
CHAPTER 10
SUPPLEMENTAL PLAN STUDIES
As awareness of flood problems increased during the development of this plan, so did
the awareness of existing data gaps which prevented resolution of committee
discussions and recommendations for some specific issues. These studies and
information are needed to focus the selection of the most economical flood actions.
Activities included data, inventories, more detailed flood impact information, planning
restrictions and design impacts. The FCZD moved forward to initiate a number of those
activities, which are listed below. This chapter discusses the status and findings of those
investigations. These items were added as a separate category of recommendations,
referred to as In -Progress FCZD activities, and were typically considered high priority.
STORMWATER DEVELOPMENT REVIEW
Due to the unique local soil and arid climate conditions of Yakima Valley a regional
storm water program was undertaken by the jurisdictions, with the Yakima County
Surface Water Division as the lead. The standard practice within the "flood -prone"
Ahtanum and Wide Hollow basins, within all three local governments, is to retain and
infiltrate the full 25 -year flood volume onsite. This is incorporated in the ordinances and
the Regional Stormwater Manual. This local design approach for new development has
been demonstrated to the Department of Ecology to eliminate increases to 100 -year flood
peak flow. The jurisdictions have adopted similar site stormwater runoff restrictions and
ordinances that contain the 25 -year runoff and limit 100 -yr runoff to predevelopment
levels. This reduces urban contribution to peak flows and channel erosion. The
ordinances have formalized existing requirements for new developments to pass the
upland 100 -yr flows so that those developments will not be flooded.
FIS RATE MAP REVIEW
The FIS remapping study was undertaken by FEMA as part of the Map Modernization
process. Inaccuracies in the existing 100 -year flood maps, which had been developed in
the 1970's had been noted, particularly following the 1996 flood. The old maps had been
plotted from a combination of 5 foot vertical contour interval mapping and surveyed
cross-sections. Current technology is to use 2 foot contour mapping interval or less.
The FCZD provided to the FIS, surveyed cross-sections, 2002 LiDAR topographic data
and data from the 1996 flood. The LiDAR contract included independent data quality
assessment and control to meet FEMA standards and was accepted by FEMA. Spacing
and accuracy of LiDAR data points was to FEMA standard. The vertical resolution as
individual LiDAR shots is with six inches while the LiDAR can be used to produce 2
foot contours. The high density, or horizontal, of the LiDAR data allows bare earth
resolution that clearly identifies local features such as embankments that are typically
missed by survey methods. Survey data were provided at all structures in the basins.
1
2 1 Ahtanum-Wide Hollow CFHMP
The FCZD also performed numerous quality checks on the hydraulics and mapping
which have resulted in a number of map revisions during map development. The draft
maps were circulated within the committee to refine the development of alternatives
and recommendations.
The NFIP maps for the two basins will be adopted in 2011 and 2012 and will provide a
more accurate tool for reducing flood hazard. The FEMA hydraulic model for the entire
basins will be made available by the FCZD to the public and roads departments for
projects and development.
PUBLIC OUTREACH FOR NEW FIS
The FCZD has fielded numerous queries from the public on the maps and insurance
requirements and options at various locations. In some instances additional survey data
provided to the FCZD was reviewed by the FEMA consultant and in many cases the
FCZD provided field reconnaissance to ensure appropriate follow up.
In addition the FCZD has been attending Planning Commission, West Valley
Neighborhood Plan, and Development meetings at the City of Yakima to facilitate
awareness of pertinent flood hazard issues.
10 AND 25 -YEAR FLOOD MAPS
The FCZD hired the FEMA mapping consultant to generate 25 -year flood profiles for
Ahtanum and Wide Hollow creeks to supplement those provided by FEMA for the 10,
50, 100 and 500 -year intervals. County GIS has produced 10 and 25 -year flood maps in
order to identify frequently inundated areas. The maps are contained in Appendix J.
The 10 and 25 -year flood maps, combined with the 100 -year FEMA floodplain and
floodway, and the bare earth LiDAR data, can be used at the planning and design level
to assess the flooding impacts from proposed changes to infrastructure (roads, bridges
and irrigation) and from proposed developments. The computer hydraulic models for
each flood level are available from FZCD to assess changes. For example, preferred lot
layouts or bridge designs that minimize future adverse flood damages could be readily
identified in the planning and NEPA process by use of these and the 100 -year FEMA
maps.
ECONOMIC FLOOD DAMAGE DATA
The FCZD has made grant application to update the County GIS database for use of the
federal Hazards U.S. Multi -Hazard (HAZUS-MH) program which calculates flood
damage loss based on 2010 Census data and existing Assessor's database. The program
would utilize depth hazard grids being developed by the FCZD from the FEMA models
and the mapping for different flood durations including the 10 and 25 -yr flood maps.
This data will be available to the communities for the use in evaluating flood economic
Chapter 10 — SUPPLEMENTAL PLAN STUDIES 13
impacts of alternate development proposals and also be used to evaluate proposed
infrastructure, including bridges and transportation routes.
SEDIMENT CLEANOUT AT COUNTY BRIDGES
In 2008 the County Roads Department cleaned the sediment and gravel bed load out of
ten County bridges (two were later annexed by the City of Yakima) on Wide Hollow
Creek as identified and requested by citizens to provide additional channel and flood
capacity:
• Wide Hollow Creek at Wide Hollow Road west of 88th Avenue (Yakima City
Bridge)
• Wide Hollow Creek at Wide Hollow Road west of 91st Avenue (Yakima City
Bridge)
• Wide Hollow Creek at 96th Avenue south of Wide Hollow Road (Bridge 301).
• Wide Hollow Creek at Dazet Road (Bridge 76)
• Wide Hollow Creek at Wide Hollow Road east of Stein Road (Bridge 63)
• Wide Hollow Creek at Wide Hollow Road west of Douglas Road (Bridge 64)
• Wide Hollow Creek at Wide Hollow Road east of Knox Road (Bridge 65)
• Wide Hollow Creek at Wide Hollow Road east of Fedderly Lane (Bridge 66)
• Wide Hollow Creek tributary at Stone Road (Bridge 62)
• Cottonwood Creek at Dazet Road (Bridge 77)
The process required permit streamlining between the involved agencies. The removal
volumes were partly limited by land owner permission beyond the road right of way
and partly by clearance limitations underneath the bridges for conventional equipment.
Excavation lengths upstream and downstream of bridges were limited to 50 foot or less
lengths. Mitigation has been required for this work which is being determined. It is
envisioned that this will be a continuing program for those bridges identified as
problematic.
BRIDGE SEDIMENT REMOVAL GUIDELINES
Sediment has been accumulating at the Wide Hollow and Ahtanum basin bridges and
contributing to increased flood risk. The sediment also becomes home to invasive
vegetation, further reducing bridge capacity. The FCZD performed a prototypical
hydraulic analysis on 20 and 30 foot wide bridges to establish sediment and gravel
removal volumes and guidelines at, upstream and downstream of the bridges.
These hydraulic guidelines were then applied to seven selected problematic bridges to
identify the hydraulic effectiveness of the removal guidelines in providing flood impact
benefits, and to ensure that these guidelines are feasible and could be applied in a cost
effective manner to the Wide Hollow, Hatton and Bachelor Creeks bridges. The
4 1 Ahtanum-Wide Hollow CFHMP
sediment removal guidelines and removal results evaluating their applicability are
contained in Appendix G. The findings were as follows:
Sediment removal to maintain and achieve 100 -year conveyance capacity may be
appropriate in most situations in Upper Wide Hollow Creek, and based on estimated
flows, many bridges on Hatton Creek. In other areas, such as most of the bridges on
Bachelor Creek and Wide Hollow below the Cottonwood/Wide Hollow confluence,
removal of sediment to pass the 100 -year flow could result in with a relatively high cost
and little benefit to reduction of flood hazard or maintenance of access during flood
events.
Also for the current bridges in these watersheds, it may be more appropriate to manage
for a lower standard of conveyance than the 100 -year flood for several reasons.
➢ First, the most benefit per amount of excavation occurs where nuisance flooding
results in frequent repeated damage to the road or other major structures. To
maximize benefits, the new 10 and 25 -year flood maps should be used to
determine where the most frequent damage occurs and concentrate on rectifying
those areas and minimizing new structures in areas with high frequency
flooding.
➢ Second, it is unlikely that there is funding available or economic justification to
retrofit all existing bridges in these watersheds.
➢ Third, in areas such as Bachelor Creek at Lynch Lane, large improvements to the
conveyance capacity of the creek, beyond what was present naturally before the
bridge induced deposition have the potential to reduce upper watershed areas of
flood storage during major events. Retention of areas that naturally act as flood
storage or natural flood overflow paths during major events should be a
consideration when deciding on bridge conveyance improvements or
replacement.
➢ Fourth, many of these streams have been relocated, straightened, or modified for
irrigation purposes and are "perched". At these locations during the 100 year
flood, adjacent areas to these perched channels will likely be flooded regardless
of the conveyance capacity of a bridge. Flood frequency in areas adjacent to
these perched channels is very high, and where improvement of conveyance
through bridges can reduce high frequency flooding in these perched channels, it
is probably of high benefit.
The case studies show that 15 foot easements at bridges are insufficient to manage the
sediment depositions created by the obstructions. It would be preferable also to provide
bridges that fully span the channel and channel side slopes to avoid producing
acceleration and deposition.
Chapter 10 — SUPPLEMENTAL PLAN STUDIES 15
INVENTORY OF PROBLEMATIC BRIDGES
In some cases, particularly within flat channel sections, where bridges are affected by
downstream structures, or where floodplain storage naturally exists, bridge cleanout
may not resolve underlying channel constraints and conditions. A Wide Hollow stream
profile showing bridge locations is contained in Appendix H. Based on the sediment
removal guidelines (Appendix G), the channel profiles (Appendix H), and the new 100,
25 and 10 -year flood maps, an inventory will be conducted to identify problematic
bridges with regard to flooding. The inventory along with the current and planned level
of service for the road system will be used to establish needs, priorities, replacement
preferences and interim measures.
BRIDGE DESIGN GUIDELINES FOR AHTANUM and WIDE HOLLOW
The results of the bridge sediment removal guidelines, the inventory of problematic
bridges and the new 10, 25 -year and 100 -year maps will be used to identify future bridge
design guidelines that reduce overall costs to infrastructure (capital and maintenance)
and residents, through the use of replacement priorities and preferred future bridge
designs.
CHANNEL SEDIMENT AND VEGETATION CONTROL PILOT PROJECTS
The FCZD has cooperated with the City of Yakima and WDFW to remove sediment and
vegetation debris in the Wide Hollow reach between 72nd and 80th Avenue bridges.
Although this project successfully demonstrated inter -agency cooperation, permitting
and implementation, considerable new debris has been placed in the channel on two
occasions in the year since, showing that landowner cooperation must be improved
through Public Outreach by the City of Yakima and FCZD. Before and after photos of
the 2010 Wide Hollow 72nd to 80th project are located in Appendix I.
The FCZD is working on two other channel and vegetation pilot projects with WDFW at
this time: one upstream on Wide Hollow, and the other in Wiley City area. The FCZD
recently completed the Wiley City channel modifications. The FCZD is willing to do
pilot capital projects so that landowners can take over long term maintenance to protect
themselves from floods.
The pilot projects will be combined with the bridge sediment removal guidelines to
estimate annual sediment budgets for financial budgeting purposes.
SEDIMENT BUDGET FOR CREEKS
Sediment has been accumulating at the bridges and within the channel as the non-native
invasive Hybrid Willow has flourished due to contributing to the inverted irrigation
hydrograph. Wide Hollow Creek profiles are provided in Appendix H that show
gradient, velocities and the location of bridges. The figures also show plan views with
the 100 year map extent. These figures are a tool to indicate problem areas. In some
cases the sediment deposits will be due to features other than bridges, such as irrigation
6 1 Ahtanum-Wide Hollow CFHMP
infrastructure, man- made modifications or natural physiological features. The results of
the sediment removal guidelines, the inventory of problematic bridges, and the channel
pilot projects and tools such as Appendix H will be used to estimate an approximate
sediment budget.
IRRIGATION INFRASTRUCTURE INVENTORY
An inventory of existing and abandoned irrigation diversions along the creeks and their
relative flood impact are required in order to provide a basis for decisions regarding
preferred revisions or removals. This will be provided at a later date.
PURCHASE AND ELEVATE REPETITIVE LOSS HOMES
The FCZD has purchased and removed one frequently flooded home on Wide Hollow
Creek through the use of a FCAAP grant. The property will be reconfigured to provide
added protect to an adjacent seven residences. The FCZD has acquired a second FEMA
grant to elevate another home on the upper Ahtanum Creek in 2012. These homes
qualified as repetitive loss properties through the NFIP.
INITIATE EMMA LANE CHANNEL RELOCATION PROJECT
The FCZD acquired a grant to relocate Ahtanum Creek near 42nd Avenue where
extensive overland flows through residential blocks are initiated during floods. This
project is identified within the recommendations. The FCZD has been working with
citizens and Yakima Nation to come up with a NEPA preferred alternative in 2012. After
acceptance this project will be completed in 2013.
PROJECT AND PLANNING GRANT APPLICATIONS
The FCZD applies for FEMA and FCAAP grants for projects as the opportunity arises.
One application submitted to FEMA for a Pre -Disaster Mitigation grant was made for
the Shaw Creek—Wide Hollow area noted in the recommendations. Also a Flood
Mitigation Grant application was made to use a FEMA supported GIS -based hazard
program in order to better define Yakima flood risks, potential economic losses and
priorities. These two grants were awarded in October 2011. A preferred alternative will
be developed as part of the NEPA process in 2012.
INSURANCE REDUCTION THROUGH COMMUNITY RATING SYSTEM
The County has applied, and been accepted into the Community Rating System as a
Level 8 Community based on existing and ongoing flood hazard mitigation. This
provides all residents within the unincorporated County with a 10% saving on their
flood insurance premiums.
WAPATO DAM ASSESSMENT
The FCZD commissioned sediment studies for the Yakima River mainstem including an
assessment of backwater from this dam, to be completed in 2011. Further collaboration
Chapter 10 — SUPPLEMENTAL PLAN STUDIES 17
with the Yakama Nation on this structure will be pursued to address impacts on the City
of Union Gap.
FLOOD RESPONSE INFORMATION COORDINATION
The FCZD provides a flood watch on Ahtanum and Wide Hollow creeks as well as other
County flood -prone creeks and rivers and keeps the Yakima Valley Office of Emergency
Management informed so that appropriate flood responses are initiated.
FUTURE FINDINGS
The Recommendations contained in Chapter 11 are based on the current status of these
studies, inventories, and pilot projects. As more information is gathered, the
Recommendations in Chapter 11 may be modified or supplemented.
8 1 Ahtanum-Wide Hollow CFHMP
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CHAPTER 11
RECOMMENDATIONS
Many of the alternatives selected in Chapter 9 are inter -related and it was necessary to
combine them to form the recommendations in this chapter. The wording of the
recommendations was compressed in this chapter to encompass the various aspects and
common elements within the selected alternatives. The omitted detail is retained in
Table 9-9 and can be tracked by the original numbering scheme and a crosswalk
contained in Table 9-9.
The recommendations, so compressed, were presented to, and discussed with, the
Committee for any changes. The result was 61 high priority recommendations, shown in
table 11-1, containing the most important issues identified in the CFHMP area, 38
medium recommendations listed in Table 11-2 and 38 low priority recommendations
listed in table 11-3.
The recommendations emphasize public hazard reduction benefits, relative urgency,
costs and consider the significant implementation aspects related to cost effective flood
hazard reduction and cooperation.
RECOMMENDATION CATEGORIES
Recommendations have been categorized as: Inventory and Study, Planning and
Regulatory, Maintenance and Management, Structural, Public Outreach, and Flood
Response. Categories are based on the work nature and main participants required for
implementation. For example, the FCZD cannot take the lead for Planning and
Regulatory because that is the responsibility of the jurisdictions. The FCZD can facilitate
Maintenance and Management for structures and properties that belong to landowners
and jurisdictions, but cannot take responsibility for the ongoing requirements on land
owned by others. The FCZD has taken a major role in Public Outreach, Flood Warning
and planning for Flood Response. Flood Response is a role for first responders within
the +Communities in addition to state and federal agencies. Implementation of these
recommendations will require an ongoing, coordinated approach to planning,
regulatory, structural, and maintenance actions and programs over the long term.
PARTNERS
Partnerships are required to mitigate existing flooding problems that affect large areas.
An awareness of overlapping mandates is required to allow joint funding of projects for
joint benefits. Projects and programs or initiatives require leads that have been identified
by the first entry in the "Partners" column of Tables 11-1 through 11-3. The first entry is
considered the lead, although partners may wish to alter the order to facilitate
1
2 Ahtanum-Wide Hollow CFHMP
implementation. As funding is a concern for the parties, conceptual level costs are also
presented in the Recommendations tables.
IMPLEMENTATION TIMELINES
Implementation depends on many factors including priority, funding and permitting. In
Tables 11-1 through 11-3 a column called "Onset" provides an initial target timeframe
and strategy for community implementation of the plan.
Actions already completed by the FCZD are denoted "C" (see Chapter 10 and
Appendices). Actions underway, are denoted "IP" for "in progress" (see Chapter 10).
Actions recommended to be initiated shortly after Plan adoption are denoted "S" for
"short term", while "L" is for "long term", again referring to start date. Actions
recommended within the next cycle of regulatory update, such as Comprehensive Plan
or Ordinance updates are denoted as "AU" for "awaiting update". Actions
recommended to be initiated as part of upcoming projects or opportunities are denoted
"0" for "opportunity". These actions recognize the need to coordinate with other
activities and the ability to provide funding, which is many cases requires cooperation of
agencies, plus the need to work in cooperation with long term planning of new and
replacement infrastructure. Funding mechanisms are discussed in Chapter 12.
The recommendations below emphasize public hazard reduction benefits, relative
urgency, costs and consider the significant implementation aspects related to cost
effective flood hazard reduction and cooperation.
Table Notation Notes
The original alternative numbering (in parenthesis) was retained during the merging of like
alternatives and can be used to obtain more detail and to track an alternative within Chapter 9
and the Appendices.
Table 11-1
High Priority Recommendations
Note: () represents the recommendation location on Table 9-8, and [ ] represents the
original alternative number(s) for that recommendation
INVENTORY AND STUDY
Description
Onset
Estimated
Costs in $
Partners
IS -1 Establish technical work groups and pilot programs on
a reach by reach basis for channel, vegetation and sediment
maintenance (including Wide Hollow coarse sediment
budget) to provide criteria and enable appropriate larger
scale maintenance programs which meets flood and habitat
needs. (1.8.A [15A-21 (See Appendix J)
IP
100,000
FCZD/WDFW
Irrigation Districts,
Landowners,
Jurisdictions
IS -2 Establish cleanout guidelines and a pilot program
bridge sediment removal and maintenance. (1.8.A) (See
Appendix G & H)
C
50,000
FCZD/ Roads, Plan
Depts.
Chapter 11— RECOMMENDATIONS 13
INVENTORY AND STUDY (cont)
Description
Onset
Estimated
Costs in $
Partners
IS -3 Inventory problematic bridges, roads and infrastructure
impacts and sediment buildup to generate action plan for
removals, etc. This includes areas of ponding (1.8.A,33.A
[12A/B-3], 3.1.0 {12D-5 & new], 3.2.8,3.3 B [12A/B-10], [12D-
5], Monitoring -Inventory [12D-31)
IP
15,000
FCZD/Roads Depts.
IS -4 Inventory flooding impacts for existing and abandoned
irrigation structures (4.2 .B, [2C-1, 5A-1, 5E-1])
IP
20,000
FCZD/
Irrigation
IS -5 Modify bridge crossing design to reduce flooding and
maintenance on case to case basis — wider spans, wider
easements upstream and downstream for channel design
and cleanout, deeper footings, to enable for scour, etc (3.1.A
[1A-1, 12A/B-7, 12A/B-6, 12A/B-1, new]) (See Appendix G)
IP
40,000 per
Bridge
Roads/ Plan Depts.
IS -6 Wapato dam impact assessment for Union Gap (7.A [4
11, 6C-7])
IP
20,000
FCZD
IS -7 Provide 10 and 25 year flood extent maps to show
chronic flooding areas where actions such as infrastructure
sizing and siting, proposed development and
redevelopment can be designed to guide flood hazard
reduction. (5.7.0 [new]) (See Appendix J)
C
50,000
FCZD
IS -8 Provide 10 and 25 year flood damage estimates using
established federal methods to guide economic and
environmental decisions.
IP
20,000
FCZD
IS -9 Study to identify Ahtanum avulsion scenarios and
existing flood issues at Mission (11.1.A through E [2A-1, 2C-
6, 2-3, 2-1, 2B-4])
S
40,000
FCZD
IS -10 Establish historical flooding areas —e.g. Wiley City &
Ahtanum-as special study areas to include all infrastructure
(5.6.B [new])
S
10,000
FCZD/Plan Depts.
IS -11 Establish historical map and identity flood risks in
Hollows (8.1.D [1D-8 & 15F-2] [15F-3 & 15F-4])
S
10,000
FCZD
IS -12 Identify & prioritize emergency response access
routes during 10, 25 and 100 year floods to incorporate into
emergency transportation and planning (3.1.E [12F-6, 12H-
8], 3.2A [12F-3, 12H-7], 9.2B [12F-41)
S
10 000
City & County
Roads/YVOEM
PLANNING & REGULATORY
Policy Development
To be implemented in the policy processes associated with the broad scale Growth Management Act processes such as
County -Wide Planning Policies, Comprehensive Plans, Capital Facilities Plan Elements, and UGA expansion.
PR -1 Ensure drainage infrastructure is properly sited, sized
and designed to minimize flood effects from stormwater
run-off. This includes establishing the relationship between
flooding and stormwater and determining
detention/retention and other stormwater standards. (2.2.D,
2.2.C, 2.2.B [4.4, 13C-4, 1D-6, 14C-7, 15G-1, 13C-1, 13C-3,
15E-2, 15F-1, 15G-2])
IP
Complete
RSPG/
Stormwater Utilities
PR -2 Petition State Noxious Weed Control Board to list
hybrid willows as invasive species as designated in other
states. (1.6.B [new])
IP
10,000
FCZD
4 Ahtanum-Wide Hollow CFHMP
PLANNING & REGULATORY (cont)
Description
Onset
Estimated
Costs in $
Partners
PR -3 Incorporate floodplain and economic impacts into
SEPA for subdivision layouts floodplain development
Plan Depts./
(losses, damages, safety, insurance, response and recovery)
from the planning to the project level, especially in urban
and urbanizing areas (5.4.F [new])
S
5,000/ yr
FCZD
PR -4 Establish policies , such as a flood hazard audit and
hazard element using the flood problem inventory in this
plan, within County -wide planning policies and
comprehensive plans in flood hazard areas to direct
preferred locations for new infrastructure such as arterials,
water and wastewater distribution mainlines, regional
stormwater facilities, parks and greenbelts. (5.6.0 [13A-11]
and Monitoring -Inventory [12D-31)
o New major arterials should be located outside of
floodplains where possible. If in floodplain, design to
minimize flood impacts. (5.4.0 [12H -4b], 5.4.E [12H -4c1)
AU
20,000
Plan Depts./
FCZD
PR -5 Retain and provide Open Space land use in all
jurisdictions using zoning easements, acquisitions and
incentives within floodplains to provide multiple public
benefits such as preserving space for flooding, greenbelts
and trails (5.3.A [13B-6, 12H4 -d, 14E-3, 13C-5, 13A-5, 14E-4],
AU
20,000
Plan Depts./ FCZD
5.4.A [14C-3, 14C-4, 14C-5], 5.5.A [15C-3, 15C-9, 15C-10],
5.5.0 [9C-10]).
PR -6 Provide open space incentives that target general
floodplain function, riparian and storage recommendations.
Juris/Interest
(1.2.A [9C-1, 7B-2, 7B-3], 5.2.A [13B-4, 9C-3, 14C-2, 13A-7,
AU
5,000/yr
Groups,FCZD
15C-4], 5.3.A [13A-3], 5.5B [15B-5, 15B-8]).
PR -7 Decide upon, designate (in flood response,
transportation and capital facilities plans) and maintain
critical access routes at 10, 25 and 100 year events (3.1E [12F-
S
10,000
Roads/YVOEM
6, 12H-8], 3.2.A [12F-3, 12H-7], and 9.2.B [1-B-3, 12F-4])
keeping non-critical routes at grade (3.1E [12D-41)
Standards and Ordinance Development - To be implemented in association with the development and approval
processes for ordinances that implement the Comprehensive Plan, and in some cases modifications to the building
codes. Some of these recommendations (work group) would need to begin well before modifications to existing
ordinances are proposed.
PR -8 Ensure all new development and redevelopment
within identified FEMA floodplains are adequately
reviewed for NFIP compliance and overall environmental
(SEPA) impacts through the use of additional review
Plan Depts./
procedures which may include; at minimum a public notice
(type 2 for the County); a signed checklist for all floodplain
items; a floodplain development permit independent of
other required permits; or establishing a floodplain overlay
zone covering the above concerns. (modified 5.6.A [13B-31)
AU
10,000/yr
FCZD
PR -9 Establish work groups to formalize regulatory
applicability of man-made and natural courses. (1.1.B [7B-7,
15E-5, 15E-6, 5D-2, 5D-3, 5D-4, 5D-5, 5D-8, 5F-4, 15E-1, 2-2,
S
20,000
Plan Depts./
FCZD
8A-3])
Chapter 11— RECOMMENDATIONS 15
PLANNING & REGULATORY (cont)
Description
Onset
Estimated
Costs in $
Partners
PR -10 Ordinance increase for residential to at least one foot
above BFE for future development to reduce community
costs and damage (6.1.A [14A-21)
AU
10,000
Bldg Officials/ Plan
Depts.
Project and Permit Level — These recommendations should be incorporated
in floodplain, mostly in relation to new subdivisions, commercial/industrial
projects.
as standards of review for development
and public and private infrastructure
PR -11 Improve compliance with NFIP on all new and
replacement bridges and culverts (6.3.A [18], 8.1B [8D-1, 4-3,
15B-6])
IP
5,000/yr
Bldg Officials
PR -12 Based on the 10 and 25 -year flood mapping, consider
them, for design requirement of land use designation
decisions in future floodplain development to minimize
frequent damages and economic impact. (5.7.0 [new])
S
25,000
Plan Depts./ WDFW
PR -13 Use SEPA and Comprehensive Plan Policies and
Goals to address flood issues/impacts associated with larger
scale proposed developments where current zoning,
subdivision or building standards are not sufficient to
mitigate flood risk. (5.1.B [13B-21)
S
5,000/yr
Plan Depts.
PR -14 Implement NPDES Regional stormwater to limit run-
off up to 100 -yr flood (2.2.A [1D-5], 2.2F [4-15]).
IP
Complete
Local Jurisdictions
PR -15 Fully utilize new FEMA models and maps, and
locally developed 10 and 25 -yr map products, including loss
data, for alternative analysis and infrastructure and land use
decision making, by providing models and mapping free of
charge. (3.1A [recommendation overview], 6.1C [new], 8,1.A
[12G-1, 12A/B-2, 12C-2, 12G-31, 8.1.B [8D-1, 4-3, 15B-6, 4-9, 4-
19, 15D-1, 15C-13, 15D-2], 8.1.D [1D-8, 15F-2])
S
2,000/ yr
Plan Depts./
Roads
PR -16 Consolidate access for floodplain crossing to
minimize flood impacts (3.3.D [12G-9], 5.6.D [12H-9, 12A/B-
9, 12H-5, 12C-4])
AU
2,000/ yr
Plan Depts./
Roads
PR -17 Ensure floodplains and floodways are identified on
final plat maps — included would be text identifying
effective map date and disclosure regarding fact that the
maps will change over time. Also consider including
identification of riverine Critical Areas buffer on plats (6.3.0
[new])
AU
2,000/ yr
Plan Depts.
PR -18 Increase flood code enforcement through adequate
funding mechanisms 6.3.A [1C-4, 1C-3,18])Enforcement
S
50,000/yr
Code
STRUCTURAL
Projects in Urban Growth Areas
ST -1 Property acquisitions and home elevations for
repetitive loss properties (5.5.A [new])
IP
150,000
FCZD/
Jurisdictions
ST -2 Emma Lane channel improvements, (12.2.A [3-1])
IP
800,000
FCZD/
Jurisdictions
ST -3 Bachelor Bridge at Ahtanum Rd. (12.4.A [3-6]) &
Ahtanum Creek & 16th Avenue bridge replacements (3.1.B
[3-131)
0
600,000
County Roads/ Plan
Depts.
6 Ahtanum-Wide Hollow CFHMP
STRUCTURAL (cont)
Projects in Urban Growth Areas
Description
Onset
Estimated
Costs in $
Partners
ST -4 Wide Hollow flooding between 64th and 101st- channel
improvements and acquisitions - recommendations include
those for Shaw Creek, plus regional retention ((10.1.E [8C-6,
8E-3])
IP
400,000
FCZD/
Jurisdictions
ST -5 Resolve Shaw Creek relocation/overflow to remove
community damages and insurance (10.1.A & B [8B-1, 8E-1
a -e, 8E-4, 8E-6 b -d new])
S
1,500,000
FCZD/
Jurisdictions, Plan
Depts.
Projects in City of Union Gap
ST -6 Wide Hollow relocation or overflow channel
incorporated in future development and proposed
infrastructure design in Union Gap (7.0 [6C-6, 11A-4, 6C-6],
and 7.J [new])
O
500,000
DOT/
Jurisdictions
ST -7 Improve grade for Spring Creek East to reduce
flooding in Union Gap (7.H [6D-2])
O
100,000
DOT/
Jurisdictions
ST -8 Mill structure - Develop shelf ready open channel
bypass design for grant application on, lower channel (7.E
[11A-51)
0
20,000
FCZD/
Jurisdictions
Projects in areas which route floodwaters overland
ST -9 Reduce catastrophic flow captures at Mission
(infrastructure and town impacts - Rutherford Road) and
preventing avulsions into Hatton and capacity issues
(11.2.A,B & C [2A-5, 2B-2, 2A-7, 2A-6], and 11.3A, 11.4A [2A-
8, 2C-2, 2C-4, 2C-5])
S
300,000
FCD/Irrigators,
Landowners, Plan
Depts.
ST -10 Flood design for John Cox diversion (new)
L
40,000
FCZD/Irrigators
MAINTENANCE & MANAGEMENT
Continuous and stable Channel and Riparian Management
MM -1 Program for sediment and debris removal, invasive
species control, replacement species in plantings, sediment
& bank stabilization (1.6.A & B [15C-2, 7A-5, 7B-8, 7A-1])
IP
30,000/yr
WDFW/FCZD
Plan Depts., NYCD
MM -2 Beaver management (1.9.A & B [9A-1, 9A-3, 9A-6,
9A-2, 9C-5 & 9A-5, 9A-7])Landowners
IP
1,000/yr
WDFW/
MM -3 Riverine Infrastructure Management - debris and
sediment maintenance (1.8.A [15A-21)
IP
10 000/ r
y
Jurisdictions/
Irrigators
MM -4 Riparian restoration, mitigation and protection to
reduce flood impacts (1.2A, B & C [9C-1„ 7B-2, 7B-3, 9C-2,
9C-4])
S
5,000/ yr
FCZD/WDFW
Jurisdictions
MM -5 Land acquisition in problem areas prior to
development (Emma Lane/Cottonwood/Shaw Creek/Union
Gap, etc.) (5.5.A [4-13, 15B-4, 15D-4, 13B-5, 9C-12])
IP
200,000
FCZD/ Juris
Landowners, Interest
groups
MM -6 Apply appropriate range management standards to
elk in confined feeding operations near riverine
environment (1.3.A [9B-3], 1.3.B [9B-2, 9B-4])
S
6,000
WDFW
MM -7 Obtain landowner access permission for problem
bridge channel maintenance. (3.3D)
IP
3,000/ yr
FCZD/ Jurisdictions
MM -8 Coordinate opening irrigation diversion gates for
flood relief, based on forecasts, channel maintenance needs,
and impact to diversion facility (9.5.B [5F-6])
IP
1,000
FCZD/Irrigators
YVOEM
Chapter 11— RECOMMENDATIONS 17
MAINTENANCE & MANAGEMENT (cont)
Continuous and stable Channel and Riparian Management
Description
Onset
Estimated
Costs in $
Partners
MM -9 Separate irrigation conveyances from streams as
practical and based on priority (1.1.A [7A-4, 7A-2, 15B-3, 5D-
71)
L
1,000,000
Irrigators/
Jurisdictions
MM -10 Consolidate irrigation diversions and remove as
become obsolete (4.1.A [5C-1, 5C-2, 5D-1])
L
200,000
BOR/BPA/
Irrigators, Juris
MM -11 Community adoption of Community Rating System
to reduce insurance rates through CRS activities (5.2.B
[new])
L
20,000
Jurisdictions
PUBLIC OUTREACH
PO -1 Information to public and local governments on New
FEMA Maps
IP
20,000
FCZD/
Jurisdictions
PO -2 Outreach to public regarding flood hazard related to
regulatory changes
IP
5,000/yr
FCZD/ Plan Depts.
