HomeMy WebLinkAbout09/10/2018 02 Comprehensive Flood Hazard Management PlanBUSINESS OF THE CITY COUNCIL
YAKIMA, WASHINGTON
AGENDASTATEMENT
Item No. 2.
For Meeting of: September 10, 2018
ITEM TITLE: Comprehensive Flood Hazard Management Plan
SUBMITTED BY: Joan Davenport, AICP, Community Development Director
SUMMARY EXPLANATION:
This is a joint Yakima City Council - Yakima County Commissioners Study Session on the draft
Cowiche Creek Comprehensive Flood Hazard Management Plan (CFHMP).
This plan includes flood risks posed by the Lower Cowiche Creek and its confluence with the
Naches River. Recent studies and flood events have demonstrated the current risks posed by
failing or undersized infrastructure in this area towards residents of the City of Yakima and
emphasized the need to plan into the future for revised flood hazard response, protective actions
and flood hazard management for this focused area. This CFHMP is a required document in
order to qualify for FEMA and other mitigation funds.
ITEM BUDGETED:
STRATEGIC PRIORITY:
APPROVED FOR ,,.
SUBMITTAL: City Manager
STAFF RECOMMENDATION:
This is a study session. The Yakima County Commissioners and Yakima City Council will conduct
public hearings in the future for adoption of the CFHMP.
BOARD/COMMITTEE RECOMMENDATION:
ATTACHMENTS:
Description Upload Date Type
D county agenda 91612018 Co r Memo
Craft Comprehensi Fbod hlazard Management Flan 8/30/2018 Backup Material
for CoWche Creek
Summary of Recommendations 9/5/2018 Backup Material
G
YAKIMA COUNTY
Upper Yakima CFHMP — 2018 Cowiche Addendum
Joint Study Session 9-10-2018
10:30 am -11:30 am
• Session Objective
• What is a CFHMP?
• Part of a larger communication process
• funding long term- local consensus brings regional & federal funds
• March 2017 & February 2016 Flood Events
• Near-term Joint actions Summer/Fall of 2017
• City of Yakima, WSDOT, Yakima County
• Establishing risk & potential solutions
• Long-term actions proposed in CFHMP
• Priorities, variety of stakeholder inputs
• City of Yakima, WSDOT, Yakima County
Upper Yakima River
Comprehensive Flood Hazard
Management Plan
--2018 Cowiche Addendum--
tyy
;Ftt!
mw
VrAf
n t
rp
d•«, w
ACKNOWLEDGEMENTS
This Upper Yakima Comprehensive Flood Hazard Management Plan, 2018 Cowiche Addendum was
prepared by Yakima County Public Services Water Resources Division with the assistance of citizens,
stakeholder groups, landowners and agency representatives listed below. We thank them for the time and
effort they spent improving the final product.
UPPER YAKIMA RIVER CFHMP ADVISORY COMMITTEE (2017-2018)
Voting Members
Affiliation
Mr. Scott Anfinson
Washington State Department of Transportation
Mr. Eric BaArand
Washington State Department of Fish and Wildlife
Mr. David Brown
City of Yakima Water/ Irrigation
Mr. Joseph Calhoun
City of Yakima Planning
Mr. Bruce Dekker
Lake Aspen Homeowner's Association
Mr. Jeff Emmons
Yakima County Office of Emergency Management
Mr. Joel Freudenthal
Yakima County Flood Control Zone District
Mr. David Garretson
Private Landowner
Mr. Bob Ingham
Private Landowner
Mr. John Marvin
Yakama Nation
Ms. Keelan McPhee
Yakima County Planning Division
Mr. Mike Price
City of Yakima Wastewater/Stormwater
Mr. Bill Sauriol
Washington State Department of Transportation
Mr. Brett Sheffield
City of Yakima Chief Engineer
Ms. Katrina Strathman
Mid -Columbia Fisheries Enhancement Group
Alternates and Non -Voting Members
Mr. Jason Clapp
Yakima County Office of Emergency Management
Mr. Mark Cleaver
Yakima County Roads Maintenance
Ms. Joan Davenport
City of Yakima Community Development
Mr. Glenn Denman
Lake Aspen Homeowner
Mr. Donald Gatchalian
Yakima County Environmental Services Director
Ms. Michelle Gilbert
Washington Department of Ecology
Mr. Byron Gumz
Yakima County Planning Division
Mr. Perry Harvester
Washington State Department of Fish and Wildlife
Mr. David Haws
Yakima County Flood Control Zone District
Mr. Terry Keenhan
Yakima County Flood Control Zone District
Mr. Dale Meck
Yakima County Flood Control Zone District
Ms. Margaret Neuman
Mid -Columbia Fisheries Enhancement Group
Mr. Connor Parrish
Mid -Columbia Fisheries Enhancement Group
Mr. Matt Pietrusiewicz
Yakima County Engineer
Mr. Scott Schafer
City of Yakima Public Works
Mr. Horace Ward
Yakima County Office of Emergency Management
TABLE OF CONTENTS
Title
7
No.
Acknowledgments.................................................................................................................... i
Tableof Contents..................................................................................................................... ii
Listof Tables............................................................................................................................. v
Listof Figures.......................................................................................................................... vi
Listof Abbreviations.............................................................................................................vii
ExecutiveSummary...........................................................................................................
ES -1
CFHMPRequirements............................................................................................................
ES -1
AdvisoryCommittee..............................................................................................................
ES -1
HydraulicAnalyses................................................................................................................
ES -2
RecommendedActions..........................................................................................................
ES -6
1. Introduction......................................................................................................................1
CFHMPRequirements..................................................................................................................1
Required Consultation with Other Agencies..................................................................1
FloodHazard Management............................................................................................... 8
AdvisoryCommittee...........................................................................................................8
Goalsand Objectives.........................................................................................................10
2. Growth Management Act.............................................................................................16
3. Background Data, Studies and Programs..................................................................19
RelatedStudies............................................................................................................................19
Yakima County Revised Flood Insurance Study (2017)........................................................22
Related Programs and Projects..................................................................................................27
Lower Naches River Partnership Projects (2005).......................................................... 27
Lower Cowiche Channel Relocation Project (2013) ...................................................... 27
4. Flood History..................................................................................................................30
Upstream Drainage and Regulation.........................................................................................30
Significant Cowiche Creek Floods............................................................................................
31
December23, 1933 Flood............................................................................................................33
January16,1974 Flood................................................................................................................34
February1995 Floods..................................................................................................................35
February9, 1996 Flood...............................................................................................................
35
February15, 2016 Flood.............................................................................................................
36
March6, 2016 Flood....................................................................................................................37
March14-16,2017 Flood.............................................................................................................37
5. Floodplain Infrastructure and Flood Control Facilities.........................................39
CreekAlignments........................................................................................................................
39
Levees............................................................................................................................................
42
11
8
Highwayand Road Crossings...................................................................................................43
U.S. 12..................................................................................................................................43
U.S. 12 Bridge.....................................................................................................................44
City of Yakima Powerhouse Road Bridge.....................................................................44
Squire -Ingham Orchard Farm Bridge.............................................................................45
Railwaysand Trails.....................................................................................................................45
Cowiche Creek Trail Bridge............................................................................................. 45
Irrigation Structures and Canals............................................................................................... 45
FormerU.S. 12 Gravel Pits.........................................................................................................45
6. Flood Issues and Infrastructure..................................................................................47
Capacity of Cowiche Creek Infrastructure..............................................................................47
Hydraulic Modeling of Cowiche Creek Infrastructure Capacities......................................47
2016/2017 Discharge Hydrographs..........................................................................................47
HydraulicSimulations................................................................................................................52
Downstream Impacts from Deficiencies of Cowiche Creek Infrastructure ........................ 53
100 -yr Flood Routing in City of Yakima.................................................................................. 54
7. Generation of Alternatives and Recommendations................................................58
Flood Preparation, Actions and Alternatives..........................................................................58
Near -Term Action Plans...................................................................................................
58
Emergency Action Plan and Public Notification....................................................58
Memorandum of Understanding and Interlocal Agreements..............................58
ChannelCleanout.......................................................................................................
59
Repair and Raising of Private Cowiche Creek Levee ............................................
59
U.S. 12 Bridge Cleanout.............................................................................................59
Divert Cowiche Creek Flood Flows West of the 40th Avenue and Fruitvale Road
Interchange............................................................................................................
59
Short and Long -Term Alternatives...........................................................................................60
Long -Term Actions...........................................................................................................
60
Construction of New Bridges....................................................................................60
WSDOT's US 12 Bridge.......................................................................................
60
Yakima County's Cowiche Creek Trail Bridge ................................................
60
City of Yakima's Powerhouse Road Bridge ......................................................
60
Squire -Ingham Orchards Farm Bridge..............................................................60
New Cowiche Creek 100 -yr Long -Term Levees Upstream of U.S. 12 .................
61
Lower Cowiche Creek Reconstruction Upstream of U.S. 12 ................................
61
Short -Term Actions...........................................................................................................
61
New Flood Insurance Rate Maps in the City of Yakima .......................................
61
Nelson Dam Reconfiguration/ Replacement ..........................................................62
Lower Cowiche Creek Reconstruction Downstream of U.S. 12 (YRBWEP) ......62
Generationof Alternatives.........................................................................................................62
Combination of Alternatives into Recommendations...........................................................
63
8. Funding............................................................................................................................71
FCAAP Applicant Eligibility..................................................................................................... 71
iii
Maintenance Project Eligibility.................................................................................................. 71
FCAAPEmergency Projects...................................................................................................... 72
Floodplain by Design Project Eligibility.................................................................................. 72
FEMAProject Eligibility............................................................................................................. 72
References.................................................................................................................................. 73
Appendices
A. Near -Term Action Plan
B. Summary Sheets on Flood Hazard Management Options
C. Advisory Committee Voting Results
ry
LIST OF TABLES
No. Title
HE
No.
ES -1 2018 Advisory Committee Ranking of Flooding Issues ............................................... ES -2
ES -2 Structural Recommendations - Long-Term........................................................................ ES -4
ES -3 Planning Recommendations - Short-Term.......................................................................... ES -5
ES -4 Flood Preparedness Recommendations - Short -Term .................................................. ES -7
ES -5 Public Awareness Recommendations - Short -Term ........................................................ ES -7
1-1 Yakima County CFHMP Advisory Committee........................................................................9
1-2 Summary of Advisory Committee Meetings..........................................................................10
1-3a Short -Term Goals and Objectives for Yakima County CFHMP...........................................11
1-3b Long -Term Goals and Objectives for Yakima County CFHMP...........................................12
1-4 Summary of Prior Pertinent CFHMP Recommended Actions.............................................14
2-1 Horizon 2040 Comprehensive Plan Flooding.........................................................................16
2-2 Horizon 2040 Comprehensive Plan Multi-Hazard.................................................................17
2-3 Horizon 2040 Comprehensive Plan Disaster Recovery.........................................................18
3-1 Summary of Recommendations from Related Studies 2000-2007 ........................................19
3-2 FEMA Adopted Discharges for Cowiche Creek Basin.......................................................... 23
4-1 Documented Flood Damage in Yakima County.....................................................................32
6-1 2018 Advisory Committee Ranking of Flooding Issues........................................................56
7-1 Planning Recommendations - Short-Term.............................................................................. 63
7-2 Flood Preparedness Recommendations - Short-Term.......................................................... 67
7-3 Public Awareness Recommendations - Short-Term..............................................................68
7-4 Structural Recommendations - Long-Term............................................................................69
v
LIST OF FIGURES
No. Title
m
No.
1-1 Vicinity Map..................................................................................................................................3
1-2 CFHMP Study Area (2006)..........................................................................................................4
1-3 CFHMP Amendment Study Area (2018)................................................................................... 5
1-4 Combined 2016 and 2017 Flood Extents.................................................................................... 6
1-5 CFHMP Planning Process............................................................................................................7
3-1 10 -and -100 -year Flow Splits: Lower Cowiche Creek............................................................. 24
3-2 Effective Flood Zone: Cowiche to N. 40th Ave........................................................................ 25
3-3 Effective Flood Zone: N 40th Ave to Myron Lake...................................................................26
3-4 Lower Cowiche Easement..........................................................................................................28
3-5 Naches River Partnership Action Area.................................................................................... 29
4-1 Cowiche Basin Map.................................................................................................................... 30
4-2 1995 Flood Damage by Drainage Area.....................................................................................35
5-1 1901 USGS map of Lower Cowiche Creek...............................................................................40
5-2 1927 Aerial photo of Lower Cowiche Creek............................................................................41
5-3 1947 Aerial Photograph of Lower Cowiche Creek Overlaid with Existing Naches River
Irrigation Diversion Schematic from Nelson Dam to the Old Union Diversion . ........ 42
5-4 Location of Canals, Culverts, Diversions, Levees and Fish Passage...................................46
6-1
Estimated Channel Conveyance...............................................................................................49
6-2
Extrapolated Cowiche Creek Rating Curve............................................................................
50
6-3
Cowiche Creek - Spring 2017 Discharge.................................................................................
50
6-4
Correlation Between Ecology Flow Data and BOR Stage Data............................................51
6-5
Reconstructed 2016/2017 Hydrographs..................................................................................51
6-6
Typical 1D/2D Model Configuration......................................................................................52
6-7
Typical Later Weir Structure Profile and Breach Scenario Configuration ..........................53
6-8
100 -yr Simulation Hydrographs...............................................................................................54
6-9
Potential 100 -yr flood Routing within the City of Yakima ....................................................
55
vi
LIST OF ABBREVIATIONS
AV—Assessed Value
BFE—Base Flood Elevation
BOR—Bureau of Reclamation
CAN --Community Alert Network
CAO --Critical Areas Ordinance
CFHMP--Comprehensive Flood Hazard
Management Plan
cfs--Cubic feet per second
CIP--Capital Improvement Program
COEU.S. Army Corps of Engineers
CRS—Community Rating System
CTEDWashington Department of
Community, Trade and Economic
Development
DNR—Washington State Department of
Natural Resources
Ecology—Washington State Department of
Ecology
EISEnvironmental Impact Statement
EOCEmergency Operations Center
EPA—U.S. Environmental Protection
Agency
EHSBEngrossed House Substitute Bill
ESSBEngrossed Senate Substitute Bill
FCAAP—Flood Control Assistance Account
Program
FEMA—Federal Emergency Management
Agency
FHO—Flood Hazard Ordinance
FHWAFederal Highway Administration
FIRM—Flood Insurance Rate Map
FIS—Flood Insurance Study
Foundation—Yakima Greenway
Foundation
FOZFloodplain Overlay Zone
FSA—Farm Services Agency
GISWeographical Information System
GMAWrowth Management Act
GO --General Obligation (bond)
HPAHydraulic Project Approval
HRCAHydrologically Related Critical
Area
vu
12
IDBIndustrial development bond
LID—Local Improvement District
LOMRLetter of Map Revision
MDNSMitigated determination of non-
significance
MOA—Memorandum of agreement
NAWQANational Water Quality
Assessment
NFIPNational Flood Insurance Program
NRCSNational Resource Conservation
Service
O&M --Operations and Maintenance
OEM --Office of Emergency Management
OHWMWrdinary high-water mark
PEO—Public education officer
PL—Public Law
RAP—Rural Arterial Program
RCWRevised Code of Washington
ROW—Right-of-way
SCS --U.S. Department of Agriculture Soil
Conservation Service
SEPA—State Environmental Policy Act
SFHASpecial Flood Hazard Area
SMP—Shoreline Master Plan
SR—State Route
TMDL—Total Maximum Daily Load
UGA—Urban Growth Area
USDAU.S. Department of Agriculture
USGSU.S. Geological Survey
WACWashington Administrative Code
WDFW Washington State Department of
Fish and Wildlife
WSDOTWashington State Department of
Transportation
YUAYakima Urban Area
13
UPPER YAKIMA CFHMP
2018 COWICHE ADDENDUM
EXECUTIVE SUMMARY
This addendum to the 2007 Upper Yakima River Comprehensive Flood Hazard Management
Plan (CFHMP) addresses the flood risks posed by Lower Cowiche Creek and its confluence with
the Naches River, located within the original CFHMP study area. These risks were not previously
addressed in the earlier CFHMP due to a lack of available information.
Recent studies and flood events have demonstrated the current risks posed by failing or
undersized infrastructure in this area towards the residents of the City of Yakima and
emphasized the need to plan into the future for revised flood hazard response, protective actions,
and flood hazard management for this focused study area.
CFHMP REQUIREMENTS
As in the case of the 1998 and 2007 Upper Yakima CFHMP, this addendum follows the Ecology
process for flood hazard management plans redefined by the 1991 Ecology guidelines. This flood
hazard management process uses a balanced approach to flood damage protection, resource
protection, environmental enhancement, and land development.
The CFHMP must identify the flood issues, flood management goals, and rank appropriate
structural and nonstructural measures to reduce flood damage. The study area may include the
entire watershed or, at a minimum, the 100 -year floodplain within a reach of the watershed, and
the reach must be of sufficient length that a comprehensive evaluation can be made of its flood
problems. The completed CFHMP and its recommendations provides the technical foundation
for future flood management measures.
The CFHMP must be adapted by the local jurisdictions within the established study area prior to
submission to Ecology for approval. An approved local and state CFHMP facilitates grant
funding for the plan's recommendations. To ensure that fishery resources are maintained, the
WDFW has review authority for the CFHMP regarding recommended flood projects. Ecology is
required to consult with WDFW before approving any CFHMP.
ADVISORY COMMITTEE
Public and agency involvement was achieved by forming an Advisory Committee whose
members—representatives of public and private organizations and agency representatives—
provided input through eleven meetings and document review. The committee had 15 voting
and 16 non-voting members, met 11 times and provided plan goals and objectives, developed
alternatives and recommended actions.
The public provides input for the CFHMP through the SEPA process and any hearings required
by the local jurisdictions prior to adoption. Additional agency representatives were contacted as
ES -1
14
needed throughout the plan preparation, and contact was maintained with Ecology to ensure
compliance with Ecology requirements.
HYDRAULIC ANALYSES
Identification of flood vulnerabilities and issues and the development of mitigation alternatives
was based on flood data and the hydraulic analyses provided in Section 6.0. The analyses were
developed at a planning level from the existing limited information, the CFHMP timeframe and
funding. Fortunately, recent LiDAR data at high resolutions was available from a November
2017 flight, in addition to findings from the FEMA FIS study. The analysis of past events and
hydraulic modeling has highlighted vulnerabilities and opportunities for flood response actions
with substantive benefits.
The committee identified and ranked the flood issues in Table ES -1 below.
TABLE ES -1
2018 ADVISORY COMMITTEE RANKING OF FLOODING ISSUES
ID
Flooding Issue
Rank
LC1
Inadequate facilities in floodplain, and hydraulic capacity of Lower Cowiche
Creek to prevent flood overflows to Cit
1
LC2
Floodplain and Flood Risk Mapping not reflective of risk
2
LC3
Improve Public Awareness and Flood Insurance knowledge
2
LC4
Improve Formal Interagency coordination
2
LC5
Revision and Consistency of Flood Hazard, Critical Areas & Shoreline
Ordinances for this location
2
LC6
Inadequate flood forecasting system
2 or 3
LC7
Define Clear Action Points to Initiate Emergency Response Activities for
Cowiche Creek overflows
3
LC8
Funding for Flood Control Works and Restoration Project elements.
3
LC9
Extensive Flood Routing in (and outside of) the City of Yakima
4
LC10
Stability of berms on Lake Aspen/Myron/Willow & Aspen drainage
4
LC11
Risk to US12 during major flood events
5
LC12
Threat of flooding to State, County, and City Roads
5
LC13
Lack of Space for Cowiche Creek Channel Migration
6
ES -2
15
TABLE ES -1
2018 ADVISORY COMMITTEE RANKING OF FLOODING ISSUES
ID
Flooding Issue
Rank
LC14
Availability of Centralized GIS Data & Modeling Impacts in planning and
inventor
6
LC15
Ownership and Standards for new/upgraded Flood Control Facilities
6
LC16
Development pressures in affected areas promoting additional harm
6
LC17
Lack of space for Cowiche Creek low flow Channel Migration
6 or 7
LC18
Operation and Maintenance of Flood Control Facilities
7
LC19
Acquisition/ Preservation of Floodplain Open Space
8
LC20
Loss of Channel Capacity due to sediment accumulation and lateral
confinement
9
LC21
Sediment accumulates in reach, reducing flood capacity
9
LC22
Nelson Dam and Fruitvale infrastructure reducing hydraulic capacity
downstream of US12
9
LC23
Erosion/Loss of Agricultural Land
The advisory committee were unable to rank some issues before others so such situations are
given the same rank.
RECOMMENDED ACTIONS
The current risk and urgency for risk mitigation within the Cowiche Creek study area led to the
need to develop near, short and long-term recommendations that match the risk with the
agencies' ability to provide the required concurrent infrastructure modifications that reduce
current flood hazard.
Near-term mitigation actions would precede the next flood season and incorporate more flood
warning and response measures pending more structural actions, long-term actions would
provide the significant infrastructure changes with long lead times, while short-term actions must
bridge the intervening period by planning and aligning ongoing infrastructure changes with the
long-term plan developed here. As several agencies will be involved in this effort, the plan must
provide enough detail to develop individual capital improvement plans (CIPs).
The near-term priorities with respect to potential flood events are: flood warning, minimizing
overflows toward the city while notifying the public, including evacuation and preparedness,
lessening exposure of existing development through redirection of flows while intercepting flood
overflows from vulnerable areas as far upstream as practical. Near term actions were put in place
for the upcoming 2017/2018 flood season prior to this plan and are contained in Appendix A. The
ES -3
M
most beneficial of these near-term actions is to reroute any Cowiche overflows back into the
Naches below reaching the Fruitvale and 40th interchange. In this regard a Memorandum of
Understanding is being formed between the City, WSDOT and the FCZD, which will extend
beyond the first flood season.
It is evident from the hydraulic capacity computations that the following long-term replacements
in Table ES -2 will be required and that the short-term actions are required to reduce risk in the
interim. They are listed in order of priority. The recommendations' explanatory text is abridged
below. The full recommendations with explanatory text and costs are contained in the
recommendations section. The first long-term structural action will be S2 which must lower the
channel by 3 feet to allow sufficient upstream capacity for the 100 -year flood overflows to be
contained. Leads are provided in the table, the first in each item is considered responsible for
ensuring implementation.
TABLE ES -2 STRUCTURAL RECOMMENDATIONS - LONG-TERM
ID
Recommendation
Lead
Entities
S1
Design and Implementation of all structural recommendations in PL1 will be
coordinated with the overall design in Recommendation PL8 and updated
City, FCZD,
during implementation of each structural element.
WSDOT
S2
Replace Cowiche channel between US12 and the Naches confluence with
capacity to pass 100 -yr flood and remove Cowiche overflows into City from
FCZD
100 -yr flood maps.
S3
Coordinate removal of Fruitvale infrastructure at Cowiche-Naches confluence
with downstream channel design.
City, FCZD
S4
Replace Cowiche channel between Powerhouse Road and US12 with capacity
to pass 100 -yr flood and remove Cowiche overflows into City from 100 -yr
City
flood maps.
S5
Provide levees in the reach between Powerhouse Road and US12 that prevent
Cowiche overflows into the City and allow for enrollment in PL84-99 program,
City
certification and accreditation, as well as connection to a new US12 bridge.
S6
Replace US12 bridge capacity to pass 100 -yr flood and remove Cowiche
overflows into City from 100 -yr flood maps
WSDOT
S7
Remove city storage pond to increase hydraulic capacity for Recommendations
S4, S5 & S6.
City
Sg
Improve Naches Trail Bridge downstream of US12 as necessary to pass 100 -yr
flood with planned wider channel.
County,
FCZD
S9
Interim structural elements will be required east of 401h Avenue based on the
Cowiche overflow drainage study.
City,
WSDOT
S10
Spillway and drainage improvements for Myron and Willow dams.
Landowners
ES -4
17
TABLE ES -2 STRUCTURAL RECOMMENDATIONS - LONG-TERM
ID
Recommendation
Lead
Entities
S11
City culvert improvements to route City overflows from Cowiche Creek
Powerhouse Road and the Naches River to eliminate Cowiche overflows into
Cit
S12
Replace Powerhouse bridge with capacity to pass 100 -yr flood and remove
WSDOT,
Cowiche overflows into City from 100 -yr flood maps.
City
The short-term recommendations are provided below by category: planning, flood preparedness
and public awareness and listed within each by priority.
TABLE ES -3 PLANNING RECOMMENDATIONS - SHORT-TERM
ID
Recommendation
Lead
Entities
PL1
Provide a new Cowiche Creek riverine infrastructure corridor between
Powerhouse Road and the Naches River to eliminate Cowiche overflows into
City,
the City.
WSDOT,
FCZD
PL2
Maintain interagency coordination, necessary flood fight ILAs and
information exchange until existing Lower Cowiche corridor replaced.
City, FCZD,
YVOEM,
WSDOT
PL3
Adopt the new Cowiche Creek FEMA preliminary maps for new development
and use overflow scenario map as guidance.
City, County
pL4
Appoint a Planning Task Force to minimize Community risk from Cowiche
Creek overflows to ensure planning and building measures are in step with
City, County
structural measures over all phases of exposure.
pL5
Incorporate the 2017 flood extent map during the interim period for flood
protection on development for drainage, stormwater, building design, siting,
City
and layout.
PL6
Provide Contingency Planning across jurisdictions & agencies as a living
document for the following overflow scenarios: current day, the intervening
City,
period when individual corridor elements are replaced, and upon completion
YVOEM,
of rehabilitated corridor.
FCZD
PL7
Provide an ILA to locate funding sources (local, state and federal) and secure
funding to replace the Lower Cowiche stream and stream crossing corridor
City,
and increase reliability of flood warning.
County,
WSDOT
PL8
Provide a rehabilitation design that is hydraulically coordinated to replace the
existing channel and crossings between Powerhouse Road and the confluence
City, FCZD,
with the Naches River (Lower Cowiche).
WSDOT
ES -5
18
TABLE ES -3 PLANNING RECOMMENDATIONS - SHORT-TERM
ID
Recommendation
Lead
Entities
PL9
Incorporate multi benefit considerations with the coordinated corridor design
such as trails, open sace, agricultural and habitat.
City, County
PL10
Acquire required land to increase the current Lower Cowiche corridor in
accordance with goals and design standards (noted in Recommendation PL8).
City, FCZD
PL11
Assess Cowiche basin need for new snow, precipitation and stream gages to
reduce risk and seek partners for regional small basin needs on the west
FCZD, City
slopes of Naches and Upper Yakima region (Cowiche, Wide Hollow and
Ahtanum). Partners should include basin data collection agencies: USGS,
Ecology and BOR
PL12
Organize community -level funding districts of local funding that construct
and maintain approved protective risk -reduction features.
City
PL13
Install the coordinated Cowiche corridor channel elements from downstream
to upstream order to maximize upstream function, minimize cost and reduce
FCZD, City
transitory impacts.
PL14
Provide a Cowiche Creek overflow drainage study through the City.
City,
Landowners
PL15
Review safety and drainage of Myron and Willow lake dams in response to
Cowiche Creek overflow drainage for current day, interim and rehabilitated
Landowners
condition. The dam owners need to assess dam safety issues related to Cowiche
Creek overflows due to consequences of low-lying development and limited
drainage
PL16
Ensure all owners of critical infrastructure (defined by consequences of
failure) develop operational plans and funding to sustain structure integrity.
City,
WSDOT
PL17
Provide during SEPA or Shorelines comment period comment to City on
development proposals in the overflow area regarding facility siting and
FCZD, City
layout based on mapping, inundation areas.
PL18
Coordinate existing ordinances to establish ability to provide interim and
long-term protection from Cowiche creek overflows and/or dam failures.
City
PL19
Allow within the planning and design process of structural elements for the
insertion of trails and future Greenway overlay to connect Naches and
WSDOT,
Cowiche trails.
City,
County,
Greenway,
WO Douglas
PL20
Establish a gravel management plan in the Lower Cowiche corridor to reduce
flood and habitat risk over the short and long-term.
City, FCZD
PL21
Emphasize more natural riverine processes downstream of US12 to maximize
habitat enhancement for current and futurespecies.
FCZD
ES -6
E9
TABLE ES -3 PLANNING RECOMMENDATIONS - SHORT-TERM
ID
Recommendation
Lead
Entities
PL22
Identify location for sediment removal and monitoring, and removal of
identified sediment, especially upstream of US12. As per recommendation 20
City, FCZD
to limit disturbances
County,
PL23
Provide a future Cowiche Upper Basin CFHMP from the siphon upstream to
WSDOT
FP2
South and North Cascade branches including hydrological effects including
FCZD
sediment releases or pulses on the reach
City, FCZD,
TABLE ES -4 FLOOD PREPAREDNESS RECOMMENDATIONS - SHORT-TERM
ID
Recommendation
Lead
Entities
FP1
Form ILAs to allow cross coordinated flood response measures.
City, FCZD,
County,
WSDOT
FP2
Provide a Cowiche Creek Overflows Flood Response Plan that includes a
public Notification Plan.
City, FCZD,
YVOEM
FP3
Provide flood fight locations on Cowiche Creek levee to minimize overflows.
City,
Landowners
FP4
Provide emergency flood fight facilities to intercept overflows and reroute
west of 401h interchange.
City,
WSDOT,
YVOEM
FP5
Emphasize short-term flood routes, maximizing Cowiche Creek overflows
returns back to the Naches as far east as practical and identified in City
City
Drainage study.