PO -3 Provide flood risk & regulatory constraints at
beginning of development process (8.2.E [13A-10, 14B-1])
S
2,000/ yr
Plan Depts.
PO -4 Outreach to Realtors, lenders, etc. about flood risks
(8.5.A & B [15C-14, 15C-15, 15C-16])
S
2,000
FCZD
PO -5 Provide information to the general public and
property owners to enhance their understanding of: specific
flood risks, beneficial functions of floodplain, and aesthetic
values of streams and floodplains for development
(8.2.A,C,D, 8.3.C,D,E, 8.5A & B [10C-1, 15C-14, 15C-16, 7B-5,
9C-11, 10A-3, 10B-2, 1D-3, 1D-7, 1B-9, 9C-7])
L
10,000
FCZD/Plan
Depts.
FLOOD RESPONSE
FR -1 Designation of evacuation routes and notification of
the public and first responders (9.2.B [10B-31)
S
5,000
YVOEM/Roads
FR -2 Implement and participate in activities for the Flood
Response Plan (9.1.A & B [10A-1, 10A-2, 12F-5, 10C-1])Jurisdictions
S
5,000/yr
YVOEM/
FR -3 EOC environmental coordination (9.8.A [10D-3, 10D-
3a,10D-3b, 10D -3c])
L
2,000/yr
EOC/WDFW
FR -4 Determine where large numbers of animals may be
kept during a flood event and distribute information to the
public. Work with Emergency Management and Red Cross
to establish animal food and shelter contingencies —
discussions may include Central Washington State
Fairgrounds, farm feed stores,
L
5 000/ r
y
Conservation
Authorities
FR -5 Coordination between Emergency Management and
the Irrigation Districts such as AID and Yakima Valley
Canal, for management during floods. Include Irrigation
Districts in communications with the EOC (9.3.B [5F-1, 5F-3,
2B-3])
0
2,000/yr
YVOEM/AID
YVCCo
8 Ahtanum-Wide Hollow CFHMP
Table 11-2
Medium Priority Recommendations
Note: () represents the recommendation location on Table 9-8, and [ ] represents the
original alternative number that recommendation
INVENTORY & STUDY
Description
Onset
Estimated
Costs in $
Partners
IS -13 Resolve run-off issues presented by DIDs (2.2.E [13C-
2, 15E-31)
S
50,000
Jurisdictions
IS -14 Document floods including aerial photos, high water
marks, etc. (9.6B [15D-51)
S
20,000/eve
nt
FCZD
IS -15 Identify high flood risk stream reaches where man-
made changes or proposed projects effect channel processes
or flooding including roads, perched channels and other
alterations (and disclosure that area is at risk of flooding)
(Monitoring -Inventory [12C-1, 15A-3, 15B-7, 15B-10])
S
10,000
FCZD/ WDFW
IS -16 Design bridges and irrigation infrastructure to reduce
potential for accumulation of debris and sediment and
creation of un -natural overflow channels/paths (2.1.0 [5B-1,
7D-3, 7D-5])
L
5,000/
Structure
Roads/FCZD Plan
Depts., WDFW
PLANNING & REGULATORY
Policy Development
PR -19 Develop flood abatement policies for high risk
floodplain areas of existing dense development within the
floodplain (such as Ahtanum and Wiley City) (5.6.B [13A-
131)
o Design drainage to meet multiple objectives
including flood alleviation, in flood -prone areas,
esp. in Wiley City and Ahtanum (5.6.B [14A-41)
0
L
30,000
10,000
Plan Depts./FCZD
FCZD/Plan
Depts.
PR -20 Identify areas that are "islands" surrounded by
floodplain and develop standards to limit density, provide
emergency access and consider transportation networks
within the context of surrounding area (6.2.A [12H-61)
L
10 000
FCZD/Plan
Depts.
PR -21 Seek land use examples for flood -prone areas from
other similar communities (5.6.E [13B-81)
L
5 000
FCZD/Plan
Depts.
PR -22 Ensure existing flood policies in the Yakima Urban
Area Comprehensive Plan are implemented through
ordinances and local jurisdiction land use decisions.
Planning for flooding is supported in Objective E7 (5.7.A
[13A-41)
0
10,000
Plan Depts.
PR -23 Incorporated principle of floodplain planning into
infrastructure & similar facilities plans (5.4.D [8C-2, 12H-2])
L
5 000
Plan Depts./Public
Works
PR -24 Preserve natural drainage including draws and
mitigate identified hollows that provide natural flood flow
paths but are not identified as FEMA floodplains.
Implementation is through drainage requirements within
stormwater, county/city drainage, grading, and long and
short subdivision ordinances (2.1.B [new])
S
5,000/ yr
Plan Depts.
Chapter 11— RECOMMENDATIONS 19
PLANNING & REGULATORY (cont)
Description
Onset
Estimated
Costs in $
Partners
PR -25 Consider development moratoriums or high
standards of proof in place where development is outpacing
flood knowledge or tools available to keep the public safe
(i.e. the area has not been mapped, or conditions have
changed since the last mapping) (5.4.A [13A-151)
0
0
Plan Depts.
PR -26 Maintain open areas near the mouth of Ahtanum
Creek for flooding such as Fulbright Park (5.3.A [11A-21)
O
20,000
Plan Depts.
Standards and Ordinances Development
PR -27 Work for consistency in zoning and development
standards across jurisdictions for developments and
buildings within floodplains. Determine gaps in the
regulatory scheme. (5.1.A & 5.1.B [13A-9 & new])
AU
10,000
Plan Depts.
PR -28 Reduce risks through subdivision development
standards to minimize new structures in harm's way (5.1.A
[15C-111)
o Integrate protection of floodplain functions
improvement/flood hazard reduction into
subdivision platting process (5.1.A [8C-5])
o At a minimum, require a buildable area outside of
the floodplain including standards for lot size and
housing location (5.1.0 [14D-11)
O
O
5,000/yr
5,000/ yr
Plan Depts.
Plan Depts.
PR -29 This includes special land use standards for industrial
uses relating to hazardous materials, storage, use, disposal
(5.7.B [11B-11) and flood -proofing for non-residential
structures, including elevating to make existing structures
less flood damage prone (6.1.B [4-8]). Jurisdictions should
adopt Appendix G of IBC.
SU
10 000
Plan Depts./
Bldg Officials
STRUCTURAL
ST -11 Make infrastructure improvements in Emma Lane
area:
o Remove abandoned fill and infrastructure in Emma
Lane area to increase flood capacity and reduce
redirection of flood flows (12.4.A & 12.4.0 [3.7, 3-
16])
o Widen bridge at 42nd Ave. (12.4.B [3-5])
IP
IP
10,000
400,000
FCZD/
Landowners
Roads
ST -12 Evaluate not filling in the existing Ahtanum channel
so it can be used for habitat if the creek is relocated near
Emma Lane (12.2.A [3-151)
IP
5,000
FCZD/
Landowners
ST -13 Perform a cost -benefit analysis for stream relocation
near Emma Lane (12.1.B [3-191)
IP
5,000
FCZD
ST -14 Improve flood conveyance and predictability by
reconfiguring modified or "perched" streams and
establishing overflow channels if relocation is not feasible
(1.7.A & B [15A-1, 15B-1, &B-6, 15B-91 such as Shaw, 10.1.0
[8A-2], and Emma Lane, 12.2.A [3-141)
L
100,000
FCZD
10 Ahtanum-Wide Hollow CFHMP
STRUCTURAL (cont)
Description
Onset
Estimated
Costs in $
Partners
ST -15 Maintain Wide Hollow flood mitigation methods in
Union Gap by retaining an overflow path along railroad
right of way and encouraging development of an 0 & M
agreement among appropriate parties for flood and fish
structures at the Mill (7.I & 7.D [11A-1 & new for Mill
recommendation])
0
20 000
City of Union
Gap
MAINTENANCE & MANAGEMENT
MM -12 Investigate irrigation infrastructure changes such as
flood gates or siphons to reduce flood routing through
irrigation systems (4.2.D [5A-2, 5A-5, 5A-4])
L
5,000
Irrigators
MM -13 Modify drainage standards for existing roads in
overflow areas to minimize flood impacts (i.e. Emma Lane
area) (2.2.G [3-121)
AU
10,000
Roads/FCZD
MM -14 Ensure replacement of damaged infrastructure
reduces future flood damage risks (3.3.E [12G-51)
0
5,000/
Structure
Roads
MM -15 Explore additional funding methods for mitigation
or reduce environmental effects (including flooding) from
existing roads or other infrastructure (3.3.0 [12G-61)
0
2,000
Roads
PUBLIC OUTREACH
PO -6 Work with landowner assistance programs to improve
appropriate streamside vegetation and provide information
about flood resistant fencing (1.5.B [7B-4, 1B-7, 1B-8])
S
10,000
FCZD
PO -7 Utilize meetings and other methods of notification to
inform developers and current and prospective residents
about flood risks for Shaw Creek (10.2.A & B [8E -6.a, 8D-4,
8D-5])
IP
5,000
FCZD
PO -8 Encourage residents and property owners who are at
high risk for flooding to purchase flood insurance even if
they are not in a mapped floodplain (8.2.B [8D-3])
IP
2,000/yr
Jurisdictions
PO -9 Provide public notice/disclosure/consultation about
planned flood projects (8.4.B [191)
0
2,000
Jurisdictions/
FCZD
PO -10 Provide information for the public about culvert
maintenance and sizing (8.2.F [12E-51)
S
2,000
FCZD/Roads
PO -11 Yakima County Flood Control Zone District to
provide technical assistance and comments regarding flood
hazards and infrastructure design (8.4.A [12G-21)
IP
2,000/
Structure
FCZD
PO -12 Encourage volunteer flood -watchers program to
provide information (9.4.0 [10C-81)
S
0
FCZD
FLOOD RESPONSE
FR -6 Public and agencies coordinate flood fight and post
flood actions with recommendations identified in the
Ahtanum-Wide Hollow CFHMP to provide a good basis for
decision whether to take emergency action (9.3.E [10D-21)
S
5,000
YVOEM
FR -7 Install gages on North Fork Ahtanum and Wide
Hollow Creeks, including telemetry (9.6.A [5F-2])
0
40,000
FCZD
FR -8 Develop warning systems including mass media (9.4B
[10-B-1])
L
10,000
YVOEM
Chapter 11— RECOMMENDATIONS 111
FLOOD RESPONSE (cont)
Description
Onset
Estimated
Costs in $
Partners
FR -9 Identify known problem locations so information is
available for first responders and include in the Flood
Response Plan (if appropriate) (9.2.A, 9.2.C, 9.3.D, 9.7.A [5Ff-
5, 10C-5, 12F-1, 1A-71)
S
5,000
YVOEM/FCZD
FR -10 Provide special flood phone line for public to call in
and provide information about current flooding — EOC &
FCZD cooperate/coordinate (9.4.D [10C-71)
L
0
YVOEM/FCZD
FR -11 Improve access to Bachelor diversion during floods
without diverting flood waters or making flood problems
worse (9.5.A [2C-31)
L
30,000
Irrigators/BOR
FR -12 Improve communication, coordination and
information dissemination between various agencies and
emergency management office during flood emergencies
(9.3.A, 9.4.A, 9.3.0 [10C-2, 10C-3, 10C-4, 10C-91)
IP
0
YVOEM
Table 11-3
Low Priority Recommendations
Note: () represents the recommendation location on Table 9-8, and [ ] represents the
oritinal alternative number for that recommendation
INVENTORY & STUDY
Description
Onset
Estimated
Costs in $
Partners
IS -17 Study use of ring dikes to protect St. Joseph's Mission
property (2A-3).
IP
500,000
Landowners
IS -18 Consider major levee construction on Mission
property to alleviate headcuts, this may not be needed if
Recommendations A & B in Hatton section are successfully
implemented. (2A-2).
IP
200,000
FCZD
IS -19 Perform an Emma Lane flood study, and develop
design guidance on acceptable flood protection levels. (3-2).
Address Ahtanum Creek flood conveyance downstream of
42nd and Ahtanum Rd. (3-18).
IP
80,000
FCZD
IS -20 Develop a Coordinated Resource Management Group
to develop joint priorities for resource management (e.g.
Wenas working group). (9B-1)
L
50,000
NYCD/WDFW
IS -21 Investigate and recommend increased maintenance
and debris cleanout of culverts and ditches on public roads
(coordinate with road maintenance crews to optimize ditch
cleaning for flood purposes) (1D-1, 12D-2, 12E-1).
L
20,000/yr
Roads
IS -22 Monitor effects of urbanization and land use
intensifications to the characteristics (runoff, time of
concentration, water quality) of the watershed over time.
Take action to mitigate for negative watershed scale effects.
(Monitoring -Inventories [12H-31)
L
100,000
FCZD
12 Ahtanum-Wide Hollow CFHMP
INVENTORY & STUDY (cont)
Description
Onset
Estimated
Costs in $
Partners
IS -23 Map non -mapped Channel Migration Zones (and
other hazards) (15G-4, 15D-3). Identify areas that are at risk
for channel migration in addition to identified CMZ, i.e. N.F.
Ahtanum, below the Narrows, at the Mission, Shaw Creek,
etc (15C-12).
0
20,000
FCZD/ FCZD
IS -24 Alter drainage systems and easements, based on
Emma Lane floodplain remap study (3-10).
O
5,000
FCZD
IS -25 Inventory of private roads acting as levees.
(Monitoring -Inventories [12D-61)
O
10,000
FCZD
IS -26 Private road culvert inventory. (Monitoring -
Inventories [12E -7b1).
0
5,000
FCZD
IS -27 Investigate funding sources or incentives for private
drainage infrastructure (Monitoring -Inventories [12G-81)
O
5,000
FCZD
PLANNING & REGULATORY
Policy Development
PR -30 Take larger scale effects to the watershed into account
when designing new transportation systems: Minimize
number of roads — maximize efficiency and design roads in
a manner to minimize flooding. (12H -4a)
AU
5,000/yr
County Rds/ Plan
Dept
PR -31 Assess the cumulative effect of road policies and
standards for new roads within the transportation element
of the comprehensive plan that act as dams or conveyances.
(12C-3).
AU
2,000
County Rds/ Plan
Dept
PR -32 Limit future development in the Emma Lane
floodplain area if structural alternatives not implemented (3-
3).
AU
2,000/yr
County Plan Dept
PR -33 Place controls on building in the flood -prone areas in
and around Emma Lane (3-17) (e.g. using zoning, utility
hook-ups, etc.).
AU
2,000/yr
County Plan Dept
PR -34 Investigate geologic hazard area standards for
applicability to high flood risk hazard categories such as
channel migration zones and alluvial fans to address
potential regulatory gaps. (Monitoring -Inventories [14E-11)
L
4 000
FCZD/ Plan Dept
Building Officials
Standards and Ordinance Development
PR -35 Adopt and implement stricter building standards in
Emma Lane area -flood -proofed homes, buildings (3-11, 3-3).
AU
10,000
County Plan &
Build
PR -36 New traffic generating developments should be
located outside of floodplains (see also Bridges & Roads)
(12H -4b).
0
150,000
Juris Plan &
FCZD
Project and Permit Level
PR -37 Improve drainage throughout the entire Emma Lane
area — culverts, roads, etc. (3-8).
IP
20,000
Roads
Chapter 11— RECOMMENDATIONS 113
STRUCTURAL
Description
Onset
Estimated
Costs in $
Partners
ST -16 Consider the following structural alternatives where
changes in the channel threaten homes, businesses,
agricultural land, or infrastructure.
o Levees, armor, buffers, CMZ (channel migration
zones) (15C-1)
o Structural flood control measures either by
individuals or government (4-7)
o Utilize "softer" solutions for bank stabilization, bio-
engineering. (15C-2)
o Levees constructed along perched channels (i.e.
Cottonwood Grove) (15B-2)
L
0
Plan Depts./ FCZD
ST -17 Expand diking along Shaw Creek to protect new and
existing development (8B-2, 8E-2, 15B-2)
L
60 000
Add Insurance
Costs
ST -18 In some locations, add wood to stream to "catch"
wood debris — this accomplishes multiple objectives — would
benefit habitat as well as reduce the volume of woody debris
that accumulates on bridges, diversions, and other
structures. (7D-4)
0
40,000
FCZD
ST -19 Armoring:
- Provide armoring of roads with act as levees
(Ahtanum/Cottonwood Canyon Rd., etc.) (12D-1).
Armor road ditches where road fill is going to
contribute to excess bedload and to protect road
prism. (12E-3).
0
10,000
FCZD
ST -20 Culverts:
- Recognize the limitations of culverts as flood
conveyance structures (12E-2)
Replace old culverts with higher capacity culverts
based on flood risk (12E -7a)
0
0
FCZD & Juris
Roads
ST -21 Identify sources of funding for removal of abandoned
irrigation structures (5E-2)
O
2,000
FCZD & Agencies
ST -22 Preserve and restore natural floodplain in places that
retain some of the floodplain function. Prioritization - allow
for flexibility while identifying critical locations, based on
CFHMP and mapping (4-12).
O
5,000/yr
FCZD
ST -23 Install a remote control floodgate that could be
opened some times of year, closed at others (on Spring
Creek floodgate) (6B-2)
0
20,000
City of UG
ST -24 Protect natural floodplain functions in Shaw Creek's
watershed, especially before it is mapped (8C-1).
O
500,000
FCZD
MAINTENANCE & MANAGEMENT
MM -16 The Spring Creek floodgate should generally be
closed except for habitat or flow enhancement for a limited
time period (see alternative F below also (6B-1)
IP
0
FCZD/ Union Gap
MM -17 Review DID management in relation to flood hazard
over the long term as land use changes (15E-4)
L
20,000
DIDs (County)
MM -18 Investigate funding for enforcement and cleanup of
illegal dumps on private ground. (1C-9, 1C-10)
0
5,000
SW, DOE &
Health Dist
14 Ahtanum-Wide Hollow CFHMP
MAINTENANCE & MANAGEMENT (cont)
Description
Onset
Estimated
Costs in $
Partners
MM -19 Improve stormwater system on Ahtanum Road to
limit Emma Lane overflows into the airport area, and
downstream to 16th (which floods the intersection at
Ahtanum Road) (3-9).
O
0
City of Yakima
MM -20 Investigate methods for the following:
- Research how other communities deal with
dumping in floodplains, particularly concrete, fill,
etc.
Research measures to deal with
illegal/contaminated dumps (meth labs, etc.)
Examine statewide laws relating to dumping and
streams to establish authorities.
(Monitoring -Inventories [1C-7, 1C-8, 1C-111)
0
8,000
SW, FCZD, Juris
MM -21 Utilize fence designs that prevent floodwaters from
backing up on fences, such as:
o Breakaway fence panels in locations that flood
frequently.
o Suspension fences, which consist of steel pipe or
cable hung high above the creek, and hanging
lighter materials down from the cable. This works
as a fence, but is not lost during floods.
Fence setbacks — hold fences back some distance from the
creek (loss of traditional land usage) (1B-1, 1B-2, 1B-3, 1B-4,
1B-5).
0
10,000/yr
NYCD/FCZD Bldg
Officials, Plan Depts.
PUBLIC OUTREACH
PO -13 Cooperate with other agencies to support or develop
public education programs, such as stream cleanup
programs and volunteer monitoring (9C-13).
IP
10,000/yr
FCZD
PO -14 Encourage citizens to report dumping in streams
(public outreach) (1C-5).
L
2,000
FCZD
FLOOD RESPONSE
FR -13 Coordinate between jurisdiction procedures in place
for expedited permit issuance during and period after a
flood event under State and County regulations (10D-1).
0
10,000
OEM, Juris, Agencies,
FCZD
FR -14 Outline emergency response to ice jams in the Flood
Response Plan (1A-3).
- Alert residences at risk. (new)
- Blast ice jams — (normally only done on very stable
ice jams) (1A-6)
Facilitate regulatory approval by Ecology and Fish &
Wildlife and local jurisdictions due to short time frame.
(new)
O
2,000
FCZD/Agencies
MAPPING TOOLS
The recently released (2011) Preliminary FIS maps for the 100 year flood increase
awareness of flood hazard, and provide a critical and more accurate regulatory tool to
minimize damage from large flood events, particularly for new development and
Chapter 11— RECOMMENDATIONS 115
redevelopment. The maps, along with the 10 and 25 year flood maps provided in
appendix J as part of this plan, also show how the existing topography and made -made
structures interact with large floods to redirect flows. The maps reflect the unique
absence of floodplains in these basins that could readily convey water back into the
channels or long distances overland. Overland flows often affect large areas, causing
substantial damage and economic disruption.
From the extent and nature of the flooding portrayed on the FEMA maps it is evident
that, despite the implementation of this plan, infrequent flood events such as the 100
year event will continue to affect large areas, causing substantial damage and economic
disruption. The plan recommendations above therefore concentrate on remedial actions
to reduce community costs through minimizing additional community exposure and
attending to more frequent flooding issues creating the most damage.
Frequent floods, from a five year interval up to the 25 year flood, produce the majority
of property damage and economic disruption to the community over time. In these two
basins actions to reduce damage over this range of floods is a more cost effective and
realistic goal than trying to provide full relief from the 100 -yr flood. The 10 and 25 year
flood maps can serve as guidelines for future infrastructure location, design and
planning. Many of the recommended actions in the categories should be implemented
and/or managed with this product in mind.
IMPLEMENTATION STRATEGY
The purpose of a CFHMP is to propose a suite of actions that will reduce flood hazards
over both the short and long term. In order to develop a long term strategy it was
necessary to understand the underlying causes and obstacles to overcome. The most
relevant new understanding attained during development of this plan, apart from the
large extent of flooding, was the pervasive and historic nature of floodplain and channel
modifications to suit agricultural practices, such as channel relocations, resizing and
removal, and the legacy that alteration presents for future urbanization of the
floodplains. The irrigation diversions and basin bridges act to increase overflows and
flood redirection.
As flood problems result from a lack of flood hazard awareness coupled with
development, or unforeseen changes in the physical or biological characteristics of the
watershed, the greatest return on investment is to increase flood hazard awareness to
allow effective decisions that minimize risk for both existing and future development.
The In -progress activities and recommendations, combined with the Public Outreach
recommendations, including distribution of this Plan, are intended to extend the
awareness of these and future changes.
As the development of the Plan increased awareness of the flood problems, there was an
increased awareness of data gaps that, if filled, would serve to increase the cost-
16 1 Ahtanum-Wide Hollow CFHMP
effectiveness of all the recommendations. To facilitate the plan effectiveness, the
Inventory recommendations received the highest implementation priority and several
were provided by the FCZD in Appendices G, H and I.
Answers to the questions "What types of actions will be effective?" and "Why will these
actions be effective?" are the critical components of an implementation strategy for the
plan. The answers to these questions differ for new and existing development.
New Development
Due to the widespread nature (generally shallow) of major floods, the disproportionate
effect of minor changes to the landscape (fences, roads, hay bales) on flood routing and
potential flood damage, and the future need to develop or redevelop large tracts of land,
a higher priority is placed on Planning and Regulatory recommendations.
The Planning and Regulatory recommendations focus on standards for the location and
analysis of development and related infrastructure, and construction standards for
development including flood elevations, bridge design, and safe evacuation routes.
Although these recommendations serve to reduce additional flooding from future
development, they will also reduce existing flooding as the opportunity for replacement
of existing infrastructure arises, such as bridges, with higher capacity spans and lower
approaches. The FEMA FIS study has provided the mapping (noted above), the
hydraulic model and means for the communities to assess infrastructure updates and
removals at reduced cost.
Existing Development
In sediment rich basins characteristic of the Pacific Northwest, a significant specific issue
is channel sediment and invasive vegetation, and the need for a maintenance program to
manage their effects. Some of the impacts can be avoided through infrastructure design
and normal replacement.
The need to implement Maintenance and Management recommendations for stream and
irrigation channels is especially important in currently urbanized areas. The need to
prevent intensive and expensive maintenance in future urbanized area should be an
implementation priority of the Planning and Regulatory recommendations, as well as
the Structural recommendations and actions. Sediment is an important contributor to
basin flooding problems. Studies to quantify the impacts of sediment at bridges and in
the channels have been initiated as a result of this Plan (Appendix G) so that
Maintenance recommendations can be more effective.
The structural alternatives primarily act to route more water into the main channels and
transfer flow capacity issues from a location of lesser channel capacity to one that is
higher and provide reduced flood impacts. Many of the recommended structural
projects addressing existing flooding are located in the Urban Growth Areas and should
Chapter 11— RECOMMENDATIONS 117
be implemented sooner rather than later — before development precludes the
opportunity for these structural alternatives and the conditions causing increased flood
hazard and damages from development are fixed in place. Some of the structural
recommendations in the plan address critical locations in these watersheds where flood
overflow paths for large floods, such as the 100 -yr flood, originate. These overflow
points are usually activated during frequent floods. Once identified, the projects focus
on these locations to reduce the frequent chronic, wide spread flooding.
Other structural recommendations are located in already urbanized areas, and will be
implemented in conjunction with planned infrastructure or redevelopment activities as
the opportunity arises.
ECONOMIC CONSIDERATIONS
The most economic action after the provision of selected Inventory recommendations is
to translate the new awareness into design and planning guidelines and building
restrictions that mitigate flood effects. Jurisdiction planning measures should
acknowledge the legacy of agricultural conversion of floodplains to more flood -prone
development, such as at lower Shaw Creek, so that effective flood reduction measures
are incorporated. The use of the provided 10, 25 and 100 -yr flood maps to guide
development and infrastructure will greatly further this goal (see Appendix J). The maps
can be used to facilitate development and design the costly infrastructure location and
replacements, such as bridges, required due to obsolescence or damage. Building code
revisions that reduce future economic burden to the citizens through flood insurance
reduction should be pursued to avoid subsidizing other more flood prone communities.
The next most economical action is to address existing flood issues specific to a cause
through wider actions such as channel maintenance.
The most expensive category is to address existing flood issues specific to a location.
Structural projects are typically very expensive for jurisdictions, particularly where
significant land is required. However, due to land pricing in development areas, projects
should be addressed as soon as practical before the land is overdeveloped or under
urbanization development pressures.
Structural projects, such as levees, also require maintenance that is a continual
commitment of resources, making them the least financially attractive. The number of
potential structural projects is limited in these basins by the wide extent of flooding
during infrequent floods, such as the 100 -year flood. Typical protection methods for
existing development such as diking, channel relocation or home relocation cannot fully
contain the problem. In most cases the structural measures are more suited to 10 and 25—
yr floods as they encompass the majority of the community losses, as determined
through economic analysis.
A Funding Strategy is presented in Chapter 12.
18 1 Ahtanum-Wide Hollow CFHMP
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CHAPTER 12
FUNDING STRATEGY
Given sufficient available funds and stakeholder acceptance, the ideal flood hazard
mitigation strategy would be to address those flood issues that generate the most public and
private burden or impacts. However, implementation of flood mitigation measures is
altered by the ability to absorb their costs and obtain public and agency agreement, which
also has associated costs. The majority of floodplain development costs are ultimately borne,
or mitigated, by the local government and landowners based on available resources and
properties protected.
Implementation of flood hazard mitigation requires a funding strategy commensurate with
available resources. A short term and long term strategy is required for each community.
For existing flooding problems that affect large areas, mitigation requires partnerships and
collaborative efforts for funding and implementation. An awareness of overlapping
mandates is required to allow joint funding of projects for joint benefits. This cooperative
approach recognizes the interests of multiple landowners and jurisdictions plus the
constraints placed by funding and non -funding agencies. The ongoing replacement of an
agricultural infrastructure with urban development and infrastructure will be required in a
manner that preferably relieves flooding and does not further contribute to flooding.
As noted in Chapter 11, the measures which provide the least community exposure and the
most community control are the planning and regulatory tools and measures recommended
in the plan. Without planning revised to utilize the additional information in this plan,
future floodplain development can increase costs, through future damages and flood
insurance for business and residences that are not effectively returned to the community.
Competition for flood projects exists for all available funds, and between flood projects. For
example, the projects of this CFHMP compete for funding with projects in the other three
CFHMP areas of Yakima County, several dozen CFHMPS in other areas of the State,
periodic emergencies and disasters, and maintenance of flood protection structures. The
high priority recommendations within this plan cost approximately $5 million. As the
current funding mechanism for the County -wide Flood Control Zone District generates
funding amounts sufficient for mitigation planning, such as this plan (Chapter 10), and for
grant match for a very small portion of the flood issues already identified in the County, the
local governments (the City of Yakima, the City of Union Gap and the County) will need to
prioritize and choose from Chapter 11 the types of actions or projects that will effectively
reduce damages and community costs to current and future residents.
1
2 1 Ahtanum-Wide Hollow CFHMP
INVENTORY AND STUDY FUNDING
The plan has identified several significant inventories necessary to improve flood hazard
awareness and decision-making that may also modify current priorities. Several of these
inventories and studies are being funded first and should continue to increase awareness
and target efforts. They can potentially modify the effectiveness of all the other
recommendations. One inventory/ study being completed shortly is for the new FEMA
flood maps funded jointly by FEMA and the FCZD. Many others are already in progress
and are being integrated with existing Flood Control Zone District, county, or city programs
to provide multiple benefits. Examples include:
• Identify sediment removal locations, including bridges and channels
• Sediment removal guidelines, meeting flood and habitat requirements
• Bridge inventories (change how inventories occur and are ranked)
• Bridge flood design guidelines (develop principles for bridge design in these basins
as a part of the next bridge design process)
• Emergency Response Routes (incorporate into disaster response planning and
transportation planning processes)
• Studies of sediment aggradation at Union Gap (already recommended in another
CFHMP and in process).
The above studies are currently funded through the FCZD and can be achieved over time
through cooperation with partners and integration of existing efforts.
PLANNING AND REGULATORY FUNDING STRATEGY
Flood water routes and overflow paths in the Wide Hollow and Ahtanum basins are
widespread and changeable due to the floodplain physiography. As noted in chapter 11 the
use of structural measures and projects typically used elsewhere, are less effective in
alleviating flooding in these basins due to the relatively large areas of shallow flooding and
the multiple, interconnected flood flow paths.
Planning and Regulatory revisions are the least expensive and most effective flood
reduction recommendations. They can reduce flood insurance premiums. Where protection
(either changing or maintaining current land use) of areas adjacent to streams or overflow
areas would also have water quality benefits, or implementation of best management
practices would have flood hazard reduction benefits, there are funding sources which
could be tapped for the joint purpose. Where the community determines that retention of
agriculture, or open space, as a public benefit is a priority in areas of high flood hazard,
there are numerous programs that can be used to:
• retain agriculture through fee -simple or easement purchase
• acquire and develop (for public purposes) open space
• acquire and restore fish and wildlife habitats or improve water quality.
Chapter 12 - FUNDING STRATEGY 13
Planning and regulatory actions are ongoing and focus on the elements of the Growth
Management Act - from individual permit decisions to development of County -wide
Planning Policies that guide the overall development in the Cities and the County of
Yakima. The Planning Departments of the jurisdictions have the tools to enact many of the
plan recommendations within existing processes. The FCZD has been, and will continue to
be involved in these processes with the jurisdictions, state, tribal and federal agencies on an
ongoing basis for the foreseeable future. Currently Surface Water Division has staff involved
in activities to support the local jurisdictions.
ONGOING MAINTENANCE AND MANAGEMENT STRATEGY
Funding for flood issues of an ongoing nature (typically annual) such as channel and bridge
maintenance, maintaining and improving flood mapping data, management of flood control
structures or property retained in open space classification require a continual dedication of
staff and resources by local jurisdictions, and in some cases, private entities. As funds for
these types of projects generally cannot be obtained through capital improvement grants
they must be prioritized and compete with other local government priorities and
requirements for available resources, particularly staff.
Public and private irrigation districts and companies will play a significant role in
management of the flow of water, and therefore flood hazard, within the Ahtanum/Wide
Hollow watershed. These entities may be particularly sensitive to either new regulatory or
requirement or changes to traditional management practices to reduce flood hazard.
Securing funding to reduce both overall management costs and flood hazard associated
with irrigation diversion and delivery systems should be an emphasis in this plan. Projects
that also reduce water use, improve water quality or improve fish passage will be much
more likely to be funded than either stand alone irrigation system or flood hazard
improvement projects.
Where management of irrigation delivery systems would result in water savings or
increases in water use efficiency as well as reduction of flood hazard, there are several
funding sources available to implement flood hazard reduction and water conservation
projects. Where land management strategies that reduce flood hazard can also improve
water quality and fish and wildlife habitat, funding can be also oftentimes be secured.
STRUCTURAL FUNDING STRATEGY
Six existing problem areas and related structural projects have been identified. While these
projects are structural in nature, they for the most part, do not include construction of flood
control facilities, such as levees. Most of these structural projects seek to solve the flooding
and often -related habitat problems through relocation of the Creek, or alteration of existing
infrastructure that increases flood risk.
Costs for structural projects are typically high. Funding augmentation sources for capital
projects are well documented in Chapter 10 of the 2007 Upper Yakima CFHMP update. That
3
4 1 Ahtanum-Wide Hollow CFHMP
chapter also provides the background funding structure for the FCZD. The availability of
Federal or State money for capital projects can only be secured through competition with
other jurisdictions and cannot be relied upon for a long term basis. Most capital funding
jointly requires habitat, watershed, and water quality or water quantity benefits. When these
additional criteria are included in a project selection process, high priority projects more are
more often limited to main stem rivers. Flood hazard reduction actions in main stem rivers
often protect major flood (levees), water (diversions) or transportation (highway)
infrastructure and also affect the habitat for larger fish populations.
While the size of Ahtanum and Wide Hollow Creeks do not allow for large fish populations,
proportionally there are significant areas of high density urbanization, transportation
networks, and flood infrastructure that should qualify the six problem areas in the Plan for
some types of capital grant funding. In general, projects on the Ahtanum will need to be
more environmentally friendly types of solutions due to the presence of ESA -listed fish
species in that basin. The Yakima Countywide Flood Control Zone District has been fairly
successful at competing for structural or capital grant funds where the projects' funding
provides multiple benefits, or the flooding problems are chronic such as the Emma Lane
42nd Avenue project funded through federal Hazard Mitigation Funds. However, the FCZD
funding source is extremely limited and continuation requires grant match including that
from the community affected.
Another area that the FCZD has been very active in is the watershed, water supply and
habitat initiatives that occur at the Yakima and Columbia Basin scales. Funding from these
programs can also provide flood benefits.
PUBLIC OUTREACH FUNDING PLAN
Public Outreach activities have been taken on as a responsibility of the FCZD and
Emergency Management Division. Currently, these activities are done mostly on an as -
requested basis, as a part of annual events (i.e. Central Washington State Fair, home shows),
or as an outgrowth of other activities related to project development, grant requirements, or
participation in a variety of planning, regulatory and ordinance development programs.
Most of the staff resources devoted to this task by the FCZD is currently working on the
development of CFHMPs and the multi -hazard plans. Once these plans are completed the
FCZD, in cooperation with other partners, will develop an actual public outreach plan for
flood hazard reduction. The Public Outreach activities need to be shared with the local
jurisdictions.
FLOOD RESPONSE FUNDING
The FCZD, in cooperation with the Emergency Management Division, will continue to
implement improvements to the Flood Response Plan. The FEMA County multi -hazard
plan, which includes the flood response plan and flood hazard mitigation projects is
updated regularly. This participation increases the ability of the flood response components
in this plan to receive funding assistance.
Chapter 12 - FUNDING STRATEGY 15
FLOOD CONTROL SUB -ZONES
The regular levy currently funding the Yakima County -wide FCZD has limitations in
addition to the cap of 50 cents per thousand dollars of assessed valuation. Washington has a
regular property tax limitation of 1 percent of a parcels' fair and true value. Within this tax
limitation of ten dollars per thousand dollars of assessed value, the combined levies for
cities, counties and junior taxing districts are limited to $5.90 per $1,000 of assessed value.
Flood Control Zone Districts are considered to be junior taxing authorities, so their levies
are reduced if more senior authorities bring property taxes up to the maximum allowed. At
this time the FCZD can collect less than the currently authorized 10 cents per $1,000 of
assessed valuation due to seniority issues. The FCZD, which requires funding for planning
and levee maintenance does not have sufficient funding for the recommendations in this
area plus the others in the County as the high priority recommendations in this CFHMP
exceed $5 million dollars.
The CFHMP objectives included consideration of sub -zones, as allowed by RCW so that
levies can be raised to fund projects within the sub -zones.
FCZDs can use several different funding mechanisms, including the following:
• A regular levy requiring authorization by the supervisors. The maximum
amount that can be levied is 50 cents per $1,000 of assessed valuation. (RCW
86.15.160)
• An excess levy as a property tax requiring annual voter approval. This type
of levy does not fall under the constitutional and statutory limitations of
regular levies. An excess levy is based on property value and would not
affect existing County revenues. The levy, if approved annually by voters,
can generate substantial revenue for overall surface water management or
flood control. However, considerable cost is involved in making voters
familiar with the issues on an annual basis, and there is no certainty of funds
from year to year. (RCW 86.15.160)
• Assessments. (RCW 86.15.160)
• Service charges including public entities. (RCW 86.15.176)
• Local improvement districts (LIDs). (RCW 86.15.160)
• May create subzones which are operated as flood control zones. (RCW
86.15.025)
• Revenue and GO Bonds (RCW 86.15.178 and RCW 86.15.170 respectively)
• Stormwater fee charges, including public property. (RCW 86.15.160)
• Voluntary assessments for flood or stormwater control. (RCW 86.15.165)
LOCAL FUNDING STRATEGIES
Below are additional funding options for local jurisdictions that are available through State
legislation.
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6 1 Ahtanum-Wide Hollow CFHMP
Local Improvement Districts
Local improvement districts (LIDs) allow jurisdictions to issue bonds for the cost of
improvements and to recover the cost through assessments based on "specially benefiting"
property. Special benefit is defined by the increased property value that results from the
improvements.
For water and sewer improvements, properties are considered specially benefiting when
they are physically connected to, or have the ability to physically connect to, the sewer or
water system. For drainage improvements, it is often difficult to demonstrate special benefit
because there is generally no physical connection and property value often is not directly
affected by the existence of a drainage system, except where flooding is frequent. Moreover,
property at the top of a hill does not specially benefit from drainage improvements, but it
does contribute to the surface water problems. Property at the bottom of the hill sees a more
positive effect from the drainage improvements, even though it contributes only a portion of
the runoff.
LIDs have been used to finance water supply, sanitary sewers, and storm drains when all
three utilities are needed in an area. An LID might be appropriate for construction of a
facility to serve several properties where the runoff contribution and benefit are similar.
Surface Water Utility
Under RCW 36.89 the County can create a County -wide utility that is implemented on a
basin -by -basin approach. The underlying concept of a surface water utility is that all
properties contribute surface water runoff to the drainage system and should pay an
equitable share of the system's O&M and capital costs. Schools, churches, and other tax-
exempt properties, as well as public entities and public property, are subject to the same
rates and charges as private properties.
The formation of a surface water utility would provide a continuous and reliable funding
source to pay for both capital improvements and ongoing maintenance and operating costs.
The primary disadvantage could be a public perception that a new charge is being imposed
for a service already being provided. This approach has been utilized in western
Washington Counties such as King and Pierce counties.
There is currently a stormwater utility for NPDES Stormwater Permit within the urbanized
area of the county. This utility is focused on water quality not water quality issues.
APPENDIX A.
ZONING AND LAND USE TABLES
Combined Yakima County and City of Yakima Land Use
Yakima County 1996 land use data was originally derived from County Assessor's land
use codes which were then grouped and edited for use in the Yakima County
Comprehensive Plan 2010. The City of Yakima data was updated by the city in 2004.
This analysis combines Yakima County and City data. It was then clipped to the study
area boundary. Current land use data was not available for Union Gap.
Table A-1 Land Use in the Study Area
Land Use Acres Percent
Agriculture 46,963.40 36.94%
Single Unit 8,637.96 6.79%
Vacant 11,167.84 8.78%
Mining 25.21 0.02%
Five or More Units 124.07 0.10%
Commercial 833.66 0.66%
State Lands 35,242.51 27.72%
Other Residential 788.77 0.62%
Wholesale\Industry 1,210.43 0.95%
Duplex-Fourplex 247.62 0.19%
Transportation\Utilities 13.36 0.01%
Not Assigned 346.56 0.27%
Parks 479.63 0.38%
Education and Government 437.41 0.34%
Forestry 20,405.90 16.05%
Mobile Home Parks 216.56 0.17%
Totals 127,140.89 100.00%
The land use shape file was then cut to the boundaries of the 1998 Effective FEMA Flood
Insurance Rate Maps (FIRM) to determine land use within the 1% annual chance (100 -
year) floodplain. The 2009 Effective FIRMs are nearly identical to the 1998 maps.
Table A-2 Land Use in Floodplain
Land Use Acres Percent
Agriculture 2,135.13 67.21%
Single Unit 510.06 16.06%
Vacant 206.75 6.51%
Mobile Home Parks 32.55 1.02%
Other Residential 50.96 1.60%
Commercial 30.24 0.95%
Duplex-Fourplex 3.41 0.11%
Five or More Units 2.56 0.08%
Wholesale\Industry 175.54 5.53%
Parks 13.91 0.44%
Not Assigned 15.80 0.50%
Totals 3,176.91 100.00%
2 I Ahtanum-Wide Hollow CFHMP
Yakima County and City Zoning
Since most of the study area is unincorporated, analysis of Yakima County zoning
provides a broad view of activities in the upper Ahtanum and Wide Hollow watersheds.
Yakima County 2005 zoning was used for this analysis.
Table A-3 Yakima County Zoning in the Study Area
Zone Acres Percent
Agriculture 13,932.04 9.1%
Local Business 27.77 0.0%
Yakima Nation Closed 8,962.44 5.8%
Forest Management 53,408.58 34.7%
Industrial District 23.58 0.0%
City Limits 11,420.92 7.4%
Light Industrial 257.12 0.2%
Mining 324.09 0.2%
Planned Development 292.40 0.2%
Single Family 4,878.81 3.2%
Single Family (urban) 736.96 0.5%
Two Family 53.37 0.0%
Multi Family 12.49 0.0%
Remote Extremely Limited 26,488.67 17.2%
Rural Settlement 288.94 0.2%
Rural Transitional 2,723.40 1.8%
Suburban Residential 984.87 0.6%
Federal land\Tribal Trust 13,630.83 8.9%
Valley Rural 15,394.94 10.0%
Total 153,842.22 100.0%
Results for the remaining tables were created by clipping the 2005 zoning data for each
jurisdiction to the same 1998 Effective FEMA Flood Insurance Rate Maps (FIRM)
mentioned above.
Table A-4 City of Yakima Zoning in the Floodplain
Code Description Acres Percent
B-1 Professional Business 3 1%
B-2 Local Business 5 1%
CBDS Central Business District Support 30 7%
LCC Large Convenience Center 0 0%
M-1 Light Industrial 243 57%
R-1 Single Family Residential 58 14%
R-2 Two -Family Residential 1 0%
R-3 Multi -Family Residential 34 8%
SR Suburban Residential 52 12%
Total 426 100%
APPENDIX A - ZONING AND LAND USE TABLES 13
Table A-5 City of Union Gap Zoning in the Floodplain
Code Description Acres Percent
C-1 Commercial District 3 1%
CBD Central Business District 16 3%
L -I Light Industrial District 95 20%
NON not classified 26 5%
PBD Public Buildings District 21 4%
PRc Planned Recreational 115 24%
PkO Parks/Open Space 118 24%
R-1 Single Family Residential 1 42 9%
R-2 Single Family Residential 2 27 6%
R-3 Multi -Family Residential 1 0%
TT Tribal Trust 6 1%
W/W Wholesale/Warehouse 13 3%
Total 483 100%
Table A-6 Yakima County Zoning in the Floodplain
Zone Acres Percent
Agriculture 661.09 16.8%
Local Business 5.90 0.1%
Yakima Nation Closed 140.20 3.6%
Forest Management 190.48 4.8%
Industrial District 9.21 0.2%
City Limits 910.39 23.1%
Light Industrial 48.04 1.2%
Mining 0.00 0.0%
Planned Development 0.08 0.0%
Single Family 494.39 12.5%
Single Family (urban) 0.00 0.0%
Two Family 0.00 0.0%
Multi Family 0.00 0.0%
Remote Extremely Limited 130.36 3.3%
Rural Settlement 100.21 2.5%
Rural Transitional 172.99 4.4%
Suburban Residential 74.64 1.9%
Federal land\Tribal Trust 263.54 6.7%
Valley Rural 739.53 18.8%
Total 3,941.03 100.0%
4 I Ahtanum-Wide Hollow CFHMP
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Appendix B - Photos
1996 Flood
42nd Avenue & Emma Lane Area
Looking Southeast
42nd Avenue & Emma Lane Area
Looking Southeast
42nd Avenue & Emma Lane Area
Looking Southeast
Rutherford Road & American Fruit Road
Looking Northeast
Rutherford Road & American Fruit Road
Looking Northeast
The Community of Ahtanum
Looking East
2 I Ahtanum-Wide Hollow CFHMP
1996 Flood
44
CO WIDE FIJJODIHG 143 FEE: 96
City of Union Gap
Looking South
Confluence of Ahtanum Creek, Wide Hollow
Creek & Yakima River - Looking Northwest
Community of Ahtanum
Looking East
80th Avenue & Wide Hollow Road
Looking South
80th Avenue & Wide Hollow Road
Looking North
Wide Hollow Road near 84th Avenue
Looking Northwest
APPENDIX B - PHOTOS 13
2003 Flood
Driveway off of Ahtanum Road
Looking North
North Fork Ahtanum Creek
Looking Northwest
42nd Avenue & Ahtanum Creek
Looking North
American Fruit Road & Ahtanum Creek
Looking West
Emma Lane - Looking South
Emma Lane- Looking North
4 I Ahtanum-Wide Hollow CFHMP
Irrigation Structures
YVCC Crossing
Wide Hollow Creek & 101st Ave
Old Hatton Diversion
Ahtanum Creek
Upper WIP Diversion
Ahtanum Creek
John Cox Diversion
Ahtanum Creek
Wide Hollow Creek Mill Structure
City of Union Gap - Looking East
North Fork Ahtanum Creek
Bank Stabilization with Fascines
A fascine is a rough bundle of brushwood used for
strengthening an earthen structure, or making a
path across uneven or wet terrain. Typical uses are
protecting the banks of streams from erosion,
covering marshy ground and so on.
APPENDIX B - PHOTOS 15
Area to be stabilized
Staking the fascines
Completed installation
6 I Ahtanum-Wide Hollow CFHMP
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APPENDIX C
FLOOD PROBLEMS BY WATERSHED AREA
Note: Comments listed below are included on Table 1 in Appendix C (geographic area
groups may differ). Any comments pertaining to proposed causes or solutions to
problems were provided by the interviewees and workshop participants and each
comment was not verified.
The problems described below were collected through public meetings, interviews and field
visits at the beginning of the CFHMP process. Understanding regarding the sources and
possible mitigations for the flood problems identified changed as additional mapping and
other information was gathered. Since this preliminary information was gathered, some
problems have been addressed and additional problems have been identified.
The initial geographic groupings for the problems (comments) below were later refined and
errors were corrected. For this reason, some problems described and identified by number
in this document are located on different geographic area maps in the final CFHMP.
Ahtanum
North Fork Ahtanum at John Cox diversion
North Fork Ahtanum Creek at the John Cox ditch headgate is an area frequently damaged
during flood events. The John Cox ditch diverts North Fork flow eastward, serving
irrigators in the Tampico area and West Valley. In 1970, the Army Corps of Engineers
installed several grade control structures upstream and downstream of the North Fork Road
bridge. The grade control structures have succeeded in holding sediment, elevating the
streambed and thereby decreasing the freeboard under the bridge. During even moderate
flood events (e.g. 2003), debris that becomes lodged behind the bridge blocks the channel
and causes overbank flow upstream of the bridge. Erosion is also frequent near the bridge
abutments. Additionally, the aggraded stream channel has caused overbank flow on the
downstream side of the bridge and has caused the Ahtanum Irrigation District (AID) move
the John Cox diversion location further and further upstream to maintain the proper head
through the gate. Overbank flow also causes water over the North Fork Road and as a result
hazardous road conditions, especially at near freezing temperatures. See comments no. 1, 2,
3, 4, 13, and 17 in Appendix C, Table 1.
Regular damage to private residential bridges on North Fork Road.
The North Fork Road is on the opposite side of the North Fork Ahtanum Creek from the
homes and therefore several private bridges cross the creek to provide access. These bridges,
which are in various states of repair, become clogged with debris and often get washed out
during flood events. See comments no. 7, 8, 14, 18, and 22 in Appendix F, Table 1.
2 1 Ahtanum-Wide Hollow CFHMP
Ahtanum Creek Transition at the Narrows
Ahtanum Creek goes through a transition from a narrow steeper gradient channel including
and above the area commonly known as The Narrows, just east of Tampico, to a shallow
low gradient stream. Low gradient streams are characterized by having slower velocities
and thereby allowing suspended sediment to settle out and become part of the stream bed.
Numerous comments regarding this transition zone pertain to a shallow creek bed and
sediment accumulation in culverts causing overbank flow. At the Narrows, the creek is
confined by the canyon walls and Ahtanum Road. The creek frequently undercuts Ahtanum
Road during flood events. During the 1996 flood, the road shoulder eroded and collapsed
where the creek nears and then bends away from the road. See comments no. 6, 16, and 20
in Appendix F, Table 1.
West Valley — North
Overbank flow on Wide Hollow Creek upstream of Wide Hollow Rd "S" curve causes
overland flow flooding at "S" curve
Several people documented flooded near the "S" curve of Wide Hollow Road. Upstream
where Wide Hollow Road crosses over Wide Hollow Creek, there are reports of overbank
flow caused by debris caught behind the bridge. Additionally, there are reports of a possible
diversion of creek water which contributes to flooding problems. Water travels across the
fields as well as down Wide Hollow Road to the "S" curve. Lack of deep roadside ditches
and conveyance prevent water from making the first 90 degree turn and water travels across
the road, flooding properties on both sides of the "S" curve. Water that does make the turn
rejoins the Wide Hollow Creek main channel just upstream of the bridge at the "S" curve.
The excess flow causes erosion on the upstream side of the bridge. See comments no. 24, 46,
and 47 in Appendix F, Table 1.
Fish historically inhabited Wide Hollow Creek
The only public comments made stating fish inhabiting this area were made in reference to
Wide Hollow Creek. It was reported that brown trout and Chinook salmon once lived in the
stream but do no longer and the stream is not in its natural condition. See comments no. 39
and 41 in Appendix F, Table 1.
Cottonwood Creek
Bridges on Cottonwood Creek have low clearance and are in various states of repair.
Photographs taken at each of the bridge locations illustrate sediment and debris
accumulation underneath the bridges, which makes them susceptible to overtopping during
floods. The stream channel upstream and downstream of bridge crossings also has areas of
deposition, as well as areas of riprap reinforcement, indicating scour. There are reports that
the creek was cleaned out near its confluence with Wide Hollow Creek. There are
approximately 6 stream crossings on Cottonwood Canyon Road. Bridge alignment is poor
and the stream is forced to make an "s" turn at each crossing. Sediment deposition and
scour are likely a result of the realignment of the channel from its natural condition. See
comments no. 48, 49, 50, 90, and 91 in Appendix F, Table 1.
Appendix C - FLOOD PROBLEMS BY WATERSHED AREA 13
Spill from Congdon Ditch
The Congdon Ditch intersects Wide Hollow Creek near Wide Hollow Road and S 101St Ave.
Spill from the ditch alters the hydrology of Wide Hollow Creek because Wide Hollow
Creek's flows decrease throughout the summer and it is not unusual for the creek to be dry
late in the summer. At this time the Congdon Ditch is flowing because it is delivering much
needed irrigation water. The altered hydrology of Wide Hollow Creek is driving the loss of
Cottonwood trees. They are being replaced by Pacific Willow, which produce large amounts
of debris that gets mobilized during flood events. See public comment no. 45 in Appendix F,
Table 1.
West Valley — South
AID diversion and access bridge to WIP diversion
The access bridge to the Wapato Irrigation Project diversion (built in 1996/1997 by the
Bureau of Reclamation), just east the Ahtanum Mission, is poorly aligned with Ahtanum
Creek. The bridge alignment pushes the thalweg of the channel toward the left bank on the
downstream side of the bridge, where overbank flow occurs during flood events causing
flooding of the west field at the Mission. The right bank upstream of the bridge is eroding
due in part to the misalignment of the bridge and also due to altered flow upstream. The left
bank of the AID diversion at Bachelor Creek, just upstream of the access bridge, experiences
erosion during every flood event. A rip rap structure was placed upstream which was
supposed to divert flow away from AID but it does not work at high flows. This may also be
contributing to the right bank erosion on the upstream side of the bridge. Additionally, the
lower end of the fish bypass structure at the AID diversion is becoming dry because the
outlet is on the left bank of the stream just above the bridge and this is where flows are
migrating further toward the right bank. See public comments no. 65, 86, 87, and 84 in
Appendix F, Table 1.
Regular overbank flow from Ahtanum Creek into Hatton Creek
Irrigation diversion and transition in stream morphology near the Mission where Bachelor
and Hatton Creek fork from Ahtanum Creek make this area unstable and unpredictable.
The channel is aggrading downstream of the Mission, near the fork of Hatton Creek,
encouraging the stream to branch into alternate channels. Ahtanum Creek experiences
frequent overbank flow downstream of the Mission, resulting in excess flow into Hatton
Creek. Bales of hay have been placed along the banks of Ahtanum Creek to prevent this
from happening during flood events. LiDAR images indicate there may be an old channel
upstream of the current Hatton Creek fork, where Ahtanum Creek experiences overbank
flow. In addition, flood flows in the west field of the Mission contribute flow to Bachelor
Creek and additional flow to Hatton Creek. See comments no. 64, 79, 88, and 89 in
Appendix F, Table 1.
4 1 Ahtanum-Wide Hollow CFHMP
Overbank flow approaching Rutherford Rd, whose roadside ditches do not have adequate
capacity to convey excess flow
During flood events, excess flow in Hatton and Bachelor Creeks travels east to Lynch Lane
and Rutherford Rd. During extreme flood events, flow exceeds the capacity of the stream
channels and flow travels as a sheet easterly. The bridges at Lynch Lane become
overwhelmed and water floods into the roadside ditches of Rutherford Rd. Additional flow
also enters Bachelor Creek at Lynch Lane. As occurred during the major flood events of 1974
and 1996, the roadside ditches exceed capacity and experience severe erosion and scour.
Culverts become blocked with mobilized debris and get washed out. The Hatton Creek
Bridge on Rutherford Rd experiences erosion and scour due to excess flows. The County
built a dike to divert flow back into Hatton Creek at the west end of Rutherford Rd, but
flood flows blow out the irrigation diversion on the other side of the creek.
Yakima County applied for a grant from the Washington Hazard Mitigation Grant Program
in 1997 to mitigate against damage to Rutherford Road and surrounding property. The
proposal stated that over topping structures would be built at the beginning of the road to
stop the flood waters from gaining uncontrolled access to the roadside ditch. Additional
control structures would be placed along the road side ditches to control the velocity of the
water in the ditch to prevent the water from washing away the road. However, the grant
was not awarded. See comments no. 53, 58, 59, 61, 66, 71, 75, 76, 78, 81, 94, and 95 in
Appendix F, Table 1.
N -S oriented roads cause back up of flood flows
Flood flow traveling easterly along Rutherford Rd and between Bachelor and Hatton Creeks
are slowed by North-South orienting roads such as Stanton Rd and Carlson Rd. Culverts
and bridges do not have adequate capacity to pass flood flows so roads acts as dams for
flood flow. Bridges become clogged by debris and flood flows erode and damage bridge
abutments. See comments no. 54, 57, 95, and 99 in Appendix F, Table 1.
Hatton Creek at Meadowbrook Road
Hatton Creek at Meadowbrook Road is shallow and has low banks. The bridge at S 101St
Ave has little freeboard, even at low flows. Excess flood flows in Hatton Creek - due in part
to diversion of Ahtanum Creek into Hatton Creek - overwhelm the channel and bridge,
causing overbank flow even during less severe flood events. Debris mobilized during a
flood becomes caught upstream of the bridge due to lack of adequate freeboard. See
comments no. 56, 68, 72, 82, and 97 in Appendix F, Table 1.
Ahtanum Creek flooding impacts S Ahtanum Rd
Flooding from Ahtanum Creek impacts homes on Lone Dove Lane. There are also reports of
flooding along S Wiley Road near the Ahtanum Canal. The Ahtanum Canal, part of the
WIP, gets shut off upstream of the Mission during flood events. See comments no. 73, 74,
and 93 in Appendix F, Table 1.
Appendix C - FLOOD PROBLEMS BY WATERSHED AREA 15
West 'Yakima
Berms surrounding fruit plant force floodwaters onto surrounding properties
Highland Fruit Company has built berms along the southern and western edges of their
property to keep Wide Hollow Creek from flooding the business. Residents to the north
have reported flooding caused by water traveling across the road and away from Highland
Fruit Company. Furthermore, Highland rebuilt their warehouse and never replaced the
culvert they removed. Residents believe this contributes to flooding on the north side of the
road. See comments no. 101, 102, 110, 113, and 114 in Appendix F, Table 1.
Shaw Creek classification and alignment
Shaw Creek is not aligned in its original channel. The creek has been rerouted as an
irrigation ditch and currently flows easterly just south of Tieton Drive until it meets S 80th
Ave and takes a 90 degree turn south to become the roadside ditch. The ditch crosses
through a culvert under S 80th Ave two times before joining Wide Hollow Creek. It was
reported that Shaw Creek flows have been diverted and the creek has been dry for an
extending period of time. Because the origin of Shaw Creek was determined to be irrigation
return flow, the stream is not regulated. One resident along the creek has expressed the
need for updated FEMA maps that eliminate the floodplain designation for this section of
stream. See comments no. 115, 117, and 128 in Appendix F, Table 1.
Constricted Channel in Wide Hollow Creek
Reaches of Wide Hollow Creek are constricted due to levees built along the banks. Channel
constriction can exacerbate flood impacts because the channel conditions are not conducive
for attenuating flows. In addition, a constricted channel may increase scour and/or erosion
along the streambed and banks. See comments no. 118, 119, 123, and 199 in Appendix F,
Table 1.
Flooding on Wide Hollow Creek impacts Wide Hollow Rd mainly west of S 80th Ave
Road damage information for February 1995 and February 1996 floods indicate that the
greatest impacts due to flooding of Wide Hollow Creek occur west of S 80th Ave and then in
the Union Gap city limits. It is unclear whether this observation is due to a lack of
information along Wide Hollow Creek west of S 80th Avenue. Alternatively, lack of
development in this area combined with a more natural stream channel may prevent severe
damage to the area east of S 80th Ave.
Southwest Yakima
90 degree turn of Ahtanum Creek at S 42nd
Ahtanum Creek was diverted from its original channel to follow a ridge to facilitate water
conveyance for irrigation. The creek follows this ridgeline until it intersects S 42nd Ave. The
creek flows under the road, takes a 90 degree turn south, and continues along S 42nd Ave
until it rejoins the original stream channel. The area described experiences frequent
overbank flow at the 90 degree turn, causing floodwaters to travel as a sheet eastward
through a residential neighborhood. There are reports of undersized and damaged culverts
6 1 Ahtanum-Wide Hollow CFHMP
and ditches along Emma Lane and intersecting roads. The abandoned Shopshire ditch
conveys flood flow through several properties in this area, which then collects at S 39th Ave
and causes backwater flooding because no structures exist under S 39th Ave to provide flow
through. Yakima County applied for a grant from the Washington Hazard Mitigation Grant
Program in 1997 to create an alternate channel for Ahtanum Creek that is more closely
aligned with what is thought to be the natural channel. However, the grant was not
awarded.
The residential community near Emma Lane also experiences flooding from Hatton Creek
and Bachelor Creek. Hatton Creek forks from Ahtanum Creek downstream of the Mission.
The creek conveys additional flow during floods that escapes over banks of Ahtanum Creek
just upstream of the Mission. Bachelor Creek accepts some flood flows at the AID diversion
in attempt to mitigate against flooding on Ahtanum and Hatton Creeks. Overbank flow near
the Ahtanum Mission also contributes to flow in Bachelor Creek. Lack of adequate
freeboard under bridges at S 42nd Ave and Ahtanum Rd causes overbank flow which travels
through the property between Ahtanum Rd and Emma Lane. See comments no. 131-139,
144-152, and 156-166 in Appendix F, Table 1.
Misaligned bridge at Ahtanum Rd and Bachelor Creek.
The bridge on Ahtanum Rd near S 38th Ave frequently causes flooding of nearby properties
due to its alignment. The bridge is not oriented perpendicular to flow and water must make
two sharps turns to remain within the creek banks. One property in this vicinity is a repeat
claims property that has experienced flood damage many times. In addition, erosion of the
creek banks near the bridge has been reported. See comments no. 135, 150, 153, and 154 in
Appendix F, Table 1.
Incorrect FEMA mapping.
Residents southeast of the Ahtanum Creek Bridge at Ahtanum Rd frequently receive
damaging flood waters. These properties are not mapped in the 100 -year floodplain and
therefore are not required to obtain flood insurance. At least one property in this area does
have flood insurance and is a repetitive loss property. See comments no. 108 and 149 in
Appendix F, Table 1.
Yakima/Union Gap
Flooding on Wide Hollow Creek near S 16th Ave
Wide Hollow travels behind Perry Technical Institute near Washington Ave, across the road
from the regional airport. The stream channel is perched and incised due to levees identified
through review of LiDAR imagery and field reconnaissance. Placement of riprap along one
bank is indicative of the need for stabilization in the channel. Flooding was reported
downstream of Pioneer Avenue near East Valley Mall Blvd. The bridge at Pioneer Lane and
Wide Hollow Creek is scheduled for removal in 2007. Reports indicate this bridge becomes
caught with debris during flood periods. Reports also indicate flooding of the bridges on S
16th Ave is frequent, but the road is scheduled for removal due to the new East Valley Mall
Blvd and Federal Aviation Administration regulations. Flooding of part of the runway
Appendix C - FLOOD PROBLEMS BY WATERSHED AREA 17
occurs when Spring Creek West and Bachelor Creek overflow their banks. See comments no.
122, 123, 176, 190, 199, and 200 in Appendix F, Table 1.
Parks serve as storage of floodwaters
Fulbright Park near the mouth of Ahtanum Creek frequently experiences flooding due to
floodwaters in the Ahtanum Creek as well as backwater flooding from the Yakima River.
There are no threatened residences in this area and the park has been seen as a means of
good floodplain management because it can serve as a place to store floodwaters. The
stream upstream of the park but downstream of Goodman Rd was re -channelized in the
early part of the Century for irrigation use. Re-channelization of the creek may exacerbate
flooding in Fulbright Park due to increased flow velocity. See comments no. 183, 195, 197,
205, and 206 in Appendix F, Table 1.
Goodman Rd floods just downstream of Bachelor Creek and Ahtanum Creek confluence
Numerous reports indicate flooding occurs on Goodman Rd at the Ahtanum Creek bridge
crossing. Bachelor Creek rejoins Ahtanum Creek just upstream of this bridge. Lack of
adequate freeboard to carry water and debris from large flood events causes flooding over
the roadway in vicinity of the bridge. See comments no. 185, 210, and 211 in Appendix F,
Table 1.
Wide Hollow Creek Impacts to Downtown Union Gap
Residents reported numerous conveyance problems and levee failures in the City of Union
Gap during flood periods. Union Gap is subject to flooding even at low flood elevations,
especially near Main Street. Union Gap is near the mouth of Wide Hollow Creek and
Ahtanum Creek. Wide Hollow Creek just west of the intersection of 4th St and White St
makes a 90 degree turn around a residential property boundary. Upstream and downstream
of the 90 degree turn, Wide Hollow Creek follows a straight channel. During flood events,
overbank flow often occurs at this turn and floods residences in downtown Union Gap.
However, upstream of the railroad tracks there is a floodgate that can alleviate flooding in
Union Gap by storing water in the fields to the west. See comments no. 180, 208, and 209 in
Appendix F, Table 1.
Spring (Chambers) Creek East floodgate issues
Spring (Chambers) Creek East currently forks from the Yakima River east of Ahtanum Rd
on the east side of Interstate 82 and flows into Wide Hollow Creek close to the I-82 and
Highway 97 interchange. The Spring (Chambers) Creek channel was altered when I-82 was
built and previously flowed directly into the Yakima River, not Wide Hollow Creek.