FP6
Increase the gaging stations in the upper watershed to increase flood response
time at Lower Cowiche levee.
City, FCZD,
Ecology,
USGS,
USBOR
FP7
Provide timely public notice of flood threat status to allow for timely private
mitigation response.
YVOEM
FP8
Design emergency facilities to minimize fish stranding.
City, WDFW
ES -7
N9
TABLE ES -5 PUBLIC AWARENESS RECOMMENDATIONS - SHORT-TERM
ID
Recommendation
Lead
Entities
PA1
Increase general Public Awareness of current risk and measures.
City, FCZD
PA2
Advise landowners on interim and long-term potential for flooding.
Cit
PA3
Share Action Plans.
City, FCZD,
OEM
PA4
Encourage local protections for individual infrastructure such as ring dikes
around homes, barns, shops.
City
PA5
Awareness of new FEMA Maps and limitations.
City, FCZD
PA6
Engage upper management and politicians in plan for flood hazard mitigation.
City, FCZD
PA7
Garner public support for capital measures to remove flood risk areas through
capital expenditures.
City, FCZD
PA8
Locate best Web sites(s) for public notification and use YVOEM response
abilities as emergency declared.
FCZD,
YVOEM
PA9
Notify public of flood threat status to allow private mitigation response.
City,
YVOEM
Implementation of the short-term recommendations above would be concurrent across the
categories: planning, flood preparedness and public awareness. Implementation, if limited by
funding, should reflect the suggested priority within each table, and can be concurrent. Many
short-term recommendations will diminish or cease with completion of the long-term
recommendations.
ES -8
UPPER YAKIMA CFHMP
2018 COWICHE ADDENDUM
1.0 INTRODUCTION
R
This addendum to the 2007 Upper Yakima River Comprehensive Flood Hazard Management
Plan (CFHMP) addresses the flood risks posed by Lower Cowiche Creek and its confluence with
the Naches River, located within the original CFHMP study area. These risks were not previously
addressed in the earlier CFHMP due to a lack of available information. The original CFHMP
study area is presented in Figures 1-1 and 1-2. The amendment study area is shown in Figure 1-
3.
Recent studies and flood events, shown in Figure 1-4, have highlighted the current risks posed
by failing or undersized infrastructure in this area towards the residents of the City of Yakima,
and emphasized the need to plan into the future for revised flood hazard response, protective
actions, and flood hazard management for this focused study area.
CFHMP REQUIREMENTS
The CFHMP must identify and rank appropriate structural and nonstructural measures to reduce
flood damage. The study 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 completed CFHMP provides
the technical foundation for future nonstructural and structural flood hazard management
measures.
State law requires that a CFHMP describe the area where any proposed project is located and the
types and locations of existing flood problems. A complete description of the information that a
CFHMP must include is contained in WAC 173-145-040. Among the required information is
certification from the Washington Department of Commerce that the local emergency
management organization is administering an acceptable comprehensive emergency operations
plan. The law allows up to three years for local authorities to complete and adopt a CFHMP.
Applications for project funding under FCAAP require the county engineer to certify that a
CFHMP plan has been completed and adopted or is in preparation. Ecology must approve the
final CFHMP, and the municipality must subsequently adopt the plan.
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 key 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.
1
22
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.
To obtain funds for flood control maintenance through FCAAP, jurisdictions must prepare a
CFHMP that, as discussed in RCW 86.26.105, accomplishes the following:
• Identifies the river's meander belt or floodway
• Establishes the need for flood control work
• Considers alternatives to in -stream flood control work
• Identifies and considers potential impacts of in -stream flood control work on the
state's in -stream resources.
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.
As in the case of the 1998 Upper Yakima CFHMP, this addendum follows the Ecology process for
flood hazard management plans redefined by the 1991 Ecology guidelines. The Ecology process,
as presented within the 1998 Upper Yakima CFHMP, delivered in a two-year period for a larger
area, is presented below in Figure 1-5.
This flood hazard management process uses a balanced approach to flood damage protection,
resource protection, environmental enhancement, and land development, as discussed below.
2
23
24
Establish participation
process
Workshop Inventory Physical
conditions
Set goals
objectives
Evaluate al e B
pati
oi�i Vii Imeasures Ii iluiul �g with respect
VIII ii' �� ill!iiill li
costs,to ben efits and
impacts
1D�e�ier�miiinerie- far
flood hazard
management measures
Idenfifly alternate flood
hazardmanagernent measures
Structural
11
I��i��l����ll��I�ill!II�NII�IIIIp ���IIII II
Workshop
optional
Complete draft plan and
FPA documentation
€gin
Submit final plan and
SEPA documentation
to Ecology
Pinar workshop to evaluate
sits whrespect to objectives
�Nofiflr Ecology that
pian is adopted'
Source, Ecology 1991
Yakima unt Figur 1-5.
PPR YAKIMA RIVEX CFHMP CFHMP PLANNING PROCESS
27
28
Flood Hazard Management
To increase the chances of success, this plan is based on flood hazard management. Flood hazard
management encompasses flood control management and floodplain management techniques,
including structural and nonstructural approaches affecting the river, the floodplain, and the
watershed beyond. Actions include flood warning and flood response measures as well as
maintenance of flood control/ protection facilities.
Flood hazard management, to be successful, must take into account the entire river system. Any
activity in a river or its watershed can change the nature of the river's flooding. Human
intervention can either exacerbate or reduce the extent of flooding and its effects on human health,
property, and the environment. The anthropogenic effects incorporated in the original goals and
objectives must be fully identified and understood before any flood control actions are
established and successfully taken. This focused study area has significant infrastructure that has
modified flood risk and available solutions.
The current risk within the Cowiche Creek study area and urgency for risk mitigation has led to
the need to develop near-term, short and long-term actions that match the ability of the agencies
to meet needed concurrent infrastructure modifications to reduce current flood hazard. Near-
term mitigation actions would precede the next flood season and incorporate more flood warning
and response measures pending more structural actions, long-term actions would necessitate
significant infrastructure changes with long lead times, while short-term actions must bridge the
intervening period and align any infrastructure changes with the long-term plan developed here.
As several agencies are involved in this effort the plan must provide enough detail to develop
their individual capital improvement plans (CIPs).
Advisory Committee
Public and agency involvement was achieved by forming an Advisory Committee whose
members—representatives of public and private organizations and agency representatives—
provided input through meetings and document review. The CFHMP is also provided with
public input through the SEPA process and any hearings required by the local jurisdictions prior
to adoption. Additional agency representatives were contacted as needed throughout the plan
preparation, and contact was maintained with Ecology to ensure compliance with FCAAP
requirements, and this process will be again followed for this amendment.
An Advisory Committee of local agencies, landowners and jurisdictions was formed within this
addendum to refine issues, provide goals and objectives, develop alternatives and develop
recommend actions. Members are listed below in Table 1-1, and the meeting agendas for the 11
meetings are presented in Table 1-2:
N7
TABLE 1-1.
YAKIMA COUNTY CFHMP ADVISORY COMMITTEE
Voting Members
Affiliation
Mr. Scott Anfinson
Washington State Department of Transportation
Mr. Eric Bartrand
Washington State Department of Fish and Wildlife
Mr. David Brown
City of Yakima Water/ Irrigation
Mr. Joseph Calhoun
City of Yakima Planning
Mr. Bruce Dekker
Lake Aspen Homeowner's Association
Mr. Jeff Emmons
Yakima County Office of Emergency Management
Mr. Joel Freudenthal
Yakima County Flood Control Zone District
Mr. David Garretson
Private Landowner
Mr. Bob Ingham
Private Landowner
Mr. John Marvin
Yakama Nation
Mr. Keelan McPhee
Yakima County Planning Division
Mr. Mike Price
City of Yakima Wastewater/Stormwater
Mr. Bill Sauriol
Washington State Department of Transportation
Mr. Brett Sheffield
City of Yakima Chief Engineer
Ms. Katrina Strathman
Mid -Columbia Fisheries Enhancement Group
Alternates and Non -Voting Members
Mr. Jason Clapp
Mr. Mark Cleaver
Ms. Joan Davenport
Mr. Glenn Denman
Mr. Donald Gatchalian
Ms. Michelle Gilbert
Mr. Byron Gumz
Mr. Perry Harvester
Mr. David Haws
Mr. Terry Keenhan
Mr. Dale Meck
Ms. Margaret Neuman
Mr. Connor Parrish
Mr. Matt Pietrusiewicz
Mr. Scott Schafer
Mr. Horace Ward
9
Yakima County Office of Emergency Management
Yakima County Roads Maintenance
City of Yakima Community Development
Lake Aspen Homeowner
Yakima County Environmental Services Director
Washington Department of Ecology
Yakima County Planning Division
Washington State Department of Fish and Wildlife
Yakima County Flood Control Zone District
Yakima County Flood Control Zone District
Yakima County Flood Control Zone District
Mid -Columbia Fisheries Enhancement Group
Mid -Columbia Fisheries Enhancement Group
Yakima County Engineer
City of Yakima Public Works
Yakima County Office of Emergency Management
9E
TABLE 1-2.
SUMMARY OF ADVISORY COMMITTEE MEETINGS
Meeting Date
Topic
October 30, 2017
Overview of CFHMP planning process, goals and objectives & review of flooding
issues.
November 7, 2017
Prior studies and Existing Conditions report review, including near-term action plan
and emergency responsiveness.
December 5, 2017
Establish overall risk and restraints. Review CFHMP goals and objectives in order to
add any that apply to the study area. Add, Refine and Rank identified flooding issues.
Discuss risk in floodplain (100 -year) and review land use and regulatory flood hazard
reduction alternatives and strategies. Begin Floodplain Hazard Management 101.
December 19, 2017
Amend goals and objectives and flood issues. Continue Floodplain Hazard
Management 101. Generate and Review land use, regulatory, emergency and structural
flood hazard reduction alternatives for the City to match identified flood issues.
Review flooding issues arising from 2016 and 2017 flood in light of 100 -year flooding.
January 9, 2018
Continue prior meeting agenda. Discuss alternatives analysis values prior to voting.
January 16, 2018
Vote on flood hazard reduction alternatives according to criteria, flood issues, residual
risk and goals and objectives. Discuss priorities for recommended actions. Complete
Floodplain Hazard Management 101.
February 6, 2018
Generate and Review land use, regulatory, emergency and structural flood hazard
reduction alternatives for the City to match identified flood issues. Amend goals and
objectives and flood issues. Discuss alternatives analysis values prior to voting. Vote on
flood hazard reduction alternatives according to criteria, flood issues, residual risk.
goals and objectives. Discuss priorities for recommended actions.
February 20, 2018
Continue February 6, 2018 agenda.
March 6, 2018
Continue February 6, 2018 agenda.
March 26, 2018
Address tabled alternatives from prior meeting and complete voting on alternatives
Finalize alternatives and goals and objectives. Discuss city drainage. Identify leads and
partners for various alternatives.
April 16, 2018
Committee presented with Recommendations and priorities generated from
recommended alternatives. Discuss which items to prioritize. Set leads and partners.
Committee requested for input on items, leads.
Goals and Objectives
The goals and objectives defined in the 1998 CFHMP were updated by the Committee in the
above meetings in order to match the Lower Cowiche flood issues. The short-term and long-term
goals are presented in Tables 1-3a and 1-3b. Recommended actions for this amendment area are
evaluated with respect to their conformance with to the goals and objectives.
10
a
TABLE 1-3a.
SHORT-TERM GOALS AND OBJECTIVES FOR YAKIMA COUNTY CFHMP
Goals
Objectives
Identify flood hazards, propose
Prepare a comprehensive flood hazard management plan to address flooding
alternatives, and select appropriate flood
problems in study area:
hazard management measures and
• At a minimum, propose permanent management measures for the
funding plans.
principal flood problems
• Review existing O&M plan.
• Select flood hazard management measures based on the following
criteria:
— Severity of problem
— Effectiveness, with emphasis on solving regional problems
— Cost
— Public acceptance
— Impact
• Prepare a Capital Improvement Program (CIP) from selected
alternatives
• Secure County, City and Ecology approval of the CFHMP.
Implement short-term actions to help
Identify maintenance actions and other changes to existing City and County
alleviate current flooding problems.
programs that can be achieved with existing resources.
Ensure that pending and near-term
Communicate with private developers to convey the results of interim
development proposals are consistent
CFHMP analyses affecting proposed development parcels.
with goals and objectives of the CFHMP.
Review development proposals to ensure consistency with flood hazard
management alternatives that are likely to be developed in the CFHMP.
Lessen flood impacts to City and related
infrastructure in the next few years while
planning and implementing long-term
solutions.
Maintain fish passage, habitat through the
Ensure that any channel scour is moderated so as to avoid formations of
action reach and reduce the potential for
headcut barriers and habitat simplification. Create adequate fish returns for
fish stranding.
overland flow back to into streams or plan for fish rescue operations upon
receding flood.
Ensure that emergency response plans
Ensure action points are established for emergency response activities.
and procedures reflect known or
suspected changes in flood impact from
Review emergency response actions after large flood events for timeliness
recent flood event.
r
and effectiveness.
After a large event, compare actual flood impact to historical impacts to
identify changes.
11
32
TABLE 1-3b
LONG-TERM GOALS AND OBJECTIVES FOR YAKIMA COUNTY CFHMP
Goals
Objectives
Remove City from 100 -year flood
mapping, where possible & desirable,
Design level -standard 100 -year protection with appropriate freeboard.
certainly east of 40th Ave, and south of
Reduce risk of a 100 -year flood by limiting the impact to residents,
US 12.
businesses, and the economy.
Provide infrastructure to route all floodwaters under/through US 12
without overflows toward the City.
Remove or relocate diversions, control structures, canals, and fishways
which artificially reduce the overall gradient of Lower Cowiche Creek
and increase backwatering effects.
Prevent the loss of life and the creation
Implement flood hazard management measures as identified and
of public health or safety problems.
recommended in the CFHMP.
Ensure integrity of dams between Myron, Aspen and Willow Lakes by
long-term inspection, maintenance and management.
Reduce disruptions to local businesses
Maintain regulations to prevent new development from causing flood
and the economy. Reduce damages to
damage or from being susceptible to damage by floods.
public and private property.
Encourage development that does not increase protection structures in
stream environment.
Limit development North of US 12.
Retrofit or remove existing infrastructure where feasible to improve
resiliency.
Maintain the varied uses of existing
Preserve opportunities for floodplain uses that are compatible with
drainage pathways and floodplains
periodic flooding. Discourage land uses in the floodplain that are
within the County.
incompatible with periodic flooding.
Adopt flood control measures that preserve or enhance existing fisheries
and wildlife habitats.
Ensure that changes in land use restore natural character and function
wherever possible.
Incorporate considerations for extending and enhancing trails and
recreational corridors in the design of flood risk reduction and habitat
restoration measures.
Enhance functioning aquatic and
Restore existing degraded aquatic and floodplain habitats with functional
floodplain habitats compatible with
riparian buffers, floodplains and channels, recognizing that these efforts
flood -risk reduction and maintenance
are also beneficial to flood hazard management and risk reduction
actions.
efforts.
Ensure that flood risk reduction measures are designed to restore,
enhance and preserve aquatic and terrestrial habitat complexity,
minimize maintenance needs, and minimize aquatic and terrestrial
habitat disruptions in emergency or planned maintenance.
Achieve channel functions and habitat
Design channel and floodplain systems which promote self -building and
conditions that approach natural
self -maintaining habitat functions, including riparian habitat
conditions. Conditions will be
development and maintenance, recruitment of large woody debris, and
consistent with the slope of the
other processes that promote natural plant community succession.
12
33
TABLE 1-3b
LONG-TERM GOALS AND OBJECTIVES FOR YAKIMA COUNTY CFHMP
landscape and the quantity and
composition of sediment being
Allow irregular channel banks that provide cover and fish refuge habitat.
transported and deposited. Target
conditions will also account for the
Minimize gravel removal required, and select removal locations to reduce
geometry of the prospective Cowiche
impacts on channel and riparian habitat.
floodplain, the necessity to route flows
through two bridges, the presence of the
Gravel removals are planned to meet fish lifecycle needs through gravel
active Naches floodplain, and the need
renewal.
to meet fish lifecycle needs through
gravel renewal.
Minimize need for ongoing large woody material management through
channel and floodplain geometry.
Minimize bank armoring.
Design floodplain and flood control features that so that flow velocities
during 10 -yr events, and more frequent floods, are able to support stable
riparian communities.
Prevent the degradation of surface and
Minimize the impact of contaminants and sediment in stormwater runoff
groundwater.
on receiving waters (Cowiche Creek, Naches River, and the Yakima
River) and groundwater aquifers.
Integrate water quality needs with flood control needs to provide
consistency in flood hazard management.
Establish and adopt a systematic and
Pursue strategies for flood hazard management that balance engineering,
comprehensive approach to flood
economic, environmental, and social factors.
hazard management in the short-term,
and with an eye to minimizing the
Evaluate goals and objectives every five years to maintain consistency
expenditure of public funds in the
with current policy, comprehensive plans, the Growth Management Act,
future.
and to anticipate and adapt to changes in climate and watershed
hydrology.
Coordinate flood hazard planning with all interested and affected parties
in both public and private sectors to solve mutual flooding problems.
Improve community awareness of flood hazard management through
public outreach efforts.
Provide for public input and the opportunity to comment on flood
hazard management decisions.
Establish additional methods for acquiring, analyzing, and distributing
locally -specific hydrologic data.
Develop structural and nonstructural measures that increase resiliency
and decrease maintenance costs and the likelihood of costly emergency
actions.
Give preference to nonstructural flood control measures such as
regulations and preservation of existing flowpaths in the urban area.
Establish a stable, adequate, and
Determine flood hazard management funding needs and alternatives
publicly acceptable long-term source of
including both capital improvements and maintenance costs.
financing.
13
34
TABLE 1-3b
LONG-TERM GOALS AND OBJECTIVES FOR YAKIMA COUNTY CFHMP
SUMMARY OF PRIOR PERTINENT CFHMP RECOMMENDED ACTIONS
Establish responsible parties for infrastructure and flood response along
with sustainable funding source.
Structural Actions
Establish funding mechanisms and partnership agreements to help
Retirement of the Fruitvale Diversion and Consolidation with the Current Nelson Dam Diversion
implement the structural and non-structural recommendations of the
The County should implement bank protection projects following established guidelines (e.g., King
CFHMP.
Plan for future flood reduction in
Cowiche watershed above Powerhouse
Plan to provide a future CFHMP to address flooding issues along
Road.
Cowiche Creek from Powerhouse Road to the upper watershed.
Improve empirical Cowiche flow data &
forecasting.
Establish stream and snowpack stations monitoring basin hydrology to
Adopt a policy requiring all new flood -control projects to define maintenance responsibilities and a
reduce uncertainty and improve designs.
Remove City from 100 -year flood
mapping, where possible & desirable,
Design level -standard 100 -year protection with appropriate freeboard.
certainly east of 40th Ave, and south of
Reduce risk of a 100 -year flood by limiting the impact to residents,
US 12.
businesses, and the economy.
Based on the county -wide road closure database, prioritize roads requiring flood damage
Provide infrastructure to route all floodwaters under/through US 12
mitigation.
without overflows toward the City.
Study
Remove or relocate diversions, control structures, canals, and fishways
Request that FEMA produce a digital floodplain map that combines all jurisdictions and reflects
which artificially reduce the overall gradient of Lower Cowiche Creek
recent data for use in the County's GIS.
and increase backwatering effects.
Table 1-4 contains 2007 CFHMP Update recommendations relevant to the Cowiche Creek
amendment area. These recommendations and subsequent intervening actions were considered
in the generation of flooding issues for the amendment area in section 6.
TABLE 1-4
SUMMARY OF PRIOR PERTINENT CFHMP RECOMMENDED ACTIONS
Issues
Addressed
Structural Actions
Retirement of the Fruitvale Diversion and Consolidation with the Current Nelson Dam Diversion
NA1
The County should implement bank protection projects following established guidelines (e.g., King
RW3, LR1, URI
County 1993 or ISPG, 2003), modified for Yakima County.
The following are recommended to address operations and maintenance issues:
RW16
Consolidate maintenance requirements into one document. (COE documents)
Adopt a policy requiring all new flood -control projects to define maintenance responsibilities and a
funding source for operations, maintenance, and repairs before acceptance by the County
Continually update and maintain a flood control facility inventory database to document the current
condition of each flood control facility (GIS).
Based on the county -wide road closure database, prioritize roads requiring flood damage
RW12
mitigation.
Study
Request that FEMA produce a digital floodplain map that combines all jurisdictions and reflects
RW1
recent data for use in the County's GIS.
Given the long-term nature of this type of flood hazard (channel migration, sediment accumulation,
RW20
erosion), a study to determine these values and to monitor sediment transport and energy should
be implemented.
14
35
TABLE 1-4
SUMMARY OF PRIOR PERTINENT CFHMP RECOMMENDED ACTIONS
Issues
Addressed
Obtain flood damage GIS coverages for recent and historical floods as they become available from
RW15
FEMA
Non -Structural Actions
(Flood Fight)
During flood events posing risk, formalize procedures for dispatching field teams and volunteers to
RW19
critical locations along rivers and creeks to manually collect real-time river information. (Complete)
Compile time delays from the BOR in flood peaks between locations along the Yakima and Naches
Rivers for various flood magnitudes (Completed)
Continue reviewing and compiling information on past flood events to create a database that
correlates road closures with river stage and discharge (Ongoing)
Develop and communicate to the public a policy on sandbag distribution during flood events (use
periodic public outreach methods to reiterate this policy) (Ongoing).
Develop a flood inundation map for distribution to the public (FEMA maps Completed)
Establish real-time, automatic gauging stations within the upper watershed of tributary creeks
(Pending)
Create a Community Alert Network for use at the EOC (Ongoing)
Non -Structural
(Funding)
Actively pursue state and federal grant programs to supplement funding provided by flood
RW13
control district.
Investigate the value and need for sub -zones within the FCZD.
RW13
Provide direction and support to secure funding for large scale actions which involve cooperation
RW13, RW17
across jurisdictions and agencies
County should provide guidance in designing private bank protection projects (Completed with
RW3, LR1, UR1
Planning).
Pursue funding through state and federal programs to purchase high -hazard floodplain properties
RW10
or development rights for open sace use.
Non -Structural
(Regulatory)
City jurisdictions should integrate flood hazard items included in the County's CAO.
RW4, RW5
Obtain from FEMA the best available digital flood hazard map that meets the objectives listed below:
RW15
Accuracy: Establish definitive and accurate representations of the floodway, 100 -year floodplain,
Special Flood Hazard Areas (SFHAs), and Base Flood Elevations (BFEs)
Completeness: Ensure that all of the items listed above are present in the GIS database and that the
database includes all jurisdictions within Yakima County
Accessibility: Enhance the County's ability to perform floodplain determinations, measure areas of
SFHAs, determine BFEs of specific locations, and realize time savings in the permit process
Community Review: Ensure that sufficient local review of flood hazard information has occurred
prior to release of that data for public use.
RW7
The 2007 Update briefly addressed concerns and opportunities on the Naches River, including
pending replacement of Nelson dam and subsequent retirement of related irrigation
infrastructure at the confluence of Cowiche Creek and Naches River.
Since 2007 the need for maintenance of Cowiche Creek levees and for management of flood risk
to the City has been identified by levee failures in 2016 and 2017.
15
99
2.0 GROWTH MANAGEMENT ACT
The Growth Management Act is a state statute pertaining to urban growth, which requires
certain cities and counties to develop community Comprehensive Plans with public input
procedures to direct and manage community development and growth. GMA growth
requirements will cover the entire County or jurisdiction are separate from CFHMP related
statutes and produce separate types of plans. GMA Comprehensive Plans provide policy for
growth which directs local planning and building ordinances.
The CFHMPs are functional plans, that are adopted into state and federal hazard mitigation
plans, and directly influence the natural hazards element within the GMA Comprehensive
Plans. The two types of plans coincide in the consideration of growth in flood hazard areas,
defined by federal and state procedures. Guidance for GMA Hazard Reduction Goals for
incorporation into the Comprehensive Plan elements is provided within "Optional
Comprehensive Plan Element for Natural Hazard Reduction", Washington State CTED, June
1999.
This CFHMP identifies the community vulnerabilities and hazard issues in a developable area
and develops hazard -related goals (see table 1-3a and 1-3b) specific to the CFHMP area and also
provides recommendations to address them that can be incorporated into the Comprehensive
Plans as policies. Yakima County's Horizon 2040 has adopted the following flood related goals
that concern development of hazardous areas and potential modification of ordinances:
TABLE 2-1.
HORIZON 2040 COMPREHENSIVE PLAN - FLOODING (Prevent the loss of life or property and
minimize public and private costs associated with repairing or preventing flood damages from
development in frequently flooded areas.)
Policies
NH 1.1
Support comprehensive flood control planning.
NH 1.2
Conduct additional analysis and mapping of frequently flooded areas in cases where the 100 -year
floodplain maps prepared by the Federal Emergency Management Agency do not adequately reflect
the levels of risk or the geographic extent of flooding.
NH 1.3
Direct new critical facility development away from areas subject to catastrophic, life-threatening
flood hazards where the hazards cannot be mitigated.
NH 1.4
Where the effects of flood hazards can be mitigated, require appropriate standards for subdivisions,
parcel reconfigurations, site developments and for the design of structures.
NH 1.5
Plan for and facilitate returning rivers to more natural hydrological conditions, and recognize that
seasonal flooding is an essential natural process.
16
37
TABLE 2-1.
HORIZON 2040 COMPREHENSIVE PLAN - FLOODING (Prevent the loss of life or property and
minimize public and private costs associated with repairing or preventing flood damages from
development in frequently flooded areas.)
Policies
NH 1.6
When evaluating alternate flood control measures on rivers:
density, level of site coverage, and occupancy to preserve the structure, values, and functions of the
• Consider the removal or relocation of structures in the FEMA 100 -year floodplain;
natural environment or to safeguard the public from hazards to health and safety.
• Where feasible, give preference to nonstructural flood hazard reduction measures over
Encourage mechanisms to restrict or minimize development in high-risk hazard areas to protect
structural measures;
public health and safety.
• Structural flood hazard reductions measures should be consistent with the County's
Maintain existing infrastructure to reduce the risk of infrastructure fail during a natural disaster.
comprehensive flood hazard management plan.
NH 1.7
New development or new uses, including the subdivision of land, should not be established when
Ensure new developments in high-risk hazard areas include secondary egress.
it would be reasonably foreseeable that the development or use would require structural flood
Develop processes and procedures for streamlining projects intended to mitigate for natural
hazard reduction measures within the channel migration zone or floodwa .
NH 1.8
Restrict subdivisions in areas subject to flooding.
TABLE 2-2.
HORIZON 2040 COMPREHENSIVE PLAN - MULTI -HAZARD (Protect property, life, and health from
impacts of multiple and cumulative natural hazards.)
Policies
NH 7.1
Ensure proposed subdivisions, other development, and associated infrastructure are designed at a
density, level of site coverage, and occupancy to preserve the structure, values, and functions of the
natural environment or to safeguard the public from hazards to health and safety.
NH 7.2
Encourage mechanisms to restrict or minimize development in high-risk hazard areas to protect
public health and safety.
NH 7.3
Maintain existing infrastructure to reduce the risk of infrastructure fail during a natural disaster.
NH 7.4
Locate critical facilities and infrastructure outside of high-risk hazard areas.
NH 7.5
Ensure new developments in high-risk hazard areas include secondary egress.
NH 7.6
Develop processes and procedures for streamlining projects intended to mitigate for natural
hazards.
17
38
TABLE 2-3.
HORIZON 2040 COMPREHENSIVE PLAN - DISASTER RECOVERY (Be prepared to recover from a
major natural disaster.)
Policies
NH 8.1
Implement Recovery Plan to guide the redevelopment, public participation process, and long-term
recovery after a natural disaster.
NH 8.2
Provide a process and procedure to streamline projects intended to provide relief and recovery from
a natural disaster.
With a clearer understanding of the level of hazard avoidance necessary for the local study area,
as identified in this CFHMP, cities and counties can define actions or strategies to minimize public
risk and achieve the above GMA goals. These actions and strategies are applied in the
implementation of vulnerable area mapping, regulatory codes and standards, and capital
investments. Strategies which can satisfy multiple objectives are important for overall success.
Coordination between jurisdictions, as watersheds and flood risks cross basin boundaries 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 infrastructure incursions
into the floodplain and exposure can be minimized, while appropriate resource utilization
practices are applied in the upper watersheds.
97
3.0 BACKGROUND DATA, STUDIES AND PROGRAMS
Background information for the CFHMP was compiled from sources including the County, state
and federal agencies, and the original Advisory Committee members. Data collected to define
the study areas physical, social, and historical characteristics included the following:
• Land use and topographic information from County Geographic Information
System (GIS) maps
• Information describing the physical setting, including climate, soil, vegetation,
hydrology, water quality, fisheries, and wildlife
• Population data
• The findings of past flood -related studies performed by the U.S. Army Corps of
Engineers (COE) and the Federal Emergency Management Agency (FEMA)
• Yakima Authorized Federal Levee Operation and Maintenance Manual, COE,
1955
• County Comprehensive Plan background documents
• Records of historical flood events and control activities including permanent
records, personal accounts and newspaper accounts
• County and City observations of the March 2016 and March 2017 Cowiche
flooding in the City of Yakima
• Yakima County - hydraulic modeling and supporting data for the updated Flood
Insurance Study on the lower Naches River and Cowiche Creek,
• Cowiche Creek Hydrologic Analysis, WEST Consultants for Yakima County and
FEMA, 2017
• Cowiche Creek FIRM analysis, WEST consultants for Yakima County, 2017
preliminary.