Floodgates were placed where Spring Creek East travels under the I-82 as well as just
upstream of where it joins Wide Hollow Creek. A small channel diverted water from Spring
(Chambers) Creek eastward back under I-82, through the second flood gate (flapper gate).
Both floodgates have been closed since January 28, 2003 and flooding has since not been a
problem. However, during flood events when the upstream gate was open, flood waters
from the Yakima River would enter Spring (Chambers) Creek through the floodgate and
cause severe flooding in downtown Union Gap. With the two gates now closed, only the
8 1 Ahtanum-Wide Hollow CFHMP
500 -year event, which would overtop the Interstate, would impact Spring (Chambers)Creek.
Although the floodgates have been closed for more than two years, a permanent closure
agreement does not exist and opening of the gates may be ordered to allow for fish passage
in Spring (Chambers) Creek. See comments no. 192 and 201 in Appendix F, Table 1.
Backwater from Wapato Dam into Ahtanum and Wide Hollow Creeks
The Wapato Dam in Union Gap on the Yakima River is a diversion project that diverts
water to the Bureau of Indian Affairs irrigation canal. During extreme flood events, the
debris collects behind the dam, causing floodwaters to back up in the Yakima River.
Backwater flooding can continue up into Ahtanum Creek and impact downtown Union
Gap.
There are plans for upgrading the Dam to stabilize the region and more easily pass
mobilized debris during flooding.
Wide Hollow Creek fish bypass near old mill
A bottleneck occurs on Wide Hollow Creek at the site of the old mill on Main Street. As a
result, overbank flow can occur upstream due to the flow backup. Also contributing to flow
back up is debris clogged behind the Main Street Bridge. The bridge has little freeboard
even during average flows. The channel is perched west of Main Street and overbank flow
travels by gravity to neighboring businesses. Eakin Fruit Company has reported frequent
flooding. See comments no. 198 and 207 in Appendix C, Table 1.
Inundated Sewage Lift Stations
There are two sewage lift stations in Union Gap which transport wastewater to the
wastewater treatment plant. These lift stations become inundated during extreme flood
events, causing discharge of wastewater directly to the Yakima River.
Appendix C — FLOOD PROBLEMS BY WATERSHED AREA 19
APPENDIX C
Table 1 Comprehensive List of Flood -Related Comments
Note: Any comments pertaining to proposed causes or solutions to problems were provided by the workshop participants and people
interviewed at the beginning of the CFHMP process and were not verified.
See Chapter 2 maps for approximate locations
Number
Geographic area
Comment
1
Ahtanum
Where John Cox diverts, bridge plugs with log debris causing log -jams. 1996 - Big flood
washed road out east of bridge. Bridge has no clearance. Bridge designed in 1974. 350 people
upstream of bridge in NF. Eroded bank on downstream side of bridge. Held up bedload. Takes
out bank.
2
Ahtanum
Home just downstream from bridge, other side of John Cox. Erosion on property when bridge
plugs up. Noticeable erosion.
3
Ahtanum
Culvert at bottom of wash plugs up from gravel, comes up road and flows toward home. Lots of
snow that melts fast from rain on snow events. Water on road freezes and creates driving
hazard everytime water on the road. County has to fix drainage. See digital photos he provided.
4
Ahtanum
Next bridge above John Cox diversion site, just upstream of John Cox ditch. Bridge jammed
with debris and gravel, caused bridge to backup and wash out.
5
Ahtanum
Logged area. Left lots of debris in the channel.
6
West Valley South
50 yards + or - downstream of bridge, creek bed shallow. Water overtops and goes down
Rutherford Road. Creek had choked for 600-800 ft downstream of the Mission.
7
Ahtanum
1.5 miles of stream adjacent to road totally blew out; Plum Creek and DNR mitigated it.
8
Ahtanum
Bedload dropped out right above the road; mitigated.
9
Ahtanum
Too small of a culvert; put one in; replace with larger pipe.
10
Ahtanum
Sediment came into slack area. Deposited bedload. Relocated road back to the bench.
11
Ahtanum
Big culvert; small stick backed up debris. Has been armored but needs to be replaced. County
road.
12
Ahtanum
Beaver pond by pit; ice jam created debris flow; almost knocked house off foundation.
13
Ahtanum
Evacuation near John Cox Ditch, Nov 2003. County road almost blown out. County road
parallels creek for 0.25-0.5 mi and restricts creek. Minimal damage from Foundation Creek.
14
Ahtanum
3 bridges. Volume coming down took out approach. 2 bridges need barbs. Series of small
channels.
10 Ahtanum-Wide Hollow CFHMP
Number
Geographic area
Comment
15
Ahtanum
This creek contributes fresh bedload to SF, blows out culvert and road. Probably could replace
culvert.
16
Ahtanum
Creek confined at this location, undercuts Ahtanum Rd, damages property and infrastructure.
High likelihood of avulsion through property owner's land at this location.
17
Ahtanum
North Fork Bridge probably too small, stream alignment also very bad (John Cox diversion here
as well). During floods stream channel aggrades. Massive LWD piles up against abutment,
decreasing conveyance through the bridge further causing more aggradation.
18
Ahtanum
Series of new private bridges that constrict the channel and may fail during any flood.
19
Ahtanum
Log jam (2 in past), builds up water to flow over road, typically breaks, releasing flows.
20
Ahtanum
The Narrows, road washes out, County knows all about it.
21
Ahtanum
Property owner put jersey curbs along property to hold water back. County was not happy
about curbs but they had already been installed. Indication of flooding problems at the South
Fork.
22
Ahtanum
Log jam, 1 mile from Tampico park. Built up private bridge.
23
Ahtanum
Driveway just west of bridge gets washed out. Happened in 2003 (small event) and 1996. Both
incidents required yards of shale and hours of repair.
24
West Valley - North
1/2 mile upstream, owner thought it would be neat to let creek meander, and diverted it so it
jumped bank and Wide Hollow Rd on 1/1/03. No ditch on inside corner of "S" curve, so water
puddles onto roadway. Culverts under driveways weren't large enough on west side of road to
carry water away. Flood picked up manure from pasture - very dirty. See photos on CD and
video.
25
West Valley - North
Owner put 2 4' culverts side by side under road (perpendicular to Wide Hollow) that didn't used
to be there. Road was built up to act as dam and culverts weren't big enough.
26
West Valley - North
Willows and debris just upstream cause diversions onto her property. Owner upstream illegally
put rip rap and was required to remove it and couldn't put it back. That rip rap helped many
neighbors. County bridge on Wide Hollow Rd upstream gets dammed up with debris, which
sends water around bridge on both sides. Some homes still have sewage piped right into the
creek, which is a health hazard.
27
West Valley - North
Cottonwood Creek flowing more than Wide Hollow
28
West Valley - North
Build up driveway with narrow bridge at NE end. New houses after 1985 flood (-20).
29
West Valley - North
Stein Rd used to be gravel with a dip in it that let water over the road that came out of course
where bridge takes a 90 degree turn. County has since raised road and installed a 36" culvert -
too small (has pictures of dip in road).
Appendix C — FLOOD PROBLEMS BY WATERSHED AREA 111
Number
Geographic area
Comment
30
West Valley - North
Two houses built in this area. New started in July. Stick and frame and manufactured home.
Water already under them now.
31
West Valley - North
Dug out creek after 1985 flood.
32
West Valley - North
Area filled in with gravel in the channel.
33
West Valley - North
Property owner would not let them dig out channel so that recently the high flows jumped out of
the channel. Other property owners got together and dug out the stream channel but she would
allow it.
34
West Valley - North
Has a home in this area. Home had 2 feet of water during the last spring flood.
35
West Valley -North
Culvert was put under driveway of group of homes. Culvert gets plugged frequently and causes
flooding. They mentioned a woman who floods all the time.
36
West Valley - North
Somewhere in this region, they think the stream has been routed out of its original channel.
37
West Valley- North
Water jumps creek around the bridge and floods around barn and house.
38
West Valley - North
Used to be a holding pond where waters get high. People moved in and diverted water.
39
West Valley - North
Brown trout, used to fish and nothing alive anymore. It seems that it's just used for flood
control. If we could get a way to get a living stream, by anchoring logs, etc. it would be fine.
40
West Valley - North
Clear out bridge, County bridge Wide Hollow.
41
West Valley - North
Big Chinook, very rarely draw floods. Connects water to Wide Hollow. 1974 was "the last" time
it happened.
42
West Valley - North
Bad sediment transport at culvert.
43
West Valley - North
Chronic channel migration in denuded pasture
44
West Valley - North
Bad culvert, bank erosion downstream, flooding.
45
West Valley - North
Spill from Congdon Ditch enters here, making the hydrology of the Wide Hollow inverted,
driving loss of Cottonwoods, to be replaced by Pacific Willow. The willow produces large
amounts of debris which is mobilized during floods and catches on fences and bridges.
46
West Valley - North
Flood waters that overtopped banks upstream travel down roadside ditch at "S" curve and
erode the ditch at its confluence with the creek just upstream of the bridge. Photos
47
West Valley - North
Upper part of "S" curve does not have a ditch on the inside of the curve. Water easily moves
over roadway and floods residences. Ditch out front of one property was dug very deep during
last big flood and she thinks this is why her property did not flood in '96.
48
West Valley - North
Bridge is undersized and rip rap is in place for stabilization of banks. Photos
49
West Valley - North
Debris placed along right bank as a berm. Photos
12 Ahtanum-Wide Hollow CFHMP
Number
Geographic area
Comment
50
West Valley - North
Low clearance. Side ditch coming in upstream of bridge. Debris downstream. No homes nearby
to worry about. Photos
51
West Valley - North
Low clearance. Rip rap upstream. Photos
52
West Valley - North
Abandoned diversion took off 100 yards east of bridge; 2 pieces of steel fencing put in to assist
dam and never removed; fish bypass put in and part of diversion removed. Beavers in area.
Note: location unknown.
53
Ahtanum
Pacific Power is losing a pole from erosion 100' below John Cox Ditch.
54
Ahtanum
Bridge 6 miles up North Fork. Bridge clogged up with debris and washed out road abutment.
Issue with cutting a path at road, erosion problem.
55
Ahtanum
Beaver dam. Large jam causes backwater. On other side of creek, erosion and digging out of
channel. 6 miles upstream of John Cox Ditch.
56
Ahtanum
Bridge plugged with debris. Backwater from the jam floods our road, leading to erosion
problem. Jam collected them broken loose carrying erosion. Depends on size of logs and flows
(mostly dead trees). NF next bridge upstream.
57
Ahtanum
Beaver dams in area, whole drainage area. Upper Ahtanum Creek area.
58
West Valley - South
Below culvert, very shallow. Flows through Christmas tree farm from Rutherford Rd
59
West Valley - South
Bedload problem (gravel) - creek plugs, causes flooding to home.
60
West Valley - South
Have many beaver dams. Beavers are digging into dikes and causing leaks in dikes.
61
West Valley - South
Dike built by County dumps water into the irrigation diversion. Irrigation ditch overtops.
62
West Valley - South
Beaver dams flood field.
63
West Valley - South
No channel and water spreads out.
64
West Valley - South
Aggradation at Hatton diversion.
65
West Valley - South
Bridge is in bad alignment with creek and fish screen is catching debris and not passing debris.
66
West Valley - South
Repeated chronic stream erosion during flood events.
67
West Yakima
Put railroad ties on flood wall around property. 1964 thigh high, about 2 ft. Snow 23 inches in
Yakima, next morning it all melted. 1973 to bottom of car doors. 1976 about the same. 1995
and 1996 have video.
68
West Valley - South
In 1996, water overflowed onto Meadowbrook Rd. Flooding also came from McCullough side
(from north). Debris in channel is a big problem. Winds cause branches of trees to come down
and debris collects in channel. Creek floods frequently. Gates (irrigation?) left open upstream
(she heard). Culverts are small and partially buried. Water seeps into ground to the east of
101st (it does not visibly flow back into creek). Photos provided.
Appendix C — FLOOD PROBLEMS BY WATERSHED AREA 113
Number
Geographic area
Comment
69
West Valley - South
Their main concern is the proposed dam. Some are saying that there are flood controls benefits
to the reservoir (documents from DOE). They are interested in non-structural improvements in
the area.
70
West Valley - South
Homes built between channels are threatened by beaver dams and ice jams.
71
West Valley - South
Redesigned drainage pipe.
72
West Valley - South
Irrigation gate was hit by snowplow. Debris in channel. AID trying to get permits for cleaning
entrances to headgates as part of maintenance. Half mile upstream many beaver dams.
73
West Valley - South
Little shed is island during flooding. Flood water coming down road goes back into creek here.
Channel/bedload movement is significant problem.
74
West Valley - South
Where water jumps creek banks. Homes have not been flooded but backyards have been.
75
West Valley - South
During 2003 flood, water on either side of bar ditch and all around house. Road replaced from
bridge to end of road.
76
West Valley - South
Low area where flood waters add to Bachelor Creek at Lynch Ln.
77
West Valley - South
Bedload deposition in creek causing water to jump banks near rock pit.
78
West Valley - South
In September 1997, Yakima County submitted a grant to the Hazard Mitigation Grant Program
to create overtopping structures at west end of road to control flows. Additional control
structures would be placed along the road. Not funded.
79
West Valley - South
Key to routing of flood waters down Bachelor and Hatton creek. Irrigation diversions and
conversion of stream channel make this area unstable and unpredictable. Channel is aggraded
downstream of Mission, resulting in routing of water down Hatton.
80
West Valley - South
Creek illegally rerouted to the south in this area, comes unglued during floods and threatens
new expensive homes along creek.
81
West Valley - South
Chronic flooding from Hatton, damages the road and access to driveways at relatively low
flows.
82
West Valley - South
High flows flood Meadowbrook Road and areas upstream, road, culverts, irrigation
infrastructure all damaged by fairly low floods.
83
West Valley - South
Constrictions, erosion of roads, driveway culverts, plugging by debris, etc.
84
West Valley - South
Bridge alignment pushes channel flow to left bank; during floods water overtops and floods
west field; fence catches debris. Bridge built in '96/'97 by Bureau, gives access to property
across creek (WIP diversion); before '96, this flood area was not an issue.
85
West Valley - South
Above AID diversion, LB blows out at every flood event. Rip rap structure placed upstream
supposed to direct flow away from AID, but doesn't work at high flow. Photos
14 Ahtanum-Wide Hollow CFHMP
Number
Geographic area
Comment
86
West Valley - South
Fish bypass structure at lower end is becoming dry because channel is moving away from it
(toward RB). Photos.
87
West Valley - South
Right bank above bridge crossing is eroding due to altered flow upstream. Photos.
88
West Valley - South
Water jumps banks upstream of driveway and floods out west field as well as blows out
driveway. Photos
89
West Valley - South
Ahtanum jumps banks below Mission and can go into Hatton Creek. Trying to prevent water
from going into Hatton. Photos.
90
West Valley - South
Debris and sediment on inside of turn in stream, under bridge. Photos
91
West Valley - South
Rip rap both upstream and downstream of bridge. Bridge undersized. Photos
92
West Valley - South
Clogged with debris, so cannot be used to relieve Ahtanum from flood flows.
93
West Valley - South
Runoff from snowmelt plugging culverts causing damage, for example at S Wiley Road. Debris
off slope is plugging ditch because there is not conveyance across ditch.
94
West Valley - South
Rutherford Road becomes conveyance. Water jumps out of creek downstream of the Mission
and at Lynch Road.
95
West Valley - South
Culvert plugs with road debris (asphalt and gravel). 90 degree angle for stream and ice jams,
causes creek to jump banks. Different grades on both roads after 1996, creates creek dam.
Bridge still not cleared after 1996 flood.
96
West Valley - South
Driveway culverts too small during floods (too large when dry).
97
West Valley - South
No creek banks or channel on Hatton upstream of her site, water comes to bank by her
property and collects. She has flooding in her basement.
98
West Valley - South
Before 1996, property owner changed channel for creek and have had problems since.
99
West Valley - South
S Marks Rd acts as a creek dam.
100
West Valley - South
Changes all the time; creek "on mtn"; channel never cleaned out.
101
West Yakima
Berm is degraded. During flood, water goes over and backs up toward house. West Yakima
Valley Community park berm was lowered on the other side. Beaver damage.
102
West Yakima
Culvert degraded on runoff ditch.
103
West Yakima
In 1994, County took them out of the flood plain. Sent a letter saying they were no longer
requiring flood insurance. Flooded in 1996.
104
West Yakima
Property owner has a bunch of stabilization permits for this area.
105
West Yakima
Developer plans development - 700 homes.
106
West Yakima
Bridge at S 91st is plugged with gravel. Property owner opens up his fence to let the water
through on the south side of the bridge to let water go through.
Appendix C — FLOOD PROBLEMS BY WATERSHED AREA 115
Number
Geographic area
Comment
107
West Yakima
Built a berm to keep the water off their property and put it back into the creek.
108
West Yakima
Bridge has 2 feet of freeboard. Beaver downstream and just beyond fruit warehouse. Little
house has made repetitive claims and has collected from FEMA four or so times. Have not
lifted their home or taken other measures.
109
West Yakima
New subdivision in the hole, been there after 1985 (5-6 years ago).
110
West Yakima
Water from Shaw Creek and Wide Hollow Creek.
111
West Yakima
Place to let water out of channel, goes through baseball diamonds.
112
West Yakima
Little creek came from SW and flowed over Washington and flowed up 64th and flooded
subdivision. Sandbagged from intersection to the west. Also dug ditch to let water out at Terry
Ave.
113
West Yakima
On west side of warehouse, property owner has bermed up the property to keep things dry, so
it shoves water across road onto another property. They rebuilt the warehouse and took the
culverts out, which sends more water across the road.
114
West Yakima
Water jumps out of creek when it's north of Wide Hollow Rd and hits property to the east.
115
West Yakima
Rough alignment of Shaw Creek (needs to be proposed in the CFHMP).
116
West Yakima
Shaw Creek undersized and perched, causing flooding of mobile home park.
117
West Yakima
Shaw Creek flooding caused by conversion of creek to irrigation ditch and re-routing across the
alluvial fan.
118
West Yakima
Out of bank flooding due to constriction, fences capturing debris.
119
West Yakima
Chronic flooding area - the dike that protects the apple warehouse across the creek forces
flood waters here - the bridge downstream is probably undersized as well.
120
West Yakima
Future land use issues with the conversion of Congdon properties.
121
West Yakima
Area where new airport/industrial development could be subject to flooding.
122
West Yakima
Bridge at Wide Hollow has pump station and water conveyance system; photos.
123
West Yakima
Upstream of bridge on WH, lots of debris; rip rap indicates bank needed stabilization. Further
upstream of bridge, levee on either side causing channelization; eroded RB levee;
downstream stream takes right turn, where rip rap is stabilizing LB. Photos
124
West Yakima
New development WH creek banks are low; looks like potential flooding at new development.
Photos.
125
West Yakima
Generally more natural channel. Photos.
126
West Yakima
Debris placed along right bank as a berm. Photos.
16 Ahtanum-Wide Hollow CFHMP
Number
Geographic area
Comment
127
West Yakima
Property owner wants to develop property and be mapped out of floodplain. She thinks
development upstream is diverting water from creek. Photos.
128
West Valley North
Cul de sac across street has culvert that plugs. Asked City to take care of culvert but they said
no because it was not part of their jurisdiction.
129
West Valley North
Bar ditch along Wide Hollow Rd not deep enough so overflows Wide Hollow Rd. Duct work
under house was lost. Photos of damage are on CDs along with video of news reel. Neighbors
involved started talking about putting in larger culverts under driveways but got conflicting info
as to who should (could) do the work.
130
West Yakima
Beaver dams on Wide Hollow Creek.
131
Southwest Yakima
8.9 acre ranch on west side of 34th Ave. 2 houses. Lower house had 3ft of water during 96
flood. Built retaining wall around 3/4 of house. Didn't work because 2003 flood, water came
from Bachelor Creek instead of Ahtanum Creek.
132
Southwest Yakima
Ditches on Emma Ln are not large enough, or do not exist. Culverts are not the same size and
sometimes too small. Water jumps over some of the gravel roads off Emma Ln.
133
Southwest Yakima
Flooding occurs at 34th and Emma. Water back up on west side of 35th.
134
Southwest Yakima
House at 42nd and Ahtanum flooded during 1996 flood at the bridge. Water overtopped the
bridge, flooding property.
135
Southwest Yakima
Bridge under Ahtanum Rd is not oriented perpendicular to creek flow. Creek must do sharp
turns to stay in channel. Creek overflows here and floods property.
136
Southwest Yakima
Flooding behind culvert.
137
Southwest Yakima
Overtopped road between Emma Ln and Meadow Ln. Water backed up behind culvert.
138
Southwest Yakima
Branches plug hog wire fence and Bachelor Creek flooded his property and others around him
in 1996. This was before he lived here and something he heard.
139
Southwest Yakima
Beaver dams causing water backup and flooding.
140
Southwest Yakima
Bridge washed out on Rutherford Rd, at S 79th or possibly a different location. She was not
sure.
141
Southwest Yakima
Culvert that passes Spring Creek does not pass flood flows. Water runs down road ditches
along Hatton and floods houses and driveways.
142
Southwest Yakima
East of bridge, willow reduces conveyance and causes backwater.
143
Southwest Yakima
Beaver dam in Hatton Creek causes flooding.
Appendix C — FLOOD PROBLEMS BY WATERSHED AREA 117
Number
Geographic area
Comment
144
Southwest Yakima
Property located on east side of 90 degree turn. Low point on property. Most flood water goes
NE toward his home, flooding west to east (low grade). Water in their pasture pretty much
every year (except 2004). Built dike with railroad ties (3 RR ties high) and made into flower box
to help divert water. The channel on S 42nd is in low area and overtops banks easily. Water
also goes through old channel. He increased his driveway culvert to 36". Did grade control for
erosion. Dike on east side of 90 degree turn was replaced once by Job Corps (about 20 years
ago in response to the 1974 flood) but has recently shown signs of degradation and leaking.
Debris in channel.
145
Southwest Yakima
Water over roadway during floods at this location.
146
Southwest Yakima
3rd home on the right. 90 degree turn in Ahtanum Creek at Emma Ln. Beaver dam fills up then
spills river bank floods. Fills up old ditch. WIP ditch spilled in 1996 and filled up back area. No
bar ditch in front of home to street. Culvert crosses under road and pushes water upstream and
under road. Not sure about flapper on culvert. Old Ahtanum Creek ran in alignment through
backyard. Creek moved in 1890s (long time ago). Ahtanum Creek flows down a piece of high
ground in its current alignment, perched above adjacent properties. County staff said, if
channel put through old channel, then need to widen bridge at 16th.
147
Southwest Yakima
Rapid snowmelt in WIP ditch flows into ditch and overloads it. Ditch gets more narrow as you
go downstream and eventually gets overloaded. 1996 was only time WIP ditch blew out.
148
Southwest Yakima
Check with news agency for pictures/videos of Emma Ln.
149
Southwest Yakima
Homes are all slab on grade, scraped off topsoil and poured foundation. Created low spot that
is slightly lower than everything else and gets these houses wet every time. All their houses are
in flood, but not mapped as in flood.
150
Southwest Yakima
At about 36th, where the creek crosses the street, there is a new bridge. It's the only new
bridge.
151
Southwest Yakima
42nd goes 90 degrees. Water floods fields - hits 42nd Ave and goes over dike (water cannot go
back into Ahtanum Creek) and floods down Emma Ln. Every 2-3 years water goes into the
ditches.
152
Southwest Yakima
Small culverts along the road cause water to back up. Not everyone maintains them.
153
Southwest Yakima
Water line put in. Bank often erodes out. Could have some problems if it breaks.
154
Southwest Yakima
Bridge is oriented in wrong direction. Flooding at bridge.
18 Ahtanum-Wide Hollow CFHMP
Number
Geographic area
Comment
155
Southwest Yakima
See statement for full story. Concerned about fill placed in floodplain on neighboring property
that impacted surrounding properties during flood; Concerned that SEPA process was not
adhered to and was not done thoroughly when neighboring property was developed. EIS on
neighboring property was not conducted because DNS was found. Looking for better
enforcement of codes, including SEPA. Property taxes increased even though he is in the
floodplain.
156
Southwest Yakima
Shopshire ditch used to go through her field but was abandoned when development went in.
East side of road, in distance, is where proposed development of 150 homes will go.
157
Southwest Yakima
S 42nd Ave at old Shopshire ditch. Headworks not near creek due to channel migration. Ditch
does not exist on other side of road - was smoothed out.
158
Southwest Yakima
Old channel of Ahtanum Creek and ditch diversion (diversion 6). Curve in creek has moved a
lot due to flood events.
159
Southwest Yakima
Beaver dam on Bachelor Creek causes flooding on right bank since left bank is higher than
right. Gillette spring feeds ditch on other side of their house.
160
Southwest Yakima
Stream restoration work. County is the planner; landowner; and AID is helping with project.
Placing rip rap, cleaning channel and making bank slopes more gradual.
161
Southwest Yakima
Garage gets flooded. No culvert under road. West side of road a lake when flooded.
162
Southwest Yakima
In September 1997, Yakima County submitted a grant to the Hazard Mitigation Grant Program
to create second channel to bypass 90 degree turn. Not funded.
163
Southwest Yakima
Floodwaters from Bachelor inundate this rapidly developing area.
164
Southwest Yakima
This whole area affected by the 42nd/Emma Lane problem. Water is routed from Ahtanum to
Bachelor and other portions of the floodplain.
165
Southwest Yakima
Bridge plugged easily and frequently.
166
Southwest Yakima
Flooding in front of property in 1974 because church put snow in ditch and therefore altered the
channel. Attorney - class action lawsuit against county for not maintaining culverts and ditches
in response to 1974.
167
Southwest Yakima
Rechannelized for irrigation; irrigation company can clean channel but property owners cannot.
Note: location unknown.
Appendix C — FLOOD PROBLEMS BY WATERSHED AREA 119
Number
Geographic area
Comment
168
Yakima/Union Gap
Water comes out of Emma Ln. Drain plugged at intersection. Backs up the storm drain. 18"
deep at corner intersection of Ahtanum and 16th. Water runs across street into storage units
and convenience store. Flows do not come from Ahtanum (down 16th). Flows get kicked back
down Ahtanum at 34th when the bridge plugs and cannot get water around the corner (bridge
is rotated at odd angle). In 2002, took 2 days to get the water from Emma Ln to 16th. Set up
barricades to block off road to drivers, which causes waves. Couldn't walk through water
because it was running too fast. Has lots of photos.
169
Yakima/Union Gap
Shortage of sandbags. Can't get enough bags.
170
Yakima/Union Gap
Kabota dealer pumped lots of water out of his property (it's a low spot). Knows lots of flooding
problems.
171
Yakima/Union Gap
Convenience store - water goes down 16th toward Ahtanum Rd (from south).
172
Yakima/Union Gap
Bridge fills with debris.
173
Yakima/Union Gap
Trailer court flooded in 1996.
174
Yakima/Union Gap
In 1996, entire area south of my residence was under water apparently from river backup;
came within a couple inches of flooding the mobile I had there; have since replaced the mobile
with one that sits higher. Planner at City of Union Gap has video of this.
175
Yakima/Union Gap
Worked at park in 1996 when park flooded. Water came from the west and south of park,
flowing east and north. Overflow from flooding on Ahtanum, west of 16th Ave. Several inches of
water in park.
176
Yakima/Union Gap
Channel incised, bank erosion, threatens homes and infrastructure in residential areas of Union
Gap and Yakima.
177
Yakima/Union Gap
Bridge undersized.
178
Yakima/Union Gap
Factory built in area of deep flooding in 1996.
179
Yakima/Union Gap
Spring Creek - management of Floodgate by County, management of stream channel under
Union Gap Critical Areas Code.
180
Yakima/Union Gap
Numerous problems with conveyance and levee failure in City of Union Gap. High hazard at
very low flood elevations, especially near Main Street.
181
Yakima/Union Gap
Very deep backwater in this undeveloped area when the Yakima River is in flood stage.
182
Yakima/Union Gap
Backwater from the Yakima.
183
Yakima/Union Gap
Some bank instability due to re -grade of the creek, probably from straightening in the early
1900s and backwater from the Wapato Dam.
184
Yakima/Union Gap
Goodman Rd. Backs up at bridge and runs/bridge undersized.
20 Ahtanum-Wide Hollow CFHMP
Number
Geographic area
Comment
185
Yakima/Union Gap
S. 3rd Ave. '70s - Washed out bridge. '96 - Not sure if it flooded. '99 - Widened existing bridge
and installed 2 or 3 box overflow structures.
186
Yakima/Union Gap
16th - 1 1/2 ft of freeboard on bridge - causing a lot of problems.
187
Yakima/Union Gap
Overflows onto Ahtanum - land overflow. Ran along the road in '96.
188
Yakima/Union Gap
Backs up on the North side of Ahtanum - was overflowing onto Ahtanum in 2003.
189
Yakima/Union Gap
Pioneer Ln. debris gets caught up on bridge. This bridge is scheduled for removal in 2007 with
Valley Mall Blvd. project.
190
Yakima/Union Gap
12th Ave. bridge - Union Gap keeps an eye on it. It has a lot of freeboard though.
191
Yakima/Union Gap
Greenway access - roadway floods.
192
Yakima/Union Gap
Freeway Ave. floods.
193
Yakima/Union Gap
1-82 is underwater in big ones.
194
Yakima/Union Gap
96 - 16th was shut down.l6th is scheduled to be closed because of the new Valley Mall Blvd.
and FAA regulations.
195
Yakima/Union Gap
Fullbright Park Rd. floods. Mostly from backup of the Yakima River. 4 out of 6 years (?). Really
aggrades if Ahtanum and Yakima are in flood stage.
196
Yakima/Union Gap
Sewage lift station- critical- very close call in '96.
197
Yakima/Union Gap
Smaller sewage lift station- often flooded.
198
Yakima/Union Gap
Old Water Mill - fish screen and ladder. More of a bottleneck.
199
Yakima/Union Gap
Levee at soccer park. Incised and straightened channel due to dike on LB. Photos
200
Yakima/Union Gap
Debris dam upstream of bridge; low banks could easily overtop at high flow; downstream of
bridge, there is backwater area. Next to channel is channelized irrigation ditch with no riparian
vegetation. Photos.
201
Yakima/Union Gap
Yakima R during high flows jumps banks into gravel pit ponds. Area unstable. Worried about
Yakima R water going into Spring Creek, which does not have the capacity for it; Flood gates
were closed Jan 28, 2003. Several drains go into Spring Creek. Photos.
202
Yakima/Union Gap
Drain pipe from Ahtanum Rd. Was supposed to be connected to pipe going under the highway,
but it was never connected.
203
Yakima/Union Gap
Spring Creek just south of property. Drains flow into creek. Water level has stayed fairly
constant since the upper flood gates were closed.
204
Yakima/Union Gap
Used to be held open by blocks, which cause flooding from Yakima R in '96. They have since
closed gate and it's no longer a problem. Property owner downstream is keeping water at high
level for flood irrigation purposes.
Appendix C — FLOOD PROBLEMS BY WATERSHED AREA 121
Number
Geographic area
Comment
205
Yakima/Union Gap
Park under water during 1996 flood on Ahtanum Creek due to WIP diversion backup. Photos.
206
Yakima/Union Gap
Sewage Lift Station under water during floods. Photos.
207
Yakima/Union Gap
Constriction in channel; not much clearance under bridge. Company gets flooded regularly due
to debris caught behind bridge and their parking lot is below channel level. Photos.
208
Yakima/Union Gap
Upstream of railroad crossing, there is a flood gate that is opened during high flows to flood
field to prevent flooding of neighborhood in Union Gap. Location not verified. Photos.
209
Yakima/Union Gap
Flood waters cannot make this 90 degree turn. Surrounding neighborhood floods. Water also
backs up in side channel, as evidenced by lots of debris. Stream banks are fairly high and
channel is straight. Photos.
210
Yakima/Union Gap
Goodman Rd experiences water over the roadway during high flows. Photos.
211
Yakima/Union Gap
Bridge clearance looks good, but Goodman Rd is known for water on roadway at bridge during
high flows. Right bank erosion downstream of bridge. Photos.
212
Yakima/Union Gap
End of runway floods. Piped water under runway. Spring and Bachelor Creeks overflow banks.
215
Yakima/Union Gap
Work will be done to expand dam. Worried about river going down canal during flood event, as
almost happened in 96. Channels above dam clog with debris halfway up the island. Photos.
216
Southwest Yakima
64th and Occidental. Drainage on County Road is not adequate. Ministorage business was
flooded as well as nearby subdivision. Water originates from Bachelor or Ahtanum (not sure
exact location) and flows North up 64th.
22 1 Ahtanum-Wide Hollow CFHMP
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APPENDIX D
DRAFT TECHNICAL MEMORANDUM
TO: John Knutson, Dianna Woods, Keelan McPhee, DATE: June 23, 2005
Yakima County
FR: Andreas Kammereck, Marketa McGuire, Golder OUR REF: 043-1238.340
Associates Inc.
CC: Mike Brown, Golder Associates Inc.
RE: • Deliverable 3.4, Assessment of the need for additional Channel Migration
Hazards Investigations in Ahtanum Creek and Wide Hollow systems
1.0 INTRODUCTION
This memorandum fulfills the requirements of the Task 3.4 deliverable addressing channel
migration hazards within the project area, as outlined in the Scope of Work for the Ahtanum
and Wide Hollow Comprehensive Flood Hazard Management Plan (CFHMP). Task 3.4
includes a review of existing information including studies and/or map resources, and the
determination of the need, or lack of need for additional channel migration hazard
assessments within the project area. This memo is not intended to provide a detailed review
of the geomorphic processes that govern channel migration. Several background documents
are provided as references that offer guidance in the technical aspects of channel migration
assessments (DNR, 2000), (DOE, 2003), (DOE, 2004). These references were utilized as
background resources for this assessment. This technical memorandum is focused on
developing an understanding for the need for additional investigation to address channel
migration hazard risks on the larger streams in the project area, including Ahtanum,
Bachelor and Hatton Creeks. Any additional investigations would be addressed in
subsequent phases of the Ahtanum/Wide hollow CFHMP. There are no plans for further
CMZ studies to be performed.
2.0 REVIEW OF EXISTING INFORMATION
In general, a channel migration zone is defined as an area within the river corridor that a
stream or river system has occupied historically, and where it is susceptible to erode or
occupy within a given timeframe (DOE, 2003). Channel migration can occur through
gradual lateral erosion and/or by more sudden changes in channel alignment called
avulsions. In both cases, historical evidence of the potential for continued channel migration
can be assessed through field investigations and review of existing available data (i.e.
2I
Ahtanum-Wide Hollow CFHMP
historical aerial photos, LiDAR data, surveys, anecdotal information, photos, etc.). Channel
migration is more apparent on larger river systems with more extensive active floodplain
areas. Channel migration zones appear as a complex topography of gravel bars, multiple
elevation floodplain surfaces, historical channel alignments, back -channel areas, swales and
ox -bows. Woody debris often plays a major role in channel migration and can govern the
movement of the channel across or outside of the active floodplain area.
The larger stream systems within the project area, including Ahtanum Creek, Bachelor
Creek, Hatton Creek, Wide Hollow Creek, Cottonwood Creek, and Spring Creek, do not
exhibit the characteristics of a larger river system with larger flow and sediment regimes,
such as the Yakima and Naches Rivers. The major streams in the project area are Ahtanum
Creek, and its two tributaries: Bachelor and Hatton Creeks. These three streams are
relatively small during normal and low -flow periods. The floodplain within the project area
is very complex due to flat and varied topography. Prediction of floodplain inundation
areas is difficult at best, and the current floodplain maps are widely recognized as being in-
accurate and/or not representative of the recent flooding conditions. Although floods in
these systems can quickly jump their banks, occupy old channel or irrigation ditch
alignments and inundate wide reaching areas throughout the project area, they do not
typically avulse into new channel alignments. That said, there are numerous historical
occurrences where flood flows have occupied road -way ditches and/or historical channels,
leading to significant erosion damage. In most cases after these events, the channel has been
re -located to pre -flood alignments.
The Bachelor and Hatton Creek systems are managed for irrigation and provide conveyance
for downstream purveyors throughout the project area. The project area has numerous
active and historical drainage and irrigation ditches/streams cross the valley floor. Irrigation
management of flows out of Ahtanum Creek have been active since the valley was settled
and developed for agriculture. As such, there are numerous old channels and drainage
ditches throughout the project area. The oldest record of the irrigation system are a series of
maps from the Ahtanum Irrigation District (AID) archives. The maps are very old paper
reproductions of the originals from 1905 that are approximately 4 feet high and as much as
14 feet long, and show the network (at that time) of drainage ditches and streams
throughout the Ahtanum valley.
The Ahtanum Creek channel has often been moved historically due to agricultural or
residential development. Several examples of areas where the channel has been relocated to
property boundaries or re -directed to facilitate drainage to agricultural land were identified
during the public meetings and in subsequent inventory activities as a part of the on-going
CFHMP. An example on Ahtanum Creek is at Emma Lane at S 42nd Avenue, where the
channel has been moved to facilitate irrigation flows, leaving the historical channel lowland
area subject to flooding. These types of locations inherently offer the potential for channel
migration hazards during peak flow events.
APPENDIX D — GOLDER CMZ MEMO 13
Public comments indicate there are two locations on Wide Hollow Creek where the stream
channel may have been altered for irrigation purposes, diversion around a property
boundary, or other reasons. Upstream of the "S" curve on Wide Hollow Road there are
reports that the Wide Hollow Creek has been rerouted. Additionally, Wide Hollow Creek
just west of downtown Union Gap make a 90 degree turn which follows the property
boundary of a private residence. Above average flow may cause the channel to migrate in
this area.
Shaw Creek, a tributary of Wide Hollow Creek in the north end of the project area, was
historically rerouted and used as conveyance for irrigation. The channel makes a 90 degree
turn as it meets S 80th Ave and crosses under the road through a culvert oriented
perpendicular to the road before it joins Wide Hollow Creek. Shaw Creek is mainly
comprised of irrigation return flows and is often dry due to diversion withdrawals. Unless
the creek conveys unusually high flows, no channel migration hazard is identified.
Yakima County completed an assessment titled "DRAFT, Channel Migration and Avulsion
Hazard Analysis for selected Shoreline Streams in Yakima County (2004)". Refer to this
document for more detail on the means and methods of the channel migration hazard
delineations. The assessment looked at channel migration hazards in the following
river/stream systems:
• Lower Yakima River, Wapato Reach, Union Gap Reach, and Selah Reaches,
• Ahtanum Creek — Main channel, North Fork, and South Fork Reaches,
• Naches River at the Mouth, the Lower Reach, Middle Reach, Lower Rattlesnake & Nile
Valley, and Upper Reaches,
• Bumping River.
The Ahtanum Creek portion of the assessment is most applicable to the Ahtanum/Wide
Hollow CFHMP, and was therefore the focus of this review. The County's assessment of
channel migration hazard in the mainstem Ahtanum Creek indicates that the channel has
been fairly stable over the course of the available period of record, with actively migrating
zones limited to areas adjacent to the main channel. The mainstem is disconnected from the
Yakima River floodplain by urban development and transportation infrastructure (Yakima
County, 2004). The mainstem generally has a single thread morphology that is heavily
influenced by irrigation management and adjacent land use activities. Irrigation
withdrawals throughout the reach have limited the occurrence of channel governing flows
to only the largest flood events (Yakima County, 2004). The decreased occurrence of channel
governing flows has therefore limited the transport of sediment through the system, in some
cases leading to aggradation within the channel between peak flows, and erosion problems
during peak floods. Riparian vegetation has been removed in overbank areas along the
main channel, increasing the risk of bank erosion (Yakima County, 2004). Channel migration
zones are limited to topographic low elevation areas, areas of recent instability due to bank
4 I Ahtanum-Wide Hollow CFHMP
erosion, and specific known problem locations. Identified channel migration zones occupy
approximately 26 percent (i.e. 756 acres) of the FEMA defined 100 -year floodplain. Thirty-
five percent of that area (i.e. 267 acres) is within the FEMA defined floodway. The active
channel comprises approximately 132 acres of this area. In general, the channel migration
zone is slightly wider in area than the FEMA defined floodway.
The North and South Forks of Ahtanum Creek have more limited available data than the
mainstem. Channel gradients transition from steeper upper basin areas to flatter valley
bottom gradients where they meet the mainstem. This leads to deposition of entrained
sediments, exacerbated by increased agricultural and residential development and historical
bank stabilization activities. The North Fork has numerous constrictions on the channel
where private landowners have installed stream crossings to gain access to properties (DOE,
2004). The South fork has similar problems, but is less populated. These locations often have
problems with debris accumulations, leading to bank erosion and damage to stream
crossing structures. In general, the North and South Forks are constrained by the valley and
experience bank erosion during peak flows, but have limited channel migration hazard
potential.
3.0 SUMMARY
The Ahtanum Creek, Bachelor Creek, and Hatton Creek systems have the potential for
channel migration hazards where the channel has been moved or re -aligned to facilitate
historical agricultural and/or residential development, and there are limited locations where
sediment accumulations are leading to overbank flooding and increasing the risk of bank
erosion. These streams do not exhibit the broader active and dynamic floodplain
topographies that are commonly seen in larger river systems. But, the same geomorphic
principals still apply, and can be used to develop an understanding for future potential
migration hazards.
The general flooding characteristics throughout the project area were well documented
during the public meetings and subsequent inventory work. Based on this information,
there does not appear to be a broad scale risk of channel migration hazards in Ahtanum,
Bachelor, or Hatton Creek systems that requires extensive continued technical
investigations. Where specific site issues have been identified as having historical problems
with bank erosion and/or channel changes, they will be addressed on a site -by -site basis
during the alternatives analysis phase of the CFHMP. An appropriate level of investigation
will be completed at that time to characterize the risk and develop recommendations either
for further study of the problem, or to support the development of mitigation strategies. We
do not therefore see the need to complete a basin wide comprehensive channel migration
assessment within the Ahtanum/Wide Hollow CFHMP project boundaries. We recommend
that any additional investigation can be addressed on site -by -site basis.
APPENDIX D — GOLDER CMZ MEMO 15
4.0 REFERENCES
(DNR, 2000), "Standard Method for Measuring Physical Parameters of Stream and Channel
Migration Zones", Department of Natural resources Forest Practices Board, 2000.
(DOE, 2003), "A Frame work for Delineating Channel Migration Zones", Department of
Ecology Publication #03-06-027, C.F. Rappe, T.B. Abbe, November 2003.
(DOE, 2004), "Ahtanum Creek Watershed Assessment", Submitted to the Washington State
Department of Ecology by Golder Associates and Fitch and Marshall, Inc., Document # 023-
1167.2300, 2004.
(Yakima County, 2004), "DRAFT, Channel Migration and Avulsion Hazard Analysis for
selected Shoreline Streams in Yakima County (2004)"
6 I Ahtanum-Wide Hollow CFHMP
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APPENDIX E
Table 1 Preliminary Field Work
NOTE: Information was collected from personal interviews during initial fieldwork - comments were not verified.
Number
Meeting Date
Structure
Description
85
March 29, 2005
Diversion
Above AID diversion, LB blows out at every flood event. Rip rap structure
placed upstream supposed to direct flow away from AID, but doesn't work
at high flow. Photos
92
March 28, 2005
Diversion
Clogged with debris, so cannot be used to relieve Ahtanum from flood
flows.
86
March 29, 2005
Fish bypass
Fish bypass structure at lower end is becoming dry because channel is
moving away from it (toward RB). Photos.
87
March 29, 2005
Bridge
Right bank above bridge crossing is eroding due to altered flow upstream.
Photos.
84
March 29, 2005
Fence
Bridge alignment pushes channel flow to left bank; during flood water
overtops and floods west field; fence catches debris. Bridge built in '96/97
by Bureau, gives access to property across creek (WI P diversion); before
'96, this flood area was not an issue.
90
March 31, 2005
Bridge
Debris and sediment on inside of turn in stream, under bridge. Photos
91
March 31, 2005
Riprap; bridge
Rip rap both upstream and downstream of bridge. Bridge undersized.
Photos
48
March 31, 2005
Riprap; bridge
Bridge is undersized and rip rap is in place for stabilization of banks.
Photos
49
March 31, 2005
Levee
Debris placed along right bank as a berm. Photos
50
March 31, 2005
Bridge
Low clearance. Side ditch coming in upstream of bridge. Debris
downstream. No homes nearby to worry about. Photos
2 I Ahtanum-Wide Hollow CFHMP
Number
Meeting Date
Structure
Description
51
March 31, 2005
Riprap; bridge
Low clearance. Rip rap upstream. Photos
123
March 29, 2005
Riprap; bridge
Upstream of bridge on WH, lots of debris; rip rap indicates bank needed
stabilization. Further upstream of bridge, levee on either side causing
channelization; eroded RB levee; downstream stream takes right turn,
where rip rap is stabilizing LB. Photos
122
March 29, 2005
Pump station; bridge
Bridge at Wide Hollow has pump station and water conveyance system;
photos
199
March 29, 2005
Levee
Levee at soccer park. Incised and straightened channel due to dike on LB.
Photos
200
March 29, 2005
Bridge
Debris dam upstream of bridge; low banks could easily overtop at high
flow; downstream of bridge, there is backwater area. Next to channel is
channelized irrigation ditch with no riparian vegetation. Photos
211
March 31, 2005
Bridge
Bridge clearance looks good, but Goodman Rd is known for water on
roadway at bridge during high flows. Right bank erosion downstream of
bridge. Photos
208
March 31, 2005
Floodgate
Upstream of railroad crossing, there is a flood gate that is opened during
high flows to flood field to prevent flooding of neighborhood in Union Gap.
Location not verified. Photos
204
March 30, 2005
Floodgate
Used to be held open by blocks, which cause flooding from Yakima R in
'96. They have since closed gate and it's no longer a problem. Property
owner downstream is keeping water at high level for flood irrigation
purposes.
202
March 30, 2005
Culvert
Drain pipe from Ahtanum Rd. Was supposed to be connected to pipe going
under the highway, but it was never connected.
201
March 30, 2005
Gravel pits
Yakima R during high flows jumps banks into gravel pit ponds. Area
unstable. Worried about Yakima R water going into Spring Creek, which
does not have the capacity for it; Flood gates were closed Jan 28, 2003.
Several drains go into Spring Creek. Photos
Appendix E - Fieldwork 13
Number
Meeting Date
Structure
Description
207
March 30, 2005
Bridge
Constriction in channel; not much clearance under bridge. Company gets
flooded regularly due to debris caught behind bridge and their parking lot is
below channel level. Photos
215
March 30, 2005
Dam
Work will be done to expand dam. Worried about river going down canal
during flood event, as almost happened in '96. Channels above dam clog
with debris halfway up the island. Photos.
APPENDIX E
Table 2 Initial Interviews
NOTE: Any comments pertaining to proposed causes or solutions to problems were provided by the interviewees and were not verified.
Number
Meeting Date
Contact
Structure
Description
9
Tuesday, Feb 15
DNR
Culvert
Too small of a culvert; put one in; replace with larger pipe.
11
Tuesday, Feb 15
DNR
Culvert
Big culvert; small stick backed up debris. Has been armored but needs
to be replaced. County road.
12
Tuesday, Feb 15
DNR
Beaver dam
Beaver pond by Herke pit; ice jam created debris flow; almost knocked
house off foundation.
13
Tuesday, Feb 15
DNR
Diversion
Evacuation near John Cox ditch, Nov 2003. County road almost blown
out. County road parallels creek for 0.25-0.5 mi and restricts creek.
Minimal damage from Foundation Creek.
14
Tuesday, Feb 15
DNR
Bridge
3 bridges. Volume coming down took out approach. 2 bridges need
barbs. Series of small channels.
15
November, 2004
Joel Freudenthal
Culvert
This creek contributes fresh bedload to SF, blows out culvert and road.
Probably could replace culvert.
17
November, 2004
Joel Freudenthal
Bridge
North Fork Bridge probably too small, stream alignment also very bad
(John Cox diversion here as well). During floods stream channel
aggrades. Massive LWD piles up against abutment, decreasing
conveyance through the bridge further causing more aggradation.
4 I Ahtanum-Wide Hollow CFHMP
Number
Meeting Date
Contact
Structure
Description
18
November, 2004
Joel Freudenthal
Bridge
Series of new private bridges that constrict the channel and may fail
during any flood.
42
November, 2004
Joel Freudenthal
Culvert
Bad sediment transport at culvert.
44
November, 2004
Joel Freudenthal
Culvert
Bad culvert, bank erosion downstream, flooding.
52
April 28 2005
Fence; Fish
bypass
Wade Kamper property; abandoned diversion took off 100 yds east of
bridge; 2 pieces of steel fencing put in to assist dam and never
removed; fish bypass put in and part of diversion removed. Beavers in
area. Note: location unknown.
70
Keelan McPhee
Beaver dam
Homes built between channels are threatened by beaver dams and ice
jams.
71
Mrs Thomas Bates
Culvert
Redesigned drainage pipe.
80
November, 2004
Joel Freudenthal
Diversion
Creek illegally rerouted to the south in this area, comes unglued during
floods and threatens new expensive homes along creek.
118
November, 2004
Joel Freudenthal
Fence
Out of bank flooding due to constriction, fences capturing debris.
119
November, 2004
Joel Freudenthal
Levee
Chronic flooding area - the dike that protects the apple warehouse
across the creek forces flood waters here - the bridge downstream is
probably undersized as well.
130
April 28 2005
Beaver dam
Beaver dams on Wide Hollow Creek.
177
November, 2004
Joel Freudenthal
Bridge
Bridge undersized.
179
November, 2004
Joel Freudenthal
Floodgate
Spring Creek- management of Gate Floodgate by County, management
of stream channel under Union Gap Critical Areas Code.
180
November, 2004
Joel Freudenthal
Levee
Numerous problems with conveyance and levee failure in City of Union
Gap. High hazard at very low flood elevations, especially near Main
Street.
184
March 4, 2005
Dennis Henne, City
of Union Gap
Bridge
Goodman Rd. Backs up at bridge and runs/bridge undersized.
185
March 4, 2005
Dennis Henne, City
of Union Gap
Bridge
S. 3rd Ave. 70's - washed out bridge. '96 - Not sure if it flooded. '99 -
widened existing bridge and installed 2 or 3 box overflow structures.
186
March 4, 2005
Dennis Henne, City
of Union Gap
Bridge
16th - 1 1/2 ft of freeboard on bridge - causing a lot of problems.
Appendix E - Fieldwork 15
Number
Meeting Date
Contact
Structure
Description
189
March 4, 2005
Dennis Henne, City
of Union Gap
Bridge
Pioneer Ln. debris gets caught up on bridge. This bridge is scheduled
for removal in 2007 with Valley Mall Blvd. project.
196
March 4, 2005
Dennis Henne, City
of Union Gap
Sewage lift
station
Sewage lift station — critical - very close call in '96.
197
March 4, 2005
Dennis Henne, City
of Union Gap
Sewage lift
station
Smaller sewage lift station - often flooded.
198
March 4, 2005
Dennis Henne, City
of Union Gap
Fish bypass
Old Water Mill - fish screen and ladder. More of a bottleneck.
6 I Ahtanum-Wide Hollow CFHMP
N This page intentionally left blank N
APPENDIX F
FLOOD PROBLEM WORKSHEETS
Issues Page
#1 In -Stream Debris (non -vegetation) F-2
#2 Ahtanum Mission F-5
#3 North Fork Bridges F-8
#4 Emma Lane F-9
#5 Inundation F-10
#6 Irrigation Infrastructure F-11
#7 Channel Issues F-14
#8 Management of Spring Creek in Union Gap F-18
#9 Shaw Creek F-20
#10 ...Vegetation Issues F-23
#11... Fish and Wildlife F-25
#12 ...Emergency Response Flood Fight F-28
#13 ...Union Gap F-31
#14 ...Transportation Infrastructure F-33
#15 ...Land Uses F-38
#16 ... Regulatory F-41
2 I Ahtanum-Wide Hollow CFHMP
NOTE: Issues #1 and #2 use slightly different organization than later issues.
#1) In -Stream Debris (non -vegetation)
1. Problem- What is the problem? (Problem Statement)
Increased inundation due to:
A. Ice jams causing flooding
B. Fences that cross stream channels catch debris
C. Historic waste (old concrete, asphalt, wood, trash) as well as current illegal dumps,
cuttings from tree pruning, etc
D. Debris from overland flow can clog road ditches, culverts, and other structures -
maintenance is needed.
E. Bedload (gravel) shifting can cause a decrease in capacity under bridges as well as
changes in channel and flow direction.
A. Ice jams causing flooding
1. Causes- What is causing the problem?
• Long periods of freezing temperatures cause the river to freeze. There are natural
inversions that make Yakima -area rivers prone to anchor ice formation and ice
jams.
2. What has already been done to address the problem?
• Ice jams are usually monitored by residents, etc. and reported to the County.
3. What has already been proposed to address the problem?
4. Are there any new solutions that have not already been proposed?
• Healthy riparian areas decrease freezing
5. What still needs to be studied?
• Inventory of locations where ice jams are known to occur- identify them in the
Flood Response Plan
6. Do these proposals address the causes of the problem?
7. Alternatives- What Alternative solutions will address the problem?
• (1A-1) More bridge capacity, and more bridges without peers to prevent backup
of ice due to lack of freeboard
• (1A-2) Monitor ice jams
• (1A-3) Outline the response to ice jams in the Flood Response Plan.
• (1A-4) Heat irrigation gates, (gates are not in operation during the winter) Some
gates are still in use for diverting stock water
• (1A-5) Increase riparian vegetation, which reduces formation of anchor ice
• (1A-6) Blast ice jams- normally only done on very stable ice jams
• (1A-7) Inventory
B. Fences that cross stream channels and catch debris
1. Causes- What is causing the problem?
• Fences cause water to back up and flood.
2. What has already been done to address the problem?
APPENDIX F — FLOOD PROBLEM WORKSHEETS 13
• One successful technique was hanging a steel pipe or cable high above the creek,
and hanging lighter materials down from the cable. It worked as a fence, but was
not lost during floods - has to swing downstream. (Suspension fence).
3. What has already been proposed to address the problem?
4. Are there any new solutions that have not already been proposed?
• Run fences parallel with creek instead of crossing it.
• Fences held back some distance from the creek
5. What still needs to be studied?
6. Do these proposals address the causes of the problem?
7. Alternatives - What Alternative solutions will address the problem?
• 1B-1. Run fences parallel with creek instead of crossing it (How?)
• 1B-2. Hold fences back some distance from the creek (How?)
• 1B-3. Breakaway panels on creeks that flood frequently
• 1B-4. Develop a program for repeat flood areas - create a riparian zone or flood
control zone in these areas. Have someone work with the landowners to provide
them with tools to deal with fencing across the creeks
• 1B-5. Utilize suspension fences - hanging a steel pipe or cable high above the
creek, and hanging lighter materials down from the cable. This works as a fence,
but is not lost during floods.
• 1B-6. Goals or policies in Critical Areas Ordinance addressing fences across
streams
• 1B-7. Identify program to people as they come in to develop their property
(fences)
• 1B-8. Pamphlets for new landowners - such as the pamphlet put out for small
land owners by the Kittitas Conservation District. - It's important to talk to
landowners just after a flood about how to better deal with fences.
• 1B-9. Examine statewide laws relating to streams
C. Historic waste (old concrete, asphalt, wood, trash) as well as current illegal dumps
1. Causes- What is causing the problem?
• Illegal and historic dumps contribute to pollution, particularly during flood
events. Sometimes the pollution can be very toxic, as in the case of meth labs.
2. What has already been done to address the problem?
• Solid waste regulations, recycling programs and facilities, and sanitary land fills
are currently in place to prevent dumping in or near streams.
• Under Washington State solid waste law, land owners are responsible for
dumping that takes place on their property. If identification is found in the
waste, then the person connected to that identification can be prosecuted for
illegally dumping on someone else's property.
3. What has already been proposed to address the problem?
4. Are there any new solutions that have not already been proposed?
• Stream cleanup programs - people clean the garbage from the creek.
5. What still needs to be studied?
4 I Ahtanum-Wide Hollow CFHMP
• Can more measures be taken to deal with illegal dumping (meth labs, etc.)?
• Can funding be found to clean up these dumps on private ground?
• Are there other sources of funding for enforcement?
6. Do these proposals address the causes of the problem?
7. Alternatives - What Alternative solutions will address the problem?
• Reconsider closing solid waste dumps
• Stream cleanup programs - people clean the garbage from the creek.
• Research how other communities deal with dumping, particularly concrete, fill
etc.
• More enforcement, especially for blatant disregard of the law
• Empower regulatory side of the equation
• Encourage citizens to report dumping
• If a jurisdiction knows about a public hazard, they are liable to enforce their laws
D. Debris from overland flow can clog road ditches, culverts and other structures -
maintenance is needed.
1. Causes- What is causing the problem?
• Debris from construction projects, roads, etc. can enter streams and ditches,
clogging drains and culverts, etc.
2. What has already been done to address the problem?
• Roads departments maintain ditches and culverts
• Irrigation Districts maintain ditches
• Many residents maintain private culverts
• Corrections crew roadside cleanup
3. What has already been proposed to address the problem?
• Stormwater regulations
4. Are there any new solutions that have not already been proposed?
5. What still needs to be studied?
• Can measures be taken to prevent runoff during floods (i.e. stormwater
standards)?
6. Do these proposals address the causes of the problem?
7. Alternatives - What Alternative solutions will address the problem?
• Roads departments maintain ditches and culverts
• Irrigation Districts maintain ditches
• Many residents maintain private culverts
• Corrections crew roadside cleanup
• Stormwater programs
• Enforcement of stormwater regulations
• Low lying areas - keeping debris from flood channels- public information (deep
and fast modeling) when people are purchasing and developing properties.
Better/different mapping products - *Would be difficult for the County to
produce*
APPENDIX F — FLOOD PROBLEM WORKSHEETS 15
E. Bedload (gravel) shifting can cause a decrease in capacity under bridges as well as
changes in channel and flow direction.
1. Causes - What is causing the problem?
• Bedload shifts during a flood, due to bridges, diversions, levees, at the
downstream ends of channels that have been straightened, and as a result of
natural seasonal processes.
• When an in -stream project is constructed, significant (and sometimes
unexpected) shifts in bedload can result.
• In many cases, channels are artificial- they are not naturally "sized" for flood
events. See "channel issues"
2. What has already been done to address the problem?
• See bridges and culverts discussion, North Fork Ahtanum bridges, and channel
issues discussion.
3. What has already been proposed to address the problem?
• See bridges and culverts discussion, North Fork Ahtanum bridges, and channel
issues discussion
4. Are there any new solutions that have not already been proposed?
• See bridges and culverts discussion, North Fork Ahtanum bridges, and channel
issues discussion
5. What still needs to be studied?
• See bridges and culverts discussion, North Fork Ahtanum bridges, and channel
issues discussion
6. Do these proposals address the causes of the problem?
7. Alternatives - What Alternative solutions will address the problem?
#2) Ahtanum Mission
Problem - What is the problem? (Problem Statement)
A. Headcuts through the fields at the Mission threaten to capture the flow of Ahtanum
Creek- this is of particular significance with Hatton Creek.
B. Flow is directed to the communities of Ahtanum, Wiley City and other developments
downstream, causing considerable damage to buildings and infrastructure
C. Damage or loss of irrigation infrastructure could affect the economy of the Ahtanum
Valley
D. Infrastructure affecting flooding
A. Headcuts
1. Causes - What is causing the problem?
• Low banks on Ahtanum Creek
• Location on the alluvial fan- three creeks/ditches proceed downstream from this
point in the valley. Risk of avulsion.
2. What has already been done to address the problem?
• 2003 - Levee, groin and road removals
6 I Ahtanum-Wide Hollow CFHMP
• 2004 - Armored headcut
• County performed emergency work this spring- new road and low levee.
• Residents have put in small levees and hay -bale structures
• Two culverts from Mission side to the reservation were removed in '95
• Gravel removal projects have been permitted in the past
3. What has already been proposed to address the problem?
• County planning surveys Fall '06 - will include detailed inventory of
infrastructure, and modeling of interactions in the area - prediction of flood
patterns. Based on model, changes to physical characteristics of infrastructure or
management of existing infrastructure.
• Major levee construction on Mission property
• Ring dikes to protect Mission buildings
• Tribe is working with the Herkes to do some stream restoration in the area
4. Are there any new solutions that have not already been proposed?
• Recreating a flood overflow channel back to Ahtanum Creek from Hatton Creek
(natural overflow channel blocked in the 1930s)
• Removal of the old Hatton diversion
• Modification of the old Hatton ditch channel below the diversion. Intent would
be to block/armor channel to prevent opportunity for formation of headcuts.
• Armoring stream channel to prevent migration of Ahtanum Creek to the North
(could cut through soft levees)
• Note - Need to address two mechanisms of channel movement in area- erosion
from downstream in the form of head cuts, and lateral channel migration from
upstream.
• County (Surface Water) is planning surveys fall '06 - will include detailed
inventory of infrastructure, and modeling of interactions in the area- prediction
of flood patterns. Based on model, changes to physical characteristics of
infrastructure or management of existing infrastructure.
5. What still needs to be studied?
• What are the historical and cultural issues on this site that we need to be
sensitive to?
• What are the potential future downstream impacts/what level of flooding is
acceptable?
B. Flow is directed to the communities of Ahtanum, Wiley City and other
developments downstream, causing considerable damage to buildings and
infrastructure
1. Causes - What is causing the problem?
• Location on the alluvial fan- three creeks/ditches proceed downstream from this
point in the valley
• Infrastructure to manage the creeks, and other infrastructure such as bridges and
levees
• Culverts and bar ditches influence the direction of floodwaters
APPENDIX F — FLOOD PROBLEM WORKSHEETS 17
• Low banks on Ahtanum Creek
• Headcuts that form in the fields at the Mission, which threaten to capture the
flow of Ahtanum Creek- this is of particular significance with Hatton Creek.
2. What has already been done to address the problem?
• 2003 - Levee, groin and road removals
• 2004 - Armored headcut
• County performed emergency work this spring- new road and low levee.
• Residents have put in small levees and hay -bale structures
3. What has already been proposed to address the problem?
• County planning surveys fall '06 - will include detailed inventory of
infrastructure, and modeling of interactions in the area- prediction of flood
patterns. Based on model, changes to physical characteristics of infrastructure or
management of existing infrastructure.
• Major levee construction on Mission property
• Ring dikes to protect Mission buildings
4. Are there any new solutions that have not already been proposed?
• Recreating a flood overflow channel back to Ahtanum Creek from Hatton Creek
(natural overflow channel blocked in the 1930s)
• Levee along Hatton to redirect flow
• Removal of the old Hatton diversion
• Modification of the old Hatton ditch channel below the diversion
• Coordination with Ahtanum Irrigation District for management during floods
5. What still needs to be studied?
• What are the historical and cultural issues on this site that we need to be
sensitive to?
• What are the potential future downstream impacts/what level of flooding is
acceptable?
• What might happen to flooding downstream on Ahtanum Creek if its floodplain
upstream is decreased? (i.e. Hatton Creek is completely cut off from being a
flood channel of Ahtanum). Might make flooding at Emma Lane longer, but
probably not add too much to the peak.
• What is the role of Bachelor and Hatton in general?
• Is there room for Ahtanum Creek to occupy old floodplain channels on the tribal
land adjacent to Ahtanum Mission?
C. Damage or loss of irrigation infrastructure could affect the economy of the
Ahtanum Valley
1. Causes- What is causing the problem?
• Irrigation infrastructure can be damaged by flood flows
• Abandoned irrigation diversions and structures potentially impact flood flows
2. What has already been done to address the problem?
• Re-routing Hatton diversion - completed in '95 - purpose of fish passage and fish
screens
8 I Ahtanum-Wide Hollow CFHMP
3. What has already been proposed to address the problem?
4. Are there any new solutions that have not already been proposed?
• Inventory of existing irrigation infrastructure (working or abandoned)
• Irrigation facility modification in order to better handle flooding
• Improved access to Bachelor Diversion during floods
• Move Bachelor Diversion upstream above the first 90 degree angle on Ahtanum
Creek.
• High flow diversion channel from Ahtanum creek
5. What still needs to be studied?
• The effects of flooding on irrigation structures and of irrigation infrastructure on
flooding patterns
#3) North Fork Ahtanum Bridges
1. Problem - What is the problem? (Problem Statement)
A. North Fork Ahtanum road closures due to flooding or bridge damage/failure
prevent access to residents - individuals, school buses, and emergency vehicles
B. Properties adjacent to bridges are threatened by erosion and increased flooding
2. Causes - What is causing the problem?
A. County and private bridges do not have enough capacity
B. Bridges affect sediment transport and erosion
C. Roadways and development constrict the channel- the stream threatens roadways
where it is constricted.
D. Sediment transport threatens bridge capacity
E. Channel migration threatens roadways
F. John Cox diversion interacts with bridge, aggravating flood problems
3. Alternatives - What Alternative solutions will address the problem?
A. What has already been proposed to address the problem?
1) Yakima County has submitted a JARPA application for work along three
bridges on the North Fork. Work includes excavating sediment and installing
weirs and bank stabilization material.