Other sources of data were historical documents, newspaper articles, and interviews with local
officials and citizens.
RELATED STUDIES
Preceding the preparation of this amendment, there were a number of recommended programs
underway in Yakima County which directly affected this area in addition to the recent County's
revised Cowiche flood insurance study. The recommended actions are listed in Table 3-1 below.
TABLE 3-1.
SUMMARY OF RECOMMENDATIONS FROM RELATED STUDIES 2000-2007
Stud (Source)
Description of General Recommendations or Problems Identified
Status
The Reaches Project
All five (Yakima River mainstem) reaches have significant
Recommended in
(2002)
potential for restoration. However, the restoration potential is
2007 CFHMP,
highest in the Union Gap reach.
applicable to Lower
Naches
19
40
TABLE 3-1.
SUMMARY OF RECOMMENDATIONS FROM RELATED STUDIES 2000-2007
Stud (Source)
Description of General Recommendations or Problems Identified
Status
The Union Gap reach depends on sediment from the Naches
Recommended in
reach. Sediment from the Selah reach is limited due to the gravel
Lower Naches
mining and Roza Dam has stopped upstream bedload sediment.
River Coord.
Sediment transport out of the Naches should be improved and
Partnership
maintained.
Recommended in
Another risk is the avulsion capture of bedload by the existing
2007 CFHMP, n/a
gravel pits. Pit capture of the river by some of the very deep
for Naches
gravel pits (-15 m or 50 ft) could disconnect groundwater -surface
In progress
water interaction across the floodplain for periods of several
through YRBWEP,
decades.
YBIP & FbD,
The acquisition of floodplain habitat in all reaches should be a
including Lower
priority, particularly those areas that yet maintain some degree of
Naches & Lower
habitat complexity. The general pattern is for the lower end of
Cowiche
each of the various reaches to maintain higher complexity.
SR 24 Project
Levees and bridge abutments in danger of erosion, New SR 24
Constructed 2006
Floodplain
bridge should be substantially longer.
Corps section 1135
Consistency Report
Floodplain function compromised for habitat, sediment
& Ramblers Park
(2003)
transport, and riverine processes.
setbacks/ Nelson
Dam 2018
Lower Naches
Remove Fruitvale Diversion, restore connection of Cowiche
After Nelson Dam -
River Coordination
Creek with Lower Naches River, combine diversions at Nelson
2019
Project (2005)
Dam.
2019
Remove Old Union Diversion, combine diversions at Nelson
2017
Dam
Acquire floodplain properties in Lower Naches River to allow
habitat restoration and flood hazard reduction projects to occur
while minimizing impact on private properties.
2019
Remove Ranney Collector dike and associated levee to improve
floodplain function and reduce flood hazard.
Complete 2010
Implement large scale bioengineering and structural repairs to
US Highway 12 in the vicinity of 161h Avenue to reduce flood
Design studies
hazard to the City of Yakima and US Highway 12, and improve
complete -construct
habitat.
2019
Improve sediment transport in this reach - lengthen current
Powerhouse/Twin Bridges/Nelson Dam constriction point,
redesign Nelson Dam to allow for better sediment transport.
20
41
TABLE 3-1.
SUMMARY OF RECOMMENDATIONS FROM RELATED STUDIES 2000-2007
Stud (Source)
Description of General Recommendations or Problems Identified
Status
Lower Cowiche
Relocate and restore Cowiche Creek channel downstream of US
Completed Design
Channel Relocation
Highway 12 following reworking of Nelson Dam infrastructure
(2014) & acquisition
Nelson Dam.
(2017), construct
(2019) after Nelson
Dam reconstruction
The upstream extent of the CFHMP amendment area is US Highway 12, just downstream of
Nelson Dam, so that the dam is located within the Naches CFHMP study area. However, actions
and changes now proposed at Nelson Dam, starting in 2019, will greatly modify current channels
and infrastructure around the Naches-Cowiche confluence in this study area. Accordingly, the
following recent relevant studies are noted below:
1. Naches River Reach Analysis and Management Plan, Lower Naches River (RM 0 - 3.75),
GeoEngineers, 2003
2. Geomorphic processes analysis in the Naches reach since the 1920s, Golder, 2003
3. Surveyed cross sections within the reach Aggett, 2003
4. Naches River Channel Migration Study. Prepared for Yakima County Public Services,
Tetra Tech/KCM, Inc. 2004
5. Naches River Comprehensive Flood Hazard Management Plan (River Mile 3.7 To River
Mile 17.5). Prepared for Yakima County Public Services. Yakima, WA, Tetra Tech/KCM,
Inc. 2005.
6. Yakima County (2006 and interim studies) hydraulic modeling and supporting data for
the updated Flood Insurance Study on the lower Naches River,
7. Lower Naches Flood Insurance Study and Maps, FEMA, 2009,
8. Geomorphic Assessment of the Water Gaps of the Yakima Basin, prepared for Yakima
County Public Services, Surface Water Management Division, Entrix Inc., 2009a
9. An annotated Bibliography of Water Gaps in the Yakima Basin, Washington, prepared for
Yakima County Public Services, Surface Water Management Division, Entrix Inc., 2009b
10. 65% Draft: Appraisal Design Report, Naches River at Nelson Dam Fish Screen and
Diversion Design, USBR, 2010.
11. Evaluation of Hydraulics and Sediment Transport for Proposed Fish Bypass Alternatives
at Nelson Dam, USBR, 2011
12. Nelson Dam Project/Power House Bridge Project, DHI, 2011 reports
• Task 1: Initial Model Review and Update: Baseline Conditions Model
• Task 2: Evaluation of Infrastructure and Sediment Removal, Scenarios 1 and 2
• Task 2: Evaluation of Infrastructure and Sediment Removal, Scenario 3
• Task 3: Evaluation of Nelson Dam Reinsertion
21
42
• Task 4: Evaluation of Nelson Dam Reinsertion- Final Report
13. Discovery Report, Naches Watershed, FEMA, 2012
14. Ramblers' Park Conveyance Projects, including levee setback, Phases I, II and III, County
of Yakima, 2012-2016
15. Preliminary Assessment of the Nelson Dam Surface Water Intake, Technical HDR, 2013
16. Lower Naches Sediment Study, Planning Assistance to the State, USCOE, 2015
17. Lower Naches River Geomorphic Atlas, NHC 2015
18. Review of Morphological Effects from Naches River Levee Setbacks, NHC 2015
19. Nelson ByPass Channel Design Project, Physical Modeling and Preliminary Design, NHC
2017
20. Nelson Dam Consolidation and Reconfiguration Preliminary Design, HDR, 2017
21. Nelson Dam Environmental Memorandum, Yakima County, 2017
Many of the above studies are summarized in relation to Nelson Dam, in the 2013 HDR report
above.
YAKIMA COUNTY REVISED FLOOD INSURANCE STUDY (2017)
The NFIP implements a comprehensive set of regulations for mitigating flood damage. Yakima
County and the City of Yakima participates in the NFIP by adopting zoning restrictions and
enforcing building standards to limit flood damage in the 100 -year floodplain. In 2008 the county
contracted with FEMA to revise the Cowiche Creek Flood Insurance Study defined 100 -year
floodplain to reflect updates in Cowiche hydrologic and hydraulic information, through inclusion
of 2005 high resolution LiDAR in the basin.
FEMA's consultant provided a detailed hydrologic analysis for the Cowiche Creek basin. There
are no long-term flow records for the Cowiche Creek watershed. Although the Washington State
Department of Ecology installed several gauges on Cowiche Creek, these gauges are no longer
active, and they collected flow for only 2-4 years. A much longer flow record is available for
upper North Fork Cowiche Creek measured through an inline weir just upstream of French
Canyon Dam. It represents the total natural inflow to the French Canyon reservoir and was used
in the study.
The recommended discharges for the Cowiche Creek basin mapping study are shown below.
22
43
Table 3-2. FEMA adopted discharges for Cowiche Creek basin.
Flooding Source and Location
Drainage
Area
Peak Discharges (Cubic Feet per Second)
(Square
Miles
10-
Percent
Annual
Chance
4-
Percent
Annual
Chance
2-
Percent
Annual
Chance
1-
Percent
Annual
Chance
0.2 -
Percent
Annua-
Chance
Cowiche Creek
At mouth
119.5
1,519
2,001
2,396
1 2,818
3,903
North Fork Cowiche Creek
At mouth
38.8
627
833
1,003
1,187
1,661
Above confluence with
Tributary 1
23.5
422
564
680
807
1,135
Above confluence with
Tributary 2
19.0
357
478
577
685
965
South Fork Cowiche Creek
At mouth
71.5
1,014
1,341
1 1,610
1 1,899
1 2,643
The above values were determined from the current U.S. Geological Survey (USGS) flood peak
discharges regional regression equations that were evaluated and found to be most applicable to
the Cowiche Creek basin. The USGS regional equations were used to calculate the 10-, 4-, 2-, and
1 -percent -annual -chance flood peak discharges, while the 0.2 -percent -annual -chance flood
discharges were estimated by extrapolating the 10-, 4-, 2-, and 1 -percent -annual -chance flood
discharges.
Flooding in the study area normally occurs in winter or spring from January through April.
Spring floods occur when warm weather and rainstorms accelerate snow melt and runoff. Winter
floods, which are more frequent and of larger magnitude, occur when rainfall on accumulated
snow and warm winds produce large volumes of runoff from snowmelt and rain.
Flood discharges are distributed along the Cowiche reaches in accordance with the above table
and any flow splits caused by the localized topography. A flow split is shown in the amendment
area on Figure 3-1 due to overflows from the channel over the private berm or levee on the south
23
44
bank of the Creek, and towards the City of Yakima prior to passing under US Highway 12. This
flow split discharge to the City of Yakima was caused by the lack of capacity in the
channel/levee/bridge infrastructure from Powerhouse Road to US Highway 12.
Figure 3-1. 10 -and -100 -year Flow Splits: Lower Cowiche Creek
The revised preliminary 100 -yr flood mapping for Cowiche Creek FIS is scheduled for release in
December 2017. FEMA mapping work maps for this reach are shown on Figures 3-2 and 3-3
below. The analysis shows the lack of protection afforded to the City of Yakima for flows
exceeding the 10 -year flood.
24
45
Figure 3-2. Effective Flood Zone: Cowiche to N. 401h Ave
25
46
Figure 3-3. Effective Flood Zone: N 4011, Ave to Myron Ave
26
47
RELATED PROGRAMS AND PROJECTS
Lower Naches River Partnership Projects (2005)
This is a cooperative project between the Washington State Department of Transportation,
Yakima County, and the City of Yakima. The project area (Figure 3-2) is from the area of Nelson
Dam/Twin Bridge to the confluence with the Yakima River. The cooperative partners all
anticipate that they will undertake infrastructure projects (some 20 at last count) within the
project area over the next several years, and each project will have common design constraints
and goals for improvement in infrastructure efficiency (transportation, irrigation), fish habitat
and habitat enhancement, and in most cases, flood hazard reduction. The objectives of the Lower
Naches River Coordination Partnership are to "make better decisions collectively, share and
accumulate data and information to complete planned projects, work together whenever possible
to complete partnership actions, and to help protect the environment for all to enjoy."
Actions recommended for anticipated infrastructure projects will be based on an understanding
of the physical and biological conditions in the reach.
These conditions have been documented and described in the recent studies listed above,
specifically studies 1 through 8, 10 through 11,148 through 18, 20 and 22.
Recommended actions that effect reduction of flood hazard include the following:
• Purchase of the majority of privately owned parcels in this reach - given the
number of projects scheduled for this reach in the future, action will maximize
floodplain function, maximize flood hazard reduction and save project costs.
• Decommission the City of Yakima's Fruitvale diversion and associated structure,
decommission the Old Union diversion and associated structure, and remove
dikes associated with City of Yakima's Ranney Well system. The Fruitvale
diversion and associated structures are a chronic flood hazard problem at the
diversion dam in lower Cowiche Creek, which is heavily modified to serve as
irrigation conveyance for a short distance. Removal of these structures will have
water quantity, flood hazard reduction and major fish habitat and fish passage
benefits. Removal of the Ranney well associated diking and other infrastructure
that currently limit Naches and Cowiche Creek sediment transport in this reach.
• Cowiche Creek Flow and Habitat Enhancement - This was proposed by YHTAP
and WDFW with potential partnering with the City of Yakima and the Yakima
County Flood Control Zone District. The County has undertaken design studies
and easement purchase for the portion within the County (see Lower Cowiche
Channel Relocation below). The City has not been engaged to date.
Lower Cowiche Channel Relocation Project (2013)
Relocate and restore Cowiche Creek channel downstream of US Highway 12 following reworking
of Nelson Dam infrastructure Nelson Dam. This is a cooperative project between Yakima County,
and the City of Yakima. The County has developed the new channel design and acquired the
27
48
relocation easement. Construction between US 12 and the Naches confluence requires removal of
existing Naches River infrastructure for Fruitvale Diversion following intake incorporation into
Nelson Dam.
Figure 3-4. Lower Cowiche Easement
Figure 3-5. Naches River Partnership Action Area
-19
4.0 FLOOD HISTORY
UPSTREAM DRAINAGE AND REGULATION
The headwaters of Cowiche Creek are located in the foothills of the Cascade Mountains. The total
drainage area of the Cowiche Creek basin is 119.5 square miles. As shown in 4-1, the Cowiche
Creek basin is separated by a high and long mountain ridge on the west and on the north, by the
Cowiche Mountains on the south, and by the Naches Heights on the east. The basin elevation is
relatively high with maximum and minimum basin elevations of 6,660 and 1,150 feet,
respectively, and mean basin elevation of 3,110 feet. Based on 1930-1957 precipitation data the
mean basin annual precipitation is about 27 inches.
Figure 4-1. Cowiche Basin Map
The main channel from the headwaters of South Fork Cowiche Creek to the mouth of Cowiche
Creek, as shown in red on figure 4-1, is approximately 33.6 miles long with an average slope of
137 feet per mile. The north and south forks of Cowiche Creek join together approximately 2
miles southeast of the town of Cowiche and form the mainstem of Cowiche Creek. Cowiche
Creek then runs for about 7.2 miles before it joins the Naches River.
The French Canyon Dam located on North Fork Cowiche Creek, is approximately 1.7 miles west
of the City of Tieton (see). The dam is owned by the Bureau of Reclamation and operated by the
Yakima-Tieton Irrigation District. During the FEMA flood study, a sensitivity evaluation of the
effect of French Canyon Dam starting levels (available flood storage) versus 10 -yr through 100 -yr
return period floods indicate no ability of the dam to reduce the 100 -yr peak flood and minimal
ability to reduce the 10 -yr flood.
30
The study area includes the lower 2.0 miles of the Cowiche Creek before it joins the Naches River.
SIGNIFICANT COWICHE CREEK FLOODS
Recent flooding in the study area occurred from rain on lower elevation snow in February 2016
and March 2017 with extensive damage that is not yet fully compiled. Prior reported events and
damages on Cowiche Creek tended to be coincident with larger snow melt events across the
Yakima basin, included the 1933, 1974 and 1996 floods.
The Yakima River basin, including the Naches River, typically produces winter and spring floods.
Spring floods are caused by snowmelt aggravated by periods of unusually warm weather and
rainstorms and their magnitude is generally moderate, but they can last 10 or more weeks,
resulting in very large total volumes of runoff and river erosion. The more frequent winter floods
are caused by rain on snow and warm winds that produce runoff from snowmelt and rain. They
typically follow precipitation periods that have saturated the soil and replenished groundwater
reserves, or extended periods of below freezing temperatures, which freezes the soil surface and
causes even minor amounts of snowmelt to generate high rates of runoff. Historically, winter
floods are the largest in magnitude, but their durations are typically less than one week, so the
total volume of runoff is not as high as that of spring floods. The largest Yakima flood of record,
the flood of December 1933, was the result of a winter rain -on -snow event. Upper basin reservoir
storage typically reduces the magnitude of winter floods, which occur after the irrigation season
when reservoir storage is available.
Major Yakima basin floods have been recorded in 1894, 1906, 1909, 1917, 1919, 1921, 1933, 1948,
1952, 1956, 1959, 1974, 1975, 1980, 1990, 1995, 1996 and 1997. Before the Cowiche flooding of the
last two years the worst reported Cowiche floods damages were 1933, 1974, 1995 and 1996,
coincident with basin -wide damages.
Mid Yakima Valley creeks draining from the Cascade Range, like Cowiche basin are susceptible
to flooding during winter Chinook weather (snow accumulation followed by a period of warming
temperatures, high winds, and heavy rainfall) due to their snow prone location and the limited
number of trees in their drainage areas. Flood damage from such events is frequent along the
Wenas, Cowiche, Wide Hollow, Ahtanum, Toppenish, and Satus creeks.
31
52
TABLE 4-1.
DOCUMENTED FLOOD DAMAGE IN YAKIMA COUNTY
Year of
Flood Event
Damage Type
Total Damage
Estimate
Source
February 9, 1996
Private
$5,000,000
1996
Lacey 1996 p.c.
Public
$5,349,861
Lacey 1996 p.c.
COE levees
$376,000
COE 1996
State Roads
$6,845,000
WSDOT 1996
Emergency Shelters
$150,000
Scofield 1996 p.c.
Total
$17,720,861
February 21, 1995
Debris Clearance
$271,000
1995
Yakima County
Road Systems
$230,000
Porn Porn Bridge
$150,000
Emergency Response
$54,000
Total
$705,000
November 26, 1990
Debris Clearance
$3,116
1990
Yakima County
Protective Measures
$2,000
Road Systems
$22,257
Water Control Facilities
$21,855
Parks
$38,110
Total
$87,338
December 27,1980
County roads and dikes
$50,000
1980
Yakima Herald -
Republic
December 2, 1977
Private homes
$1,300,000
1977
Yakima Herald -
Dikes and Levees
$280,000
Republic
Local business
$147,500
Roads and Bridges
$45,000
Other
$90,000
Total
$1,862,500
December 4,1975
Public facilities
$400,000
1975
FEMA (1994)
January 16,1974
Homes in Yakima County
$5,400,000
1974
Yakima Herald -
Agricultural Damage
$3,000,000
Republic
State Highways
$2,000,000
Indian Res. Roads, Bridges
$1,500,000
County Roads
$1,000,000
Total
$12,900,000
January 31, 1965
County Roads in West and
$30,000
1965
Yakima Daily
Upper Valleys
Republic
December 23,1933
Farmers
$534,190
1936
War Department,
Industries
$112,000
Office of the Chief of
Utilities
$87,200
Engineers, January 20,
Non -Fed Irrig., Dikes
$50,350
1936
Res/Bus Properties Homes
$75,000
Municipalities
$19,675
Counties
$113,900
Fed. Irrigation Works
$187,500
County Roads
$83,000
Total
$1,262,815
32
53
TABLE 4-1.
DOCUMENTED FLOOD DAMAGE IN YAKIMA COUNTY
Year of
Flood Event
Damage Type
Total Damage
Estimate
Source
November 17, 1906
Northern Pacific
$150,000
1906
Yakima Daily
North Yakima & Valley Rail
$60,000
Republic
Northwest Light & Water
$50,000
Cascade Lumber
$50,000
Yakima County Bridges
$15,000
Mttitas County Bridges
$15,000
Canal Companies
$30,000
Individuals
$30,000
Total
$400,000
Impacts on Cowiche Creek were noted during the basin -wide 1933, 1974, 1995 and 1996 floods
noted above, and are briefly described to allow a comparison between historical flooding
conditions and recent flooding characteristics. All the flood events were winter floods involving
rain on snow.
DECEMBER 23,1933 FLOOD
The 1933 flood was a winter flood caused by rain on snow in the lower valley; it is the largest
Yakima flood on record. Precipitation in the upper watershed was 500 percent above normal.
Approximately 3 inches of rain per day fell in the upper watershed prior to peak flow. Over 16.5
inches of rain was reported at Keechelus Lake from December 17 through 22. Flow in the Yakima
River at Parker peaked at 65,000 cfs and was estimated at approximately a 200 -year flood event
(see Table 4-1).
The flood caused extensive damage in the Yakima Valley, estimated as exceeding $1 million (1933
dollars). This amount is considered low in view of the community, state and federal response to
Yakima flooding Newspaper accounts report water rushing over both approaches to the Terrace
Heights Bridge, Naches Bridge being washed out, loss of the Union Gap bridge approach, and
isolation of the City of Yakima due to loss of train and highway service for 36 hours. The Cowiche
Creek overflowed and drained around the sediment pond. Any water not passing under the US
12 and railway bridges and not entering Fruitvale diversion was routed back to the river across
US 12 near the current 40th Avenue intersection. The incident is reported to have resulted in the
building of the flood fight levee north south adjacent to the storage pond, and may have resulted
in some raising of the east west berm.
The high level of damage in 1933 resulted in Yakima County being incorporated in the federal
Flood Act of 1935 and 1938 that authorized construction of the extensive federal levee system of
approximately 25,000 feet of right bank levees protecting the City of Yakima, 10,700 feet of left
bank levees protecting Terrace heights, and associated closure structures and culverts between
Selah Gap and the Moxee bridge. Construction began in July 1947 and the primary system was
completed in March 1948. The 1933 flood also resulted in Yakima County being identified and
33
54
incorporated in State Flood act of 1935 which created 18 flood zones across the State, including
Yakima, which were administered by the State.
JANUARY 16,1974 FLOOD
The January 16, 1974, flood was a significant winter flood event. Rain showers, rising
temperatures, snowmelt, and ice debris in the river produced typical winter flood conditions.
The January 1974 event resulted in ice jams near Selah allowing floodwaters to back up until ice
debris dislodged. This produced a small flood wave and additional bank erosion along the
Yakima River. Peak flow on the Yakima River at Parker reached 27,700 cfs. The Naches River
peaked at 10,800 cfs. Aerial photographs indicate overtopping of the Cowiche east -west berm and
not the north -south berm. Overtopping at the City storage pond into the City is apparent.
Excluding the 1933 flood, the January 1974 flood produced the greatest damage before the
February 1996 flood. Yakima County was declared a federal disaster area. Six major bridges
were damaged and two were completely washed out. Military helicopters were brought in to
assist with evacuations and drop supplies. White Swan could not be reached by road. More than
500 people were forced to leave their homes.
An estimated $13 million of damage was reported, most of it outside the study area. Agricultural
damage was estimated at $3 million, and $4 million of damage occurred to roads, highways, and
other public facilities. Seventy-seven homes were destroyed and 383 others received major
damage; 1,115 families were affected, and two fatalities were reported (FEMA 1994). Damage to
private homes was estimated at about $5.4 million.
Flood damage was region -wide, with concentrations in the Lower Valley. Flooding affected
properties along the Yakima River, in addition to smaller tributaries, as follows:
• Upper Valley—East Selah and the golf course were inundated. North Wenas Road
was covered with floodwaters near Gibson Road.
• Mid-valley—Yakima Air Terminal was closed due to floodwaters covering half
the runway. Citizens dug a drainage channel through South 47th Avenue to divert
floodwaters away from homes.
• West Valley—All West Valley school districts were closed due to flooded roads.
Many homes were flooded along Wide Hollow and Ahtanum Creeks. Lynch Road
bridge on Ahtanum Creek washed out. Downed electrical poles caused a power
outage near the North Fork of Ahtanum Creek. The entire Ahtanum Road was
undercut.
• Lower Valley—White Swan was completely isolated by floodwaters from
Toppenish Creek. Twenty-five homes were evacuated along Satus Creek. U.S.
Highway 97 (Toppenish to Goldendale), SR 22 (Toppenish to Prosser and
Toppenish to Buena), and SR 220 experienced flooding and structural damage.
The U.S. Highway 97 bridge and dirt roads and bridges from Lateral A east were
washed out along Toppenish Creek. Several families were stranded in Granger.
Granger's sewage treatment plant was surrounded by floodwaters. Numerous
34
55
roads were closed, including Sunnyside-Mabton Road, all roads in the White Swan
Area, roads along Satus Creek, and Mabton-Bickleton Road.
FEBRUARY 1995 FLOODS
January 1995 was the wettest January on record in the City of Yakima and the City's third wettest
month on record, with a total precipitation of 3.67 inches; the wettest months on record were
December 1964, with 4.19 inches, and December 1931, with 3.75 inches. These amounts are very
high for an area with average annual precipitation of only 8 inches. Saturated soils, continued
precipitation, and unseasonably warm temperatures produced typical winter flooding in
February 1995.
The region's smaller tributary streams produced the primary flood damage. High water was
experienced in Wenas, Cowiche, Ahtanum, Cottonwood, Wide Hollow, Satus, and Toppenish
Creeks. The most extensive flooding was experienced in the West and Lower Valleys.
Figure 4-2.
1995 FLOOD DAMAGE BY DRAINAGE AREA
Figure 4-2 shows where County roads were damaged. Damage near Wide Hollow, Cottonwood,
and Cowiche Creeks contributed approximately 26 percent of the total.
FEBRUARY 9,1996 FLOOD
The February 9, 1996, flood was the second largest Yakima basin flood of record. Flow crested
on the Yakima River at Parker at 57,500 cfs, which exceeded the then predicted 100 -year event of
35
Cowiche Creek
Pom i. #
9
Wenas Creek
Bridge%
25% Naches River
ils
3%
19%
Mid Valley
16%
Cottonwood
Wide Hollow
Creek
Creek
Figure 4-2.
1995 FLOOD DAMAGE BY DRAINAGE AREA
Figure 4-2 shows where County roads were damaged. Damage near Wide Hollow, Cottonwood,
and Cowiche Creeks contributed approximately 26 percent of the total.
FEBRUARY 9,1996 FLOOD
The February 9, 1996, flood was the second largest Yakima basin flood of record. Flow crested
on the Yakima River at Parker at 57,500 cfs, which exceeded the then predicted 100 -year event of
35
-M
56,300 cfs. Water elevations exceeded flood stage by over 6 feet at Parker. This flood was a typical
winter event caused by unseasonably warm weather and rainfall on a significant snow pack.
Weather conditions produced flood flows from snowmelt combined with rainfall runoff.
Keechelus Reservoir reported over 11 inches of precipitation within a three-day period; 5 inches
of rain fell in 24 hours on Wednesday, February 7. Flooding conditions were aggravated by ice
jams on the Yakima River near Selah Gap and along tributary creeks.
Flood damage was region -wide, occurring both along the Yakima mainstem and tributary creeks.
Areas receiving the greatest damage included the Cowiche, Upper Naches, Selah, Ahtanum,
Wapato, White Swan, and Toppenish Creeks. More details on the County -wide damages are
contained in the CFHMP.
Yakima County was declared a federal disaster area. As of May 23, 1996, FEMA had received
over 1,780 applications for disaster assistance. Requests for private assistance were estimated to
exceed $5.0 million and requests for public assistance were estimated at over $92 million (Lacey,
E.,1 March 1996, personal communication). As of May 23,1996, FEMA had provided $5.3 million
in assistance for public facilities. This figure does not include funding provided by other agencies
such as COE and American Red Cross. Protective measures and road systems accounted for the
largest portion of requested federal funding assistance (Figure 4-5).
According to personal anecdotes the north south levee was raised during this event to
accommodate overflows from Cowiche Creek and the east -west levee along Cowiche Creek was
raised post flood.
FEBRUARY 15, 2016 FLOOD
The February 15th, 2016 flood was caused by a persistent late -season snowpack in the lower
elevation portions of the Cowiche Creek watershed (from 1500 feet to 3500 feet), coupled with a
pronounced, multi -day warm-up event. Overnight low temperatures at the WSU Ag Station near
the town of Cowiche went from generally near or below freezing before February 14th to over 43
°F on the night of February 14th. Daytime peak temperatures went from the low 40's on February
13th to nearly 60 °F on the afternoon of February 15th. From 10pm on the 14th, to 10pm on the 15th,
the temperature did not drop below 50 °F. Flows peaked at around 12:15pm at the Ecology gage
and around 4:45pm at the Bureau of Reclamation gage on Powerhouse Road. The peak stage
recorded at the Ecology gage was 9.14 ft. The peak stage recorded at the BOR gage was 6.94 ft.
The rating curve for the Ecology gage ends around 7.2 feet, but extrapolation of the rating curve
suggests a peak flow of approximately 1,200 cubic feet per second. Snow Water Equivalent (SWE)
records at the Green Lake SNOTEL site indicate that very little snowmelt-related runoff occurred
at the higher elevations of the watershed. No significant precipitation occurred with this flood
event.
Flood flows overtopped the east -west berm between Powerhouse Road and Highway 12. This
overflow volume accumulated behind the north -south berm until it burst (the break caused a 25
foot, full -height opening in the 10 -foot -high structure). There was some damage to the east -west
berm from piping and overtopping as well as to the City's concrete irrigation reservoir due to the
overflow heights and duration. This dam -break event (and continued overflow from the rising
Creek) sent water through the adjoining orchard, along the south side of Highway 12, through
36
57
the northern end of the Riverview Manor mobile home park, and then east on along the south
side of the Highway 12 off -ramp. Flows temporarily went northwards under Highway 12 to the
Naches River via the Fruitvale canal (running backward). By early evening the peaking
floodwaters had overwhelmed the canal and had reached the Fruitvale Blvd and 40th Avenue
interchange. The intersection was shut -down to traffic. Floodwaters continued causing damage
along the south side of Fruitvale Blvd as far eastward as Revolution Cycles and to a number of
businesses along the primary overflow path between Fruitvale Blvd and Myron Lake. Flows
receded overnight. By early morning on the 16th, the intersection was largely re -opened and flows
were fully contained by the creek banks.