B. Are there any new solutions that have not already been proposed?
1) Change the maintenance regime for bridges (i.e. channel clean out).
2) Replacement and redesign of bridges and road location, including standards for
new private bridges.
3) Planning requirements to minimize the number of new bridges built as
development increases.
4) County/other agency assist adjacent landowners in bank protection (levees
and/or armor/bioengineering).
5) Gravel removal
6) Purchase of threatened property
APPENDIX F — FLOOD PROBLEM WORKSHEETS 19
7) Purchase of undeveloped property that would require bridge access
8) Modify channel conditions adjacent to bridges
C. What still needs to be studied?
1) Sediment transport rates/stream energy
#4) Emma Lane
1. Problem - What is the problem? (Problem Statement)
A. This area experiences the most frequent flooding problems in the watershed
B. Floodwaters flood the Emma Lane neighborhood, north to Bachelor Creek, the
airport, and the 16th/Ahtanum intersection
C. Some locations in the affected area are not mapped in the 100 year floodplain.
2. Causes - What is causing the problem?
A. The area is a natural alluvial fan, and Ahtanum Creek was diverted onto the
highest point on the fan to facilitate irrigation conveyance. There is a natural
propensity for flooding at this location. However, the area is no longer used
extensively for agricultural purposes.
B. The creek takes a (manmade) 90 degree turn at the 42nd Avenue Bridge - water
often overtops banks at this location. Gravel builds up in the channel upstream
from bridge, increasing flooding.
C. Bachelor Creek Bridge on Ahtanum is angled "backwards" (up gradient), so creek
backs up and floods at that location.
D. Culverts, roads, and the slope of the valley to the east and north, convey water
throughout the area - some areas pond.
E. Many houses along Ahtanum Road were built slab on grade construction, which
makes them more prone to damage from flooding.
F. These areas of known high flood risk are also poised for rapid growth.
3. Alternatives - What Alternative solutions will address the problem?
A. What has already been proposed to address the problem?
1) Move the creek to the low point in the floodplain. Requires:
a) Cooperation with the Yakama Nation
b) Acquisition of at least two homes
c) New bridge
d) Filling in of the old channel
e) Deciding how to deal with potential flooding at the top of the alluvial fan
2) A flood study, and some design guidance (i.e. How much flood protection do
we really want/level of protection?)
3) Limiting future development in this area and/or strict development standards
4) Re -mapping of FEMA flood maps
5) Widening of bridge at 42nd
B. Are there any new solutions that have not already been proposed?
10 I Ahtanum-Wide Hollow CFHMP
1) Reconfigure the Bachelor Creek Bridge on Ahtanum Rd.
2) Elimination of the Shropshire ditch.
3) Improve drainage throughout the entire area - culverts, roads, etc.
4) Improving stormwater system on Ahtanum Road- limit flow into the airport
area, and downstream to 16th (which floods the intersection at Ahtanum Road).
5) Based on floodplain re -map, alter drainage systems- requires associated
drainage easements.
6) Building standards - flood -proofed homes, buildings. Improved standards for
roads
7) Improved conveyance at 16th
8) Open space plan which includes flood hazard reduction
9) Construction of a controlled side channel, rather than moving the creek.
10) Design that does not include filling in the old Ahtanum Channel- looking at
the existing channel as habitat. The main flooding issue is groundwater.
11) Old fill removed on South side on Yakama Nation land just south of Emma
Lane. Remove fill.
12) Controls on building
C. What still needs to be studied?
1) Conveyance downstream of 42nd and Ahtanum Rd.
2) Re -mapping is currently underway
3) Use of Unnumbered A -zones (Regulatory Parking Lot) on maps
4) Project study on the Emma Lane area
5) Cost -Benefit Analysis
#5) Inundation
1. Problem - What is the problem? (Problem Statement)
A. Some places in the study area, particularly in Union Gap, are subject to being
inundated by floodwaters, resulting in flood damages, and interruption in services
and transportation.
2. Causes - What is causing the problem?
A. "Inundation" is a category used to describe locations that are under water during
floods, due to their location, and not due to some other identified cause. The three
major causes of inundation in the Ahtanum-Wide Hollow are:
1) People live in the floodplain
2) Some areas naturally have high water tables
3) Backwater from Yakima River up the channel in Union Gap
3. Alternatives - What Alternative solutions will address the problem?
A. What has already been proposed to address the problem?
1) National Flood Insurance Program
2) Critical Areas Code
APPENDIX F — FLOOD PROBLEM WORKSHEETS 111
3) Re -mapping, so that standards and maps are more accurate
4) Stormwater design standards
5) More stringent development standards (i.e. prohibit land divisions in the
floodplain).
6) Buy people out/provide incentives for landowners who provide floodplain
storage
7) Structural flood control measures either by individuals or government
8) Flood—proof, elevate, make existing structures less flood damage -prone.
B. Are there any new solutions that have not already been proposed?
1) Include areas of high water table in the floodplain maps.
2) Improve sediment transport along the Yakima River (Refer to the Upper
Yakima CFHMP)
3) Modify Wapato Dam
4) Preservation and restoration of floodplain in places, while allowing
development in others.
5) Relocation of residents in areas subject to inundation
6) Coordinate with City of Yakima on checking old regulations against
comprehensive plan updates.
7) Stormwater utility
8) "Full Build -out Mapping"
C. What still needs to be studied?
1) Causes and rates of channel aggradation in the Yakima River.
2) Changes on the Yakima River that affect water tables
3) Delineation of high groundwater areas for inclusion in FEMA maps
#6) Irrigation Structures (Draft 1/04/07)
1. Problem - What is the problem? (Problem Statement)
A. Irrigation ditches route water during floods, causing flooding in locations that
shouldn't usually flood.
B. Debris tends to accumulate on irrigation diversions, causing flooding (i.e. John Cox
diversion).
C. Flooding threatens irrigation structures themselves
D. Live streams have been converted into irrigation. We try to manage them as both
ditches and creeks.
E. Abandoned and unmaintained irrigation structures can play a role in flooding
problems.
F. Currently, there is little coordination between irrigation districts and other
government entities for responding to floods.
G. Water from other watersheds enters into the system from Cowiche/Naches,
affecting total amount of water, and riparian vegetation patterns in the basin.
2. Causes - What is causing the problem?
12 I Ahtanum-Wide Hollow CFHMP
A. Irrigation has altered the nature of the Ahtanum-Wide Hollow watershed in terms
of flow paths, overflows, vegetation and flooding.
B. Some of the irrigation structures are well-maintained and monitored. Others are
abandoned or forgotten.
C. Perched channels (for the purpose of irrigation) place water at a higher elevation
than surrounding land, contributing to flooding (addressed in "channel issues"
PARKING LOT).
D. Altered water schemes caused by irrigation schedules causes growth of Pacific
Willow, which causes flooding problems (addressed in "vegetation issues"
PARKING LOT).
E. Irrigation structures attempt to fix the stream location both laterally and vertically,
which changes the hydraulics of the stream.
F. Gravity diversion structures raise water surface locally to work correctly.
Especially true of wheel -powered fish screens.
G. Irrigation diversions create a hard point, which increases local erosion.
3. Alternatives - What Alternative solutions will address the problem?
A. Irrigation ditches route water during floods, causing flooding in locations that
shouldn't usually flood.
1) What has already been proposed to address the problem?
2) Are there any new solutions that have not already been proposed?
a) Identify where problem locations are.
b) Install floodgates on diversion in some locations, based on an inventory
which takes into account the scale of problems.
c) Create hard structures in ditches and diversions, preserving natural
drainages - Eric wondered if we were referring to partitions or cut-offs in
the (artificial) watercourses
d) Undershots - siphons through gullies and depressions under the ditch -
prevents mingling of flow.
e) Gates that are removable- retrofit structures and new structures in the
irrigation system.
3) What still needs to be studied?
B. Debris tends to accumulate on irrigation diversions and ditches, causing flooding.
1) What has already been proposed to address the problem?
a) Better design of irrigation infrastructure
2) Are there any new solutions that have not already been proposed?
a) Temporary or sacrificial diversion structures adapted to existing channel
locations and physiographies.
b) Remove irrigation pumps, etc. when flooding occurs (removable
structures) -(potential problem with ice in this situation)
c) Maintenance of debris on structures- proactive debris removal
3) What still needs to be studied?
C. Flooding threatens irrigation structures themselves
APPENDIX F — FLOOD PROBLEM WORKSHEETS 113
1) What has already been proposed to address the problem?
2) Are there any new solutions that have not already been proposed?
a) Consolidation of irrigation diversions to minimize stream impacts
b) Irrigation upgrades, such as piping
3) What still needs to be studied?
D. Live streams have been converted into irrigation. We try to manage them as both
ditches and creeks.
1) What has already been proposed to address the problem?
a) Irrigation system could be diverted to a pressure -based system (i.e. Pine
Hollow)
2) Are there any new solutions that have not already been proposed?
a) Make choices as to status as stream or irrigation ditch, or urban stream
b) Unified management plans for the irrigation ditches, streams, and "urban
streams"
c) Regulatory changes to account for streams with dual uses
d) Recommend a study to address streams with dual uses
e) Water conservation plan that includes designation of fish habitat and other
uses
f) Irrigation out of the creeks- separate irrigation from creeks
3) What still needs to be studied?
a) Institutional and regulatory obstacles
E. Abandoned and unmaintained irrigation structures can play a role in flooding
problems.
1) What has already been proposed to address the problem?
2) Are there any new solutions that have not already been proposed?
a) Study - inventory of old drainage and irrigation systems that are affecting
flooding
b) Identify sources of funding for removal of abandoned structures
3) What still needs to be studied?
F. Currently, there is little coordination between irrigation districts and other
government entities for responding to floods.
1) What has already been proposed to address the problem?
2) Are there any new solutions that have not already been proposed?
a) Include Irrigation Districts in communications with the EOC (emergency
operations center)
b) Install a North Fork gage
c) FCZD should communicate potential risks to irrigation systems to Irrigation
Districts
d) Management of creeks to prepare for flood overflow, such as on Bachelor
and Hatton.
e) address hot spots on Hatton -
f) Forecasting of flooding, coordinate opening gates for flood relief.
3) What still needs to be studied?
14 I Ahtanum-Wide Hollow CFHMP
PARKING LOT - riparian vegetation, channel issues
#7) Channel Issues (Capacity and Overflow) (Draft 7/26/07)
1. Problem - What is the problem? (Problem Statement)
A. Man-made alterations in the stream channel (levees, armor and straightening)
contribute to flooding in places throughout the study area (See also Irrigation
Infrastructure and Infrastructure).
B. Perched irrigation conveyances are at a higher elevation than much of the land
around them. This setup was useful for former irrigation practices, but is not
compatible with natural flooding patterns and development.
C. Natural changes in the channel become a problem when they threaten homes,
businesses, agricultural land, or infrastructure.
D. Unidentified overflow routes can cause flooding where it was not expected
E. Artificial channels and Drainage Improvement District (DIDs) facilities may not be
properly sized to handle flood flow, or are not located in natural drainage ways.
Some may be "decommissioned" in the future.
F. Some hollows flood during lower frequency flood events- in hollows, flooding is
very unpredictable, and often occurs as sheet flow. Hollows are not identified on
maps as a hazard, which places new developments at risk from unexpected
flooding.
G. Loss of floodplain capacity contributes to flooding (See Land Use, Regulatory
PARKING LOT).
H. There are bedload problems in many locations in the upper watershed -High
energy water picks up sediment, then dumps its load when the gradient
decreases- (downstream from Wide Hollow, Pine Mountain, John Cox- east of
Carson Rd. Bridge 107 - island in the creek- used to be 10 ft. wide, now it's 20+.)
I. Brush/trees overgrown due to de -watering of creek from irrigation (Wiley Road -
Hatton Creek).
J. Incision of channel at the airport.
2. Causes - What is causing the problem? (lettering identifies the problem the cause
relates to)
A. There have been wholesale changes to natural drainage patterns in many areas of
the basin (i.e. the Bachelor/Hatton system, the pre-Rimrock Yakima-Tieton
irrigation system, etc.) (A)
B. Ditches and drains convey flood waters to areas outside the natural floodplain. (B)
C. Natural channels have been altered to direct creeks in a certain direction (i.e. both
Ahtanum and Wide Hollow Creeks have 90° angles). Straightened channels cause
increased velocity. During high water, the creeks back up at 90° angles and flood
surrounding neighborhoods. (C)
APPENDIX F — FLOOD PROBLEM WORKSHEETS 115
D. Creek channels naturally change over time (migration, aggradation, erosion,
sedimentation, etc.) (C,D)
E. Many hollows never had a channel, but did convey floodwaters. Channels
constructed in these areas are not sized for floods and do not respond to floods
predictably. Shaw Creek is the prototypical example of a hollow. Weather event
timing (winter, frozen ground, snow cover, etc.) particularly important. (E,F)
F. Floodplain loss from development (PARKING LOT See Land Use issues,
Regulatory) (G)
3. Alternatives- What Alternative solutions will address the problem?
A. Man-made alterations in the stream channel (levees, armor and straightening)
contribute to flooding in places throughout the study area (See also Irrigation
Infrastructure and Infrastructure).
1) What has already been proposed to address the problem?
a) Channel reconfiguration and reconstruction at Emma Lane and Shaw Creek,
and lower Wide Hollow in Union Gap and the Mission.
b) Periodic channel maintenance (Stream clean out)
2) Are there any new solutions that have not already been proposed?
a) Identify areas where man-made alterations are affecting flooding (i.e.
Fulbright Park, Upstream of 64th and Diversion #14, and The Narrows) to
allow for cooperative projects.
3) What still needs to be studied?
B. Perched irrigation conveyances are at a higher elevation than much of the land
around them. This setup was useful for former irrigation practices, but is not
compatible with natural flooding patterns and development.
1) What has already been proposed to address the problem?
a) Channel reconfiguration and reconstruction at Emma Lane and Shaw
Creek/ditch, and lower Wide Hollow in Union Gap.
b) Levees constructed along perched channels (i.e. Cottonwood Grove)
c) Separate irrigation conveyance from natural streams (i.e. Build Pine Hollow
and pipe the irrigation water) based on studies where it is shown this
would be effective.
d) Acquisition/easement of land surrounding flood problem areas (i.e. West
Valley Park) (See also Land Use)
e) Preserve off-site storage (existing pastures, alfalfa) (storage of water and
sediment), possibly with floodplain easements- maintaining farmland. (See
also Land Use)
f) New floodplain mapping and modeling leading to more accurate locations
of floodplains on maps and consistent application of land use regulations.
2) Are there any new solutions that have not already been proposed?
a) Identification of areas that are near perched channels (disclosure that the
area is at high risk for flooding). Identify areas that are of particular concern.
16 I Ahtanum-Wide Hollow CFHMP
b) Protection of farmland (as a use) in areas that flood near perched channels,
in areas of particular concern. If it's all under one ownership, the creek/ditch is
more likely to be maintained for both purposes - irrigation and flood
control.
c) Flood overflow channels/conveyances where channels are perched
3) What still needs to be studied?
a) Identify other perched stream locations
C. Natural changes in the channel become a problem when they threaten homes,
businesses, agricultural land, or infrastructure.
1) What has already been proposed to address the problem?
a) Levees, armor, buffers, CMZ (channel migration zones)
b) "Softer" solutions for bank stabilization (plantings, etc.)
2) Are there any new solutions that have not already been proposed?
a) Buyouts/relocation/easements and flood -proofing for areas threatened by
meandering and erosion.
b) Agricultural subsidies allowing flooding on some farmland. Depends on
erosion verses sheet flow. Compensation program for productive ag land
lost to erosion. Linked to property loss protection program (?).
c) Property buyouts for lost property
d) Flood easements
e) Minimize new homes/structures etc. in harm's way.
f) Identify areas that are at risk for channel migration in addition to identified
CMZ.
g) Complete floodway mapping in the region
h) Information about flood history to realtors, lenders, etc. in proposed new
developments
i) Required disclosure of flood history by realtors
j) Workshops and other outreach for realtors
3) What still needs to be studied?
a) Clarification: Define threatening. Centers around erosion and the potential for land
and buildings lost. Is there a threshold level of risk?
D. Unidentified overflow routes can cause flooding where it was not expected
1) What has already been proposed to address the problem?
a) New floodplain mapping and modeling leading to more accurate locations
of floodplains and consistent application of land use regulations.
b) Regularly scheduled updates
c) Mapping of Channel Migration Zones and Hazards mapping
d) Acquisition/easement of land surrounding flood problem areas (i.e. West
Valley Park)
2) Are there any new solutions that have not already been proposed?
a) Documentation of floods (air photos, etc.) Open contract with flights
3) What still needs to be studied?
APPENDIX F — FLOOD PROBLEM WORKSHEETS 117
E. Artificial channels (not streams) and Drainage Improvement District (DIDs)
facilities are not properly sized to handle flood flow, or are not located in natural
drainage ways delete. Identify streams- designation and a better definition. Note:
(Commissioners have designated Bachelor, Hatton as a stream....) Some DIDs may
be "decommissioned" in the near future.
1) What has already been proposed to address the problem?
2) Are there any new solutions that have not already been proposed?
a) Size drainage facilities for future build -out and flood flows.
b) Limit new connections to existing undersized systems
c) Decommission DIDs as land use changes
d) Designate stream or ditch based on a variety of factors (damage to people,
damage to wildlife, etc.)
e) Re -define regulatory measures for artificial drainages (what regulations are
streams subject to, what regulations are ditches subject to?) (Regulatory)
3) What still needs to be studied?
F. Some hollows flood during lower frequency flood events- in hollows, flooding is
very unpredictable, and often occurs as sheet flow. Hollows are not identified on
maps as a hazard, which places new developments at risk from unexpected
flooding.
1) What has already been proposed to address the problem?
a) Drainage systems
2) Are there any new solutions that have not already been proposed?
a) Process for identifying overflow areas aside from the formal FEMA
mapping process
b) Identify critical hollows through risk assessment and through flood benefit
(for protection measures)
c) Identify special flood protection measures for hollows
3) What still needs to be studied?
G. Loss of floodplain capacity due to development contributes to flooding (See land
use, regulatory PARKING LOT).
1) What has already been proposed to address the problem?
a) Stormwater standards for detention and retention - On-site and regional
stormwater detention facilities.
2) Are there any new solutions that have not already been proposed?
a) Size drainage facilities for future build -out and flood flows.
b) (See Regulatory)
c) (See Land Use)
3) What still needs to be studied?
4) Model flood effects of build -out
a) Mapping of Channel Migration Zones and Hazards mapping
Notes:
18 I Ahtanum-Wide Hollow CFHMP
1. There are bedload problems in many locations in the upper watershed -High energy
water picks up sediment, then dumps its load when the gradient decreases -
(downstream from Wide Hollow, Pine Mountain, John Cox- east of Carson Rd. Bridge
107- island in the creek used to be 10 ft. wide, now it's 20+.)
2. Brush/trees overgrown due to de -watering of creek from irrigation (Wiley Road -
Hatton Creek).
3. Incision of channel at the airport.
4. consistency of staffing/programs in regulating agencies
5. Fill - inconsistently dealt with, based on thresholds
#8) Management of Spring Creek in Union Gap (Draft 1/25/07)
1. Problem- What is the problem? (Problem Statement)
A. Spring Creek was a natural side channel of the Yakima River with associated
water rights prior to construction of I-82. Since construction of I-82 the Yakima
River channel elevation has risen.
B. A history of flooding along Spring Creek prompted the installation of a floodgate
where Spring Creek travels under I-82. The floodgate has been closed for two
years. There is no agreement for permanent closure and opening of the gates may
be desired for improved fish usage of Spring Creek. Similar to other areas, such as
Shaw Creek, there is some disagreement on the classification of all or portions of
Spring Creek, regarding the Hydraulic code and the Critical Areas code of Union
Gap and Yakima County.
C. When I-82 was constructed, culverts were placed under the freeway to allow
Spring Creek to flow back into the Yakima River, and a new irrigation channel was
constructed parallel to the freeway to serve existing irrigation rights. Migration
and aggradation of the Yakima River caused water to flow backwards through
these culverts and flood adjacent mobile home park and areas downstream along
the irrigation channel.
D. Both lower Spring Creek and lower Wide Hollow Creek are flooded by backwater
from the Yakima River via Wide Hollow culverts under the freeway and Hwy. 97.
This area has the greatest predicted depth of water during a 100 year flood event
in Yakima County (over 9 feet). The City of Union Gap's wastewater pump station
is located in this area and has been damaged in the past, and is threatened by
future damage.
2. Causes - What is causing the problem?
A. Migration and aggradation of the Yakima River since the construction of I-82.
B. Because of changes in the Yakima River, drainage patterns have been altered and
drainage infrastructure does not function as designed.
C. Spring Creek is an active side channel of the Yakima River - without the floodgate
in place, floods affect the Spring Creek area.
APPENDIX F — FLOOD PROBLEM WORKSHEETS 119
D. Spring Creek also receives drain water from the Ahtanum Road drain and drains
facilities under downtown Union Gap. There are reports of runoff increasing since
Union Gap has experienced development.
3. Alternatives- What Alternative solutions will address the problem?
A. Spring Creek was a natural side channel of the Yakima River with associated
water rights prior to construction of I-82. Since construction of I-82 the Yakima
River channel elevation has risen.
1) What has already been proposed to address the problem?
a) See Upper Yakima CFHMP recommendations
2) Are there any new solutions that have not already been proposed?
3) What still needs to be studied?
B. A history of flooding along Spring Creek prompted the installation of a floodgate
where Spring Creek travels under I-82. The floodgate has been closed for two
years. There is no agreement for permanent closure and opening of the gates may
be desired for improved fish usage of Spring Creek. Similar to other areas, such as
Shaw Creek, there is some disagreement on the classification of all or portions of
Spring Creek, regarding the Hydraulic code and the Critical Areas code of Union
Gap and Yakima County.
1) What has already been proposed to address the problem?
2) Are there any new solutions that have not already been proposed?
a) Keep the floodgate closed for the foreseeable future
b) Remotely controllable floodgate that could be opened some times of year,
closed others
c) Coordinate with restoration plan (WDFW)
3) What still needs to be studied?
C. When I-82 was constructed, culverts were placed under the freeway to allow
Spring Creek to flow back into the Yakima River, and a new irrigation channel was
constructed parallel to the freeway to serve existing irrigation rights. Migration
and aggradation of the Yakima River caused water to flow backwards through
these culverts and flood adjacent mobile home park and areas downstream along
the irrigation channel.
1) What has already been proposed to address the problem?
2) Are there any new solutions that have not already been proposed?
a) If the Yakima River and the lower Wide Hollow floodplain continues to
aggrade, relocation or floodproofing of the pump station and the mobile
home park may be required, or allow for massive filling.
b) Diking around the pump station
c) New mapping may impact homeowners' decision to elevate (floodproof)
d) Stricter ordinances - (i.e. Base flood plus 2 or 3 feet)
e) Construct floodgates on Wide Hollow culverts if action below is
implemented:
20 I Ahtanum-Wide Hollow CFHMP
f) Re-route Wide Hollow into Ahtanum Creek. (See also Union Gap
discussion)
g) Wapato dam modifications - addressed in Upper Yakima CFHMP
3) What still needs to be studied?
a) What kind of future flood impacts may occur as a result of aggradation?—
What are the rates of aggradation?
D. Both lower Spring Creek and lower Wide Hollow Creek are flooded by backwater
from the Yakima River via Wide Hollow culverts under the freeway and Hwy. 97.
This area has the greatest predicted depth of water during a 100 year flood event
in Yakima County (over 9 feet). The City of Union Gap's wastewater pump station
is located in this area and has been damaged in the past, and is threatened by
future damage.
1) What has already been proposed to address the problem?
a) WSDOT has plugged or repaired culverts. Recent observations indicate they
are once again backwatering. They either need to be plugged and repaired
or sealed.
2) Are there any new solutions that have not already been proposed?
a) Improve conveyance downstream of the culverts on the Spring Creek
irrigation channel by increasing grade- would help in most flood events
(possibly not in large-scale flooding).
b) If the Yakima River and the lower Wide Hollow floodplain continues to
aggrade, relocation or floodproofing of the pump station and the mobile
home park may be required, or allow for massive filling.
c) Construct floodgates on Wide Hollow culverts if action below is
implemented:
d) Re-route Wide Hollow into Ahtanum Creek. (See also Union Gap
discussion)
3) What still needs to be studied?
a) If the Yakima River and the lower Wide Hollow floodplain continues to
aggrade, relocation or floodproofing of the pump station and the mobile
home park may be required, or allow for massive filling.
b) Construct floodgates on Wide Hollow culverts if action below is
implemented.
c) Re-route Wide Hollow into Ahtanum Creek. (See also Union Gap
discussion)
*Potential restoration plan for fish habitat at Spring Creek. Restoration plan- restoring
fish passage will help with flood (gradient)
APPENDIX F — FLOOD PROBLEM WORKSHEETS 121
#9) Shaw Creek (Draft 2/12/07)
1. Problem - What is the problem? (Problem Statement)
A. Many people and organizations consider Shaw Creek a man-made feature.
Protection of the creek/ditch as fish and wildlife habitat as required under both
Hydraulic code and Critical Areas code conflicts with managing it as an artificial
irrigation and drainage facility.
B. Flooding that originates in Shaw creek has a high probability of causing significant
damage to existing and future high density residential developments which are
currently not in the mapped floodplain.
C. Many residents who may be affected by flooding do not have flood insurance.
D. Shaw Creek at Pear and Tieton Dr. has a history of flooding Tieton Dr. and areas
downstream.
E. There is potential for water quality problems in Shaw Creek during a flood, since
floodwaters will likely utilize city streets as conveyances, particularly in the new
Cottonwood Grove subdivision.
2. Causes - What is causing the problem?
A. Criteria in both the Hydraulic Code and Critical Areas Ordinance include the
creek as fish and wildlife habitat even though it may be entirely artificial or highly
altered from its natural state and is not currently serving any of the purposes for
which it was originally constructed.
B. Shaw Creek/Ditch has been moved and perched above its natural floodplain for
former farming and irrigation practices.
C. Shaw Creek/Ditch goes through a rapidly developing high density area.
D. No parts of Shaw Creek/Ditch are included in the Flood Insurance Rate Maps.
E. Artificial channels are insufficient for handling flood volumes due to small channel
size and low gradient.
F. The Wide Hollow Creek watershed behaves like a hollow in some locations -
meaning that sheet -flow enters the creek during rain on snow/ice events.
3. Alternatives - What Alternative solutions will address the problem?
A. Many people and organizations consider Shaw Creek a man-made feature.
Management of the creek/ditch as fish and wildlife habitat as required under both
Hydraulic code and Critical Areas code conflicts with managing it as an artificial
irrigation and drainage facility.
1) Classification of Shaw Creek
2) Reconfiguration of Shaw Creek to function as floodplain and fish and wildlife
habitat.
3) Shaw Creek stops at 80tH
4) Modified natural channels - drainage or irrigation
22 I Ahtanum-Wide Hollow CFHMP
See discussion under b and c.
B. Shaw Creek/Ditch has been moved and perched above its natural floodplain for
former farming and irrigation practices.
1) What has already been proposed to address the problem?
a) Relocation of Shaw Creek to the low point in the drainage to allow for more
natural stream and floodplain function, and less maintenance.
b) Diking along Shaw Creek to protect new development
2) Are there any new solutions that have not already been proposed?
3) What still needs to be studied?
a) Relocation of Shaw Creek and the potential for a larger solution that
includes concurrent considerations on Wide Hollow Creek
C. Shaw Creek goes through a rapidly developing high density area.
1) What has already been proposed to address the problem?
a) Protection of natural floodplain functions in Shaw Creek's watershed
b) Critical Areas Ordinance
c) Integrate; protect the floodplain function in association with Capitol
facilities improvements. Tieton Drive, Orchard, and 96th, proposed "Nob
Hollow" connector.
2) Are there any new solutions that have not already been proposed?
a) Change zoning code/amend the Comprehensive Plan to allow for less
development, and protection of floodplain function.
b) Administrative designation of floodplain based on historic flood patterns in
the Shaw Creek area prior to updating of the FIRM maps.
c) More effectively integrate protection of floodplain functions/flood hazard
reduction in individual subdivision platting process.
d) Large-scale detention/retention/flood water conveyance facilities, and
associated maintenance. Identify potential locations.
e) Design of subdivisions and homes should incorporate flood risks.
3) What still needs to be studied?
D. No parts of Shaw Creek are included in the Flood Insurance Rate Maps.
1) What has already been proposed to address the problem?
a) Mapping the floodplain for NFIP rate maps, and enforcing NFIP standards
for new development.
2) Are there any new solutions that have not already been proposed?
a) Model the watershed at full build -out
b) Residents can purchase flood insurance even if they are not in a mapped
floodplain.
c) Hold neighborhood meeting for residents living near Shaw Creek (public
outreach).
d) Send information about Shaw Creek flooding to residents at risk of flooding
(public outreach).
3) What still needs to be studied?
APPENDIX F — FLOOD PROBLEM WORKSHEETS 123
E. Shaw Creek at Pear and Tieton Dr. has a history of flooding Tieton Dr. and areas
downstream.
1) What has already been proposed to address the problem?
a) Relocation of channel
(i) School owns property, and may be amenable to relocation.
(ii) Nob Hollow Road possibly a problem, possibly remove bridges,
which would help with conveyance on Wide Hollow.
(iii) If all creeks diverge on Wide Hollow during a major flood, it won't
get past 80th and West Valley Park.
(iv) Address Zeigler's property
(v) Move Wide Hollow Creek South of Wide Hollow Road (if Nob
Hollow is not constructed).
b) Diking along creek
2) Are there any new solutions that have not already been proposed?
a) Regional retention upstream of Tieton Dr
b) Certain vacant properties - find ways to keep them undeveloped.
3) What still needs to be studied?
F. There is potential for water quality problems in Shaw Creek during a flood, since
floodwaters will likely utilize city streets as conveyances, particularly in the new
Cottonwood Grove subdivision. Shallow drainfield at school - also a potential
problem.
1) What has already been proposed to address the problem?
2) Are there any new solutions that have not already been proposed?
3) What still needs to be studied?
*This problem/watershed is a high priority*
Should we be trying to address this now? —
1. Recommend quick actions which allow us to keep options open:
A. Notify developers and prospective residents of the current flood hazard
B. Require drainage easements,
C. Keep at -risk areas undeveloped and,
D. Allow for high density development in areas that are not at risk.
#10) Vegetation Problems (Draft 2/15/07)
1. Problem - What is the problem? (Problem Statement)
A. Vegetation (particularly Pacific Willow and Reed Canarygrass) grows into streams
and decreases capacity.
B. Branches and debris from vegetation pile up on impediments, causing flooding.
C. Lack of riparian vegetation causes greater variation in temperature throughout the
year, which can result in more and/or anchor ice formation. Lack of riparian
vegetation allows for increased bank erosion
24 I Ahtanum-Wide Hollow CFHMP
D. Natural rates of large wood inputs are essential for habitat development and
reduction of stream energy. Even in the natural environment, large wood can
reduce conveyance, cause flooding and increase bank erosion. In addition, large
wood can accumulate or negatively affect infrastructure such as bridges and
irrigation diversions and conveyance systems (from "Debris" Parking Lot).
2. Causes - What is causing the problem?
A. Irrigation -fed streams (particularly Wide Hollow, Bachelor and Hatton creeks) are
affected by an inverse hydrologic cycle. These creeks experience higher flows in
the summer due to irrigation tail water. Pacific Willow and Reed Canarygrass
thrive in this regime, and grow into the creeks, decreasing the capacity of the
channel. Reed Canarygrass makes streams more prone to avulsion.
B. Protection of stream -side vegetation can conflict with landowner and agency land
management objectives - maximize agricultural/residential/public uses on a
limited land base, or amenity values (I want to see the creek!), or pose a hazard to
adjacent structures.
C. In many locations in the watershed, channels have been straightened and
subsequently incised. This results in an environment where riparian vegetation
does not establish.
D. Noxious weeds invade unmanaged, vacant land, preventing reestablishment of
riparian vegetation.
E. Natural process of wood recruitment to stream
3. Alternatives - What Alternative solutions will address the problem?
A. Vegetation (particularly Pacific Willow and Reed Canarygrass) grows into streams
and decreases capacity.
1) What has already been proposed to address the problem?
a) Removal and long term management of Pacific Willow- may be at different
scales- site specific or throughout the watershed (i.e. for some distance
upstream and downstream of bridges on Wide Hollow has a more
aggressive Willow control program.)
b) Alteration of the hydrologic regime - eliminate/reduce conveyance of
irrigation water in Wide Hollow and tributaries -Lower Wide Hollow and
Ahtanum Creek are influenced by the water table of the Yakima River,
which also has a non -normative hydrograph.
2) Are there any new solutions that have not already been proposed?
a) Changes in regulations or region -wide permits for management of the
undesirable riparian plant communities
b) As part of mitigation for piping of irrigation waters, create a more
normative conveyance schedule.
3) What still needs to be studied?
a) Other types of vegetation that can be substituted for Pacific Willow over the
long term - may include non-native plant communities
APPENDIX F — FLOOD PROBLEM WORKSHEETS 125
B. Branches and debris from vegetation pile up on impediments, causing flooding.
Breakdown products of this debris also causes stream to lose conveyance, etc.
1) What has already been proposed to address the problem?
(i) See a and d
2) Are there any new solutions that have not already been proposed?
3) What still needs to be studied?
C. Lack of riparian vegetation causes greater variation in temperature throughout the
year, which can result in more and/or anchor ice formation. Lack of riparian
vegetation allows for increased bank erosion.
1) What has already been proposed to address the problem?
2) Are there any new solutions that have not already been proposed?
a) Regulations that protect or encourage restoration of riparian vegetation
(Critical Areas Code)
b) Incentive programs to protect riparian vegetation (i.e. Conservation Reserve
Enhancement Program, YTAHP (Yakima Tributary Access and Habitat
Program), Open Space taxation incentives)
c) Acquisition/legal protection of riparian zones (easements, agreements, Fee
Simple, etc.). This is most often done with multiple objectives -Fish and
Wildlife habitat protection, Open Space, parks, trail and other non -
motorized transportation corridors, public access.
d) Other landowner assistance programs (i.e. Conservation Districts)
e) Public education and examples of the values and esthetic appeal of riparian
corridors/open space
f) Stream relocation away from high-intensity uses, or restoration of incised
stream channels to allow for natural riparian/flood function.
g) Distinguish between areas that should be natural functions and processes
(Ahtanum), as opposed to areas that should be managed for high intensity
land use (much of Wide Hollow Creek). Refer to "Fish and Wildlife" for
identification of these alternatives.
3) What still needs to be studied?
a) Appropriate plant communities for denuded riparian areas
D. Natural rates of large wood inputs are essential for habitat development and
reduction of stream energy. Even in the natural environment, large wood can
reduce conveyance, cause flooding, and increase bank erosion. In addition, large
wood can accumulate or negatively affect infrastructure such as bridges and
irrigation diversions and conveyance systems (from "Debris" Parking Lot).
1) What has already been proposed to address the problem?
a) Riparian setbacks and buffers
b) Site-specific response to log jams
c) Improve design of bridges and irrigation diversions to reduce potential for
debris accumulation.
2) Are there any new solutions that have not already been proposed?
26 I Ahtanum-Wide Hollow CFHMP
a) In some locations, addition of wood to stream to "catch" wood debris- this
accomplishes multiple objectives - would benefit habitat as well as reduce
the volume of woody debris that accumulates on bridges, diversions, and
other structures.
b) Reduce or minimize the number of bridges and irrigation diversions that
can accumulate debris
c) Distinguish between areas that should be natural functions and processes
(Ahtanum), as opposed to areas that should be managed for high intensity
land use (much of Wide Hollow Creek). Refer to "Fish and Wildlife" for
identification of these alternatives.
3) What still needs to be studied?
#11) Fish and Wildlife (Draft 3/12/07)
1. Problem - What is the problem? (Problem Statement)
A. Beavers create dams that can aggravate flooding, and can make it difficult to
reestablish riparian zones.
B. Elk populations contribute to erosion and may change flood timing in higher
elevations
C. Channel, riparian and floodplain processes have been drastically altered in the
watershed. Habitat quality and quantity have been reduced or eliminated. Native
fish and wildlife were dependent on these natural processes. These resources are
managed as a trust for the benefit of the citizens of Washington State and the
treaty Indian Tribes. Riparian areas play an important role in sustaining wildlife
species by supplying unique or limited habitats, or acting as migration corridor
(i.e. birds)
D. Some creeks have sources that aren't natural- Distinguish between areas that may
not have the sources of water in the future for fish and wildlife, and areas that will
have water for the long term.
2. Causes - What is causing the problem?
A. Beaver populations are rebounding (expanding). Yakama Nation and WDFW are
encouraging this expansion, because they provide critical ecosystem functions,
and the beaver population was once depleted due to over -trapping.
B. Beaver dams are a site-specific problem. In some situations they are beneficial, but
they are often in conflict with infrastructure or the built environment, resulting in
increased flood risk.
C. There is an unnaturally large concentration of elk in the high elevation areas of the
Ahtanum and Wide Hollow watershed. Grazing animals (elk and cattle) may
contribute to erosion, and therefore aggravate flooding in the upper reaches of
Wide Hollow Creek.
APPENDIX F — FLOOD PROBLEM WORKSHEETS 127
D. People commonly think that fish and wildlife conservation is in conflict with flood
control, when in fact, good flood management and fish and wildlife conservation
are generally mutually compatible.
3. Alternatives - What Alternative solutions will address the problem?
A. Beavers create dams that can aggravate flooding, and can make it difficult to
reestablish riparian zones.
1) What has already been proposed to address the problem?
a) Deal with beavers on a case by case basis - use discretion based on situation
(is the floodplain function provided by the beaver a good thing or a bad
thing?)
b) Lethal trapping or relocation of "problem beavers."
c) Removal of "problem" beaver dams, under permits from the Department of
Fish and Wildlife (CAO, Cities, Yakama Nation).
d) Beaver proof culverts (don't normally function well during floods).
Alternatives for water passage through beaver dams.
e) Regulatory measures (buffers, setbacks, etc.) to allow for localized
flooding/changes in water surface level or the channel.
f) General WDFW Adaptive Management procedure- if people affected by a
dam can deal with it by hand, they don't need a permit. If it needs more
work to remove, a permit is required.
g) Critical Areas Ordinance- vegetative buffers should address beaver dams
2) Are there any new solutions that have not already been proposed?
3) What still needs to be studied?
a) Are there areas where beavers should not be allowed? (i.e. dense urban
areas, irrigation, artificial ditches)
b) Who is responsible? Identify protocols for beaver management.
B. Unnaturally dense concentrations of elk contribute to erosion and may change
flood timing in higher elevations
1) What has already been proposed to address the problem?
2) Are there any new solutions that have not already been proposed?
a) (Coordinated Resource Management Group) (i.e. similar to the Wenas
working group)
b) Incorporation of watershed management when managing elk (i.e. Maintain
a good sized buffer to prevent elk from entering the stream, appropriate
carrying capacity, etc.). Recognize this issue as a high priority.
c) Move elk feeding stations to other areas
d) Feeding station management - apply similar management standards to
feeding operations as livestock operations, alter locations, etc.
3) What still needs to be studied?
C. Channel, riparian and floodplain processes have been drastically altered in the
watershed. Habitat quality and quantity have been reduced or eliminated. Native
fish and wildlife were dependent on these natural processes. These resources are
28 I Ahtanum-Wide Hollow CFHMP
managed as a trust for the benefit of the citizens of Washington State and the
treaty Indian Tribes.
1) What has already been proposed to address the problem?
a) Federal, State and local regulations attempt to;
(i) Limit rates of habitat loss (i.e. Endangered Species Act, Growth
Management Act, and Hydraulic Code).
(ii) Maintain watershed and channel processes (i.e. Clean Water Act, In -
stream flow rules).
b) Dedicated habitat restoration protection and restoration programs (i.e.
Salmon Recovery Funding Board, Northwest Power and Conservation
Council). Other programs and funding sources that encourage habitat
protection (i.e. YRBWEP, FCAAP, Centennial Clean Water, FEMA, Federal
Highways).
c) Landowner incentive programs (i.e. Conservation District, Cost- Shares,
Open Space taxation and other tax breaks - these programs can be very
rigid, which may discourage participation)
d) Private habitat restoration organizations (i.e. Land trusts, Greenway, other
non-profit programs).
2) Are there any new solutions that have not already been proposed?
a) Encourage beavers in areas where their presence could restore degraded
watershed function.
b) Being more proactive in planning for these needs.
c) Create a program that is prepared to educate landowners before and after a
flood event.
d) Develop pre and post -disaster program for implementation of habitat goals
in flood hazard reduction/recovery projects/programs.
e) Environmental benefits should be considered in funding processes.
f) Encourage organizations (neighborhoods, County/City/Yakama Nation or
others) to purchase floodplain areas
g) Inform people about the importance of the functions of streams, rivers, and
natural drainage ways. Public education about how riparian and flood
hazard management goals complement each other.
h) Address maintenance of drainage easements -establish who is going to
enforce maintenance
i) Public education programs, such as stream cleanup programs and volunteer
monitoring.
3) What still needs to be studied?
a) How to integrate with Yakama Nation policies or plans for parcels adjacent
to Ahtanum Creek?
APPENDIX F — FLOOD PROBLEM WORKSHEETS 129
#12) Flood Fight / Flood Response (Draft 3/6/07)
1. Problem - What is the problem? (Problem Statement)
A. Even with the best planning, floods are a normal and regular occurrence.
Predicting the behavior of any given future flood is impossible, so communities
need to be prepared to protect life and property before, during, and after flood
events.
B. Floods can result in deaths, injuries, economic and significant personal hardship,
as well as inconvenience to many people.
C. Effective flood response involves many levels of government, and requires that
government agencies be prepared to respond in a coordinated fashion. Programs
are in place at the local, state and federal level to respond to different levels of
emergencies and disasters. Local government personnel, such as law enforcement
officers and public works employees, as well as first responders, are on the front
lines of the "flood fight" and protection of life and property. The most significant
and pressing issues facing those responsible for responding to floods are keeping
people safe, and preventing chaos. A coordinated, well planned effort is required.
D. What actions can be taken during a flood? Even during flood emergencies, actions
by agencies or individuals need to comply with regulations. Actions taken during
a flood that do not comply can result in the subsequent need to remove, alter, or
mitigate for actions taken during the flood. These post -flood actions are often not
eligible for funding related to the disaster.
2. Causes - What is causing the problem?
A. Complex natural processes interact unpredictably with the built environment.
Changes or growth in the built environment in floodplains increases
unpredictability of these interactions.
B. Major flooding occurs on an infrequent basis in the Yakima area. Many individuals
(residents, public employees, and decision -makers) are unfamiliar with or
unaware of the hazards and potential responses to conditions during a flood.
C. Lack of predictive power (in the form of models and monitoring of watershed
conditions) before and during flood events, specifically in the Ahtanum-Wide
Hollow basin.
D. Some areas are more prone to flooding and flooding damage than others. In areas
subject to repetitive flood damage, insufficient programs (or use of those
programs) to reduce or eliminate the flood hazard, increases the frequency of
costly flood fight/flood response, damage, etc.
E. Changes in government programs and how they are administered (i.e. the role of
FEMA in the Department of Homeland Security) can reduce the effectiveness of
response.
F. Insufficient communication between agencies, public, etc.
30 I Ahtanum-Wide Hollow CFHMP
3. Alternatives - What Alternative solutions will address the problem?
A. Even with the best planning, floods are a normal and regular occurrence.
Predicting the behavior of any given future flood is impossible, so communities
need to be prepared to protect life and property before, during, and after flood
events.
1) What has already been proposed to address the problem?
a) Parking Lot - See Regulations Discussion
b) Yakima County has both policy and structures for Emergency Management,
and has faced natural disasters before (Mt. St. Helens, 1996 flood). More
discussion of the effects of the Katrina disaster.
c) Comprehensive Emergency Management Planning effort- The Yakima
County Flood Response Plan has been adopted as part of the Emergency
Management Plan.
2) Are there any new solutions that have not already been proposed?
a) Individual preparation for floods - public education directed to residents,
farms and businesses.
3) What still needs to be studied?
B. Floods can result in deaths, injuries, economic and significant personal hardship,
as well as inconvenience to many people.
1) What has already been proposed to address the problem?
a) Warning systems (mass media)
b) Public education about potential flood hazards on their property, and
means of responding to a flood.
2) Are there any new solutions that have not already been proposed?
a) Designation and notification of the public and first responders of evacuation
routes.
3) What still needs to be studied?
C. Effective flood response involves many levels of government, and requires that
government agencies be prepared to respond in a coordinated fashion. Programs
are in place at the local, state and federal level to respond to different levels of
emergencies and disasters. Local government personnel, such as law enforcement
officers and public works employees, as well as first responders, are on the front
lines of the "flood fight" and protection of life and property. The most significant
and pressing issues facing those responsible for responding to floods are keeping
people safe, and preventing chaos. A coordinated, well planned effort is required.
1) What has already been proposed to address the problem?
a) Emergency Response Plan (Get Ready — Set — Go - Recover procedures)
b) Infrastructure or technology in place for better communication between
agencies (EOC)
c) Recognition of potential flood hazard during a flood (Flood Control Zone
District's primary function during a flood event).
d) This plan involves all agencies that may be involved during a flood
emergency in Yakima County, such as (for example) Yakima County
APPENDIX F — FLOOD PROBLEM WORKSHEETS 131
Emergency Management, Cities, the Bureau of Reclamation, the Yakima
County Health District, and the Irrigation Districts.
e) The Flood Control Zone District is currently developing databases
containing information on all parcels that may be affected by different level
flood events. These models correspond to re -mapping FEMA flood maps:
therefore, the Ahtanum-Wide Hollow area is next in line.
2) Are there any new solutions that have not already been proposed?
a) Open contract for aerial observation during floods
b) Special phone line for public to call in and provide intelligence
c) Volunteer program — flood watchers provide information
d) Interagency coordination, including WDFW, Irrigation Districts, and
Yakama Nation Natural Resources, Fisheries and Engineering
3) What still needs to be studied?
D. What actions can be taken during a flood? Even during flood emergencies, actions
by agencies or individuals need to comply with regulations. Actions taken during
a flood that do not comply can result in the subsequent need to remove, alter, or
mitigate for actions taken during the flood. These post -flood actions are often not
eligible for funding related to the disaster.
1) What has already been proposed to address the problem?
a) Under State and County regulations, procedures exist for expedited permit
issuance during a flood event.
b) Ahtanum-Wide Hollow CFHMP recommendations, since they require
approval by WDFW and Ecology, provide a good basis for deciding
whether to take emergency actions, which will be consistent with
regulations.
c) Permitting agencies are a component of the Emergency Management Plan,
and are present in the EOC during a declared emergency. General
guidelines for taking action during a declared or non -declared emergency
are:
(i) permitting personnel do a site visit
(ii) choose minimum action, or action that will meet the intent of the
regulations - i.e. better protect/enhance the resources
(iii) follow up- 6 months after a declared disaster to come into compliance
2) From Parking Lot: Ice jams - who responds to whom?
#13) Urban Union Gap - Lower Wide Hollow (3/1/07)
1. Problem - What is the problem? (Problem Statement)
A. Flooding of Wide Hollow Creek in Union Gap can affect a large area of existing
industrial, commercial and residential uses.
B. Areas of low intensity land uses (i.e. pasture, grazing) have recently been
converted to industrial, residential and commercial uses, in flood prone areas, and
this trend is likely to continue.
32 I Ahtanum-Wide Hollow CFHMP
C. Inaccurate floodplain mapping makes it unenforceable for Union Gap
2. Causes - What is causing the problem?
A. Union Gap is subject to flooding even at low flows, because of its location near the
mouths of both Ahtanum and Wide Hollow Creeks, and its proximity to the
Yakima River.
B. Wide Hollow Creek has been modified to allow for operation of the water wheel at
the mill, which has existed since the 1860's. (Its original location is not known). In
the existing residential and commercial areas of Union Gap, the creek is
channelized, and has lost its floodplain.
C. Wide Hollow Creek backs up at the mill dam just below Main St. Bridge,
frequently causing levee failure on the south side of the creek.
D. The Fines diversion dam raises the water surface elevation over five feet, and has
caused channelization.
E. Lands near Union Gap are desirable due to their location near Union Gap and its
(expanding) transportation and utility infrastructure. Floodplain areas are under
development pressure. Large capitol inputs are required to make these areas
suitable for high intensity use.
F. Vegetation problems (See Vegetation).
G. Union Gap is located is surrounded by the Yakima River, Ahtanum Ridge, and the
City of Yakima- where can it expand?
3. Alternatives - What Alternative solutions will address the problem?
A. Flooding of Wide Hollow Creek in Union Gap can affect a large area of existing
industrial, commercial and residential uses.
1) What has already been proposed to address the problem?
a) Retention of overflow path along the railroad right of way.
b) Maintain open areas near the mouth of Ahtanum creek for inevitable
flooding (i.e. Fulbright Park and adjacent areas).
c) Incorporation of floodplain/open space/retention into site plans (e.g.. La
Salle High School)
d) National Flood Insurance Program (See also "Inundation")
e) Critical Areas Code (See also "Inundation")
f) Re -mapping, so that standards and maps are more accurate (See also
"Inundation")
g) Stormwater design standards (See also "Inundation")
h) More stringent development standards (i.e. prohibit land divisions in the
floodplain). (See also "Inundation")
i) Buy people out/provide incentives for landowners who provide floodplain
storage (See also "Inundation")
j) Structural flood control measures either by individuals or government (See
also "Inundation")
APPENDIX F — FLOOD PROBLEM WORKSHEETS 133
k) Flood—proof, elevate, make existing structures less flood damage -prone.
(See also "Inundation")
2) Are there any new solutions that have not already been proposed?
a) Relocation of Wide Hollow Creek into Ahtanum Creek at some point
upstream of urbanized Union Gap.
b) Removal or modification of the mill dam
c) Include areas of high water table in the floodplain maps. (See also
"Inundation")
d) Improve sediment transport along the Yakima River (Refer to the Upper
Yakima CFHMP) (See also "Inundation")
e) Modify Wapato Dam (See also "Inundation")
f) Preservation and restoration of floodplain in places, while allowing
development in others. (See also "Inundation")
g) Relocation of residents in areas subject to inundation (See also
"Inundation")
3) What still needs to be studied?
B. Flood prone areas of low intensity land uses (i.e. pasture, grazing) have recently
been converted to industrial, residential and commercial uses, and this trend is
likely to continue.
1) What has already been proposed to address the problem?
2) Are there any new solutions that have not already been proposed?
a) Special land use standards for industrial uses relating to hazardous
materials, storage, use, disposal- are they flood proofed?
b) Limit service extension to flood prone areas
C. What still needs to be studied?
#14) Roads, Bridges and Culverts (Draft 4/26/07)
1. Problem - What is the problem? (Problem Statement)
A. In many places in the watershed, bridges constrict the channel, which restricts
flood flow with the potential for bridge failure, increasing levels and area of
inundation, or directing flow in undesirable directions.
B. In some locations, bridges and roads affect channel processes, creating channel
instability upstream and downstream. This may also cause failure or damage to
adjacent infrastructure or private property. Construction of new roads and bridges
will, in most instances, change flooding patterns and flood hazard. These changes
may be desirable or undesirable to agencies, adjacent property owner, etc.
C. Roads act as either conveyances or dams, causing increase in flow velocity and
associated damage, or ponding.
D. Historically, many roads were constructed adjacent to creeks and drainage ways,
and act as levees. For the most part, these structures were not designed as levees
and are subject to failure.
34 I Ahtanum-Wide Hollow CFHMP
E. Culverts can be washed out or plugged during flood events - they are undersized
for those events. Private Driveway culverts are property owner's responsibility.
"Bridge culverts" are bridges with a span of less than 20 ft. - these are classified
under state bridge classification systems, and are public culverts.
F. When bridges and culverts are inundated, it creates a direct safety threat and
economic impact, as well as hindering access to homes and businesses by
residents, employees, school buses and emergency services.
G. Altering and building new transportation infrastructure is very expensive for
government and private citizens. Improving flood conveyance capacity, building
more effective drainage systems, and designing and constructing the roadway to
be able to pass/withstand flood events increases this expense in the short term, but
may reduce expense and damage over long term.
H. In the future, the extent and capacity of transportation infrastructure will increase
due to increased human population and development pressure. Reducing or
eliminating future flood hazard associated with this expansion will require careful
design of the transportation network (from small, private roads to major highway
systems) and the density and intensity of land uses served by the network.
2. Causes - What is causing the problem?
A. General under -capacity of existing bridges and culverts, due to:
1) Outdated/inappropriate design standards for conveyance and/or changes in
levels of service of the road.
2) Lack of knowledge or consideration of flooding patterns when
building/rebuilding roads and culverts
B. The physical conditions of streams and floodplains are altered by new
infrastructure. Due to the inherent complexity of stream channels and floodplains
(natural and anthropogenic variability), forecasting and predicting future physical
conditions (flood frequency and magnitude, channel erosion and migration) at a
given site is not an exact science. Therefore, there is always some degree of risk
associated with new projects.
C. The nature of Ahtanum Creek, with its multiple overflow channels, causes
floodwater to utilize roads as flood channels. East -west running roads move
floodwater down the roadside ditches at high velocities, eroding driveways and
often the roads themselves.
D. Streams are not static environments. Over time, channels adjacent to bridges and
culverts change. These changes may reduce flood capacity or damage the bridge.
E. Floodplains are not static environments. Development in the floodplain may alter
drainage patterns, overwhelming existing drainage systems.
F. The population of the Yakima area is growing. The Wide Hollow and Ahtanum
areas contain urban cores where uses will change and intensify. Existing
developments are mixed with areas of remaining agriculture/open space. Demand
is high for residential and commercial development within the Ahtanum-Wide
APPENDIX F — FLOOD PROBLEM WORKSHEETS 135
Hollow watershed. Utilities and transportation services are also expanding to
service current and future demand.
3. Alternatives - What Alternative solutions will address the problem?
A. In many places in the watershed, bridges constrict the channel, which restricts
flood flow, creating potential bridge failure, and/or increasing levels and area of
inundation and/or directing flow in undesirable directions.
B. In some locations, bridges and roads affect channel processes, creating channel
instability upstream and downstream. This may also cause failure or damage to
adjacent infrastructure or private property. Construction of new roads and bridges
will, in most instances, change flooding patterns and flood hazard. These changes
may be desirable or undesirable to agencies, adjacent property owners, etc.
(These problems (a and b) combined for alternatives)
1) What has already been proposed to address the problem?
a) State hydraulic code requires that "new" bridges convey 100 year flow over
state waters.
b) The process of remapping the floodplains will generate more accurate
hydrology and hydraulics for bridge and roadway design.
c) Inventory and ranking of problem bridges throughout the watershed,
incorporate into Capitol Improvement Plans of local and state jurisdictions.
[(County Roads currently has an inventory, Surface Water is currently
working on as part of FEMA re -mapping). The rate of replacement of
infrastructure is limited by funding, and to some extent standards in the
funding programs.]
d) Active monitoring and management of channels adjacent to bridges to
improve and maintain bridge capacity. (Armor or sediment removal in
poorly functioning bridges, and management of vegetation debris.)
e) For new structures, include in -stream actions to maintain conveyance as
part of the design and construction.
2) Are there any new solutions that have not already been proposed?
a) Design new bridges to allow natural channel processes where they occur. In
areas where natural channel processes have been lost or altered, or where
natural processes are highly unpredictable, design conservatively?
b) New standards and policies for bridges in the floodplain, specifically the
effect of the bridge relative to floodplain width and function. Successful
implementation of such standards and policies will require the
development and sharing of tools and data between agencies and the public
at large.
c) Monitoring of channel and floodplain conditions post construction. If
significant unforeseen problems develop, respond to them.
d) Limit/restrict/reduce the number of bridges and bridge crossings, especially
small private bridges and culverts. [This can be accomplished through road
36 I Ahtanum-Wide Hollow CFHMP
standards, combining existing access points or limiting development
density on land that must be accessed by a bridge.]
3) What still needs to be studied?
a) Integrating existing or new funding programs into strategic program for
addressing problem bridges. See (i.3) above.
b) Inventory of channel process problems
C. Roads act as either conveyances or dams, causing increase in flow velocity and
associated damage, or ponding.
1) What has already been proposed to address the problem?
a) Better floodplain mapping and modeling to allow for better infrastructure
design.
2) Are there any new solutions that have not already been proposed?
a) New road design standards and policies for infrastructure in floodplains.
Issues addressed should include roadway flood passage, level of service,
access to critical facilities, and access to residences.
3) What still needs to be studied?
a) The cumulative effect of new policies and standards.
b) What should the level of service standard for designing roads be?
D. Historically, many roads were constructed adjacent to creeks and drainage ways,
and act as levees. For the most part, these structures were not designed as levees
and are subject to failure.
1) What has already been proposed to address the problem?
a) More armoring of roads which are acting as levees.
2) Are there any new solutions that have not already been proposed?
a) Inventory and rank potential road failure.
b) Design site-specific solutions based on the inventory and current and future
road classification; solutions may include armoring or changes to road
configuration, or elimination of the road and selection of alternate route.
Incorporate findings into transportation planning.
c) Consider putting in roads at grade
d) Lower some roads
3) What still needs to be studied?
a) Inventory of private roads
E. Culverts can be washed out or plugged during flood events - they are undersized
for those events. Private Driveway culverts are property owner's responsibility.
"Bridge" culverts are bridges with a span of less than 20 ft. - these are classified
under state bridge classification system, and are public culverts.
1) What has already been proposed to address the problem?
a) Increased maintenance and debris cleanout of culverts and ditches on public
roads.
2) Are there any new solutions that have not already been proposed?
a) Recognize the limitations of culverts.
APPENDIX F — FLOOD PROBLEM WORKSHEETS 137
b) Armor or redesign road prism to withstand flood damage adjacent to
culverts.
c) Identify road ditches that serve as flood conveyance, thus placing them at a
high priority for maintenance (i.e. Rutherford Rd).
d) Public education about maintaining driveway culverts, and correct sizing
and maintenance of culverts.
e) Replace old culverts with higher capacity culverts depending on level of
risk.
f) New public and private culverts should be designed with adequate volume
capacity to minimize the risk of the culvert blowing out, or should be
designed to overtop or be bypassed without failure.
3) What still needs to be studied?
a) Private road culvert inventory
b) Private driveways built to grade, where culverts are not preferable.
F. When bridges, culverts and roads are inundated, it creates a direct safety threat
and economic impact, as well as hindering access to homes and businesses by
residents, employees, school buses and emergency services.
1) What has already been proposed to address the problem?
a) Flood responders concentrate patrol and response on known problem
bridges and roads.
b) More maintenance at known problem bridges
2) Are there any new solutions that have not already been proposed?
a) Standards and policies for critical access routes
b) Develop alternative access routes and incorporate into transportation
planning
c) Flood response planning
3) What still needs to be studied?
a) Future development and critical access routes
G. Altering and building new transportation infrastructure is very expensive for
government and private citizens. Improving flood conveyance capacity, more
effective drainage systems, and roadway flood passage increases this expense in
the short term, but may reduce expense and damage over long term.
1) What has already been proposed to address the problem?
a) Improved flood mapping and modeling to assess risk to new and existing
infrastructure and designing new infrastructure.
b) Flood Control Zone District providing technical assistance and comments
regarding flood hazards and infrastructure design.
c) Identify overflow paths and critical bridges.
d) Existing and amended floodplain and critical areas codes.
2) Are there any new solutions that have not already been proposed?
a) When transportation infrastructure is damaged during flood events, it
should be replaced in a manner that reduces vulnerability to future flood
hazard.
38 I Ahtanum-Wide Hollow CFHMP
b) Federal and state funding programs to reduce or mitigate the environmental
effects (including flooding) of existing road systems do exist- explore ways
to take better advantage of these programs.
c) Place higher priority on these issues at the federal, state, tribal and local
level.
d) Funding sources or incentives for private drainage infrastructure
e) Work with landowners up and downstream of new infrastructure to
appropriately design their access to property.
3) What still needs to be studied?
H. In the future, the extent and capacity of transportation infrastructure will increase
due to increased human population and development pressure. Reducing or
eliminating future flood hazard associated with this expansion will require careful
design of the transportation network (from small, private roads to major highway
systems) and the density and intensity of land uses served by the network.
1) What has already been proposed to address the problem?
a) Stormwater management standards for new and reconstructed roads.
b) Growth Management and Capitol Facilities planning processes should
ensure that expansion of the transportation network is consistent with
CFHMPs.
2) Are there any new solutions that have not already been proposed?
a) Monitor the effects of transportation system expansion changes to the
characteristics (runoff, time of concentration, water quality) of the
watershed over time. Take action to mitigate for negative watershed scale
effects.
b) Take larger scale affects to the watershed into account when designing new
transportation systems:
(i) Minimize number of roads - maximize efficiency.
(ii) New major arterials and new traffic -generating developments should
be located outside of floodplains (See also Land Use).
(iii) Limit access to major arterials where they cross or are adjacent to
floodplains.
(iv) Encourage the retention of open space in floodplains with the
development of non -motorized transportation systems.
c) Special standards by road functional type and private road classification for
roads in floodplains. Matrix - functional classification by stream or
floodplain type.
d) There are areas (e.g. Emma Lane, towns of Ahtanum and Wiley City) in the
watershed that are composed of "islands" of non -floodplain surrounded by
floodplain areas. Transportation networks in these areas (even if they are
zoned as low density) should be planned to take into account surrounding
properties, rather than a standard site-specific approach. See also "Land
Use"
APPENDIX F — FLOOD PROBLEM WORKSHEETS 139
e) ID and maintain critical access routes at 10, 25 and 100 year events. These
roads should be designed to be elevated and accessible using design
standards with minimal effect on flood flows.
f) Roads that are not identified as critical access routes should be built at grade
to avoid altering flood patterns.
g) County (and Cities?) evaluate access needs on a case by case basis.
3) What still needs to be studied?
PARKING LOT - Private Levees
To PARKING LOT - development in areas with floodplain "islands"
Require increased elevation of new structures in the floodplain and flood -proofed
utilities.
#15) Land Use Draft 5/30/07
1. Problem - What is the problem? (Problem Statement)
A. If flooding issues are not taken into account in the development of the Ahtanum-
Wide Hollow area, residents, businesses and infrastructure (present and future)
will be at increased risk for damage from flooding. This is especially true of high-
intensity urban development located within the floodplain, which has a strong
tendency to result in filling in the floodplain, and diverting flood flows onto other
properties (including properties that are not normally flood prone).
B. There are known high hazard areas where development is occurring or proposed.
[i.e. Bachelor and Ahtanum Creek floodplains from 42nd Ave. to 3rd St., Wiley City,
town of Ahtanum and areas east to 64th, area around Meadowbrook and
Rutherford Road (Hatton Creek and Ahtanum) south of Wiley City.]
C. In existing urbanized and rapidly urbanizing areas, the
design/effectiveness/maintenance of stormwater systems can significantly affect
flood hazard
2. Causes - What is causing the problem?
A. The Ahtanum-Wide Hollow watershed has topography that makes it unusually
flood -prone. This is due to:
1) Extensive, widespread, unpredictable flooding patterns.
2) Minor changes to watershed resulting in major changes in flooding
(Downstream impacts from small changes in creek)
3) Lack of knowledge of changes in flooding patterns in the watershed
4) The narrow flood corridors within the study area make the consequences of hi -
intensity development within them more pronounced.
B. There is considerable development pressure for single family homes in West
Valley, and for light industrial development in the floodplain, within the city
40 I Ahtanum-Wide Hollow CFHMP
limits of Yakima and Union Gap. Increase in density of development in the
Ahtanum-Wide Hollow watershed will potentially exacerbate flooding patterns.
C. The historical approach to Land Use Planning has not taken floodplains into
consideration when establishing broad "future land use" designations in planning
and zoning documents within the Urban Growth Area. This has established an
expectation in the public's mind that all land (including floodplain land) within
the UGA can or will be developed to a high intensity of use.
3. Alternatives - What Alternative solutions will address the problem?
A. If flooding issues are not taken into account in the development of the Ahtanum-
Wide Hollow area, residents, businesses and infrastructure (present and future)
will be at increased risk for damage from flooding. This is especially true of high-
intensity urban development located within the floodplain, which has a strong
tendency to result in filling in the floodplain, and diverting flood flows onto other
properties (including properties that are not normally flood prone).
1) What has already been proposed to address the problem?
a) Existing zoning (status quo) - Flood overlay district, open space designation
b) NFIP standards (Regulatory standards)
c) Parks in frequently flooded areas (Fulbright Park and West Valley Park)
d) Planning Policies. For example, the Yakima Urban Area Comprehensive
Plan, Objective E7 is "Ensure development compatibility within the
floodplain and frequently flooded areas." Furthermore, it goes on to say, "It
is more costly to remedy property losses than to conserve and protect
them." (Yakima Urban Area Comprehensive Plan, page IX -5)
2) Are there any new solutions that have not already been proposed?
a) Policies and standards for open space retention for expansion of UGA's and
individual developments. Meet each local jurisdiction's open space and
park needs (GMA) by identifying stream corridors.
b) Using Critical Areas update policies to establish open space
c) Incentives or bonuses for developers who actively protect these areas. (10%
density bonus). Specificity in zoning ordinance.
d) Focus lower -intensity development within the floodplain corridors, while
focusing higher intensity developments to the sides of the flood corridor.