Post -flood debris was removed from the upstream face of the Highway 12 bridge and also from
the channel and channel bank just upstream.
MARCH 6, 2016 FLOOD
An isolated thunderstorm event occurred in March of 2016 and dropped a substantial amount of
rain in in the valleys and foothills west of Yakima. The WA-YK-8 CoCoRaHS weather station
recorded 1.12 inches of rain on March 6th, 2016. The peak stage recorded at the Ecology gage on
Cowiche Creek was 8.8 ft (1100 cfs). This event did not overtop the banks of Cowiche Creek
between Powerhouse Road and Highway 12 (possibly as result of emergency flood response
efforts for the February event).
MARCH 14-16,2017 FLOOD
The 2017 flood event on Cowiche Creek occurred with peak flows observed on both the evening
of March 14th (approximately 1,200 cfs) and again the evening of March 15th/morning of March
16th (approximately 1,100 cfs). The event was largely caused by the rapid melt of a persistent (late -
season), low -elevation snowpack (conditions similar to the 2016 event), plus a moderate rain on
snow event at the upper elevations. This yielded a more sustained high-water event, with a
significantly larger total runoff volume than the 2016 event, with a bimodal or 'double -peak'
hydrograph occurring over two days. Overnight low temperatures at the Green Lake SNOTEL
site went from around 20°F on March 7th to above freezing on the evenings of March 13th and
March 14th. Daytime temperatures at the Green Lake SNOTEL site went from below freezing on
the 7th, to nearly 50°F on the 13th. Approximately 0.6 inches or rain was recorded at the site on
March 14th. The recorded Snow Water Equivalent (SWE) dropped nearly 2 inches from March 14th
to March 17th. Conditions were even warmer in the lower portion of the watershed. At the WSU
Ag Station near Cowiche, the average temperature went from 31°F on March 7th, to 50°F on March
15th. Peak temperatures on the 15th reached 62°F.
Similar to the event in 2016, flood flows overwhelmed the south bank of the creek between
Powerhouse Rd and US Highway 12, breached the east -west and north -south berms and flowed
eastward toward the City of Yakima along the southern side of the highway. Flows did not pass
over/ through the City's irrigation reservoir as was observed in 2016, but breached the south bank
of the creek approximately 230 feet upstream, immediately upstream of a significant woody
debris jam. The initial breach occurred on the morning of the 15th and continued until City crews
were able to locate and remove the debris jam on the 16th. The peak flow rate into town may have
37
58
been as high as 300 cfs. The Fruitvale Canal (again) conveyed a portion of the flows back under
Highway 12 and into the Naches River before it was overwhelmed allowing flood flows to head
towards the 40th and Fruitvale intersection.
The extended duration of the hydrograph and the breached berm resulted in larger runoff
volumes reaching Myron Lake which overflowed into Willow Lake and then Aspen Lake. The
higher water level in the lakes caused considerable street and structure flooding in the
surrounding commercial and residential area. A portion of the overland flood flows eventually
crossed 16th Avenue. Urban stormwater drainage systems and infiltration into the ground
diminished overland flows and prevented further damages to the east.
The 2016 and 2017 flood extents within the City are shown on Figure 1-4.
-7
5.0 FLOODPLAIN INFRASTRUCTURE AND FLOOD CONTROL FACILITIES
This chapter describes flood control and flow conveyance facilities provided in the amendment
study area, the infrastructure required as part of development that effect floods, and documents
the historic channel realignments undertaken to enable this infrastructure. Examination of flood
causes and former alignments can indicate potential solutions.
CREEK ALIGNMENTS
Examination of the 1901 USGS maps (see Figure 5-1) indicate the original Creek alignment, delta
and confluence was to the north of its current alignment, passing several hundred feet east of the
current Clover Lane interchange. The Naches Cowiche and Yakima Valley Canal (formerly
Congdon Canal) alignments are also shown, which would have constrained the Cowiche Creek
main channel alignment at their crossings.
North Pacific Railway (NPR) formed a subsidiary, North Yakima and Valley Railway (NYVR), in
order to construct several Branch lines including the Naches (1906) and Cowiche (1913) branches.
The Branches served fruit warehouses and a lumberyard in Naches. The Naches spur -crossed the
original creek alignment, while the Cowiche Branch alignment constrained the rivers floodplain
to the north. The Cowiche Branch Creek, as well as servicing the Fruit Packers in the upper basin
also provided for transport of material to the Bureau dams in the Cowiche basin.
The Cowiche Branch alignment along Cowiche Creek and its tie in to Naches Branch near the
Cowiche canyon mouth pushed the creek approximately 1000 feet southward, cut-off the channel
path to its confluence, which was then north of its current location and narrowed the effective
floodplain of Cowiche Creek. This was the initial displacement below the old Powerhouse Road
of the Cowiche Creek off of its delta.
At that time Powerhouse Road alignment was west of the current alignment and warehouses that
occupied the infilled floodplain were built on either side of Powerhouse Road and already
confined the Creek.
39
M
Figure 5-1.1901 USGS Map of Lower Cowiche Creek.
The 1927 photo (see Figure 5-2) shows the Cowiche Creek realignment both upstream and
downstream of the old Powerhouse Road. Downstream of the current Powerhouse Road the
channel and floodplain were wholly confined by the Northern Pacific Railway Cowiche Branch
and its connection to the Naches Branch until its Naches Branch bridge crossing further south of
the 1901 alignment. The modified channel and floodplain is shown on the figure. In 1927 the
channel is fully contained to the south on the current Holtzinger property (parcel 181309-42004),
until it reached the junction of the Naches Branch. Despite this northern constraint the 1927
channel alignment was still entirely to the north of its current alignment.
Upstream of Powerhouse Road the channel was wider, occupying the Shooting Range parcel
(parcel 181309-42402), and the Yakima Valley Canal Company parcel (parcel 181309-42017). All
of these parcels have since been raised through filling. At the location of the current Powerhouse
Road alignment Cowiche Creek extended more than 200 feet to the north of its current alignment,
and covered a much larger area. Upon crossing Powerhouse Road, its alignment, initially pointed
northeast before meandering southwesterly towards the City storage pond.
From the photo, ditches along the south side of NYPR Cowiche Branch reconnect to the Cowiche
channel indicating the cutoff floodplain formerly lying to the north. Soil textures/ moisture in the
1927 photo indicate cutoff of a large Cowiche Creek delta and confluence to Naches River north
of NYR railway, in agreement with the 1901 USGS alignment.
R
M
Figure 5-2.1927 Aerial Photograph of Lower Cowiche Creek.
The storage pond, built around 1917, was built following the 1913 Cowiche channel railway
induced realignment and ordinary high-water line, and forced the channel to go around the north
side of the pond, hugging the pond along the pond's northern side until the channel runs against
the railway crossing, deflecting the creek south before reaching the only railway bridge crossing
to the southwest. The City took over the irrigation facilities at this location in 1926, including the
storage pond. Also visible on the photos is a north south ditch adjacent to the storage pond, along
the current alignment of the current north south berm and drainage line from the City's uphill
reservoir. The 1927 photo shows the railway bridge location as much as 400 feet southwest of its
current location towards Yakima. Any old pre -railway channel alignments to the east of the
railway had been long filled in for farming by 1927.
Powerhouse Bridge was constructed in 1935 as part of State Route 5. State Route 5 to Naches and
Yakima was moved and converted to Primary State Highway 5 in 1937 and its current alignment
is shown on the 1947 photo (Figure 5-3). This second Cowiche Creek PSH5 bridge crossing was
located immediately north and adjacent to the City storage pond, with the creek now aligned
between PSH5, and the railway for 400 plus feet before passing under the railway.
Primary State Highway 5 was converted to US 12 with the reconstruction of US Highway 12
(formerly PS5) in the 1960's, with it's the provision of additional bridge span at the same location
41
62
Figure 5-3. 1947 Aerial Photograph of Lower Cowiche Creek Overlaid with Existing Naches
River Irrigation Diversion Schematic from Nelson Dam to the Old Union Diversion.
to accommodate the additional 2 lanes, starting in 1963, which resulted in abandonment of the
railway bridge crossing located 430 feet southwest of the storage pond.
In summary, Cowiche Creek alignment has been greatly modified upstream of the Naches
railway route to match railway, landowner, road, irrigation, storage pond and Highway
configurations and reconfigurations, discussed further below.
LEVEES
Aerial photos indicate southward movement and straightening of Cowiche Creek between 1927
and 1947 into its current alignment upstream of the sediment storage pond. This straightening
and channel excavation would have been required berms/levees. The constructed east -west
creek containment levees (indicated on Figure 5-3), were most likely created by the landowners r
to maximize the orchard space and contain flows. The channel is currently raised above the
floodplain by several feet and the east -west containment levees would likely have been reinforced
42
63
in response to floods over time. The southern east -west levee was overtopped in 2016 and failed
in the 2017 flood.
The 1955 Federal Authorized Project (Yakima Levee system) O&M manual page 11, Section 4.04,
notes the existence of a separate private north -south levee protecting the City of Yakima from
Cowiche flood overflows flows: "Cowiche Creek Levee - in addition to the main levee system
described in the preceding paragraph, a privately -owned levee prevents Cowiche Creek flood
waters from flowing into the City of Yakima. This levee is approximately 4 feet high and extends
from the right (southwest) abutment of the current U.S Highway 12 bridge in a southerly
direction approximately 400 feet to high ground". Plate I of that document shows the location of
the north -south levee next to the existing City storage pond and the highway bridge. That bridge
was incorporated and extended in the 1960's with the upgrade of U.S. Highway 410 to four
divided lanes.
Discussions with local residents and operators of the Naches Cowiche irrigation system indicate
that the north -south levee attached to the storage pond was built in response to the 1933 flood
and then raised during the 1996 flood, when flood waters passed over the structure into the City.
The north -south levee is located on top of the buried reservoir overflow line leading to the storage
pond. The 1927 photos do not show the north south berm structure, but show instead a ditch
where the city reservoir line was installed - likely this was the line under construction.
Examination of the lower 4 feet of the berm reveal it is composed largely of large rock indicating
it was probably constructed as a flood fight levee built to withstand the conditions of flowing
water. The 1955 O& M Corps manual verifies that the structure was not yet raised to its current
height. The structure is now ten feet tall and has steep side slopes and is less than six feet wide at
the top, indicating that it has an added -on vertical feature, without lateral extension for stability.
The material in the upper six feet is fine sands and likely prone to piping due to the narrow
section. This north -south levee failed in the 2016 flood.
HIGHWAY AND ROAD CROSSINGS
Within the study area there is a section of State/Federal Highway between 40th Avenue and the
Naches Railroad bridge near 6th Street that acts as a levee to the Naches floods and provides 100 -
year level of protection for the City of Yakima to FEMA requirements, and displayed on the NFIP
flood maps. The Cowiche crossing bridge was constructed in the 1930s well before the 1968 Act
creating the National Flood Insurance Program. The two components as they effect the Naches
and Cowiche floods are as follows:
US 12 - US 12 highway alignment along the Lower Naches River (historically aka SR5 and SR410)
was constructed as two lanes in the 1930s and expanded to four lanes in between 1963 and 1971—
Historically the Naches River floodplain extended beyond Fruitvale Avenue in the City of
Yakima and in areas of Yakima County upstream to the current study area limit at the US 12
crossing of the Naches. Based on the FEMA 2009 remap the current four lane configuration of
US 12 contains the Naches River 100 and 500 -year floods to the north, protecting a large area of
the City of Yakima from flooding by the Naches River. Failure of US 12 during a Naches River
flood event would prove catastrophic to large areas of Yakima as there are currently no facilities
43
64
to let floodwaters exit the City and return to the Yakima or Naches rivers. Repeated damage to
US 12 upstream of the 16th Avenue Exit, even during relatively minor flood events, presents high
levels of flood hazard not only due to loss of transportation infrastructure, but also due to the key
role that this portion of highway plays in providing a high level of flood protection to a large
urbanized area.
US 12 Bridge - US 12 bridge crossing of the Lower Cowiche creek (historically aka SR5) was
constructed in the 1930s as a two-lane span and expanded to four lanes between 1963 and 1971—
The Cowiche Creek floodplain was modified by the City storage pond bridge alignment and
thence by Highway 12. The Highway alignment in the 1930's cut of the northeast corner of the
pond. In 1963, in preparation for the four lanes the WSDOT bridge was expanded initially for two
lanes and the railway bridge moved 400 feet north. When the highway was expanded to four
lanes in 1971 the two-lane bridge opening was extended upstream towards the storage pond
creating a 110 -foot bridge length along the channel. A retaining wall was built between the
storage pond and the 1970 two-lane bridge extension. Modifications for piping to the pond were
also accomplished at this time. The Recent FIS studies noted above establish that this portion of
the highway does not provide 100 -yr protection from Cowiche Creek as the bridge is undersized
for this FEMA generated 100 -yr flow. The bridge is still within its life span. This bridge without
channel excavation does not pass the 10 -year flow. Floodwaters overtop the southern river berm
upstream side of the bridge and head toward town. The original two-lane bridge was built
decades prior to current federal and state standards that use the 100 -yr flood, since the National
Flood Insurance Program was passed in 1968. Modeling has indicated that this span of bridge
cannot pass the 100 -yr flood even with excavation, so that a replacement or sister bridge would
be required to pass the 100 -yr flood. Review of 1963 WSDOT design drawings show the Cowiche
Creek channel invert 3 feet lower than today, indicating a significant build-up of sediment in the
channel over the last 54 years upstream of the US 12 bridge. However, investigation of the
floodplains and LiDAR suggests this may have been a transcription error, as it would mean a
significant trough in the stream gradient plus separation from the floodplain, as well as erosion
of a downstream City water main. Replacement of this bridge is not currently on WSDOT's capital
improvement plan.
City of Yakima Powerhouse Road Bridge - It is the original State Route #5 bridge built in
1930. This bridge is past its design life and barely passes the 10 -year flow. It was designed
according to standards at the time and all of the related infrastructure around it has already or
will be modified this year. A new bridge would require more depth and width, but there is not
much width upstream which would allow to gain upstream benefits as well. This bridge is
located in what should be a 3 -lane section and bike lane, so this bridge ideally would not only
have a greater span but a much greater overall travelled lane width. Yakima County Roads
provided a design for this bridge when it was in the County, before it was annexed by the City.
Squire -Ingham Orchard farm bridge - The orchard downstream of US 12 along Cowiche Creek
currently uses a small 16 -foot -wide bridge for both farming access and hauling freight out of both
orchards toward US 12 on Clover Lane. Provision of alternative farm and haul routes for the
orchard also needs to be considered as the widening of the bridges on US 12 may make
construction of a relatively narrow bridge infeasible.
65
RAILWAYS AND TRAILS
Yakima County's Cowiche Creek Trail Bridge on the old Naches Spur line - This bridge is
newly constructed and does pass the 100 -year flow. However, if the US 12 replacement wider
bridge alignment results in misalignment or we sister a new bridge span adjacent to the existing
structure, the realignment will probably require another trail bridge. So, impacts and changes to
the County bridge need to be considered within the study area.
IRRIGATION STRUCTURES AND CANALS
Four irrigation withdrawals are made from the Naches River in this reach, two at Nelson Dam
(Naches-Cowiche and City of Yakima) and two just downstream of Cowiche Creek confluence
(Fruitvale and Old Union). These intakes and canal systems were provided in the 19th century.
They create a labyrinth of piping, siphons, fish passage structures and open canals in this area the
complexity of which is depicted in Figure 5-1. Crossings with this infrastructure, particularly
Naches Cowiche has confined potential channel alignments. The Fruitvale Canal diversion
structure has also restrained the Cowiche alignment at its confluence with the Naches River.
These actions led to the subsequent development and in -filling of the Cowiche floodplain both
upstream and downstream of the current Powerhouse Road alignment and the eventual
relocation of the creek southward of its historic delta deposits.
FORMER US 12 GRAVEL PITS
During the construction of US Highway 12 as a four -lane divided highway in starting in 1963,
three large gravel supply pits were created and built exterior to the river based on highway
alignment. They are Myron, Willow and Aspen Lakes listed in upstream to downstream order
along the Naches River. Due to the gradient along the Naches River the pits were separated to
minimize constructed depths and construction pumpage. The lake elevations for the resultant
pits determined by constructed drainage features are approximately 1125, 1109 and 1102 feet, for
Myron, Willow and Aspen lakes respectively with corresponding surface areas of 14.6, 28.7 and
22.6 acres.
During highway construction the three pits were each provided with 18 -inch outlet pipes and
flap gates to the Naches River plus connecting overflow piping from upstream pond to
downstream. Ownership of Willow and Aspen Lakes was transferred by WSDOT through a
developer to Homeowner groups. Figure 5-4 shows their physical location and includes fish
passage and other structures.
45
M
Figure 5-4. Location of Canals, Culverts, Diversions, Levees and Fish Passage
67
6.0 FLOOD ISSUES AND INFRASTRUCTURE
CAPACITY OF COWICHE CREEK INFRASTRUCTURE
During the recent FIS study flood restricting infrastructure in this reach was identified. The
infrastructure providing restrictions to 100 -yr floods are Powerhouse Road bridge, the channel
capacity downstream of Powerhouse Road, the east west berm height on both sides of the
channel, the storage pond height, Highway 12, the Yakima County trail bridge, the protective
berm on Ingham s property and the channel capacity and grade downstream of the trail bridge.
During this study, more detailed hydraulic investigations were provided below.
HYDRAULIC MODELING OF COWICHE CREEK INFRASTRUCTURE
CAPACITIES
FCZD staff created and refined a hydraulic model of the Cowiche - Naches confluence as part of
a coordinated technical response to the flood events of 2016 and 2017, and as part of the initial
data gathering efforts associated with the preparation of this addendum to the CHFMP. The
hydraulic model was originally developed as a linked 1D -2D HEC -RAS (version 5.0.3) simulation
tool. It was aimed at re-creating the events of 2016 and 2017 with the goal of then estimating
current channel capacities and to evaluate potential emergency actions that could be taken to
reduce flood risk before the next flood season.
The model initially informed two maintenance actions in summer/fall 2017, performed by the
City of Yakima (brush trimming, levee access improvements) and WSDOT/Yakima County
(sediment removal under US Highway 12 and the trail bridge). The model was later expanded
as additional information became available (survey, and new LiDAR) to include a number of
different simulations, including fully 2D simulations and a range of small and large flood flow
events (e.g. 2 -yr, 10 -yr, 100 -yr, etc.). Estimated channel conveyance capacities are shown in Figure
6-1.
2016/2017 DISCHARGE HYDROGRAPHS
Flow estimates were required to simulate the 2016 and 2017 flood events. Ecology maintains a
flow gage on Cowiche Creek just downstream of the confluence of the North Fork and the South
Fork. The gage is largely targeted at informing reach water quality and provides good quality
flow/ temperature data for the predominant flow conditions. It is not intended as a flood flow
gage for measuring peak flood discharges. The published rating curve for the 2017 WY was
limited to flows of less than 540 cfs. At flows above this magnitude (both the 2016 and 2017 flood
events), the station only reports the observed stage. To recreate the runoff hydrograph for the
2016 and 2017 events, the rating curve was extrapolated to flows around 1200 cfs as shown in
Figure 6-2. Extrapolation of the rating curve assumes that the relationship between depth and
flow area remains consistent even as flows rise above the upper limit of the published rating
curve. Field observation of the gaging site suggests this may be a reasonable assumption up to
about depths of 5 feet (corresponding to stage readings of about 9 ft) and flows around 1,200 cfs.
47
68
Above that flow level, significant amounts of overbank/floodplain flow would occur and the
rating curve would become increasingly inaccurate.
The Bureau of Reclamation maintains a stage -only gage on Cowiche Creek at the upstream side
of the Powerhouse Road bridge. As a second check on the reasonableness of the extrapolation,
this stage data was compared to the flows recorded at the Ecology gage upstream (see Figure 6-
3). Peak flows at the Powerhouse bridge occurred about 5 to 8 hours after peak flows were
observed at the Ecology gage upstream. Figure 6-4 shows the relatively close correlation between
observed stage data on the upstream side of the Powerhouse Rd bridge, the time -shifted flow
data recorded at the Ecology gage, and the rating curve for the Powerhouse Bridge section (from
the HEC -RAS model). This reinforces the conclusion that the flow peak estimates yielded by the
extrapolation of the rating curve are indeed reasonable and provides an estimate of the potential
error (50 to 100 cfs).
Estimated hydrographs for both the 2016 and 2017 event are shown in Figure 6-5 along with the
corresponding flows that were observed in the Naches River during the 2017 event. The analysis
indicates that both flood peaks were very nearly 1200 cfs with the 2017 event exhibiting a second
peak and persisting for a significantly longer duration.
Figure 6-1. Estimated Existing Conveyance Capacities for Cowiche Creek
70
cowiche creek Rating curve
12001
Flow (cfs) = 39.6*stage2 - 277.55*stage+ 484.41
1000 (stage in feet) ##
80
600
40
Published Rating curve
200 Extrapolated
3.5
4 4.5 5 5.5 6 6.5
Stage (ft)
7 7.5 8 &5
Figure 6-2. Extrapolated rating curve for Cowiche Creek at the Ecology gage (2017 WY)
owiche Creep - Spring 2017 Discharge
1400 ............................................................................................................................................................................................................................................................................................... 12
—Flow (L rE 1'1EE7 rating t.LIrvc,) �
Flow exrE't:pol Itc d 1200
E.E
Bur'eaLi SL .Igo D} iLa �iL P{,dwc,r11101.Ixse Fid .1.0 w.
rJ 1V0.
9
W y
800 2
{J5
5-8 Pars 7
600
}0 5
4
200
2
�? 2
3/1212011 311412017 311612011 3/18/2017 3/20/2011 3/22'2017
Da tc=
Figure 6-3. Reconstructed hydrograph versus recorded stage
50
Correlation between Ecology flow data and BOR stage data
(January 1,2Q17 May 9th,2OI7,assuming a 6 -hr delay)
400
71
] IS 4 4.5 5 5,5 § 6,5
°
Correlation Points within rating curve
�
Extrapolated Points
—Rating Curve for Powerhouse Bridge (HEC RAS K8ode|),RK85E=55cfs
Figure 6-4.Correlation between Ecology flow data and BOR stage data
[ovviche[reek'Reconstructed2O16 & 2 017 hyd rogra pha
u 1800 6000
oo 1600
5000
-�
�U �
1200 4800 mm
�
�
1000 -~
�
3000 �
800 ^
.2
GOO 2000 ^�
400 �
1000 mc
�
200
�
_2 O O
LL 3/12/17 3/13/17 3/14/17 3/15/17 3/16/17 3/17/17 3/18/17 3/19/17 3/20/17 3/21/17 3/22/17
Rnconstructed 2O17HydrnQrnnh - - - -~ Reconstructed 2Ol6Hydrn8,aphNme-ohiKnd]
Figure 6-5. Reconstructed 2016/2017 hydrographs
51
72
HYDRAULIC SIMULATIONS
Hydraulic simulations were conducted using a 1D -2D model initially built from 2005 LiDAR
topography and cross-sectional bridge survey data from the 1D RAS model that had been
assembled as part of the 2011 Flood Insurance Study and flood map update for Cowiche Creek
(West, 2011). Field observations of flood flows and local site conditions indicated the need for
additional surveyed cross-sections and improved hydraulic structures to adequately model the
Highway 12 bridge, the south berm of Cowiche creek, and overflow flood routing resulting from
berm breaching. The model evolved into a 1D -2D linked simulation that used 1D sections for the
main channel of Cowiche Creek connected to a 2D overbank floodplain domain via lateral
structures (weirs) along the levee crests that could be breached during simulations. The spatial
configuration of the model is illustrated in Figure 6-6 which shows the 1D sections, the break -
lines and grid cells (— 30 ft) of the 2D domain, and the alignment of the various lateral weir
structures used in the model. The model included a variety of flows in the Naches and extended
upstream to Nelson Dam and downstream to just east of 40th Avenue (flood waters into the City
of Yakima were not simulated). The weir profile and a typical breach simulation for the south
bank of Cowiche creek between Highway 12 and Powerhouse Road is shown in Figure 6-7.
Simulations were typically run with a computation timestep of 5 seconds using the Full
Momentum equation set.
Figure 6-6. Typical 1D/2D model configuration
52
73
Using the hydrograph developed for the 2017 event, and reasonable assumptions for roughness
values, and breach widths matching those observed in the field, the model yielded flood flow
behavior and maximum inundation extents comparable to those observed in the field. The model
was not calibrated further. Additional simulations were then developed to model larger flood
flows and how the system would respond to various short-term maintenance actions (dredging,
levee raising, etc.). The model was then updated to reflect the maintenance actions performed by
the City, County, and WSDOT which included improved levee access, brush cleanup, and
sediment removal. The model was again updated when 2017 LiDAR became available.
Using this latest version of the model and the larger flood flow simulations, the current estimated
capacity of each creek section was estimated as shown in Figure 6-1. The range reflects
uncertainty in the assumptions used for the roughness value (Manning's n value) and variability
within the reach. These are estimates based on the condition of the channel in early 2018. The
morphology of the channel is expected to continue to respond and evolve as flood flows interact
with the maintenance action at the Highway 12 bridge and the recent re -construction of the
Naches-Cowiche Canal Association's inverted siphon located just downstream of Powerhouse
Road.
DOWNSTREAM IMPACTS FROM DEFICIENCIES OF COWICHE CREEK
INFRASTRUCTURE
0 200 400 600 B00 1000
Station (ft)
Figure 6-7. Typical lateral weir structure profile and breach scenario configuration
The new FIS 100 -year floodmaps provide flood extents within Yakima City but are limited to east
of 401h as Myron Lake was considered the downstream extent of the study. The flood extents
noted during the March 2017 overflows on Figure 6-1 provide flood extents for a higher frequency
Cowiche flood. The flood extents are much further into the City. To assess potential 100 -yr
53
74
Cowiche flood extents into the City a hypothetical simulation was provided. This assumption
limits outflows to Naches River under US 12.
100 -YR FLOOD ROUTING IN CITY OF YAKIMA
Despite the flood risk reduction efforts completed after the 2016 and 2017 flood events, the
updated conveyance capacity estimates revealed that a 100 -yr event would still send significant
flood flows into the City. To help inform the stakeholder group during the CFHMP, a set of
derivative simulations were developed to consider potential flood routing within the City of
Yakima under such a scenario. The model was built with an upstream boundary condition
located along the south side of Cowiche creek between Highway 12 and Powerhouse Rd (the
location where the creek failed in both 2016 and 2017). The fully 2D model domain was extended
downstream as far as Yakima Ave on the south boundary, to US Highway 12 on the north, and
to US Highway 82 to the east. To simulate overflows from the creek (through a breached south
bank levee), the 2016 storm hydrograph was scaled up to the 100 -yr peak flow for Cowiche Creek
of Q = 2818 cfs, (West, 2011) reduced by the amount of water estimated could remain in the creek
channel which would pass under Highway 12. The resulting hydrograph is shown in Figure 6-8.
The hydraulic model did not include any stormwater infrastructure and assumed a single
representative roughness value for the entire domain. It assumes a fixed bed without any
infiltration of floodwaters into the ground. It was intended as an initial, limited look at the
potential severity of such an event and to develop potential risk areas for further study and
analysis. The model was not calibrated. The simulation does not reflect actual risk to individual
100 -yr Simulation Hydrograph
3000
Overflow Hydrogruph
25{00 � � 100yr Hydro raph
2000
15i}Q
N
1000
.z
500
0
6 2 4 6 8 10 12 14 16 18 20 22 24 26 28 36 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60
Figure 6-8. 100 -yr Simulation hydrographs
Simulation irne, hours
54
Figure 6-9. Potential 100 -yr inundation routing within City of Yakima.
55
76
structures due to the assumptions but provides a measure of 100 -year flood overall risk without
taken actions. The simulated inundation results are depicted in Figure 6-9.
Following review of the above material the advisory Committee developed and ranked the Flood
issues.
TABLE 6-1 FLOOD ISSUES TABLE
2018 ADVISORY COMMITTEE RANKING OF FLOODING ISSUES
ID
Flooding Issue
Rank
LC1
Inadequate facilities in floodplain, and hydraulic capacity of Lower Cowiche
Creek to prevent flood overflows to Cit
1
LC2
Floodplain and Flood Risk Mapping not reflective of risk
2
LC3
Improve Public Awareness and Flood Insurance knowledge
2
LC4
Improve Formal Interagency coordination
2
LC5
Revision and Consistency of Flood Hazard, Critical Areas & Shoreline
Ordinances for this location
2
LC6
Inadequate flood forecasting system
2 or 3
LC7
Define Clear Action Points to Initiate Emergency Response Activities for
Cowiche Creek overflows
3
LC8
Funding for Flood Control Works and Restoration Project elements.