Lower density for subdivisions in the floodplain.
e) Consistency in zoning standards for developments and buildings.
Information about properties up -front (no surprises).
f) Policies directing preferred locations for the siting of new infrastructure such
as major and minor arterials, water and wastewater distribution mainlines,
regional stormwater facilities, parks and greenbelts.
g) Make changes to comprehensive planning and zoning documents and maps
to focus lower intensity development within floodplain corridors and focus
higher intensity development outside floodplain corridors.
APPENDIX F — FLOOD PROBLEM WORKSHEETS 141
h) Local governments should establish specific comprehensive plan policies to
use floodplains and other critical areas to meet their GMA requirements for
providing Parks and Open Space. This can substitute for planning specific
large blocks of private land for Parks and Open Space.
i) Policies for areas of existing dense development within the floodplain (such
as Ahtanum and Wiley City)
j) Policies for retrofitting and re -development of stormwater facilities and flood
water routing in existing urbanized areas.
k) Development moratoriums or high standards of proof- Is development
outpacing knowledge or tools available to keep the public safe?
3) What still needs to be studied?
B. There are known high hazard areas where development is occurring or proposed.
[i.e. Bachelor and Ahtanum Creek floodplains from 42nd Ave. to 3rd St., Wiley City,
town of Ahtanum and areas east to 64th, area around Meadowbrook and
Rutherford Road (Hatton Creek and Ahtanum Creek) south of Wiley City
1) What has already been proposed to address the problem?
a) Status quo- New developments must meet development standards and go
through the planning process.
2) Are there any new solutions that have not already been proposed?
a) Recognize that in some places, the issues associated with larger scale
proposed developments are not adequately addressed by current standards.
This often results in an unpredictable and contentious hearings/approval
process.
b) Special zoning designations for development in high flood hazard areas
(flood overlay zone). Objectives of flood overlay zone should be to protect
the public and retain flood storage.
c) Special incentives - (clustering, density bonuses, Transfer of Development
Rights) for retention of floodplain function in development design.
d) Acquisition - fee simple or easement, for a variety of purposes consistent
with floodplain function
e) Open space taxation - specifically including these problem areas in the
public benefit rating.
f) Reconfiguration of the floodplain area (concentrating floodplain in one area
and uplands in another) for purposes of flood storage or urban
development.
3) What still needs to be studied?
a) Examples from other similar areas?
C. In existing urbanized and rapidly urbanizing areas, the
design/effectiveness/maintenance of stormwater systems can significantly affect
flood hazard
1) What has already been proposed to address the problem?
a) Regional Stormwater Program for the Yakima Urbanized Area.
42 I Ahtanum-Wide Hollow CFHMP
b) Historically, Drainage Improvement Districts (DIDs) have also served as
stormwater drainage systems [they were not sized or designed for this
purpose].
2) Are there any new solutions that have not already been proposed?
a) Establish a relationship between stormwater standards and development
standards in floodplains. (Stormwater systems don't work very well in most
floodplains due to frequency of flooding, high water table and low
gradient).
b) Site design to reduce stormwater runoff.
What still needs to be studied?#16) Regulatory Issues
1. Problem - What is the problem? (Problem Statement)
A. Regulations surrounding flooding are necessary in order to keep people safe, but
there is often resistance to stricter standards.
B. Classification of some waterways as to whether they are ditches or streams
complicates management for flood risks. Some streams that flood are not
identified on FEMA flood hazard maps, placing residents with no flood insurance
at risk for flooding.
C. Lack of information and communication among permitting agencies and people
trying to get permits causes confusion and frustration.
D. It is important for residents and businesses to understand their flood risk, and to
understand what they can do about it, and which agencies they need to work with.
2. Causes - What is causing the problem?
A. Flood regulations are in place for the protection of life and property. In addition,
development projects near waterways are subject to the Shoreline Management
Act, the Critical Areas Ordinance, Land Use Regulations, and numerous other
Federal and State statutes. The sheer number of regulations pertaining to
waterways causes a problem with coordination of the permitting process.
B. Regulating development based on FEMA flood hazard management maps can be
problematic, especially in a watershed like the Ahtanum-Wide Hollow, where
small changes to the stream channel can create big changes in flooding patterns.
C. Political pressure to move floodplains on maps or allow exceptions can create
major problems.
3. Alternatives - What Alternative solutions will address the problem?
A. What has already been proposed to address the problem?
B. Are there any new solutions that have not already been proposed?
1) From Parking Lot: Setting aside areas as flood storage/open space
2) Use of unnumbered A -zones (from Emma Lane Parking Lot)
APPENDIX F — FLOOD PROBLEM WORKSHEETS 143
C. What still needs to be studied?
D. Do these proposals address the causes of the problem?
4. List Alternatives- Proposals that address the causes of the problem are listed as
Alternatives, as well as instances where further study is required. Additional
Regulatory meeting — Draft June 14th, 2007
*On -Screen Exercise*
Local Regulations/Policies CFHMP Can Address
These may apply to all jurisdictions in the study area.
Parking Lot Issues:
1. Below is a list of regulatory measures we may want to address in the CFHMP. It is not
comprehensive, so please bring up anything you think is being missed. All of these
alternatives (and issues) listed are from the Parking Lot during other discussions
(listed in italics).
A. There is a loss of floodplain capacity due to development (from Channel Issues)
B. Loss of floodplain capacity contributes to flooding (from Channel Issues)
2. Regulatory Tools:
A. Floodplain Ordinance (Flood Damage Prevention Ordinance)
1) Standards for development in areas with floodplain "islands" (from
Infrastructure) define size of "island". — Examples - Road bed at grade?
Implement standard for access- "Texas crossing," culverts, set a backwater
standard. Emergency Access.
2) Require increased elevation of new structures in the floodplain and flood -
proofed utilities. (from Infrastructure)
3) Stricter ordinances- (i.e. Base flood plus 2 or 3 feet) in floodplain areas of Union
Gap (from Union Gap)
4) Policies for areas of existing dense development within the floodplain (such as
Ahtanum and Wiley City) (From Land Use)- Better drainage- i.e. in Wiley City,
water can't get out through drain -used to use the railroad ditch (which has
been filled in) - this lack of drainage causes sheet flow. Study better ways to
drain before development occurs (Land Use). Possible function of Flood Control
Zone District.
B. International Building Code- International Residential Code - City and County
Code
1) Early application of IBC standards to developments. Policies for disclosing
information about properties up -front (no surprises). (From Land Use)
2) Standards in the IRC (International Residential Code) are not as strict as those in
the IBC.
C. Zoning/Floodplain Overlay Zone - Yakima Urban Area Zoning Ordinance
44 I Ahtanum-Wide Hollow CFHMP
1) Standards for development in areas with floodplain "islands" (from
Infrastructure)
2) Incentives or bonuses for developers who actively protect flood hazard areas.
(10% density bonus). Specific development standards in zoning ordinance.
(From Land Use)
3) Reduce density in the floodplain through various methods -
a) Focus lower -intensity development within the floodplain corridors, while
focusing higher intensity developments to the sides of the flood corridor.
Lower density for subdivisions in the floodplain. (From Land Use)
b) Make changes to comprehensive planning and zoning documents and maps
to focus lower intensity development within floodplain corridors and focus
higher intensity development outside floodplain corridors. (From Land Use)
c) Policies for areas of existing dense development within the floodplain (such
as Ahtanum and Wiley City) (From Land Use)
4) Floodway fringe - standards for parking lots
5) Zero or 0.1 foot rise - specifying practice in IBC, amending code, writing it in the
Floodplain overlay zone.
D. Subdivision Code -
1) Standards for subdivision in the floodplain - at the minimum require a
buildable area outside of the floodplain. Standards for lot size and housing
location.
2) Incentives or bonuses for developers who actively protect flood hazard areas.
(10% density bonus). Specific development standards in zoning ordinance.
(From Land Use)
3) Focus lower -intensity development within the floodplain corridors, while
focusing higher intensity developments to the sides of the flood corridor.
Lower density for subdivisions in the floodplain. (From Land Use)
E. Critical Areas Code
1) Standards for geologic hazard areas? Channel migration zones and alluvial fans
- Emphasize keeping homes safe as well as environmental goals.
2) Using Critical Areas update policies to establish open space (From Land Use)
3) Policies and standards for open space retention for expansion of UGA's and
individual developments. Meet each local jurisdiction's open space and park
needs (GMA) by identifying stream corridors. (From Land Use)
4) Local governments should establish specific comprehensive plan policies to use
floodplains and other critical areas to meet their GMA requirements for
providing Parks and Open Space. This can substitute for planning specific large
blocks of private land for Parks and Open Space. (From Land Use)
F. Open space taxation policies
G. Stormwater standards
H. Better system of checks and balances within local government for agencies to buy
in.
I. Enforcement of policies - Enforce policies that already exist
APPENDIX F — FLOOD PROBLEM WORKSHEETS 145
J. Public notice/disclosure/consultation when projects are planned
APPENDIX H
WIDE HOLLOW CREEK PROFILES
Wide Hollow Creek profiles are provided that show gradient, velocities and the location of bridges.
The figures also show plan views with the 100 year map extent. These figures are a tool to indicate
conveyance and problem areas that can be applied for several purposes, including sediment deposition
patterns and preferred road system locations. The profiles along with other tools, such as the bridge
removal guidelines, and the 10 and 25 year maps will help to indicate problematic bridge locations that
can be modified during bridge replacement. The problematic bridge inventory along with the current
and planned road system level of service will be used to establish needs, priorities, replacement
preferences and interim measures.
In some cases the sediment deposits will be due to features other than bridges, such as irrigation
infrastructure, man- made modifications or natural physiological features.
2 I Ahtanum-Wide Hollow CFHMP
Wide Hollow Creek
100 Year Flow Profile 1 of 19
Average slope 0.0057 ft/ft
Average velocity 3.70 ft/s
—Velocity —100 yr water surface elevation • Culvert • Bridge 0 Mill structure
1035 'O
1030 -
J t+ N W A In m V CO b
VELOCITY FT/SEC
1025 -
Area influenced by backwater flooding from the Yakima River
1020 -
/ ►
1015 -
1005 -
''''..)
1005 -
1000 -
0 995 -
O
Q 990
985 -
w
980 -
975 -AM
970 -
+_
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/1
965 -
♦ ��� •
960 -•
955 -
•
♦ .
950 -
♦♦ HWY 97 •. _. • ®
♦
945
•
5000 4500 ♦ 4000 3500 3000 2500 2000 1500 1000 500 0
♦ STREAM STATION FT /
Stream Station
100 Yr Floodplain
•
•
•
•
•
•
•
•
♦ 5730
CITY OF UNION GAP
APPENDIX H - WIDE HOLLOW CREEK PROFILES 1 3
Wide Hollow Creek
100 Year Flow Profile 2 of 19
Average slope 0.0044 ft/ft
Average velocity 3.526 ft/s
—Velocity —100 yr water surface elevation • Culvert • Bridge
1060 'n
1055
—
1050
1045
1040
1035
1030
1025
LL
Z 1020
O
1015
VELOCITY FT/SE
Q
1010
w
1005
1000
995
990 -
985 -
W - ,
980 -�
• ma• AI
975 -
970
‘ White '.•
•
% u
10000 9k00 9000 5500 5000 7500 7000 6500 6000 5500 J000
• STREAM STATION FT
•
Stream Station
100 Yr Floodplain
4 I Ahtanum-Wide Hollow CFHMP
Wide Hollow Creek
100 Year Flow Profile 3 of 19
Average slope 0.047 ft/ft
Average velocity 4.07 ft/s
—Velocity
—100 yr water surface elevation
• Culvert
• Bridge
1075
n 01 V W CD
V FT/SEC
1070
1065
1060
1055
1050
1045
1040
i—
z 1035
Q 1030
A
w 1025
, k
r
1020
,
-
1015
1010
Pvt
n.
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♦
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•n YP.rr.■
1000
♦
995 -__%,
♦
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985
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f,
1450`
14000
13500 13000
12500
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11500
11000
10500
16000
15000
♦
STREAM STATION FT
;
Stream Station
100 Yr Floodplain
APPENDIX H - WIDE HOLLOW CREEK PROFILES 1 5
Wide Hollow Creek
100 Year Flow Profile 4 of 19
Average slope 0.005 ft/ft
Average velocity 3.355 ft/s
1100
—Velocity
—100 yr water surface elevation
♦ Culvert
■ Bridge
1095 -
1090 -
1085 -
1080 -
1075 -
1070 -
1-
1065 -
A In 01
VELOCITY FT/SEC
Z
1060 -
0
i
1055
E
w
1050 -
1045 -
1040 -
1035 -
10th Ave
1030 -
R
1025 -
1
■
1
1020
1015 -
,
. 'Ve
4
1/4
1010
19500
%
19000
18500
18000
17500
17000
16500
16000
15500
115000
20000
•
STREAM STATION FT
i
•
•
•
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•
Stream Station
100 Yr Floodplain I J
•
•
•
1
1
1
1
I
I
6 I Ahtanum-Wide Hollow CFHMP
Wide Hollow Creek
100 Year Flow Profile 5 of 19
Average slope 0.006 ft/ft
Average velocity 4.18 ft/s
ELEVATION FT
1125
1120
1115
1110
1105
1100
1095
1090
1085
1080
1075
1070
1065
1060
1055
1050
1045
1040
1035
—Velocity
100 yr water surface elevation
0 Culvert
■ Bridge
25000 24500% 24000 23500 23000 22500 22000
•
STREAM STATION FT
21500
21000
20500
10
9
8
7
6 w
N
5 r
V
0
4 j
3
2
20000
•
Stream Station
100 Yr Floodplain
•
1
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•
STREAM STATION FT
21500
21000
20500
10
9
8
7
6 w
N
5 r
V
0
4 j
3
2
20000
•
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100 Yr Floodplain
•
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APPENDIX H - WIDE HOLLOW CREEK PROFILES 1 7
Wide Hollow Creek
100 Year Flow Profile 6 of 19
Average slope 0.007 ft/ft
Average velocity 3.996 ft/s
—Velocity —100 yr water surface elevation
0 Culvert
• Bridge
1150
D t+ N W A M al V CO b lz
VELOCITY FT/SEC
1145 -
1140 -
1135 -
1130 -
1125 -
1120 -
1115 -
H
Z
1110 -
O
1105
P
w
1100 -
ii
1095 -
1090 -
.
_
1085 -
1
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%
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1060
30000
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9500
29000 28500
28000
27500
27000
26500
26000
25500
2
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STREAM STATION FT
1
Stream Station
100 Yr Floodplain
f
/45' 177
8 I Ahtanum-Wide Hollow CFHMP
Wide Hollow Creek
100 Year Flow Profile 7 of 19
Average slope 0.005 ft/ft
Average velocity 3.53 ft/s
—Velocity —100 yr water surface elevation
• Culvert
• Bridge
'n
1180
'+ N W A U N V M b li
VELOCITY FT/SEC
1175 -
1170 -
1165 -
1160 -
1155 -
1150 -
1145 -
H
z
1140 -
O
Q
1135
1130 -
A
i
�'
1125 -
1120 -
1115 -
,
1110 -
1105 -
40th Ave
1100 -
Pvt
1095 -
1090
``
35000 34500 34000 33500
`t
33000
32000
31500
31000
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STREAM STATION FT
i
•
•
•
Stream Station
100 Yr Floodplain
s
op vs, ,I rt.`:'
t
itt9v2al '1'1'
: :
•
,
0
0,
L
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ashington Ave
APPENDIX H - WIDE HOLLOW CREEK PROFILES 1 9
Wide Hollow Creek
100 Year Flow Profile 8 of 19
Average slope 0.005 ft/ft
Average velocity 3.226 ft/s
® Bridge
—Velocity
—100 yr water surface elevation
O Culvert
^^
1205
-
o I+ NI w A to orn 1 CO ID '
VELOCITY FT/SEC
1200 -
1195 -
1190 -
1185 -
1180 -
1175 -
1170
L
Z
1165 -
O
1160
Q
>
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w
1155 -
1150 -
1145 -
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%
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,
37000
,
36500
36000
,
35500
,f
35000
40000
%
STREAM STATION Frt
1
•
•
•
Stream Station
100 Yr Floodplain
•
\/ Nob Hill Blvd
•
•
•
72,
•
14,
C
10 I Ahtanum-Wide Hollow CFHMP
Wide Hollow Creek
100 Year Flow Profile 9 of 19
Average slope 0.003 ft/ft
Average velocity 3.22 ft/s
—Velocity
—100 yr water surface elevation • Culvert
• Bridge
'n
1230
1225 -
1220 -
1215 -
1210 -
1205 -
1200 -
1195
vl
LOCITY FT/SEC
H-
Z
1190 -
O
1185
Q
>
LM
1180 -
w
1175 -
1170 -
1165 -
1160 -
1155 -
it
1150
%
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1145 -
`
1140
45000 ``
44500 44000
43500
43000 42500 42000
41500
41000
40500
Z000
STREAM STATION FT
•
Stream Station
100 Yr Floodplain
a �
07-
%W Nob Hill Blvd
W Nob Hill Blvd
,,e
fri
N
Q
D W Mead Ave
Lo
iLtlb
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APPENDIX H - WIDE HOLLOW CREEK PROFILES 1 11
Wide Hollow Creek
100 Year Flow Profile 10 of 19
Average slope 0.010 ft/ft
Average velocity 3.045 ft/s
—Velocity —100 yr water surface elevation • Culvert • Bridge
1245
1240
1235
1230
.
1225
1220
1215
1210
I -
Z 1205
0
P
1200
w 1195
1190
1185
■
A L. .
1180
1175
_\
1170
1165
``
1160
1155
\
5000 li 49500 49000 48500 48000 47500 47000 46500 46000 45500 '50
STREAM STATION FT 1
Stream Station
100 Yr Floodplain
W Nob Hill Blvd
• Imo''
1
•
10
9
7
6
u
5 F
V
O
4 j
3
2
0
0
12 I Ahtanum-Wide Hollow CFHMP
Wide Hollow Creek
100 Year Flow Profile 11 of 19
Average slope 0.008 ft/ft
Average velocity 3.50 ft/s
—Velocity —100 yr water surface elevation O Culvert • Bridge
1275 +^
1270 -
1265
1260 -
1255 -
1250
1245 -
1240 -
F
Z 1235
0
1230
/ELOCITY FT/SE
Q
1225
w
1220
1215 -
II
i 1�
„
1210 -
1205 -
1
1 ' wi--Wiir
1200 -
1195 -
1 7.th Av ,
1
1190 -�
1185
55000
1 *
1 54500 54000 53500 53000 52500 52000 51500 51000 50500 • 50000
1 1
STREAM STATION FT
Stream Station 1
100 Yr Floodplain n
i 1 1
/
/
/
/
/
I
/
APPENDIX H — WIDE HOLLOW CREEK PROFILES 1 13
Wide Hollow Creek
100 Year Flow Profile 12 of 19
Average slope 0.011 ft/ft
Average velocity 4.035 ft/s
ELEVATION FT
1305
1300
1295
1290
1285
1280
1275
1270
1265
1260
1255
1250
1245
1240
1235
1230
1225
1220
1215
—Velocity —100 yr water surface elevation
• Culvert
• Bridge
60000
59500t
59000 58500 58000 57500 57000
STREAM STATION FT
56500
56000
55500
10
9
8
7
6 N
5 r
O
4 >
3
2
0
51000
Stream Station
100 Yr Floodplain
•
A
zet
\
Ph 981. 1,44441111II
\ 96t
\ Pvt 9508
1 wt.
I
60000
59500t
59000 58500 58000 57500 57000
STREAM STATION FT
56500
56000
55500
10
9
8
7
6 N
5 r
O
4 >
3
2
0
51000
Stream Station
100 Yr Floodplain
•
A
14 I Ahtanum-Wide Hollow CFHMP
Wide Hollow Creek
100 Year Flow Profile 13 of 19
Average slope 0.01 ft/ft
Average velocity 3.54 ft/s
—Velocity —100 yr water surface elevation • Culvert ■ Bridge
'n
1.350
1345 -
r N W A to O� V 00 b
VELOCITY FT/SEC
1340 -
1335 -
1330 -
1325 -
1320 -
1315
Wide Hollow Rd
LL
Z 1310 -
O
1305
4
-
1300 -
w
tl ..
U
`
1295 -
1290 -
1
1
in
1285 -
1280 -
1
1
Pvt 112
1275 -
1270 -
1
1 Pvt 1081.
1265 -
1260
1
1
1i .,
65000 1 64500 64000 63500 63000 62500 62000 61500 61000 60500 f 60000
1 STREAM STATION FT I
Stream Station 1
100 Yr Floodplain
Average slope 0.007 ft/ft
Average velocity 3.52 ft/s
ELEVATION FT
1405
1400
1395
1390
1385
1380
1375
1370
1365
1360
1355
1350
1345
1340
1335
1330
1325
1320
1315
APPENDIX H — WIDE HOLLOW CREEK PROFILES 1 15
Wide Hollow Creek
100 Year Flow Profile 14 of 19
—Velocity —100 yr water surface elevation
0 Culvert
■ Bridge
70000
61500
69000 68500 68000 67500 67000
STREAM STATION FT
66500
66000
65500
10
9
8
7
6
5
4
3
2
1
65000
VELOCITY FT/SEC
i
I
1
I
1
7. iJ ice
Pvt 124
-�
I
i
Po
Rd 1211
I
1
70000
61500
69000 68500 68000 67500 67000
STREAM STATION FT
66500
66000
65500
10
9
8
7
6
5
4
3
2
1
65000
VELOCITY FT/SEC
16 I Ahtanum-Wide Hollow CFHMP
Wide Hollow Creek
100 Year Flow Profile 15 of 19
Average slope 0.012 ft/ft
Average velocity 4.20 ft/s
ELEVATION FT
1450
1445
1440
1435
1430
1425
1420
1415
1410
1405
1400
1395
1390
1385
1380
1375
1370
—Velocity —100 yr water surface elevation
• Culvert
• Bridge
75000
74500
♦
74000 73500 73000 72500 72000
STREAM STATION FT
71500
71000
70500
10
9
8
7
6 w
LL
5
O
4 >
7400
3
2
0
Stream Station
100 Yr Floodplain
ide Hollow Rd
y0
0.
Mir
(i
•
q y
31n �Y4i
1
R
♦ Gromore R•
\
\
♦
141
\
♦
\00...."'%.%.
\
♦
♦ Wide Hollow Roa• i
\
75000
74500
♦
74000 73500 73000 72500 72000
STREAM STATION FT
71500
71000
70500
10
9
8
7
6 w
LL
5
O
4 >
7400
3
2
0
Stream Station
100 Yr Floodplain
ide Hollow Rd
y0
0.
Mir
(i
•
q y
31n �Y4i
Average slope 0.011 ft/ft
Average velocity 3.86 ft/s
ELEVATION FT
1515
1510
1505
1500
1495
1490
1485
1480
1475
1470
1465
1460
1455
1450
1445
1440
1435
1430
1425
APPENDIX H — WIDE HOLLOW CREEK PROFILES 1 17
Wide Hollow Creek
100 Year Flow Profile 16 of 19
—Velocity —100 yr water surface elevation
Culvert
• Bridge
80000
Stream Station
100 Yr Floodplain
79p00
79000 78500 78000 77500 77000
STREAM STATION FT
76500
76000
75500
10
9
8
7
6
5
4
3
2
45000
VELOCITY FT/SEC
If
Pvt 146
Pvt 146
` wu
Pvt 145
Pvt 1
80000
Stream Station
100 Yr Floodplain
79p00
79000 78500 78000 77500 77000
STREAM STATION FT
76500
76000
75500
10
9
8
7
6
5
4
3
2
45000
VELOCITY FT/SEC
18 I Ahtanum-Wide Hollow CFHMP
Average slope 0.02 ft/ft
Average velocity 3.93 ft/s
ELEVATION FT
1570
1565
1560
1555
1550
1545
1540
1535
1530
1525
1520
1515
1510
1505
1500
1495
1490
1485
1480
Wide Hollow Creek
100 Year Flow Profile 17 of 19
—Velocity —100 yr water surface elevation
• Culvert
• Bridge
85000 1 84500
Stream Station 1
100 Yr Floodplain li
84000 83500 83000 82500 82000
STREAM STATION FT
81500
81000
80500
10
9
7
6
5
4
3
2
(0000
1
VELOCITY FT/SEC
1 *. 2225 4
1
1
1
1
1
1
1
• 51
180
I
1•
1
1
1
1
Pv1164
•
1
1
1
1 Pic
1 4
85000 1 84500
Stream Station 1
100 Yr Floodplain li
84000 83500 83000 82500 82000
STREAM STATION FT
81500
81000
80500
10
9
7
6
5
4
3
2
(0000
1
VELOCITY FT/SEC
APPENDIX H — WIDE HOLLOW CREEK PROFILES 1 19
Wide Hollow Creek
100 Year Flow Profile 18 of 19
Average slope 0.018 ft/ft
Average velocity 4.4 ft/s
❑ Bridge
—Velocity
—100 yr water surface elevation
0 Culvert
'n
1650
-
1645
:' .
1640 -
1635 -
\
1630 -
\
1625 -
;
Pvt 141
40
1620 -
\
1615 -
\
A U .
VELOCITY FT/SEC
Stone Rd
•
z 1610 -
0
\
Q 1605
\
9 1600 -
\
L. 1595 -
.......4\
1590 -
\
1585 -
\
1580 -
\
1575 -
\
1570 -
\
1565 -
\
\
1560
90000
8950\ 89000
88500
88000
87500
87000
86500
86000
85500
$000
ere CA
ernrInni ET
/
20 I Ahtanum-Wide Hollow CFHMP
Average slope 0.016 ft/ft
Average velocity 4.5 ft/s
ELEVATION FT
1740
1735
1730
1725
1720
1715
1710
1705
1700
1695
1690
1685
1680
1675
1670
1665
1660
1655
1650
Wide Hollow Creek
100 Year Flow Profile 19 of 19
—Velocity —100 yr water surface elevation • Culvert • Bridge
95000
94500
94000
93510
93000 92500 92000
STREAM STATION FT
91500
91000
Stream Station
100 Yr Floodplain
90500
1
10
9
8
7
6
• r-
5
u
O
4
3
2
Alb00
1'
fOgi I
End of study 4
1
1
1
1
1•-
1
1 NI
1 Ph, ,'•
1
1 Burnham R•
1
1
1
1
1 Rurnhan+R
95000
94500
94000
93510
93000 92500 92000
STREAM STATION FT
91500
91000
Stream Station
100 Yr Floodplain
90500
1
10
9
8
7
6
• r-
5
u
O
4
3
2
Alb00
1'
fOgi I
Wide Hollow Creek 72nd — 80th Conveyance Project
Winter 2009-2010
Project Area
Large woody debris created from collapsing hybrid willows and beaver dams have drastically
reduced conveyance of Wide Hollow Creek. Due to these conditions, the creek would leave its
banks and produce minor flooding problems during normal water flows.
2 I Ahtanum-Wide Hollow CFHMP
Scope of Work
Remove the woody debris and beaver dams from the creek's channel. Remove woody debris
less than 8 inches in diameter off site, leave the larger woody debris on site. Remove two foot
bridges, straighten the channel in two locations and re -vegetate the disturbed areas and areas
void of vegetation.
APPENDIX I - WIDE HOLLOW CREEK 72ND - 80TH 1 3
Before
After
4 I Ahtanum-Wide Hollow CFHMP
Before
after
APPENDIX I - WIDE HOLLOW CREEK 72ND - 80TH 1 5
Before
After
Beaver Dam
6 Ahtanum-Wide Hollow CFHMP
New
main
channel
Original
channel.
now a
bypass
channel
IL =
Original
channel
Additional
channel
-•=. 7
•, _ -4.-.
:•: -'.-'..:--.. 1 •-• .c.r
'0,....• \t• • '
4
. '
A._ • t
MEMORANDUM OF AGREEMENT
BETWEEN THE
YAKAMA NATION
AND
YAKIMA COUNTY
RELATING TO
FLOOD MANAGEMENT
FOR THE YAKAMA RESERVATION REACHES
OF THE YAKIMA RIVER AND AHTANUM CREEK
I. INTRODUCTION
This Memorandum of Agreement (MOA) is entered into by the Yakama Nation (Nation) and
Yakima County (County) for the purposes stated below.
II. PURPOSE AND SCOPE
A. Purpose
The parties agree that there is a lack of sufficient information regarding the flooding potential and
damage to structures and property of the Nation and County for the Yakama Reservation Reaches
of the Yakima River and Ahtanum Creek. The parties further agree that future development
within the flood prone area of this reach should be conducted based upon complete knowledge of
flood hazards and with a thorough effort to avoid loss of human life, damage to property, and loss
of ecological floodplain functions.
B. Scope
The scope of this MOU will be planning for stormwater management and flood events ranging
from 6 month to 100 year events and shall include analysis of current development, extent of
damage to current development, means to conduct future development within the Reach to avoid
continued damage, and means to develop and preserve floodplain/river interaction to minimize
flood damage in this and adjacent reaches. Water quality and ecological considerations shall be
included in this project.
ROLES OF NATION AND COUNTY IN STUDY
A. The Nation shall co -manage the project(s) and will provide technical expertise and may at its
discretion, complete tasks related to hydrology, hydrogeology, physical engineering, and fisheries
enhancement. It is recognized that the Nation will not be responsible for the outlay of funds to
conduct this planning effort but will contribute to the planning effort through `in-kind' and paid
contribution of professional services by Nation staff. The Nation will submit invoices to the
County during the project for payment of project related work.
S. The County shall co -manage the project(s), provide surface water and flood management expertise
and expertise in state planning and zoning, and GIS services. The County will provide financial
compensation to the Yakama Nation for project related work. The County shall utilize a portion
of project funds to conduct its legally binding duties under state law, pay for County project
related work, and administer any consultant contract.
C. The Nation and the County will, upon initiation of a project, designate their respective Project
Managers who will then meet to develop a scope of work. Based upon the scope of work, the
Nation and County project managers will work cooperatively to assign tasks and related funds to
Nation staff, County staff, or a Consultant. The Nation and County project managers shall
develop and execute an agreement for compensation of Nation staff time and expenses. The
2 I Ahtanum Wide -Hollow CFHMP
Nation and County project managers will work cooperatively to solicit consultant proposals and
select and manage a preferred consultant. Both the Nation and County, project managers will
ensure that tasks assigned to their respective staff are completed within the agreed upon budget
and on schedule. During a project, changes in budget and schedule will be determined by joint
consultation of the project managers.
D. This planning process is entered into by each party as a cooperative study to protect and provide
for their respective interests. Participation in this study is to produce an advisory document that
will be forwarded to the policy body of each entity for their planning benefit.
JV. GOALS OF PLANNING EFFORT
A. The goal of this cooperative relationship will be the development of prescriptions for the future
use of the Yakama Reservation reaches of the Yakima River and Ahtanum Creek. The
prescriptions will include detail as to increasing the floodplain capacity of the Yakima River to
diminish the flood potential of frequent and infrequent flood events, provide fish restoration
measures such as hyporheic zone recharge, side -channel habitat, biologically suitable temperature
regimes, fluvial geomorphology appropriate for preservation of fish habitat values, wildlife values
including nesting, security, over wintering habitat and diverse riparian habitat.
Additional goals shall include minimization of property susceptible to flood damage, minimization
of damage to existing County and private structures, and the consideration of appropriate
structures to protect essential floodplain development such as bridges and road surfaces.
B. It shall be the goal of the County and Nation to perform this task in a cooperative fashion and
produce a document that provides clear guidance for the beneficial use and protection of this
floodplain reach.
V.
A.
B.
PROVISOS
Nothing in this MOA is intended to create any rights in any party not a party to this MOA nor
third party beneficiaries.
Nothing in this MOA creates a resource obligation outside that stated within the agreement.
YAKAMA NATION TRIBAL COUNCIL
Robert N. Wahpat., Chairman
; -
r - O- 'er
-70
�7vit 11113 t��1,`,`
BOARD OF YAKIMA COUNTY
COMMISSIONERS
Excused
Ro>ld F. Gamache, Chairman
AL a'l.e-1
/ATTEST thiW' —day oftkr, 2002.
0{(/.1 1 ' (Lk/4_
Carla M. Ward, Clerk of the Board
Approved as to form:
Depury Prosecuting Attorney
1 1 References
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