3
LC9
Extensive Flood Routing in (and outside of) the City of Yakima
4
LC10
Stability of berms on Lake Aspen/Myron/Willow & Aspen drainage
4
LC11
Risk to US 12 during major flood events
5
LC12
Threat of flooding to State, County, and City Roads
5
LC13
Lack of Space for Cowiche Creek Channel Migration
6
LC14
Availability of Centralized GIS Data & Modeling Impacts in planning and
inventor
6
LC15
Ownership and Standards for new/upgraded Flood Control Facilities
6
LC16
Development pressures in affected areas promoting additional harm
6
LC17
Lack of space for Cowiche Creek low flow Channel Migration
6 or 7
LC18
Operation and Maintenance of Flood Control Facilities
7
56
77
TABLE 6-1 FLOOD ISSUES TABLE
2018 ADVISORY COMMITTEE RANKING OF FLOODING ISSUES
ID
Flooding Issue
Rank
LC19
Acquisition/ Preservation of Floodplain Open Space
8
LC20
Loss of Channel Capacity due to sediment accumulation and lateral
confinement
9
LC21
Sediment accumulates in reach, reducing flood capacity
9
LC22
Nelson Dam and Fruitvale infrastructure reducing hydraulic capacity
downstream of US 12
9
LC23
Erosion/Loss of Agricultural Land
57
78
7.0 GENERATION OF ALTERNATIVES AND RECOMMENDATIONS
FLOOD PREPARATION, ACTIONS AND ALTERNATIVES
The flood mitigation preparation, including identification of vulnerabilities, was completed
using the hydraulic analysis in Section 6.0 combined with the existing limited information, time
available and funding. Fortunately, recent LiDAR data at resolutions smaller than 0.1 feet was
available from a November 2017 flight, in addition to bridge sections from the FEMA FIS study.
The analysis of past events and hydraulic modeling has highlighted vulnerabilities and
opportunities for flood response actions with substantive benefits.
Recommendation actions are separated into near, short, and long-term. The near-term priorities
with regard to potential flood events are: flood warning, minimizing overflows toward the city
while notifying the public, including evacuation and preparedness, lessening existing
development exposed including redirection of flows from vulnerable areas as far upstream as
practical. Near-term actions were put in place for the upcoming 2017/2018 flood season and are
not subject of this plan. The most beneficial of these actions is to reroute any Cowiche overflows
back into the Naches below reaching the Fruitvale and 40th interchange. In this regard an ILA is
being formed between the City, WSDOT and the FCZD, which will extend beyond the first
flood season.
NEAR-TERM ACTION PLAN
The near-term action plan developed outside of this CFHMP is provided in Appendix A and
the main components were to provide early public notification, reduce the frequency of
overflow from Cowiche creek and the impacts of such overflows. The main components of the
Near -Term Action Plan are listed below.
Emergency Action Plan and Public Notification - Cooperative notification through the Yakima
Valley Office of Emergency Management has been set up with information provided by the
Yakima FCZD, the City and WSDOT. Elements of this action should include: Monitoring of
flood flows during Cowiche Creek and Regional flood events, Public Notification including
evacuation based on warning times, Monitoring of flood berm stability during Cowiche Creek
and Regional flood events.
Memorandum of Understanding and Interlocal Agreements - The City of Yakima has
engaged in flood fights in association with the Corps of Engineers on their levee adjacent to the
City Wastewater Treatment Plant. The City has not in the past stockpiled materials for flood
fighting such as sandbags, riprap and other quarried rocks. The County and Flood Control
Zone District has reserves of sandbags and riprap, and a larger fleet of trucks, equipment and
operators. The City and FCZD should agree to coordinate on flood fighting actions in the city,
including coordination of the declarations of Emergency by the City Council and Board of
County Commissioners to allow cooperation during flood events, and the use of the Flood
79
Control Zone District by either Office of Emergency Management. This cooperation would be
extended by an ILA that also includes the Washington Department of Transportation.
Channel Cleanout- The current gradient of the stream limits the effectiveness of and ability to
improve conveyance capacity in this reach. The City of Yakima has removed a significant
amount of vegetation from the channel to increase conveyance, and cleared the top of the
southern (towards City of Yakima) 3000 -foot berm to allow for the 2017 survey of the channel,
and also allow for visual inspection of the stream and berms on either side during flood events.
It was reported that much of the 2017 event overflow was increased by a buildup of woody
debris trapped in streamside vegetation in that narrow riparian corridor. In 2016 a large tree
obstructed flow under the US1'2 bridge was also removed.
Repair and Raising of Private Cowiche Creek Levee The channel cleanout combined with the
clearing of vegetation and raising of the berm with a gravel road will reduce the frequency of
flood waters overflowing into Yakima. Having an equipment access to the channel along the
berm will allow flood fighting including removal of vegetation and debris preceding and
during flood events.
US 12 Bridge Cleanout -The US 12 bridge will benefit from removal of sediment trapped under
the highway bridges and downstream through the new trail bridge. The trail bridge sediment
is creating a downstream plug for sediment. Sediment removal of this nearly 200 -foot -long plug
in October increased conveyance capacity from below the 10 -year flow to just above it. Until a
more natural, steeper channel gradient downstream of the trail bridge is restored through lower
Cowiche Creek relocation and restoration, the capacity of the existing bridges is limited to this
sediment plug removal. In the medium term, the channel and conveyance capacity of the
channel and bridges should be monitored and actions taken to maximize conveyance until the
longer-term actions can be implemented.
The above 2017 cleanouts have raised the capacity of the reach to pass the 10 -year flow of 1500
cfs.
Divert Cowiche Creek Flood Flows West of the 40th Avenue and Fruitvale Rd Interchange -
As floodwaters move from Cowiche Creek, they travel along US 12, flooding the Riverview
Manor Mobile Home Park, then continuing along US 12 to the Fruitvale Canal Culvert outlet,
then continues to the intersection of 40th and Fruitvale. Without any diversion, some water
will flow down Fruitvale, while the majority of water flows down the Greenway Trail, across
the Parking Lot of Lakeside Court, or down the Myron Lake access road, all ending in Myron
Lake. During the long duration flood event of 2017, water filled Myron Lake, and overflowed
across the berm to Willow Lake, and Willow overflowed into Aspen Lake, and Aspen Lake
eventually filled to the elevation of 16th Avenue, with water flowing across 16th to the east and
down 16th to the south.
59
80
SHORT AND LONG-TERM ALTERNATIVES
Short and long-term flood mitigation priorities vary from the near-term priorities in accordance
with their increased timelines. Long-term alternatives are geared to provide the required and
agreed upon Cowiche Creek hydraulic capacity (within this plan), say 100 -yr, to avoid routing
of overflows into the City, and will have the longest timelines due to larger capital outlays and
funding timelines. Short-term alternatives are required to bring about the interim changes
before the long-term recommendations are in place and provide risk reduction actions can be
undertaken to either increase hydraulic capacity, flood responsiveness and public awareness to
minimize the potential damages from Cowiche overflows reaching the City. The goals and
objectives for the short and long-term are contained in Tables 1-2 and 1-3 and are used in
conjunction with the flood ranking issues in Table 6-1 to generate alternatives.
During the short-term, priorities during events would also focus on elements identified in the
near action plan above such as intercepting overflows as far upstream as possible to minimize
damages.
LONG-TERM ACTIONS
It is evident from the hydraulic capacity computations that the following long-term
replacements will be required:
Construction of New Bridges - Cowiche Creek is crossed by 3 transportation routes - the
Naches Greenway Trail, US 12, and Powerhouse Road. Both the road crossings have very low
flood conveyance capacity.
WSDOT's US 12 Bridge - This four -lane bridge requires replacement. Modeling has
indicated that this span of bridge cannot pass the 100 -yr flood even with excavation, so
that a replacement or sister bridge would be required to pass the 100 -yr flood.
Yakima County's Cowiche Creek Trail Bridge - if the US 12 replacement wider bridge
alignment results in misalignment or we sister a new bridge span adjacent to the existing
structure, the realignment will probably require another trail bridge.
City of Yakima Powerhouse Road Bridge -This bridge barely passes the 10 -year flow. I
was designed according to standards at the time, but it is old. All of the related
infrastructure around it has already or will be modified this year, probably
Squire -Ingham Orchard farm bridge - The orchard downstream of US 12 along Cowiche
Creek currently uses a small 16 -foot -wide bridge for both farming access and hauling
freight out of both orchards toward US 12 on Clover Lane. Provision of alternative farm
81
and haul routes for the orchard also needs to be considered as the widening of the bridges
on US 12 may make construction of a relatively narrow bridge infeasible.
New Cowiche Creek 100 Year Long -Term Levees Upstream of US 12 - Even with the
replacement of the US 12 and Powerhouse Road Bridges the reach of Cowiche Creek between
the bridges will need construction of a flood control structure to keep floodwaters from moving
south from the Creek, downhill into the City of Yakima. Due to the economic consequences this
levee would benefit from locations that reduce velocities, levee damages and failure risk. This
reach lies on an alluvial fan and can be expected to aggrade over time, especially during long
duration flood events. We expect that the area interior to the levee will require periodic
cleanout (5 yrs?) of accumulated gravels The more channel and floodplain width allowed for
the creek in this reach, the lower the frequency of needed cleanout and risk of damages and
failure. This levee should be constructed to a standard that it can be enrolled in the USACE
PL84-99 program, and ideally certified as a 100 -year levee.
Lower Cowiche Creek Reconstruction Upstream of US 12 - The historic realignments of
Cowiche creek downstream of Powerhouse Road by the Railroad Upstream of US 12, the Creek
also needs reconstruction, other irrigation infrastructure upstream has been designed and will
be constructed to allow for lowering of the channel bed and expansion of channel conveyance.
The YBIP capital program currently contains some funding for this action. The most impoertant
chage in this action, determimed by Hydraulic analysis in this study is that the Cowiche Creek
bed requires lowering by 3 feet from previousl computations to allow containment of the 100 -
year flood in the corridor upstream of SR12. This drop would be continued upstreamo
Powerhouse Road.
Both of the channel construction options can be started in the short-term if their design is
coordinated with the remaining structural replacements. Their early design with lower inverts
for example will increase the capacity of the bridges.
SHORT-TERM ACTIONS
Actions beyond those provided in the near-term Action Plan to reduces overflows into the City
are required in the interim period before the long-term actions can be funded and constructed.
Some of the more obvious are:
New Flood Insurance Rate Maps in the City of Yakima Currently, the residential structures
that lie in the flood path are not required to have flood insurance, nor do the
commercial/industrial facilities aware that they may want to find private flood insurance, at
least in the near-term. The 2018 FIS flood maps, once adopted do not cover the complete
Cowiche overflow threatened area. If a long-term corridor system for protecting the City from
61
82
flooding during a 100 -year event cannot be implemented, as noted above due to financial or
physical constraints, flood insurance maps that include the threatened City areas are required.
A critical element in determining the desired level of flood protection for the City and the
economic rationale for the construction of long-term flood control works will be the annual
insurance costs, both private and public, and the cost and effect of the increased construction
standards (building elevation, floodproofing and overall site design) which will result from
National Flood Insurance Program and related Building Code regulations for development in
the mapped 100 year floodplain.
Nelson Dam Reconfiguration/Replacement - this project should occur in 2019 or 2020. The
reconfiguration/replacement of Nelson Dam will allow the removal of the Fruitvale and Old
Union Diversion facilities on the Naches River just downstream of the confluence with Cowiche
Creek. Once the diversion infrastructure is removed, lower Cowiche Creek can be substantially
re -configured to restore floodplain function and habitat with significantly improved channel
and levee alignments and a higher overall conveyance capacity. While studies have found that
the proposed reconfiguration of Nelson Dam will increase sediment transport to this reach,
potentially increasing the bed elevation of the Naches River in the vicinity of Cowiche Creek,
the change is expected to be gradual as much of the accumulated bed material behind Nelson
Dam is currently immobilized by riparian vegetation. The flood risk reduction benefits of
removing the irrigation infrastructure far outweigh the potential for a muted hydraulic
aggradation trend at the confluence. Rather, the reconfiguration/replacement of Nelson Dam is
a key action towards reestablishing a more predictable sediment transport regime in the Naches
River and is critical toward enabling other infrastructure consolidation on Cowiche Creek to
reduce flood risks.
Lower Cowiche Creek Reconstruction Downstream of US 12 (YRBWEP) - The historic
realignments of Cowiche creek downstream of Powerhouse Road by the Railroad and State
Highways has led to extensive modification of lower Cowiche Creek, including loss of its delta,
loss of floodplains and conveyance capacity due to levees and bridge constrictions. Combined
with starvation of Naches River below Nelson Dam and Fruitvale canal intake there has been
significant alterations in the Cowiche Creek gradient. Yakima County Flood Control District has
designed a new stream channel below US 12 and purchased an easement from Squire -Ingham
Orchards to construct the channel. The new channel will have a 100 -year flood conveyance
capacity, lower the bed of the creek 3-4 feet downstream of the highway, and restore the steeper
channel gradient. This action can be implemented prior to reconstruction of Nelson Dam and
retirement of the Fruitvale Canal Diversion, but it would be more efficient to perform the
retirement of the diversions and floodplain restoration/levee setback all at the same time.
GENERATION OF ALTERNATIVES
The Advisory Committee was provided with a list of updated generic flood hazard mitigation
alternatives originally developed in the 1998 CFHMP, which is contained in Appendix B. Tables
of their relative impacts and costs plus a summary table are also contained in appendix B. Flood
62
83
hazard mitigation alternatives were then generated for each of the Flood Issues listed in Table 6-
1, then voted on need for inclusion within the recommendations. The generated alternatives and
voting is contained in Appendix C. During that process the goals and objectives were reviewed
and modified to ensure adequate containment within the recommendations.
COMBINATION OF ALTERNATIVES INTO RECOMMENDATIONS
The recommendations were created by combining the accepted (voting) alternatives from
Appendix B. and then separated into functional implementation categories: Planning, Flood
Preparedness, Public awareness and Structural Recommendation. The long-term Structural
recommendations are contained in Table 7-1. The short-term recommendations, which bridge the
gap prior to full implementation of the Structural alternatives are in Tables 7-2, 7-3 and 7-4
separated by their functional category, such as Planning. Each table is ordered by approximate
implementation priority.
TABLE 7-1 PLANNING RECOMMENDATIONS - SHORT-TERM
ID
Recommendation
Estimated
Lead
Cost in $
Entities
PL1
Provide a new Cowiche Creek riverine infrastructure corridor
between Powerhouse Road and the Naches River to eliminate
See below
City,
Cowiche overflows into the City.
WSDOT,
FCZD
PL2
Maintain interagency coordination, necessary flood fight ILAs and
information exchange until existing Lower Cowiche corridor
10,000/yr
City, FCZD,
replaced.
YVOEM,
WSDOT
PU
Adopt the new Cowiche Creek FEMA preliminary maps for new
development and use overflow scenario map as guidance. Early
10/000/yr
City, County
community adoption of the FEMA maps reduces community risk,
pL4
Appoint a Planning Task Force to minimize Community risk from
Cowiche Creek overflows to ensure planning and building
10/000/yr
City, County
measures are in step with structural measures over all phases of
exposure. The Task Force should provide corridor replacement
timelines and sunsets for the measures.
pL5
Incorporate the 2017 flood extent map during the interim period for
flood protection on development for drainage, stormwater,
5,000
City
building design, siting, and layout. Regulatory use of the actual
2017 flood extent and development guidance using the hypothetical
100 -year overflow maps presented herein will reduce risk exposure
within the City for the interim period prior to lower Cowiche
Corridor replacement.
63
84
TABLE 7-1 PLANNING RECOMMENDATIONS - SHORT-TERM
ID
Recommendation
Estimated
Lead
Cost in $
Entities
PL6
Provide Contingency Planning across jurisdictions & agencies as a
living document for the following overflow scenarios: current day,
5,000/yr
City,
the intervening period when individual corridor elements are
YVOEM,
replaced, and upon completion of rehabilitated corridor.
FCZD
Contingency Plans must reflect changed conditions for all newly
introduced infrastructure in addition to current lower capacity
infrastructure. This coordination will require emergency
preparedness, including action planning, and require supplemental
basin data collection specifically for rain on snow storms, drainages
studies for the vulnerable City areas, use of new flood risk maps and
formation of a Planning Task forces to use the information and
studies for decision making on interim measures.
PL7
Provide an ILA or MOU to locate funding sources (local, state and
federal) and secure funding to replace the Lower Cowiche stream
10,000
City,
and stream crossing corridor and increase reliability of flood
County,
warning. Funding (local, private, state, and federal), needs to be
WSDOT
established to permit the land acquisition and infrastructure
replacement and be cooperative across agencies, including basin
proponents, to ensure maximum support and effective utilization of
public funds. Infrastructure leads should seek and secure local, state
and federal funding to make improvements to this reach of Cowiche
Creek. The CFHMP, and an overall hydraulic design study outlining
benefits and common goals should be used and developed as a
planning document to justify funding requirements.
PL8
Provide a rehabilitation design that is hydraulically coordinated to
replace the existing channel and crossings between Powerhouse
60,000
City, FCZD,
Road and the confluence with the Naches River (Lower Cowiche).
WSDOT
The channel's capacity will be increased to pass the 100 -year
discharge with adequate freeboard to meet FEMA flood mapping
requirements. Jurisdictions and owners will coordinate the overall
design. The model would be provided by the FCZD and designs of
individual elements must fit within the agreed overall design that
ensures removal of the City of Yakima from the extended 100 -year
floodplain from Cowiche Creek overflows, minimize design and
operational risk failures from the features and interfaces of features.
Due to the Yakima and Cowiche basin recovery value provided by
this reach the overall and component designs will allow for habitat
enhancement requirements outlined in the goals and objectives and
for the planned removal of Fruitvale irrigation infrastructure at the
Cowiche-Naches confluence. The new channel inverts made possible
will result in a channel bed reduction of up to 3 feet along most of the
channel length. The design will be sensitive to capital, operating and
M
85
TABLE 7-1 PLANNING RECOMMENDATIONS - SHORT-TERM
ID
Recommendation
Estimated
Lead
Cost in $
Entities
life cycle costs and provide costing numbers necessary for funding.
Sediment passage elements required in this design are expected at
Powerhouse and US 12 bridges, and sediment removal locations at
channel segments upstream and downstream of US 12. The new trail
bridge may require an extension.
PL9
Incorporate multi benefit considerations with the coordinated
corridor design such as trails, open space, agricultural and habitat.
5,000
City, County
Preserve and/or expand open space and land uses including
agricultural and recreational that not only reduce flood risk but
enhance other preservation, nature benefits. Trail location options
should be investigated.
PL10
Acquire required land to increase the current Lower Cowiche
corridor in accordance with goals and design standards (noted in
200,000
City, FCZD
Recommendation PL 8). In order to reduce risk to an appropriate
level the current corridor must be expanded to allow for the
expansion of stream bed and stream crossing footprints and the
necessary operational maintenance and access required to sustain
and respond to the natural processes. The width of the corridor
should also be designed to minimize need for ongoing sediment
removal and large woody material management, and ensure that the
low -flow channel supports typical flow conditions that are beneficial
for fish and water quality. The variety of ownership requires
coordination in accordance with design to promote adequate real
property interests transfer and satisfactory incorporation of
landowner concerns.
PL11
Assess Cowiche basin need for new snow, precipitation and stream
gages to reduce risk and seek partners for regional small basin
100,000
FCZD, City
needs on the west slopes of Naches and Upper Yakima region
(Cowiche, Wide Hollow and Ahtanum). Partners should include
basin data collection agencies: USGS, Ecology and BOR
PL12
Organize community -level funding districts of local funding that
construct and maintain approved protective risk -reduction
N/A
City
features.
PL13
Install the coordinated Cowiche corridor channel elements from
downstream to upstream order to maximize upstream function,
N/A
FCZD, City
minimize cost and reduce transitory impacts. Pursuit in this order
lowers the channel bed bottlenecks by as much as three feet and
increases hydraulic and habitat capacities for all components. This
will require some existing infrastructure adjustments and retirements
(existing City waterline and soon to be retired Fruitvale canal intake
structure). It provides overall cost reductions to all replacement
infrastructure noted in Recommendation PL1.
65
86
TABLE 7-1 PLANNING RECOMMENDATIONS - SHORT-TERM
ID
Recommendation
Estimated
Lead
Cost in $
Entities
PL14
Provide a Cowiche Creek overflow drainage study through the
City. This study will provide Contingency Planning guidance
60,000
City,
required in Recommendation PL6, identify problematic areas from
Landowners
Cowiche Creek overflows through town such as Cowiche drainage of
Aspen Lake across 16th Avenue, routing through Myron and Willow
lakes, and overflow drainage between 16th and 6th Avenues plus
drainage options back to Naches River at or west of 6th Avenue,
along with alternate drainage scenarios and preferences. Identify and
retain routes to Naches River.
PL15
Review safety and drainage of Myron and Willow lake dams in
response to Cowiche Creek overflow drainage for current day,
60,000
Landowners,
interim and rehabilitated condition. The dam owners need to assess
dam safety issues related to Cowiche Creek overflows due to
consequences of low-lying development and limited drainage
PL16
Ensure all owners of critical infrastructure (defined by
consequences of failure) develop operational plans and funding to
5,000
City,
sustain structure integrity. These operational plans should be
WSDOT
incorporated in overall and individual project and life cycle costs and
ensure enhanced hydraulic and habitat performance with regard to
potential overflows over structure life.
PL17
Provide during SEPA or Shorelines comment period comment to
City on development proposals in the overflow area regarding
5,000 yr
FCZD, City
facility siting and layout based on mapping, inundation areas. The
FCZD does not have a regulatory role but can provide relevant flood
specific information. This information transfer would be enhanced
should the City provide a drainage study under Recommendation 14
with proposed measures and timelines.
PL18
Coordinate existing ordinances to establish ability to provide
interim and long-term protection from Cowiche creek overflows
20,000
City
and/or dam failures. Development in the overflow area should be
designed to reduce incurred interim damages. The ordinance
revision should be one of the topics of the Task Force in
recommendation PL4.
PL19
Allow within the planning and design process of structural
elements for the insertion of trails and future Greenway overlay to
10,000
WSDOT,
connect Naches and Cowiche trails. The feasibility of success of this
City,
measure is dependent on early discussions with all parties including
County,
landowners and trail groups. Various routes need to be investigated
Greenway,
as noted in Recommendation PL9.
WO Douglas
PL20
Establish a gravel management plan in the Lower Cowiche corridor
to reduce flood and habitat risk over the short and long-term.
20,000 &
City, FCZD
Gravel removals are expected to be more critical upstream of US 12
1,000/yr
87
TABLE 7-1 PLANNING RECOMMENDATIONS - SHORT-TERM
ID
Recommendation
Estimated
Lead
Cost in $
Entities
FP1
due to the confinement above Powerhouse Road. Design of the
entire reach should result in minimal gravel removals and vegetation
completed
City, FCZD,
preventing removals. There will be preferred areas for removals
County,
noted above. Lower frequency floods should not overly disrupt
WSDOT
FP2
design elements requiring excessive disturbance.
PL21
Emphasize more natural riverine processes downstream of US 12 to
Ongoing-
City, FCZD,
maximize habitat enhancement for current and future species. This
100,000
FCZD
reach is important for ESA species- steelhead and bull trout and
action plan
FP3
habitat enhancement would be enhanced by the retention of
agriculture/pastoral uses versus development and the emphasis on
10,000
City,
gravel and sediment transport and deposition through this reach.
Landowners
Specific zoning should be pursued.
PL22
Identify location for sediment removal and monitoring, and
removal of identified sediment, especially upstream of US 12. As
See PL20
City, FCZD
per recommendation PL20 to limit disturbances
& ongoing
WSDOT,
PL23
Provide a future Cowiche Upper Basin CFHMP from the siphon
YVOEM
upstream to South and North Cascade branches including
100,000
FCZD
hydrological effects including sediment releases or pulses on the
reach
TABLE 7-2 FLOOD PREPAREDNESS RECOMMENDATIONS - SHORT-TERM
ID
Recommendation
Estimated
Lead
Cost in $
Entities
FP1
Form ILAs or MOUS to allow cross coordinated flood response
measures. This enables multiple parties to assist City during
completed
City, FCZD,
Cowiche overflows.
County,
WSDOT
FP2
Provide a Cowiche Creek Overflows Flood Response Plan that
includes a public Notification Plan. The response plan should
Ongoing-
City, FCZD,
assign preferential road closures and evacuation routes.
Near -Term
YVOEM
action plan
FP3
Provide flood fight locations on Cowiche Creek levee to minimize
overflows. City should affect arrangements with landowner to allow
10,000
City,
flood fighting at this most upstream section in order to improve
Landowners
public safety, based on PL20.
FP4
Provide emergency flood fight facilities to intercept overflows and
reroute west of 401h interchange. This requires coordination across
Completed
City,
landowners, WSDOT and resource agencies by the City
& ongoing
WSDOT,
YVOEM
67
88
TABLE 7-2 FLOOD PREPAREDNESS RECOMMENDATIONS - SHORT-TERM
ID
Recommendation
Estimated
Lead
Cost in $
Entities
FP5
Emphasize short-term flood routes, maximizing Cowiche Creek
overflows returns back to the Naches as far east as practical and
10,000
City
identified in City Drainage study. Based on PL20
FP6
Increase the gaging stations in the upper watershed to increase
flood response time at Lower Cowiche levee. This requires funds
30,000/yr
City, FCZD,
and basin hydrologic assessment.
Ecology,
PA3
Share Action Plans. City developed action plans need to be publicly
USGS,
available on web and other means, including permitting
5,000
USBOR
FP7
Provide timely public notice of flood threat status to allow for
OEM
PA4
timely private mitigation response.
N/A
YVOEM
FP8
Design emergency facilities to minimize fish stranding. This
5,000
City
requires discussion between City and WDFW This requires
N/A
City, WDFW
coordination across landowners, and resource agencies by the City
TABLE 7-3 PUBLIC AWARENESS RECOMMENDATIONS - SHORT-TERM
ID
Recommendation
Estimated
Lead
Cost in $
Entities
PA1
Increase general Public Awareness of current risk and measures.
Include landowners with large risk in specific discussions, including
5,000
City, FCZD
flood insurance implications.
PA2
Advise landowners on interim and long-term potential for
flooding. Landowners and developers need to know risk and the
5,000
City
goals of the CFHMP to gage their response
PA3
Share Action Plans. City developed action plans need to be publicly
available on web and other means, including permitting
5,000
City, FCZD,
OEM
PA4
Encourage local protections for individual infrastructure such as
ring dikes around homes, barns, shops. This allows specific structure
5,000
City
related protections versus protection of entire property which would
not be allowed because of impacts on others.
PA5
Awareness of new FEMA Maps and limitations. The new maps are
not representative of the large failure consequences as evidence by
10,000
City, FCZD
the condition of Cowiche levees during the 2017 flood and will
require further restrictions. FEMA map replacement will be made
once new infrastructure are completed.
PA6
Engage upper management and politicians in plan for flood hazard
mitigation. Funding for the new interim and long-term infrastructure
N/A
City, FCZD
will not be attainable without political support by local jurisdictions
89
TABLE 7-3 PUBLIC AWARENESS RECOMMENDATIONS - SHORT-TERM
ID
Recommendation
Estimated
Lead
Cost in $
Entities
PA7
Garner public support for capital measures to remove flood risk
areas through capital expenditures.
10,000
City, FCZD
PA8
Locate best Web sites(s) for public notification and use YVOEM
WSDOT
response abilities as emergency declared.
5,000
FCZD,
and objectives and incorporate sediment management and other
YVOEM
PA9
Notify public of flood threat status to allow private mitigation
response.
5,000
City,
performance.
YVOEM
TABLE 7-4 STRUCTURAL RECOMMENDATIONS - LONG-TERM
ID
Recommendation
Estimated
Lead
Cost in $
Entities
S1
Design and Implementation of all structural recommendations will
be coordinated with the overall design in Recommendation PL8
20,000
City, FCZD,
and updated during implementation of each structural element.
WSDOT
The designs for each element will support habitat and sediment goals
and objectives and incorporate sediment management and other
operational issues. Develop design and maintenance standards,
procedures and funding to ensure enhanced hydraulic and habitat
performance.
S2
Replace Cowiche channel between US 12 and the Naches
confluence with capacity to pass 100 -yr flood and remove Cowiche
800,000
FCZD
overflows into City from 100 -yr flood maps. Widen the active
floodplain to minimize need for ongoing sediment removal and large
woody material management, and ensure that the low -flow channel
supports typical flow conditions that are beneficial for fish and water
quality. Lower the channel by 3 feet to allow upstream capacity.
S3
Coordinate removal of Fruitvale infrastructure at Cowiche-Naches
confluence with downstream channel design. This measure will
10,000
City, FCZD
maximize flood and habitat benefits for the Naches and Cowiche
floodplain confluence.
S4
Replace Cowiche channel between Powerhouse Road and US 12
with capacity to pass 100 -yr flood and remove Cowiche overflows
2,000,000
City
into City from 100 -yr flood maps. Design channel and floodplains to
minimize the need for gravel and debris removal while still allowing
for unplanned removals, as outlined in Recommendation PL8.
S5
Provide levees in the reach between Powerhouse Road and US 12
that prevent Cowiche overflows into the City and allow for
700,000
City
enrollment in PL84-99 program, certification and accreditation, as
TABLE 7-4 STRUCTURAL RECOMMENDATIONS - LONG-TERM
ID
Recommendation
Estimated
Lead
Cost in $
Entities
well as connection to a new US 12 bridge. FCZD can provide
guidance on standards.
S6
Replace US 12 bridge capacity to pass 100 -yr flood and remove
Cowiche overflows into City from 100 -yr flood maps. This design
10,000,000
WSDOT
must match all other replacement infrastructure at this point.
S7
Remove city storage pond to increase hydraulic capacity for
Recommendations S4, S5 & S6.
100,000
City
Sg
Improve Naches Trail Bridge downstream of US 12 as necessary to
pass 100 -yr flood with planned wider channel.
100,000
County,
FCZD
S9
Interim structural elements will be required east of 401h Avenue
based on the Cowiche overflow drainage study.
50,000
City,
WSDOT
S10
Spillway and drainage improvements for Myron and Willow dams.
Landowners will establish safe drainage of these lakes to minimize
60,000
Landowners
downstream consequences.
S11
City culvert improvements to route City overflows from Cowiche
Creek The means to move water downstream with the least damage
10,000
City
should be established along with any eventspecific actions.
S12
Replace Powerhouse bridge with capacity to pass 100 -yr flood and
remove Cowiche overflows into City from 100 -yr flood maps.
2,000,000
City
Design will accommodate adjacent infrastructure and prevent
overflows down Powerhouse Road to the City and to the north into
Warehouse District.
70
8.0 FUNDING
FCAAP APPLICANT ELIGIBILITY
Counties, cities, and other entities with flood control responsibilities, such as flood control
districts and diking districts, are eligible to receive state funding for flood control maintenance
projects. Eligible entities must file a flood control budget with Ecology by February 15 each year.
To receive funding for flood control maintenance projects, the county, city, or town having
planning jurisdiction over the project area must have its floodplain management activities
approved by Ecology. The requirements include the following:
• Participation in the National Flood Insurance Program (NFIP)
• Certification of the local emergency response plan by the State Department of
Emergency Management
• Restriction of land uses to flood -compatible uses within a river's meander belt or
floodway.
Adoption of a Shoreline Master Program is also required.
MAINTENANCE PROJECT ELIGIBILITY
Evaluation of proposed FCAAP projects is based on cost -benefit relationships, local priority of
projects, severity of local flood hazard management problems, and information in the CFHMP.
Maintenance projects must reflect a comprehensive approach to flood hazard management
planning and must meet specific guidelines with respect to project goals. Typical structural
measures funded through FCAAP include installation of riprap on eroding stream banks, repair
of riprap embankments, and the construction and maintenance of levees.
FCAAP legislation describes in general terms the type of maintenance work eligible for funding,
including "maintaining and restoring the normal and reasonably stable river and stream channel
alignment and capacity" and "restoring, maintaining, and repairing natural conditions, works
and structures." State participation can also include "restoration and maintenance of natural
conditions, works, or structures for the protection of lands and other property from inundation
or other damage by the sea or other bodies of water" (RCW 86.26.090).
Funding for enhancement of flood control facilities was authorized by Engrossed Senate
Substitute Bill (ESSB) 5411, enacted in July 1991. This expands FCAAP project eligibility to
include purchase of flood -prone property or land to be used for flood storage, but only if these
measures are identified in the applicable CFHMP (Ecology 1991).
Permits such as the Hydraulic Project Approval (HPA), Shoreline Substantial Development, and
Conditional Use must be obtained before the project is funded by Ecology. All projects must be
planned and designed in accordance with applicable SMPs and CFHMPs, and must benefit the
public, as opposed to strictly private interests.
71
FCAAP EMERGENCY PROJECTS
A portion of the available FCAAP funding is reserved by law for emergency use. Projects
considered emergencies are those that must be done immediately to protect life and property
from "unusual, unforeseeable, and emergent flood conditions' (WAC 173-145-100). Release of
emergency funds is contingent on an emergency declaration by the appropriate authority.
Depending on the emergency measure, a shoreline permit or HPA may be required.
FLOODPLAIN BY DESIGN PROJECT ELIGIBILITY
This is a bi-annual state fund initiated in 2013 by efforts of the Nature Conservancy to combine
flood and environmental benefits in response to basin wide river deficiencies, particularly in
Puget Sound. East side applications that meet these goals are also welcome. Yakima and Pearce
Counties have been two of the more successful applicants due to setback of levees proposals.,
receiving grants in each biennium. Typically, these funds are given to mainstem rivers like
Yakima and Naches Rivers. The proximity of this Cowiche Creek reach to the Naches confluence
and the basin tributary goals for fish passage and species reintroduction and augmentation for
Cowiche Creek, makes this a potential source of funds. The County FCZD submitted a 2019-2021
biennium FBD pre -application for this reach for levee setbacks in February 2018, which was
successfully accepted for the subsequent application stage in August 2018. The application covers
parts of Recommendations PL8, PL20, PL22, S1 and S2
The fund is administered by the Department of Ecology. Awards over the 3 grant periods have
ranged between $30 and 50 million. Local match is 20 percent.
FEMA PROJECT ELIGIBILITY
FEMA has multiple funding sources. The most favorable for this reach would be Pre -Disaster
Mitigation grant, which allows applications up to $4.5 million and must display favorable cost
benefits, and significant potential flood damages. The application process and award processes
are lengthy requiring significant labor inputs before formal allocation of funds. This period can
be up to 5 years for successful applications, so that construction can take 7 years.
72
REFERENCES
Aggett. 2003. Surveyed Cross Sections Within the Reach.
Bonnel, R.G. 1991. Construction, Operation, and Evaluation of Groundwater -Fed Side Channels
for Chum Salmon in British Columbia. Fisheries Bioengineering Symposium, Symposium 10.
Cederholm, C.J. 1991. The Beaded Channel: A Low -Cost Technique for Enhancing Winter
Habitat of Coho Salmon. Fisheries Bioengineering Symposium, Symposium 10.
Citizens of the Greater Yakima Area. 1992. Vision 2010, Planning for Yakima County's Next
Twenty Years, Upper Valley Visioning Report. Citizens of the Greater Yakima Area. January
1992.
Citizens of the Lower Yakima Valley. 1992. Focus 2010, Planning for Yakima County's Next
Twenty Years, Lower Valley Visioning Report. Citizens of the Lower Yakima Valley. January
1992.
DHI. 2011. Nelson Dam Project/ Powerhouse Bridge Project. 2011
Dunne, T. 1976. The Yakima River Regional Greenway Master Plan, Hydrology. Appendix A.
Jones and Jones, Seattle, Washington.
Dunne, T. 1988. Geomorphologic Contributions to Flood Control Planning. John Wiley and
Sons, New York, New York.
EarthInfo. 1994. Climate data and Hydrodata - CD ROM of National Climate and Hydrologic
Data Center. EarthInfo, Inc., Boulder CO.
Entrix Inc. 2009. Geomorphic Assessment of the Water Gaps of the Yakima Basin. Prepared for
Yakima County Public Services, Surface Water Management Division. 2009.
Federal Emergency Management Agency (FEMA). 1986. Flood -Proofing Non -Residential
Structures.
Federal Emergency Management Agency (FEMA). 1989. Design Manual for Retrofitting Flood -
Prone Residential Structures.
Federal Emergency Management Agency (FEMA). 1990. Appeals, Revisions, and Amendments
to Flood Insurance Maps: A Guide for Community Officials. January 1990.
Federal Emergency Management Agency (FEMA). 1994a. National Flood Insurance Program:
Community Rating System, CRS Coordinator's Manual. July 1994.
Federal Emergency Management Agency (FEMA). 1994b. Flood Insurance Study, Yakima
County, Washington, Unincorporated Areas. Community Number 530217. Preliminary.
December 21, 1994.
73
Federal Emergency Management Agency (FEMA). 1995. Revised Preliminary Flood Insurance
Study, Yakima County, Washington, Unincorporated Areas. Community Number 530217.
December 7, 1995.
Federal Emergency Management Agency (FEMA). 1997. Write Your Own and Direct Data by
State, then County, Washington. February 25, 1997.
Federal Emergency Management Agency (FEMA). 2009. Lower Naches Flood Insurance Study
and Maps. FEMA. 2009.
Federal Emergency Management Agency (FEMA). 2012. Discovery Report, Naches Watershed.
2012.
Fischenich, J.C. 1989. Channel Erosion Analysis and Control. In: Woessmer, W. and D.F. Potts,
eds., Symposium Proceedings Headwaters Hydrology. Amer. Water Resources Assoc.
GeoEngineers. 2003. Naches River Reach Analysis and Management Plan, Lower Naches River
(RM 0-3.75).
Golder. 2003. Geomorphic Processes Analysis in the Naches Reach Since the 1920s.
Higgens, D., and H. Copp. 1974. Model Development and Systems Analysis of the Yakima River
Basin, Hydraulics of Surface Water Runoff. State of Washington Water Research Center,
Washington State University and the University of Washington, Pullman, Washington.
November 1974.
HDR, Inc. 1993. City of Yakima Comprehensive Stormwater management plan. Draft. HDR
Engineering, Inc., December 1993.
HDR, Inc. 2013. Preliminary Assessment of the Nelson Dam Surface Water Intake. 2013
HDR, Inc. 2017. Nelson Dam Consolidation and Reconfiguration Preliminary Design. 2017
Irrigation & Hydraulics. 1991. Yakima River Flood Evaluation. Prepared for Yakima County
Diking District No. 1 by Irrigation & Hydraulics Unlimited. March 1991.
King County. 1993. Guidelines for Bank Stabilization Projects in Riverine Environments of King
County. King County Surface Water Management. June 1993.
Lacey, E. 1 March 1996. Personal communication (GIS flood data supplied to Robert W. Molacek,
KCM, Inc., Seattle, WA). FEMA, Bothell, WA.
Northwest Hydraulic Consultants, Inc. 2015a. Lower Naches River Geomorphic Atlas. 2015.
Northwest Hydraulic Consultants, Inc. 2015b. Review of Morphological Effects from Naches
River Levee Setbacks. 2015.
74
Northwest Hydraulic Consultants, Inc. 2017. Nelson Bypass Channel Design Project, Physical
Modeling and Preliminary Design. 2017.
Scofield, R. 30 April 1996. Personal Communication (telephone conversation with Robert W.
Molacek, KCM, Inc., Seattle, WA). American Red Cross, Yakima, WA.
Simonson, R. 15 March 1995. Personal communication (telephone conversation with R. Molacek,
KCM, Inc. Seattle, WA). Yakima County Department of Public Works, Yakima, WA.
Tetra Tech/ KCM, Inc. 2004. Naches River Channel Migration Study. Prepared for Yakima County
Public Services. 2004.
Tetra Tech/KCM, Inc. 2005. Naches River Comprehensive Flood Hazard Management Plan
(River Mile 3.7 To River Mile 17.5). Prepared for Yakima county Public Services. 2005.
Thompson, D. 6 May 1996. Personal Communication (telephone conversation with R. Molacek,
KCM, Inc., Seattle, WA). U.S. Bureau of Reclamation.
U.S. Army Corps of Engineers (COE). 1955. Yakima River at Yakima, Washington, Flood Control
Works, Operations and Maintenance Manual. U.S. Army Corps of Engineers, Seattle District.
February 1955.
U.S. Army Corps of Engineers (COE). 1970. Flood Plain Information, Yakima and Naches Rivers,
Yakima - Union Gap. Washington. Prepared for Washington Department of Water Resources.
U.S. Army Corps of Engineers, Seattle District. May 1970.
U.S. Army Corps of Engineers (COE). 1973. Flood Plain Information, Yakima River, City of Selah
and Vicinity, Washington. Prepared for Yakima County and City of Selah. U.S. Army Corps of
Engineers, Seattle District. June 1973.
U.S. Army Corps of Engineers (COE). 1977. The Columbia River and Tributaries Study, Interim
Report, Yakima - Union Gap Flood Damage Reduction, Yakima River Basin, Washington. U.S.
Army Corps of Engineers, Seattle District. Two Volumes. May 1977.
U.S. Army Corps of Engineers (COE). 1986. Yakima -Union Gap Flood Control Project. U.S.
Army Corps of Engineers, Seattle District. April 1986, Unpublished.
U.S. Army Corps of Engineers (COE). 1990. Surface Water Observation Tabulation Sheet: Yakima
River, Yakima and Selah Valleys. November 25, 1990 Flood.
U.S. Army Corps of Engineers (COE). 1991. Emergency Employment of Army and Other
Resources, Natural Disaster Procedure. U.S. Army Corps of Engineers. March 11, 1991.
U.S. Army Corps of Engineers (COE). 1996. Memorandum for Commander, North Pacific
Division. Subject: Yakima River, WA, Yakima County, Public Law 84-99, Levee Restoration,
Authorized Flood Project, Job No. YAK -5-96.
75
U.S. Army Corps of Engineers (COE). 2015. Lower Naches Sediment Study. Planning Assistance
to the State. 2015.
U.S. Bureau of Reclamation (BOR). 1974. Inventory of Yakima River Basin - Washington
Diversions and Return Flows 1973 -1974. U.S. Department of Interior - Bureau of Reclamation.
U.S. Bureau of Reclamation (BOR). 2010. Appraisal Design Report, Naches River at Nelson Dam
Fish Screen and Diversion Design. 2010.
U.S. Bureau of Reclamation (BOR). 2011. Evaluation of Hydraulics and Sediment Transport for
Proposed Fish Bypass Alternatives at Nelson Dam. 2011.
U.S. Geological Survey (USGS). 1991. National Water Summary 1990-91: Hydrologic Events and
Stream Water Quality. Water Supply Paper 2400.
U.S. Geological Survey (USGS). 1993. Water Resources Data, Washington, Water Year 1993. U.S.
Geological Survey Water -Data Report WA -93-1.
U.S. Soil Conservation Service (SCS). 1985. Soil Survey of Yakima County Area, Washington U.S.
Department of Agriculture Soil Conservation Service.
Washington State Department of Community, Trade and Economic Development (CTED). 1995.
Revised Washington State Flood Damage Reduction Plan. May 1995.
Washington State Department of Ecology (Ecology). 1991. Comprehensive Planning for Flood
Hazard Management Guidebook. Washington State Department of Ecology.
Washington State Department of Ecology (Ecology). 1994. Yakima River Suspended Sediment
Total Maximum Daily Load Evaluation, General Overview with a Quality Assurance Project Plan
and Scope of Work for Phase 1. Joe Joy and Barbara Patterson, Washington State Department of
Ecology. October 1994.
Washington State Department of Transportation (WSDOT). 1996. Memorandum from Guy
Couture. Subject: February Flood Damage. May 19, 1996.
Weber, J. 16 March 1995. Personal Communication (interview with Robert W. Molacek, KCM,
Inc., Seattle, WA). U.S. Army Corps of Engineers, Seattle District.
Weber, J. 19 June 1996. Personal Communication (telephone conversation with Robert W.
Molacek, KCM, Inc., Seattle, WA). U.S. Army Corps of Engineers Seattle District.
WEST Consultants, Inc. 2011. Cowiche Creek Hydrologic Analysis. Prepared for Surface Water
Division/ Flood Control Zone District. March 24, 2011
Yakima County. 1995. Plan 2015: A Blueprint for Yakima County Progress. Draft Demographic
Section. Yakima County Planning Department. March 14, 1995.
76
Yakima County. 1996. Plan 2015: A Blueprint for Yakima County Progress. Draft Plan. Yakima
County Planning Department. July 1996.
Yakima County. 2006. Hydraulic Modeling and Supporting Data for the Updated Flood
Insurance Study on the Lower Naches River. 2006
Yakima County. 2010. Yakima County Shoreline Master Program. Yakima County Planning
Department. Adopted September 5, 1974; amended November 1, 1981; amended December 18,
2007; approved by Department of Ecology February 25, 2010.
Yakima County. 2017a. Horizon 2040: Yakima County, WA Comprehensive Plan. Yakima
County Public Services, Planning Division. June 27, 2017.
Yakima County. 2017b. Nelson Dam Environmental Memorandum. 2017.
Yakima Greenway Foundation (Foundation). 1995. Yakima Greenway Master Plan Update.
Yakima Greenway Foundation (Foundation). 1996. Summary of Flood Damage, February 1996.
May 1996.
Yakima Daily Republic. November 17, 1906. "Naches and Yakima Rivers Almost Normal: Losses
in Valley Will Sum Up About $400,000 - Fuel Famine on N.P. - Repairs Going On."
Yakima Herald -Republic. January 25, 1974. "Damage totals from flood went higher and higher."
Yakima Herald -Republic. December 30, 1980.
Yakima Herald -Republic. November 28, 1990. "Valley checks for damage as water recedes."
Yakima Herald -Republic. February 2, 1995. "Floods produce a sea of troubles: Situation eases
somewhat, but many forced to grin and bag it."
Yakima Herald -Republic. February 13, 1996. "Road, bridge repairs could top $3 million."
Yakima Herald -Republic. February 16, 2016. "Keeping all eyes on rising waters: Cowiche Creek
overflow affects Tieton, Cowiche; water covers numerous roads; flood warning in effect today for
Yakima River."
Yakima Herald -Republic. March 7, 2016. "Waters rise in Yakima Valley: Naches River near flood
stage with more rain in forecast."
Yakima Herald -Republic. March 16, 2017. "Coming weather shift promises a reprieve: Floodwaters
expected to recede after levee failure contributes damage, disruption in Yakima."
Yakima Herald -Republic. March 17, 2017. "Overflowing Aspen Lake floods parts of Yakima: Traffic
disrupted and homes threatened as flooding continues."
77
M
Appendix A
Near -Term Action Plan
October 16, 2017 Meeting Agenda
Cowiche & West Valley Joint (City/County/WSDOT) Flood Preparedness
ATTENDANCE
Bill Sauriol................................................................................ Washington State Department of Transportation
Scott Anfinson.........................................................................
Washington State Department of Transportation
ScottSchafer..................................................................................................................................
City of Yakima
DavidBrown...................................................................................................................................
City of Yakima
MikePrice......................................................................................................................................
City of Yakima
Charles Erwin..........................................................................
City of Yakima Office of Emergency Management
Matt Pietrusiewicz.........................................................................Yakima
County Department of Public Services
Jeff Emmons...........................................................................Yakima
County Office of Emergency Management
Horace Ward..........................................................................Yakima
County Office of Emergency Management
Terry Keenhan....................................................................................Yakima
County Flood Control Zone District
Joel Freudenthal.................................................................................Yakima
County Flood Control Zone District
Dale Meck..........................................................................................Yakima
County Flood Control Zone District
David Haws.........................................................................................Yakima
County Flood Control Zone District
MEETING AGENDA
1. Discuss Cowiche joint flood response roles, communication & coordination of resources for this
fall/winter
2. Set Cowiche flood fight common priorities and understanding /communication/ coordination
between agencies through discussion of this fall/winter planned short term joint actions (see
meeting action summary below - all parties).
3. Discuss role of emergency management in communication including public notice
4. Discuss Upper Yakima CFHMP public participation and current longer term thoughts on actions
5. Discuss West Valley this fall/winter runoff period planned short term actions in order to identify
emergency response as in 2 above
MEETING ACTIONS SUMMARY
Below is a summary list of meeting discussed short term (pre -flood & during flood) actions and
commitments by agency that were developed over several meetings from limited technical
investigations so that each agency can coordinate potential actions. These were established
after review of the County established flood model and a quick estimate of capacity of
Myron/Willow and Aspen lakes to receive water.
The hydraulic effort for the lakes was limited by available data and will be resumed in mid-term
actions. The review did reveal a need to limit inflows towards the lakes due to capacity
concerns. The short-term actions are separated by timeline in relation to flood onset.
Emergency management would coordinate information flow and directives to the public. The
below actions will be incorporated in the CFHMP amendment as a first step.
m
The below action plan, once finalized after the 23 to 27 October field trip, will act as the flood
response plan for this fall/winter.
DRAFT (BEFORE FIELD TRIP) ACTION PLAN
Actions to be completed prior to flood season (before December 2017)
County Completed
- Facilitated Interagency coordination meetings
- Advice on initial clearing of south berm and debris along vulnerable reach
- Provided initial Levee fill materials (excluding rock)
- Extra survey and Hydraulic modeling (1d & 2d) expanding FEMA model of Cowiche Creek
between Powerhouse Road and trail bridge plus modeled overflow area (2d) to Fruitvale in
order to establish vulnerabilities, capacities, priorities and potential short term actions.
- Develop hydraulic model for vulnerability analysis and provide to WSDOT
- Transfer of Corps and FEMA threshold requirements and probable profiles to City for future City
incorporation of levee in federal PL 84-99 or FEMA accreditation
- Quick analysis of Willow, Myron and Aspen lakes routing capacity from non -surveyed materials
- Quick Ownership analysis (currently incomplete and passed to mid- term actions) of flood and
drainage facilities from Powerhouse Road to Aspen Lake.
- Historic compilation of Cowiche Creek realignments, infrastructure crossings, confinements and
realignments in order to assess probable needs
- Provide HPA for excavation below SR12 and trail bridges
- County Excavation below trail bridge of 1 to 2 feet (with WSDOT)
- Arrange joint meeting with City & County emergency management
- Assessment of available rock materials at Summitview pit
County Pending
- Provide contour map for field trip week of 23-27 October (date being finalized)
- Draft CFHMP text for amendment to Upper Yakima CFHMP to be passed to the jointly selected
CFHMP Amendment Advisory Committee that include short term actions and target mid and
long term actions that are consistent with short term actions.
- City and County prepare council and Commission for joint session of CFHMP
City Completed
- Removal of large vegetation mass obstructing bridge inflows along south berm at storage pond
just upstream of WSDOT bridge
- South berm clearing, repair in 2 phases of 1500 feet each (June and September)
- Channel clearing for Cross Sections and flood monitoring
- South berm temporary easement for flood fight and repairs
- Ingham permission to remove protective berm downstream of trail bridge during floods
- Preparation of stop log and related structure to block overflows into storage pond
- Establish materials stockpile for flood fight (use Ramblers and have Contractor assemble)
Establish feasibility of potential breaks in Fruitvale ditch to increase overflow capacity
City Pending
- Pre -prepare emergency declaration to limit time needed
- Pre -prepare emergency contract for flood fight on berm
- Public Notice flyer to be sent to City and County Office of Emergency Management and
residents (area determined by City)
- Establish feasibility of new inlet for abandoned pipe just north of Riverview Manor to route
overflows under highway
In
- Establish feasibility of overflow acceptance for inlet in middle of Riverview Manor for potential
routing under highway
- City and County prepare council and Commission for joint session of CFHMP
WSDOT Completed
- Excavate under US12 bridge 1 to 2 feet
- Bridge excavation investigations
WSDOT Pending
- Modify ditch in front of Riverview Manor to accept more flows with less flooding
- Identify best method to block ramp overflows at Subway (see field trip 23-27 October) to
underpass before reach Fruitvale interchange to allows rerouting into Fruitvale ditch
- Have this group establish joint management team to discuss future SR12 bridge replacement
YVOEM Pending
- Use dispatch to mobilize FCZD
- Public Notice flyer for residents (area determined by City) received from City
- Communication plan received from City re reverse 911 etcetera
All Pending
- Field trip 23-27 October by WSDOT, City and County with contour map to confirm actions and
where best to intercept water passing over repaired Cowiche berm.
- Establish joint management team to discuss future SR12 bridge replacement
Actions to be undertaken prior to flood (preparedness) or during emergency (flood imminent)
County Preparedness
- Monitor local gauges and weather for mid -elevation snowpack/ provide warning to agencies
and Emergency Management- some concerns expressed about overreliance on warning due to
rapidity of basin response and weekends/after-hours staff availability matchup.
- Provide some of emergency levee fill materials (non -rock at Ramblers, rock dependent on
availabilty)
Provide joint (4 agencies) flood response plan (this list) to all parties after finalization as a result
of October 23-27 field trip
County Emergency
- Provide support to Emergency Management, City, WSDOT and County Roads if event arises
City Preparedness
- Work towards supplying Cowiche flood warning guage to reduce risk to citizens
- Stockpile/coordinate rock and levee materials for potential use on South side Cowiche berm
- If feasible construct inlets at Riverview Manor,
- Provide Northside Riverview manor emergency berm if landowner amenable
- Establish material requirements for Northside Riverview manor emergency berm
City Emergency
- Declare Emergency, provide contractor, activate materials stockpile for flood fight
- Flood watch south side Cowiche berm to address threat and address need for flood repairs
- Provide Northside Riverview manor emergency berm if not done before
- If feasible activate abandoned pipe inlet just north of Riverview Manor for inlet routing under
highway
- If feasible activate inlet in middle of Riverview Manor for routing under highway
- Make breaks in Fruitvale ditch to increase overflow capacity
WSDOT Preparedness
Monitor need to clean bridge US12 inlet
Materials preparation for blockage of US12 ramp
102
WSDOT Emergency
- Modify ditch in front of Riverview Manor to accept more flows with less flooding
YVOEM Emergency
- Use dispatch to mobilize FCZD
- Communication plan received from City for both Cowiche and Wide Hollow Creeks— updates
during event including reverse 911
103
Appendix B
Summary Sheets on Flood Hazard
Management Options
TABLE B-1
PROBLEM ADDRESSED AND ENVIRONMENTAL IMPACT OF GENERIC FLOOD
HAZARD MANAGEMENT
MEASURES
Problem Solved
NS
Impact
+ = problem solved;
0 = problem
not addressed; - = problem
aggravated
+ =positive
impact;
0 = no impact;
- = negative impact
U
\
C
b-0
O
.U.
o
°�°
ro'
U
o
a
o
o
0
Non-Structural Alternatives
W
ro
U
ink'
Q
P.
a
c
Flood Preparedness/ Emergency
,. 0
0
0
+
0
+
+
0
0
0
0
0
0
Management
CommunityRatin S stem
g Y
......
Flood warrun s stems
0
0
0
+
0
+
+
0
0
0
0
0
................g...� .........
Increase reliability of flood
0..
0
0
+
0
0
+
0
0
..0
0
0
0
0
warnin a es, etc.)
____________________________________
___
__
________________
���
Intera enc action Tans
Y......... p........
0__
0
0
+
0
0
+
0__
0
0
0
0
0
... .........
Thresholds for evacuation plans
0
0
0..
+
0
+
+
0
0
0
0
0
...
0
Public Information Program
0
0
0
+
0
+
+
0
0
0
0
0
0
FEMA or local map
0
0
0
+
0
+
+
0
0
0
0
0
0
determinations
Outreach projects
0.. .,
0 ....
0.
+. .,
_0
+
0 ...
0...
0..
0.....
0.....
0..
_ _..
Hazard disclosure
0
0
1 0
+
0
-
+
-
+
0
0
0
0
0
0
A flood protection librar-----------------
A Y
_____0__
0
0
+
0
+
+
0_______
0
0
0
0
0 --------------
......._ .........
Flood protection assistance
.........
.......
................
.......
.......
.........
.......................
Flood preparedness programs
0
0
0
+
0
+
-
0
0
0
0
0
0
Regulatory Measures/Mapping
+
0
+
+
0
0
+
0
0
0
+
0
0
Elevation certificates
0
0
0
+
0
+
+
0
0
0
0
0
0
Interim development standards ...........
..............
......
........
...............................
.................................
.........
or moratorium until risk
+
0
+
+
0
0
+
0
0
0
+
0
0
abatement
E
Higher regulatory standards
+
0
0
+
0
0
+
+
+
+
+
0
+
Zoning/Land use designations
+
0
+
+
0
0
+
+
+
+
+
0
+
en space reservation
+
0
+
+
0
0
+
0
+
+
+
+
+
_CpO ---
Low densit zonin
Y......... g.........
_ _______
+
0
_________
+
+
0
0
________________
+
0__
__
0
0
+
0
0 ��
.........
Stormwater management
.........
.......
........
.......
.......
.......................
.............
........
Ordinance consistency
+
0
+
+
0
0
+
0
0
0
0
0
0
Interagency agreementsy
0
0
+
+
0
+
+
0
0
0
0
0
0
Additional flood data, more________
0 _---------------------------------______+_
_
______�
�+ _
______+ _____
�_______
�___
�___
�___
_�___
_�_____
accurate floodplain ma in
p. pp.........ging
..................
.........
................
......... .........
.......................
............................................
....
........ .........
.........
..............
Flood data maintenance
0
0
+
+
0
+
+
0
0
0
0
0
0
Flood Damage Reduction of
0
+
+
+
+
+
+
0
0
0
0
0
0
Existing Structures
Seek fundin
lg____________________________________________
0
0
+
+
0
+
+
0
0
0
0
0
0
Flood facility maintenance________________
+___
___
+_
_______
________________
--___
--___
--______
Sharing information on river
_____0__
------
_�
_-±__
________________
__�___
__�___
characteristics for infrastructure
+
+
+
+
+
+
+
+
+
+
+
+
+
siting/design
Acquiring and relocating or
removing flood-prone structures
Levee maintenance program
Dam safe t ro rams
y.p.....g
0
0
+
+
+
+
0
+
..........................................
Developing repetitive loss Tans
0
0
0
+
+
+
+
0
0
0
0
........
0
..........
0
105
New infrastructure
+
0 + +
0 +
+
0
0 +
0
0 +
Interagency agreements
ncY a€r
+
0 + +
0 +
+
0
0 +
0
0 +
_
Im roved design and satin
P......... ..................................................................
+
+ 0 to + +
......... r ........ .........
+ +
......... ...r.....
+
.....
0
0 +
0
0 +
Info sharrn on design and sitin
........................................................................
......... ................ ......
........ ...
...... ..
...............................
........ ........
.........
......... .........
Promote fish habitat
enhancement
No critical facilities in flood -
0
0 0 +
0 +
+
0
0 0
0
0 0
tune areas
Im
TABLE B-2
PROBLEM ADDRESSED AND ENVIRONMENTAL IMPACT OF GENERIC
FLOOD HAZARD MANAGEMENT MEASURES
Problem Solved
NS
Impact
+ = problem solved;
0 = problem
not addressed; - = problem
aggravated
+ =
ositive impact;
0 = no impact;
- = negative
impact
O
U
O
by
v
\ C
r.o°
75
p
w-75�U
ro
0
Structural Alternatives
3
Q
a
o
°
- 75
ro
w
ocn�6.0
QP.
V
o
w
o
J)
V
V
Alignment Control
+
+
-
+
-
0
-
0
-
-
0
-
0
Spur Dikes
+...
+.
+
0
+
0
0
+
0
0
.........
Channel Realignment and
........
.........
......
...............
Widenin
+
+
+
+
+
0
0
+
Flow Realignment
+...
+.
+
0
..................
Vane Dikes
+
+
.......
_
+
..............
0
.................
....................................
...............
_
........
+
...................
0
Cutoff channels
.........
.........
.................
............
0
....................................
..................
.........
.........
.....................
Bank Protection
+
+
-
+
0
0
$ -
0
0
0
+
0
0
Reducing Bank Depth...
+.
++
0
0
0
0
0
0
0
0
0
0
Gabions
..
....
Bioengineering.
+.
+
0
+
0
0
+
+
+
+
0
0 ..
Cabling Trees
+
+
-
+
0
0
+
+
+
0
0
0
Approach Dikes/Guide Banks
+
+
_
+
_
0
-
-
-
-
-
0
_Fencm..
g
+
+
+
0
0
+
0
0
+
0
0
.....................................................................v................
Windrow Revetment
+
+
r..............................Y................v........................r...............................................
-
+
-
0
-
...
0
.........Y..................r
0
...............................
0
r...............................
+
0
................
0
Reducing Bank Slope.........
+...
+.
+
0
0
0
0
0
0
0
0
0
0
Trench Fill/ Ri ra
+
+
.......
-
........
+
........
.....
0
....................................
.........
-
........
+
........
0
..........
0
Conveyance Capacity
+
+
+
+
+
0
-
+
+
+
+
0
+
Gravel Bar Scalping
0.
++
+
+
0
0
0
0...
Overflow (Pilot) Channels
+
+
+
+
+
0
+
+
0 to +
...
+
+
0
+
Channel & Floodplain Space
+
+
+
+
+0
-
+
+
+
+
0
+
Sediment Budget & Transport+
+
+
+
+
Design Management
+
+
+
0
-
+
+
0
Reverse Channel A radation
g
+
+
+
+
+
0
+
+
+
+
0
+
_________ _______ __ __
Vegetation &Debris Removal
__
0
_______
-
0
__
0
______ ____
- or +
0
__
___ ___
______
0
__
to 0
Channel Widening/ Deeenin
+
+
+
+
+
0
-
-
0 -
to 0
0
-
to 0
Floodplain Protection
+
0
-
+
0
-
0
0
0
0
0
+
Setback Levees
+
0
_
+
+
0
_
+
+
+
+
0
+
Low Dikes (Floodplain Levees)
+
0
-
+
0
-
-
0
-too
-
-
-
Rin Levees ....
g.......
+.
+
0
0
0.......... .....
-too
0
0 .....
Cutoff Levees
+
........
-
........
-
..........
+
........
0
-too 0
0
0.....
0............
Storage Reservoirs
g...
.........
+
.........
+
........
+
.......................
.............
0
.................
....................................
......... .................................
to 0
to 0
+
.....................
+
River Return Structures/Routes
+
+
+
+
..
-
.........
0
-
+
+
+
0
0
+
Flood roofin of Structures
0
0
0
+
0
0
-
0
0
0
0
0
0
Streambed Control+
+
0
0
+
0
-
-
-
+
0
0
Stabilizers-
+
-
0
+
0
-
-
-
-
0
0
0
Lowering of Channel
.......................r
+...
........
+
...............
+
v................
..............„.................................
+
0
.................
.........
0
.........
0
Y.................„...........................................................
0
+
0
r
....................
0
Drop Structures
.................
++
0
+
.....
0
_
.................
_
_
+
0
0
107
a. See Appendix G for further
information on flood hazard
reduction alternatives
108
GENERIC ALTERNATIVES
Floodprb
Env
2018 Alternatives Grouping
2018 Appendix Generic Alternatives
SOLVED
COST
IMPACT
Essentials of Generic Alternatives Yellow 2018 addition
Non -Structural
Public Information
(moved from here)
Map Determination
2
0
maps publicly available, jurisdiction adopt overflows map, new 100 year, wait too long for new maps
Outreach Programs
2
1
0
advise citizens of flood hazards specific to their location and availability of insurance and flood fight resourcess- meeting with City to discuss
Hazard Disclosure
2
1
0
advises prospective property owners and real estate agent of flood hazards prior to purchase
Flood Protection Library
2
1
0
provide sufficient flood hazard management & insurance information for public/municipalities (FEMA, COE)
Flood Protection Assistance
2
1
0
Provide flood protection advice to interested Landowners -how to prepare
Flood Preparedness InformationProgram ''
2
-1
0
provide flood protection procedures to jurisdictions and landowners prior to event Specific to areas -coordinate internal with Outreach programs
Mapping & Regulations
Higher Regulatory Standards
2
1
0
Above minimum -Critical Areas, Shorelines, SEPA, Flood Overlay Zone,Prohibit Critical Facilities,density limits, use hazard maps
Promote Floodplain Open Space Preservation
2
1
0
Preserve space for floodplain natural function- Land Use change, local open space ordinance, zoniing designation, public acquisitions
Ordinance Consistency
2
1
0
Consisitency City & County -flood hazard ordinance/critical areas
Interagency Agreements
2
1
0
Political mechanism for cross jurisdictional consistency, forum and roles in flood hazard management
Additional Flood Data
2
1
0
Informed decision making with hydrology, sediment budget, infrastructure inventory,aerial photographs
Flood Data Maintenance
2
1
0
Quick & Efficient availability through GIS ( High water marks,flood extents,road closures,flooded structures)
Stormwater Management
6
1
6
Limit future development flooding impacts, Return overflows back to river, gates and weirs
Elevation Certificate (moved to here)
2
1
0
provide accurate building elevation data for flood insurance for all mortgaged buildings - first floor info
Interim Regulatory Standards
3
1
1
Flood Zone overlay? Critical Area -FFA?
Zoning/Land Use Designations
3
1
0
City? Methods to minimize potential damages for threatened citizens
Flood Damage Reduction
Acquisition and Relocation
6
-2
6
Remove vulnerable structures, Establish public vs private ownership
Repetitive Loss Projects
3
-1
0
for FEMA repetitive loss properties -projects to remove or elevater
Drainage System Maintenance
3
-1
-1
Keep overflow route clear, have routes
Seek Funding - Existing Structures
3
1
0
New Buildings & related Infrastructure
Info sharing on siting/design
6
1
2
City and WSDOT?
Area Specific Interagency agreements
5
1
2
City and WSDOT?
Improved design & siting
6
1
2
use hazard maps, drainage maps
Promote fish habitat enhancement
6
-1
6
often good for flood hazrd if designed right
SEEK FUNDING New structures'
3
2
0
Organize timelines- interagency cooperation
Flood Preparedness/Emergency Mngmt
Community Rating Program (CRS)
2
1
0
Reduces insurance premiums, City join?
Comprehensive Planning
6
1
6
CFHMP-identify flood issues and solutions
Flood Warning System
2
1
0
timely flood identification transmiited through community
Levee and Flood Facility Maintenance Program
3
1
-1
Need ownership and designs to facilitate design levels- Standards, O&M manual and inspections/repairs
Dam Safety
3
-1
0
Reduce probability of dam failure, available to community and emergency mgmt
Interagency Action Plans
5
1
2
Near term, short term
Increase gage reliability
2
-1
0
Planning agency & funds
Thresholds for evacuation
5
2
Dependent on near and short term measures
Structural
Alignment Control
Spur Dikes/Barbs
1
-1
2
reduce energy along channel bank
Flow Realignment
1
-1
-6
redirect flow near bridges, bends
Vane Dikes
1
-1
-3
for meandering rivers -to stabilize planform
Cutoff Channels
1
-1
2
Reduce flood stages -moves energy downstream with impacts
(moved from here)
Channel Realignment& widening
5
-1
5
To increase channel conveyance & reduce flood stage through increased cross sectional area and better alignment with topography and/or laterally confining structures such as bridges
Bank protection
Cabling Trees
2
-1
3
Initial matrix for sediment accumulation -habitat friendly- not downstream bridge/structure friendly
Approach Dikes/Guide banks
1
-1
-5
aligns flow at bridges, increases discharge, reduces approach erosion
Gabions
1
-1
-5
provides small structures to orient/control flow and reuce erosion- not good in high energy environment
Fencing
2
-1
0
90 degrees to flow, reduces coneyance to save property, deflects flow onto others
Windrow Revetment
1
-1
1
Stone placement in anticipation of falling into ersion hole
Bank Slope Reduction
3
0
0
Reduces steep bank failure slopes
TrenchFill/Riprap revetment
1
-2
-2
Large stone engineered material bank protection, high cost land protection
Bioengineering (moved to here)
2
1
4
provides structural support to eroding banks & habitatfriendly- only possible for lower velocities and sediment removal locations
Conveyance Capacity
Gravel Bar Scalping
4
-1
-3
Increase channel flood conveyance area -lower stage
Overflow (Pilot) Channels
6
-1
5
Reduces main channel velocities and stage by taking percentage of flow, creates high value habitat and may capture main channel
Selective Vegetation & Debris Removal
3
-1
-4
Reduce roughness, increase conveyance
Channel Widening or Deepening
6
-2
-3
Enlarge channel cross sectional are, increase velocity, reduce stage . Common COE solution
N/A
upstream development limited -already under permit
N/A
upstream development limited -already under permit
Channel &' Floodplain j'Expansion '
5
-2
5
Widen both elements to reduce velocities and stage through increasing flow top -width over a range of flows
Manage Sediment Budget & Transport in design
5
-1
6
Allow for in design & have gravel mangement plan
Reverse channel aggradation
5
6
Techniques required where aggradation is a problem. Good design and still need removal locations
Floodplain Protection
Setback Levee
4
-2
5
Pull existiing levee back or new levee, both allowing active floodplain
Low Dikes (Floodplain levees)
0
-1
-5
Placed on river bank cutting off floodplain
Ring Levee
-1
0
-1
Encircling structure(s) with a levee- common with WWTP & WTPs
Cut-off Levee
-2
-1
-2
Levees 90 degrees to stream to prevent overflow paths & damage
Floodproofing Structures
1
-2
0
Design or alteration of existing structures to reduce or eliminate flood damages, or elevate
Storage Reservoirs
2
-3
-2
Not feasible short term
River Return Structures
3
-1
0
To return river flooding behind levees to the river minimizing damage. Overflows routed back to river in channel designed to minimize damage
Streambed Control
Stabilizers/Grade Control Structures
0
1
-3
Buried weirs to limit upstream channel scour & degradation
Lowering of channel ''
3
-1
1
To increase conveyance and reduce flood stage through excavation. increases freeboard and safety - must be in concert with overall gradient not to infill
Drop structure
2
-2
-2
not foreseen as desirable in Cowiche
Im
Appendix B
Non -Structural Alternatives
HE
Lower Cowiche Comprehensive Flood Hazard Management Plan
NONSTRUCTURAL ALTERNATIVES
GROUP: PUBLIC INFORMATION
PURPOSE: To provide building elevation data for accurate flood insurance
rating and promote awareness of flood insurance.
DESCRIPTION. • The National Flood Insurance Program requires communities to
maintain a record of the elevation of the lowest flood for any new
building or substantial improvements made to buildings in the
Special Flood Hazard Area (SFHA). SFHA are shown on a
community's Flood Insurance Rate Map. Elevation and related
building information should be available for public inspection
and insurance rating. To standardize the data records, FEMA
provides elevation certificate forms. The elevation certificate
contains property, Flood Insurance Rate Map (FIRM), building
elevation, community, and certification information.
IMPLEMENTATION. • Complete an elevation certificate for each building constructed in
a Special Flood Hazard Area.
AGENCY CONTACTS: Local Community Building Official, Federal Emergency
Management Agency, U.S. Army Corps of Engineers.
Lower Cowiche Comprehensive Flood Hazard Management Plan
NONSTRUCTURAL ALTERNATIVES
GROUP: PUBLIC INFORMATION
PURPOSE: Provide flood hazard information as a public information service.
DESCRIPTION.• Map determinations tell inquirers if a property is in a Special
Flood Hazard Area (SFHA), which flood zone it is, and the base
flood information. The public information service help banks,
insurance and real estate agents, and anyone else who needs
flood hazard information. Map determinations may include:
• Reading a Flood Insurance Rate Map (FIRM) in response
to a telephone call.
• Helping a person who walks into the office to read the
FIRM.
• Completing a map determination form.
• Refer inquirers to a commercial map determination
service.
IMPLEMENTATION.• Provide the public service by dedicating staff trained in
interpreting FIRMS and publicizing the service to the community.
AGENCY CONTACTS: Yakima County Flood Control Zone District, Planning
Department of local communities, Federal Emergency
Management Agency.
112
Lower Cowiche Comprehensive Flood Hazard Management Plan
NONSTRUCTURAL ALTERNATIVES
GROUP: PUBLIC INFORMATION
PURPOSE: To advise people of flood hazards and the availability of flood
insurance and/or flood protection methods.
DESCRIPTION. • Research has proven that flood hazard awareness is not enough;
people need to be told what they can do to reduce flood damage.
A local public information program can effectively relay this
information and motivate property owners to protect themselves
from flood damage. The program can be in a form of newsletters,
newspaper publications, brochures, public meetings, radio and
television advertising, or flood awareness weeks. It should
provide information on the local flood hazard, location of flood
hazards, flood warning system, flood safety, flood insurance,
property protection measures, floodplain development permit
requirements, substantial improvement requirements, drainage
system maintenance, and natural and beneficial functions of the
floodplain.
IMPLEMENTATION. • Allocate funding resources to develop a program as outlined in
FEMA's Community Rating System Credit for Outreach
Proj ects.
AGENCY CONTACTS: Yakima County Flood Control Zone District, Federal Emergency
Management Agency.
113
Lower Cowiche Comprehensive Flood Hazard Management Plan
NONSTRUCTURAL ALTERNATIVES
GROUP: PUBLIC INFORMATION
PURPOSE: Advises prospective property purchasers and real estate agents of
possible flood hazards prior to a real estate transaction.
DESCRIPTION. • This alternative involves requiring a statement such as "This
property is located within the FEMA -mapped floodplain and may
be subject to flood damages" on all future deeds of sale for
transfers or financing of parcels in floodplain areas. The same
statement should be attached to the recorded plat map.
IMPLEMENTATION. • The best way to implement this activity is to have Realtors
provide written notification to potential purchasers that the
property exists in a special flood hazard area and requires the
purchase of flood insurance. The State is currently developing
this as a regulatory requirement.
AGENCY CONTACTS: Federal Emergency Management Agency, Yakima Association
of Realtors, Yakima County Auditor, Yakima County Assessor.
114
Lower Cowiche Comprehensive Flood Hazard Management Plan
NONSTRUCTURAL ALTERNATIVES
GROUP: PUBLIC INFORMATION
PURPOSE: To ensure there is sufficient reference material on floodplain
management and flood insurance for interested parties.
DESCRIPTION. • The local library should maintain documents related to flood
insurance, flood protection, floodplain management, the natural
and beneficial functions of floodplains, local information on
flood warnings, how to be prepared for a flood, and what to do in
case of a flood. Publications should be kept and distributed by the
local libraries along with local contacts for additional
information. In addition, local libraries may hold public
information campaigns with displays and lectures.
IMPLEMENTATION. • Provide a listing or copies of the numerous publications
published by FEMA, U.S. Army Corps of Engineers, U.S.
Natural Resources and Conservation Service, and state and local
agencies and announce the availability of publications through
local newspapers.
AGENCY CONTACTS: Yakima County Flood control Zone District,Federal Emergency
Management Agency, U.S. Army Corps of Engineers, U.S.
Natural Resources and Conservation Service, State National
Flood Insurance Program Coordinator, Yakima County Planning.
115
Lower Cowiche Comprehensive Flood Hazard Management Plan
NONSTRUCTURAL ALTERNATIVES
GROUP: PUBLIC INFORMATION
PURPOSE: Provide flood protection advice to interested property owners.
DESCRIPTION.• As a public service, a qualified person advises interested
residents on flood insurance and flood protection. The advisors
should be confident and willing to respond and help floodplain
residents. Advice available should include:
• How to prepare for a flood
• What to do in case of a flood
• Site visits to review flood hazards
• Contractors available to flood proof homes or construct
flood protection measures
• How to obtain flood insurance and reduce the premiums
• Base flood elevations and building elevations
• Areas of high flood hazard
IMPLEMENTATION.• Staff a technical position in floodplain management. Periodically
advertise the public service.
AGENCY CONTACTS: Local Communities, Yakima Flood Control Zone District,
Federal Emergency Management Agency, U.S. Army Corps of
Engineers, State National Flood Insurance Program Coordinator.
ow
Lower Cowiche Comprehensive Flood Hazard Management Plan
NONSTRUCTURAL ALTERNATIVES
GROUP: PUBLIC INFORMATION
PURPOSE: Provide flood preparedness and protection procedures to partners
and to at risk citizen group through public outreach.
DESCRIPTION. • Measures specific to at risk areas are developed beyond the wide
scale generic measures for flood preparation available on
websites.
IMPLEMENTATION. • Requires coordination between the County, Cities and the
Yakima Valley Office of Emergency Management.
AGENCY CONTACTS: Yakima Valley Office of Emergency Management, Local
Jurisdiction websites, Yakima County Flood Control Zone
District, US Army Corps of Engineers, Federal Emergency
Management Agency.
117
Lower Cowiche Comprehensive Flood Hazard Management Plan
NONSTRUCTURAL ALTERNATIVES
GROUP: MAPPING AND REGULATIONS
PURPOSE: To provide more flood protection than the minimum required by
the National Flood Insurance Program (NFIP), and reduce public
and private expenditures during floods.
DESCRIPTION. • Numerous flood -related regulations can be integrated into floodplain,
zoning, shoreline, critical area, and land division ordinances to reduce
flood damage. Although minimum NFIP standards provide flood
protection, damages can be further reduced by adopting additional or
stricter regulatory measures. These measures may involve:
• Modification of the zoning ordinance to include a floodplain
overlay zone (FOZ) that references pertinent floodplain
regulations.
• Modification of the zoning ordinance to have only flood
tolerant zoning designations in the floodplain.
• Adequate buffer zones and setbacks near critical areas.
• Update building standards to reduce flooding impacts.
• Modification of floodplain ordinances to require lowest levels
of buildings be higher than the 100 -year flood elevation or
prohibit construction in or adjacent to the floodplain.
• Modification of floodplain ordinances to prohibit critical
facilities in the 500 -year floodplain (requirement of federal
funding) or require the lowest level elevation to be 3 feet above
100 -year flood.
• Prohibit filling within floodplain areas or require compensatory
storage.
• Prohibit development in highly erosive areas.
• Update building standards to protect foundations from erosion
and settlement.
• Require full compliance with floodplain management
regulations for proposed building improvements.
• Require dry land access during a 100 -year event for all
development.
IMPLEMENTATION. • Requires drafting a new ordinance, legal notice, public meetings,
public hearings, SEPA checklist, state review, and final adoption
by Commissioners.
AGENCY CONTACTS: WA Department of Ecology, WA Department of Commerce,
Yakima County Planning, Yakima County Building, Federal
Emergency Management Agency.
118
Lower Cowiche Comprehensive Flood Hazard Management Plan
NONSTRUCTURAL ALTERNATIVES
GROUP: MAPPING AND REGULATIONS
PURPOSE: To preserve specific land types and designated environmentally
sensitive areas from future development. Open space
preservation allows the floodplain to provide its natural function
and minimizes possible future flood damage.
DESCRIPTION. • Open space preservation is provided by land purchases,
easements, tax incentives, transfer of development rights,
development of density credits, and zoning requirements. Open
space includes public land such as state and local parks,
easements, nature preserves, and areas which have restrictive
development regulations such as cluster developments and low-
density zoning.
IMPLEMENTATION. • Open space preservation is achieved by adopting an open space
ordinance consistent with Revised Code of Washington 84.33
and 84.34 or modifying local zoning ordinances. Open space
ordinances provide tax incentives to property owners who agree
to preserve specific land types and can also include a funding
mechanism for land purchases. Zoning ordinances can also
increase open space by limiting development densities and
requiring specific conditions to protect sensitive areas.
AGENCY CONTACTS: Yakima County and city of Yakima Planning,
Federal Emergency Management Agency.
ow
Lower Cowiche Comprehensive Flood Hazard Management Plan
NONSTRUCTURAL ALTERNATIVES
GROUP: MAPPING AND REGULATIONS
PURPOSE: To ease the regulatory burden and ensure that the desired level of
flood protection is being provided throughout and adjacent to the
floodplain.
DESCRIPTION. • Flooding does not respect political boundaries. Watershed and
floodplain areas extend over city, county, state, and federal
jurisdictions. Therefore, regulations affecting flood hazard
management can vary dramatically and possibly be contradictory.
For example, shoreline and critical areas ordinances may have
different buffer requirements or city and county floodplain
ordinances may have different flood fringe development
standards.
A comprehensive review of all ordinances relating to
development and environmental issues should be performed to
eliminate inconsistencies, simplify permit requirements, and
bring the overall regulatory requirements up to a common
standard.
IMPLEMENTATION. • Review ordinances and make recommendations to combine,
clarify, and simplify them to achieve consistency with overall
flood management goals.
AGENCY CONTACTS: Local communities, Federal Emergency Management Agency,
Washington Department of Ecology, Yakima County Attorney,
City Attorneys.
120
Lower Cowiche Comprehensive Flood Hazard Management Plan
NONSTRUCTURAL ALTERNATIVES
GROUP: MAPPING AND REGULATIONS
PURPOSE: Provide a political mechanism to create consistent flood hazard
management across political boundaries.
DESCRIPTION. • An Interagency Task Force could be established to focus on
regional flood hazard concerns. The Task Force provides a forum
to exchange information between al agencies, to discuss technical
issues, and recommend potential actions consistent with regional
concerns. Each Task Force member is responsible for
implementing the recommendation agreements within their local
jurisdiction.
IMPLEMENTATION. • Implementation is dependent on the regional issues and the
number of agencies involved. In general, implementation
involves defining the specific goals and objectives of the
interagency task force, assigning a lead agency to monitor and
direct progress of the Task Force, and conducting meetings and
public hearings in which agencies seek consensus before arriving
at recommendations.
AGENCY CONTACTS: Federal Emergency Management Agency, U.S. Army Corps of
Engineers, U.S. Soils Conservation Service, U.S. Environmental
Protection Agency, Washington Department of Ecology,
Washington Department of Natural Resources, Washington
Department of Fish and Wildlife, Yakima County Planning, City
of Yakima Departments of Planning & Community
Development, Yakama Nation.
121
Lower Cowiche Comprehensive Flood Hazard Management Plan
NONSTRUCTURAL ALTERNATIVES
GROUP: MAPPING AND REGULATIONS
PURPOSE: Allows informative floodplain management decisions.
DESCRIPTION. • Additional flood data provides a better understanding of natural
processes affecting flooding. Informed management of flood
hazards depends on information produced from detailed
hydrologic, hydraulic, and environmental studies. Data collection
will depend on existing flood issues but is likely to include:
• Defining historic areas of flood water inundation and
water surface elevations.
• Information on critical areas such as wetlands, alluvial
fans, mudflows, moveable streambeds, and habitat areas.
• A bank erosion inventory.
• Collection of sediment supply, transport, and deposition
data to assess sediment movement through the river
system.
• River flow and precipitation gaging for flood forecasting.
• Collection of historical aerial photographs to assess river
migration.
• Inventory of structures within the floodplain.
• An inventory of critical facilities within the floodplain.
• Levee inventory.
IMPLEMENTATION. • Collecting additional data involves 1) defining precisely the
information needed to resolve and outstanding flood management
issue, 2) developing a plan for data acquisition and data analysis
that provides the information needed, 3) allocating funding and
staff resources, 4) administering the plan for data collection and
analysis.
AGENCY CONTACTS: Yakima County Flood Control Zone District, Federal Emergency
Management Agency, U.S. Army Corps of Engineers,
Washington Department of Ecology, U.S. Bureau of
Reclamation.
122
Lower Cowiche Comprehensive Flood Hazard Management Plan
NONSTRUCTURAL ALTERNATIVES
GROUP: MAPPING AND REGULATIONS
PURPOSE: To manage and archive available and future data such that useful
information is provided quickly and efficiently for flood
management decisions.
DESCRIPTION. • This alternative requires a long-term commitment to maintain
data in a usable format. It typically involves digital geographic
information system (GIS) mapping of historic flood boundaries,
NFIP floodway, floodplain delineation, and flood elevations, plus
historic flood elevations. Flood information is mapped in
conjunction with physiographic features, parcel systems,
corporate limits, zoning designations, critical areas, and
watershed boundaries.
Flood data maintenance can be used to update Flood Insurance
Rate Maps (FIRM). Maps can be updated to a standard higher
than required by FEMA, expanded to include historic flood
hazard areas not covered by the FIRM, or modified to account for
areas which have experienced changing conditions.
Flood data maintenance may also include developing databases
containing flood elevations throughout the floodplain, structures
in the floodplain and their lowest flood elevations, road closures
during flooding, and precipitation and river flow data.
IMPLEMENTATION. • Implementation involves dedicating resources to acquire,
develop, update, and maintain the information system.
AGENCY CONTACTS: Yakima County Flood Control Zone District, Federal Emergency
Management Agency, U.S. Army Corps of Engineers, U.S.
Bureau of Reclamation.
123
Lower Cowiche Comprehensive Flood Hazard Management Plan
NONSTRUCTURAL ALTERNATIVES
GROUP: MAPPING AND REGULATIONS
PURPOSE: To limit flooding and water quality impacts from future
development and redevelopment.
DESCRIPTION. • As a watershed becomes more developed, stormwater runoff and
pollutant availability increases. This results in more frequent and
severe flooding and greater pollutant transport to receiving
streams. Stormwater management involves developing the
regulatory framework to control quantity and quality of
stormwater runoff.
Federal and state regulations have been promulgated to control
stormwater runoff Regulations require federal stormwater
discharge permits, basic stormwater programs for most cities and
counties, and comprehensive programs for urbanized areas.
Stormwater programs may include:
• Adoption of ordinances requiring stormwater controls for
new development and redevelopment.
• Incorporating Best Management Practices (BMPs) for
water quality into new development and redevelopment.
• Operations and maintenance programs for all public and
private stormwater facilities.
• Identifying and ranking significant pollutant sources and
their relationship to the drainage system and receiving
waters.
• Investigations and corrective actions of problem storm
drains.
• Water quality response programs.
• Establishment of funding for stormwater programs
through surface water utilities.
• A public education program.
IMPLEMENTATION. • Stormwater management is implemented by developing a
comprehensive program to address stormwater issues.
AGENCY CONTACTS: U.S. Environmental Protection Agency, Washington Department
of Ecology.
124
Lower Cowiche Comprehensive Flood Hazard Management Plan
NONSTRUCTURAL ALTERNATIVES
GROUP: MAPPING AND REGULATIONS
PURPOSE: Provide regulatory standards for high at risk locations while in
waiting for implementation of short and long term flood risk
mitigation measures.
DESCRIPTION. • Regulatory measures will take advantage of existing specific
knowledge and delineation of the at -risk areas and are in addition
to the wide scale existing regulatory measures for flood
preparation available on websites. Potential vehicles include
frequently flooded areas definition in critical areas, shoreline
regulations, SEPA and the use of a Flood Overlay Zone.
Mechanisms use for future development could limit development
through density, interim open space, floodproofing or a
moratorium before 100 -year protection. Measures for existing at -
risk development should include notification and potential
regrading.
IMPLEMENTATION. • Requires the identification of most effective interim measures
and the approval by the elected Board.
AGENCY CONTACTS: Local Planning Department, Federal Emergency Management
Agency, State Department of Ecology, Yakima County Flood
Control Zone District.
125
Lower Cowiche Comprehensive Flood Hazard Management Plan
NONSTRUCTURAL ALTERNATIVES
GROUP: MAPPING AND REGULATIONS
PURPOSE: Provide regulatory standards for high at risk locations while in
waiting for implementation of short and long term flood risk
mitigation measures.
DESCRIPTION. • Regulatory measures will take advantage of existing specific
knowledge and delineation of the at -risk areas and are in addition
to the wide scale existing regulatory measures for flood
preparation available on websites. Potential vehicles include
zoning ordinance and use of a Flood Overlay Zone. Mechanisms
could limit high risk development through density and interim
open space, before 100 -year protection.
IMPLEMENTATION. • Requires the identification of most effective interim and long
term measures and the approval by the elected Board.
AGENCY CONTACTS: Local Planning Departments, Federal Emergency Management
Agency, State Department of Ecology, Yakima County Flood
Control Zone District.
126
Lower Cowiche Comprehensive Flood Hazard Management Plan
NONSTRUCTURAL ALTERNATIVES
GROUP: FLOOD DAMAGE REDUCTION
PURPOSE: To remove buildings from the flood hazard areas.
DESCRIPTION. • The most effective way to protect a structure from flood damages
is to remove it from the floodplain. This typically involves
acquisition of flood hazard property by a government agency and
building demolition or building relocation to a location outside
the floodplain.
IMPLEMENTATION. • Develop agreements between property owners and funding
sources for property acquisition.
AGENCY CONTACTS: Federal Emergency Management Agency, Department of
Ecology, U.S. Natural Resources and Conservation Service, U.S.
Army Corps of Engineers.
127
Lower Cowiche Comprehensive Flood Hazard Management Plan
NONSTRUCTURAL ALTERNATIVES
GROUP: FLOOD DAMAGE REDUCTION
PURPOSE: To address repetitive flooding problems.
DESCRIPTION.• This activity documents the location of repetitive loss areas and
prepares, adopts and implements a plan to reduce the flood
problems in these areas. The activity involves:
• Obtaining and reviewing the repetitive loss list produced
by the Federal Emergency Management Agency (FEMA).
• Mapping the repetitive loss areas.
• Identifying the causes of the repetitive flooding.
• Implementing a program to reduce losses from floods.
IMPLEMENTATION.• Each year the Federal Emergency Management Agency (FEMA)
produces a list of repetitive loss properties within each National
Flood Insurance Program (NFIP) community. This list can be
obtained from FEMA regional offices. The community should
review this list for accuracy and develop flood hazard reduction
alternatives to address repetitive loss areas. Recommended
alternatives should only include measures that the community
can implement either through its own resources or from a
confirmed outside source.
AGENCY CONTACTS: Federal Emergency Management Agency, U.S. Natural
Resources and Conservation Service, U.S. Army Corps of
Engineers.
128
Lower Cowiche Comprehensive Flood Hazard Management Plan
NONSTRUCTURAL ALTERNATIVES
GROUP: FLOOD DAMAGE REDUCTION
PURPOSE: To maintain the conveyance and storage capacity of natural
drainageways or channels, man-made storm sewers and ditches,
and detention/retention basins.
DESCRIPTION. • This activity involves:
• Developing and implementing an inspection and
maintenance plan for all drainageways.
• Drainage inspections of catch basins, drainage channels,
detention facilities, flow control structures, and pump
stations.
• Maintenance operations to clean catch basins, remove
channel debris, clear culvert operations, remove sediment
from detention facilities, vegetation planting to control
channel erosion, removal of intrusive vegetation to
increase channel conveyance capacity, and trash cleanup.
• Adopt stream dumping regulations and inform residents
about the regulations and how to report violations.
• Developing an erosion protection program for areas
susceptible to streambank, head cutting, and coastal
erosion.
IMPLEMENTATION. • Implementation begins by conducting and maintaining a
complete drainage inventory. All drainage channels, stormwater
control facilities, piping networks, and natural channels should be
inventoried and mapped. Based on the inventoried facilities, a
maintenance plan can be developed. The plan should outline
scheduled maintenance for each facility, clearly define who is
responsible, outline reports to be used for inspection
documentation, and detail what can and cannot be removed.
Implementing agencies can include cities, counties, flood control
districts, or drainage districts.
Implementation should also include the adoption of stream
dumping regulations. Public outreach programs (e.g. mailings or
stream clean-up days) should be conducted to inform affected
residents and detail how to report violations. "No Dumping"
signs should be posted near problem areas.
AGENCY CONTACTS: Local Community, Irrigation Districts, Department of Ecology,
EPA, Corps of Engineers, Federal Emergency Management
Agency, U.S. Natural Resources and Conservation Service.
129
Lower Cowiche Comprehensive Flood Hazard Management Plan
NONSTRUCTURAL ALTERNATIVES
GROUP: FLOOD PREPAREDNESS
PURPOSE: To reduce flood insurance premiums and increase public
knowledge of flood hazards by implementing nonstructural flood
damage reduction alternatives through the Federal Emergency
Management Agency's (FEMA) Community Rating System.
DESCRIPTION. • FEMA's Community Rating System program provides a
reduction of flood insurance premiums for communities that
initiate flood protection activities beyond the minimum National
Flood Insurance Program (NFIP) requirements. Credits are
earned by public education, mapping and regulatory, flood
damage reduction, and flood preparedness activities.
IMPLEMENTATION. • A CRS program requires dedicated staff to administer, document,
and promote the program. Community participation in the
Community Rating System is voluntary. Any community in full
compliance with the rules and regulations of the NFIP may apply
for CRS classification. To be recognized by the Community
Rating System, community floodplain management activities
must be described, measured, and evaluated. FEMA's CRS
schedule sets forth the application procedures, creditable
activities, and credit points assigned to each activity. The
community submits complete application worksheets with
appropriate documentation to the FEMA Regional Office for
review and possible flood insurance rate reductions. Each year
the community must reverify that it is continuing to perform the
activities credited by CRS.
AGENCY CONTACTS: Local community, Federal Emergency Management Agency.
130
Lower Cowiche Comprehensive Flood Hazard Management Plan
NONSTRUCTURAL ALTERNATIVES
GROUP: FLOOD PREPAREDNESS
PURPOSE: To guide a community through its flooding problems by
identifying flooding issues and describing appropriate solutions
to reduce flood damage and protect the natural functions of the
floodplain.
DESCRIPTION. • The comprehensive floodplain management plan involves the
following planning steps:
• Problem identification.
• An inventory of existing and future land use conditions in
flood hazard areas including number and types of
buildings, development trends, development constraints
(soils, ownership, regulations), critical facilities
(hospitals, fire stations, chemical storage), areas of natural
beneficial uses (wetlands, sensitive areas, wildlife habitat)
and community needs, goals, and plans for the area.
• Coordination with neighboring communities and other
agencies that implement floodplain management activities
by creation of an advisory committee.
• Identification of flood issues, plus goals and objectives.
• A review of possible flood reduction alternatives.
• Developing an appropriate action plan with recommended
alternatives that clearly identifies who does what, when it
will be done, and how it will be funded.
• Obtaining public input on the draft plan.
• Adoption and implementation by the community's
governing body.
• Periodically evaluate and update the plan.
IMPLEMENTATION. • Implementation requires a commitment by the governing agency.
The adopted plan should not sit on a shelf gathering dust but
should be reviewed periodically for progress, updated, and
appropriately funded to reach the plans goals.
AGENCY CONTACTS: Yakima County Flood Control Zone District, Washington
Department of Ecology, Federal Emergency Management
Agency, Yakima County Planning Department.
131
Lower Cowiche Comprehensive Flood Hazard Management Plan
NONSTRUCTURAL ALTERNATIVES
GROUP: FLOOD PREPAREDNESS
PURPOSE: To provide timely identification of impending flooding,
communicate warnings to floodplain occupants, and coordinate
flood response activities so that protective measures can be taken.
DESCRIPTION: Combining a flood threat warning system and emergency response plan
will greatly reduce flood damage. The National Weather Service
provides flood warnings for specific locations on the Yakima and
Naches Rivers; however, communities can augment flood threat
information by developing their own flood warning system for urban or
smaller streams. Flood warning systems involve:
• Meteorological and hydrologic data collection and analysis.
This may include volunteer monitoring of upstream river
stages and rain gages, gathering or electronically accessing
USGS, NOAA, U.S. Army Corps of Engineers, U.S. Weather
Service, or other agency rainfall and river flow data, and use of
hydrologic computer models to convert river and rainfall data
to a flood prediction.
• A documented emergency response plan keyed to specific
flood levels. The plan should detail standard operating
procedures, responsible agencies or staff, coordination
activities, communication protocols, and use of critical
facilities and resources during flood response efforts (e.g.
shelters, sandbags, etc.)
• Periodic drills and/or appropriate training of emergency
response personnel.
• Timely dissemination of flood warnings through radio, TV, the
Emergency Broadcast System, sirens, telephone, or door-to-
door floodplain resident contact.
• Post -flood recovery program to assist residents, assess
damages, repair impacted public roads and facilities, and
evaluate performance of the warning system.
• Public outreach programs to inform residents on emergency
response procedures.
IMPLEMENTATION: Implementation involves developing an emergency response plan,
developing institutional knowledge of levee performance and
vulnerabilities; training personnel, and performing mock drills to
ensure readiness.
AGENCYCONTACTS: National Weather Service, YFCZD, U.S. Army Corps of Engineers
Washington Emergency Management Division.
132
Lower Cowiche Comprehensive Flood Hazard Management Plan
NONSTRUCTURAL ALTERNATIVES
GROUP: FLOOD PREPAREDNESS
PURPOSE: To ensure levees are properly maintained and operated.
DESCRIPTION. • This activity involves routine inspection and repair of existing
levees in accordance with operation and maintenance procedures.
Levees accorded National Flood Insurance Program (NFIP)
accreditation must be certified by owners to those standards. The
levee operations and maintenance program should include:
• Levee locations and level of protection.
• A detailed maintenance schedule.
• Levee design standards and typical sections for repairs.
• Emergency response plan that specifies actions for
various flood stages.
IMPLEMENTATION. • All county levees are inventoried, mapped, and evaluated for
level of protection. The levees' level of protection is agreed with
the U.S. Army Corps of Engineers or another federal agency and
inspections performed by a professional engineer to ensure
program (NFIP, PL84-99) enrollment requirements are met.
Substandard levees should be prioritized and repaired.
AGENCYCONTACTS: Levee owners (County, City or private), U.S. Army Corps of
Engineers, U.S. Natural Resources and Conservation Service.
133
Lower Cowiche Comprehensive Flood Hazard Management Plan
NONSTRUCTURAL ALTERNATIVES
GROUP: FLOOD PREPAREDNESS
PURPOSE: Reduce the probability of dam failure.
DESCRIPTION. • This activity involves a dam safety program that includes:
• Operation and maintenance procedures and Checklists
• Annual reports on the safety and operations status.
• Regular Inspections
• Communication checks between dam operators and
emergency officials.
• Emergency response and community notification
procedures when a dam appears threatened by high water.
• Dam failure inundation maps.
• Evacuation routes and warning procedures.
• Periodic mock exercises of emergency action.
IMPLEMENTATION. • Coordination between YVOEM, communities and dam operators
to ensure dam safety programs are up to date and address
warning and evacuation procedures for downstream
communities.
AGENCY CONTACTS: Dam owners, Washington Department of Ecology, Yakima
Valley of Emergency Management, U.S. Army Corps of
Engineers
Lower Cowiche Comprehensive Flood Hazard Management Plan
NONSTRUCTURAL ALTERNATIVES
GROUP:
FLOOD PREPAREDENESS
134
PURPOSE: To provide watershed data more representative of the rapid flood
response on smaller basins. The National Weather Service
predictions require more local basin snow, rain and stream gage
data before and during flood actual events.
DESCRIPTION. • Stream gage responses on the Cowiche existing stream gages
appear to provide only a few hours warning as opposed to
Ahtanum Creek upper watershed stream gages. Rain, radar, snow
and stream gages in the upper watershed promote better flood
action responses.
IMPLEMENTATION. • Implementation would require the identification of a responsible
party and data collection agency along with funding.
AGENCY CONTACTS: Yakima County Flood Control Zone District, Yakima City,
WSDOT, State Department of Ecology, Federal Emergency
Management Agency.
135
Lower Cowiche Comprehensive Flood Hazard Management Plan
NONSTRUCTURAL ALTERNATIVES
GROUP: FLOOD PREPAREDENESS
PURPOSE: Provide a cross agency operational action plan to provide a
coordinated resource management and response to flood events.
DESCRIPTION. • The plan identifies flood response actions for specific area(s) and
responsible parties to allow more seamless implementation and
transfer of resources when responding to the flood event. The
plan would also identify means of communication which would
be spearheaded through the Yakima valley Office of Emergency
Management. At a minimum the City, County, WSDOT and the
Yakima valley Office of Emergency Management would be
represented and draw up the plan.
IMPLEMENTATION. • The afflicted area be it the City or County would initiate the
Action Plan with the YVOEM and as the event escalate, require a
Declaration of State of Emergency in order to mobilize
maximum resources as quickly as possible.
AGENCY CONTACTS: Yakima County Flood Control Zone District, Yakima City,
WSDOT, State Department of Ecology, Federal Emergency
Management Agency.
136
Lower Cowiche Comprehensive Flood Hazard Management Plan
NONSTRUCTURAL ALTERNATIVES
GROUP:
FLOOD PREPAREDENESS
PURPOSE: Provide event and area specific thresholds for evacuation of
citizens and businesses incorporated in action plans and
connected to flood predicted risk.
DESCRIPTION. • The thresholds are related to predicted flood flows and
predicted/observed response of the flood protection facilities. The
detail is dependent on downstream vulnerabilities and the local
jurisdictions ability to reroute dangerous flows back to less
dangerous routes. The thresholds would be in the flood action
plan that would combine predicted and observed conditions.
Communication which would be spearheaded through the
Yakima valley Office of Emergency Management and the local
jurisdiction. At a minimum the City, County, WSDOT and the
Yakima valley Office of Emergency Management would agree
on the thresholds to be included in the action plan.
IMPLEMENTATION. • The afflicted area, either the City or County, would initiate the
Action Plan thresholds with the YVOEM and as the event
escalates, require a Declaration of State of Emergency in order to
mobilize maximum resources as quickly as possible.
AGENCY CONTACTS: Yakima County Flood Control Zone District, Yakima City,
WSDOT, State Department of Ecology, Federal Emergency
Management Agency.
137
Lower Cowiche Comprehensive Flood Hazard Management Plan
NONSTRUCTURAL ALTERNATIVES
GROUP: FLOOD DAMAGE REDUCTION -NEW INFRASTRUCTURE
PURPOSE: Provide a political mechanism to implement consistent flood
hazard measures and establish funding.
DESCRIPTION. • An interagency Task Force could be established to focus on flood
hazard concerns in chronic high risk areas. The Task Force
would provide a forum to exchange technical information and
present recommendations on future course of action. The
agreement can also establish a joint approach for funding
required actions. At a minimum the City, County, WSDOT and
the Yakima valley Office of Emergency Management would be
represented.
IMPLEMENTATION. • In general, implementation involves defining the specific goals
and objectives of the interagency task force, assigning a lead
agency to monitor and direct progress of the Task force, and
conducting meetings in which agencies seek consensus before
arriving at recommendations.
AGENCY CONTACTS: Yakima County Flood Control Zone District, Yakima City,
WSDOT, State Department of Ecology, Federal Emergency
ent
138
Lower Cowiche Comprehensive Flood Hazard Management Plan
NONSTRUCTURAL ALTERNATIVES
GROUP: FLOOD DAMAGE REDUCTION -NEW INFRASTRUCTURE
PURPOSE: To incorporate the shared information on flood risk from the
Flood Control Zone District in evaluating proposals for existing
and proposed infrastructure or developments and housing. This
information will be utilized to reflect short and long term flood
risk mitigation in at risk areas.
DESCRIPTION. • The hydraulic and physical conditions and risk provided by the
Flood Control Zone District to Planning and Engineering
divisions of the City, County, WSDOT and the Yakima valley
Office of Emergency Management will be used to modify siting
and designs to minimize risk.
IMPLEMENTATION. • The FCZD transfers data and models to all parties for planning
and design usage.
AGENCY CONTACTS: Yakima County Flood Control Zone District, Yakima City,
WSDOT, State Department of Ecology, Federal Emergency
Management Agency
139
Lower Cowiche Comprehensive Flood Hazard Management Plan
NONSTRUCTURAL ALTERNATIVES
GROUP: FLOOD DAMAGE REDUCTION -NEW INFRASTRUCTURE
PURPOSE: Provides the technical knowledge of depths, velocities and routes
of overflow flood paths to improve location selection for new
facilities to obtain lower risk options for both proposed and
existing structures. These measures are while in waiting for
implementation of short and long term flood risk mitigation
measures.
DESCRIPTION. • The hydraulic and physical conditions for at risk scenarios are
provided by the Flood Control Zone District to Planning and
Engineering divisions of the City, County, WSDOT and the
Yakima Valley Office of Emergency Management. This
information provides justification for interim and higher
regulatory standards that the City wishes to implement and
enables the planning and engineering of these parties to operate
on a common information platform. This information could be
provided on the jurisdiction's website.
IMPLEMENTATION. • The FCZD transfers data and models to all parties.
AGENCY CONTACTS: Yakima County Flood Control Zone District, Yakima City,
WSDOT, State Department of Ecology, Federal Emergency
Management Agency.
140
Lower Cowiche Comprehensive Flood Hazard Management Plan
NONSTRUCTURAL ALTERNATIVES
GROUP: FLOOD DAMAGE REDUCTION -NEW INFRASTRUCTURE
PURPOSE: Provide the opportunity in flood hazard reduction projects to
enhance fisheries habitat directly and indirectly through the
restoration of natural river and floodplain functions. Typically,
these are coincident with flood reduction benefits and funding
but should be consciously prescribed.
DESCRIPTION. • Vested, interested and mandated agencies and staff should be
included in the design to allow habitat benefits to all species and
in particular ESA and salmon species. In some cases, additional
floodplain habitat benefits to wildlife should also be incorporated
particularly in and climates where the floodplain has particular
significance. Naturally varying habitats present additional value.
IMPLEMENTATION. • Implementation involves defining the specific habitat goals and
objectives for a specific location and may require monitoring to
evaluate success.
AGENCYCONTACTS: Washington Fish and Wildlife, NOAA, NMFS, US Fish and
Wildlife, Washington Department of Ecology, Yakima Nation,
Yakima County Flood Control Zone District, Yakima City.
141
Appendix B
Structural Alternatives
142
Lower Cowiche Comprehensive Flood Hazard Management Plan
STRUCTURAL ALTERNATIVES
GROUP: ALIGNMENT CONTROL
PURPOSE: Reduce the energy along the bank by moving the faster flowing
water towards the center of the channel.
DESCRIPTION. • A structure is installed at an angle with the bank (determined
through engineering analysis) to deflect flow towards the center
of the river. The structure may consist of a low rock berm, trees
or a combination of both. The length of the barb is determined by
its location (in a crossing, bend, cutoff channel, etc.), amount of
channel constriction desired, and spacing of dikes in a system.
SKETCH. • See Next Page
IMPACTS: Well-designed structures can improve channel fish habitat(+) and
water quality.
IMPLEMENTATION.•
Design Requirements: Analysis of change in effective channel cross-section, estimate of
design flood stage, site survey, design drawings.
Materials: Rock, timber, native plantings materials.
Equipment Needs: Drag line with clam bucket, haul trucks.
Typical Permits: Yakima County Critical Areas or Shoreline Permit, DOE
Stormwater Permit, Temporary Modification of Water Quality
Criteria, SEPA Checklist, WDFW and/or Yakima Nation HPA,
COE Individual Permit, Floodplain Certification.
MONITORING/ Replace materials as needed. Observe performance and stability
MAINTENANCE: of structure, particularly during high flows.
143
Lower Cowiche Comprehensive Flood Hazard Management Plan
STRUCTURAL ALTERNATIVES
Erosion Hazard Area W
144
Lower Cowiche Comprehensive Flood Hazard Management Plan
STRUCTURAL ALTERNATIVES
GROUP: ALIGNMENT CONTROL
PURPOSE: Redirect flow around bends, and/or near bridge approaches.
DESCRIPTION. • The channel is moved by redirecting the energy and reinforcing
the banks to create a better approach to a bridge or other
structure.
SKETCH. • See Next Page
IMPACTS: Fish, wildlife, scenic/ aesthetic/historic resources, navigation,
water quality, hydrology and recreation. Well-designed
structures can improve the above.
IMPLEMENTATION.•
Design Requirements: Analysis of effect of realignment on channel scour, bridge
hydraulics, and bank erosion, site survey, design drawings.
Materials: Large rip rap, woody debris, native plantings for revegetation.
Equipment Needs: Bulldozer with appropriate blade (for moving rip rap and site
access if necessary), excavator with thumb, dump trucks.
Typical Permits: Yakima County Critical Areas or Shoreline Permit, DOE
Stormwater Permit, Temporary Modification of Water Quality
Criteria, SEPA Checklist, WDFW and/or Yakima Nation HPA,
COE Individual Permit, Floodplain Permit.
MONITORING/ Resurvey channel one year after construction to verify stability
MAINTENANCE: of realigned reach. Observe channel changes during high flows.
145
Lower Cowiche Comprehensive Flood Hazard Management Plan
STRUCTURAL ALTERNATIVES
146
Lower Cowiche Comprehensive Flood Hazard Management Plan
STRUCTURAL ALTERNATIVES
147
Lower Cowiche Comprehensive Flood Hazard Management Plan
STRUCTURAL ALTERNATIVES
GROUP: ALIGNMENT CONTROL
PURPOSE: Stabilize and improve the alignment of meandering rivers, with a
concurrent deepening of the channel in these locations.
DESCRIPTION. • Low longitudinal stone fill structures are placed in the stream in
orientations nearly parallel to the flow in order to constrict and
deepen the channel and direct the flow without increasing the
roughness. Flow will occur over and between the vanes at higher
discharges and the longitudinal orientation will result in minimal
increases in roughness.
SKETCH. • See Next Page
IMPACTS: Negative: Fish resources; wildlife, scenic, navigation; recreation;
and hydrology. Water quality can improve.
IMPLEMENTATION.•
Design Requirements: Observation or dye testing of flowpaths so that data on velocity
vectors can be used in determining appropriate placement of
structures, site survey, design drawings.
Materials: Rock
Equipment Needs: Excavator or clam bucket, haul trucks.
Typical Permits: Yakima County Critical Areas or Shoreline Permit, DOE
Stormwater Permit, Temporary Modification of Water Quality
Criteria, SEPA Checklist, WDFW and/or Yakima Nation HPA,
COE Individual Permit, Floodplain Permit.
MONITORING/ Replace materials as needed, observe performance and stability
MAINTENANCE: of structure, particularly during high flows.
148
Lower Cowiche Comprehensive Flood Hazard Management Plan
STRUCTURAL ALTERNATIVES
149
Lower Cowiche Comprehensive Flood Hazard Management Plan
STRUCTURAL ALTERNATIVES
GROUP: ALIGNMENT CONTROL
PURPOSE: Eliminate bank erosion along river bends and reduce stages.
DESCRIPTION. • Construction of a cutoff channel in an area where a natural
cutoff is developing will result in a more gradual and controlled
shift in river regimen and associated erosional processes. A pilot
channel is excavated in the dry, with a plug left in the excavated
cut until construction is completed. The plug can be removed
after construction is completed or designed to be overtopped and
washed out by the river at a specific design discharge. The pilot
channel is designed to be enlarged to full channel dimensions
through the erosive action of the river over time. If conditions
are such that a pilot channel will not enlarge satisfactorily, the
full cross section of the channel should be excavated. Large
woody debris should be incorporated and grade control
structures may be necessary at each end and throughout the
channel if the gradient is steep enough.
SKETCH. • See Next Page
IMPACTS: Well-designed channels can improve fish habitat, water quality,
and recreation.
IMPLEMENTATION.•
Design Requirements: Analysis of historical changes in river alignment using aerial
photography, site survey, design drawings, hydraulic analysis.
Materials: Stone or other materials for armoring bank and training new
channel, soil, large woody debris, and vegetation for bank fill
and stabilization, other materials as needed depending on
concurrent use of other structural alternatives. Natural materials
should be available on site.
Equipment Needs: Excavator, bulldozer, haul trucks.
Typical Permits: Yakima County Critical Areas or Shoreline Permit, DOE
Stormwater Permit, Temporary Modification of Water Quality
Criteria, SEPA Checklist, WDFW and/or Yakima Nation HPA,
COE Individual Permit, Floodplain Permit.
MONITORING/ Monitor new channel for stability, particularly during high
MAINTENANCE: flows.
150
Lower Cowiche Comprehensive Flood Hazard Management Plan
STRUCTURAL ALTERNATIVES
LARGE WOODY
y DEBRIS
MAIN NNE
MAIN CHANNEL
CUT OFF CHANNEL
GRADE' CONTROL
151
Lower Cowiche Comprehensive Flood Hazard Management Plan
STRUCTURAL ALTERNATIVES
GROUP: ALIGNMENT CONTROL
PURPOSE: To reduce velocities and stage through increasing flow top -width
in the channel and floodplain over a range of flows.
DESCRIPTION. • Channels and floodplains that have been confined laterally,
previously realigned or do not align well either with lateral
constrictions or topography benefit from channel and floodplain
expansion. The expansion of available floodplain may require
new floodplain channels. If so, the main channel may not need
expansion as it could contract in reponse. Channel design should
consider historical channels at the location for probable
reoccupation. Evidence of modern depositional areas should
consider pilot or starter channels, sediment transfer and sediment
budget in design to reverse the process.
SKETCH See Next page
IMPACTS Positive Impact to Fisheries, Wildlife, Scenic/ Aesthetic, Water
Quality and Recreation if designed to establish benefits.
IMPLEMENTATION.•
Design Requirements: Hydraulic and hydrologic analysis, analysis of sediment transport
regime (i.e., determining whether there is an upstream sediment
source), site survey (multiple cross sections), design drawings,
estimates of quantities to be removed.
Materials: Removal of channel/floodplain materials. Vegetation and other
materials contingent on structural alternatives used.
Equipment Needs: Bulldozer, front end loader, haul trucks.
Typical Permits: Yakima County or City Critical Areas or Shoreline Permit, DOE
Stormwater Permit, Temporary Modification of Water Quality
Criteria, SEPA Checklist, WDFW and/or Yakima Nation HPA,
COE Individual Permit, Floodplain Permit.
MONITORING/ Yakima County Flood Control Zone District or proponent.
MAINTENANCE:
Lower Cowiche Comprehensive Flood Hazard Management Plan
STRUCTURAL ALTERNATIVES
GROUP:
ALIGNMENT CONTROL
152
PURPOSE: To increase channel conveyance and reduce flood stage through
increased cross sectional area and better alignment with
topography and/or laterally confining structures such as bridges.
DESCRIPTION.•
SKETCH
IMPACTS
IMPLEMENTATION.•
Channels and floodplains that have been confined, previously
realigned or do not align well with lateral constrictions or
topography benefit from realignment. In some cases, the channel
has been moved from its original alignment and produces
additional risk through floodplain overflows. Channel design
should consider any design changes to levees or bridges. Where
minimal floodplain is present the alignment should provide for
floodplain widths allowing channel self- readjustment and
maintenance.
See Next page
Positive Impact to Fisheries, Wildlife, Scenic/ Aesthetic, Water
Quality and Recreation if designed to establish benefits.
Design Requirements: Hydraulic and hydrologic analysis, analysis of sediment transport
regime (i.e., determining whether there is an upstream sediment
source), site survey (multiple cross sections), design drawings,
estimates of quantities to be removed.
Materials: Removal of channel/floodplain materials. Vegetation and other
materials contingent on structural alternatives used.
Equipment Needs: Bulldozer, front end loader, haul trucks.
Typical Permits: Yakima County or City Critical Areas or Shoreline Permit, DOE
Stormwater Permit, Temporary Modification of Water Quality
Criteria, SEPA Checklist, WDFW and/or Yakima Nation HPA,
COE Individual Permit, Floodplain Permit.
MONITORING/ Yakima County Flood Control Zone District or proponent.
MAINTENANCE:
153
Lower Cowiche Comprehensive Flood Hazard Management Plan
STRUCTURAL ALTERNATIVES
GROUP: BANK/IN-STREAM STRUCTURE PROTECTION
PURPOSE: Protect banks and shorelines that are actively eroding.
DESCRIPTION. • River Willow, Red Osier Dogwood, or other suitable vegetation
are placed into streambanks and along shorelines to stabilize
them and provide structural support. Bioengineering may be
used in conjunction with other structural alternatives such as
barbs or bank stabilization (for stabilizing lower banks). Site
must be graded prior to vegetation placement and protected
during the initial growth stage.
SKETCH.•
See Next Page
IMPACTS: Construction activity needs to be planned to have minimal
impact on the riverine system. Positive impacts to fisheries,
wildlife, scenic, water quality and recreation.
IMPLEMENTATION.•
Design Requirements: Site survey, design drawings.
Materials: Live plant cuttings, wooden stakes, iron bar to produce starter
holes, fill and topsoil, seed, rip rap.
Equipment Needs: Bioengineered projects typically constructed by hand. Front end
loader to place and grade fill or existing soils as needed prior to
installation, haul trucks.
Typical Permits: Yakima County Critical Areas or Shoreline Permit, DOE
Stormwater Permit, Temporary Modification of Water Quality
Criteria, SEPA Checklist, WDFW and/or Yakima Nation HPA,
COE Individual Permit, Floodplain Permit.
MONITORING/ Monitor to ensure plants are growing and bioengineered
MAINTENANCE: structure is stable. Maintain with new plant materials as needed.
154
Lower Cowiche Comprehensive Flood Hazard Management Plan
STRUCTURAL ALTERNATIVES
T a
dMWWcM APPMOM46. 81WM.rAd to #*
�Iq� I���II� I�IIuiN�IIpI��INpIU���� p���������MMMII�llllllll!I�II�Ii��i9�lll'�III'�
t
cansuudw
s
155
Lower Cowiche Comprehensive Flood Hazard Management Plan
STRUCTURAL ALTERNATIVES
appmIrrAft. dawfts not to sca
156
Lower Cowiche Comprehensive Flood Hazard Management Plan
STRUCTURAL ALTERNATIVES
19
Lower Co¥Qh Comprehensive Flood Ha a JMa Jg me zPl n
STRUCTURAL /fTRIV/ T V \
•ƒ�\`~��11 �.
. 77 .....>. ,
158
Lower Cowiche Comprehensive Flood Hazard Management Plan
STRUCTURAL ALTERNATIVES
159
Lower Cowiche Comprehensive Flood Hazard Management Plan
STRUCTURAL ALTERNATIVES
GROUP: BANK/IN-STREAM STRUCTURE PROTECTION
PURPOSE: Provide a matrix for bank stabilization and create cover for fish.
DESCRIPTION. • Trees 4 inches or greater in diameter with branches still on the
trunk are cable anchored to rocks, existing trees, or "deadheads."
Placement occurs along the tow of eroding banks, the edge of
low flow channels, or on a diagonal into the stream to create fish
habitat. Sediment accumulation around trees stabilizes the
structure and bank. (This alternative contrasts with
bioengineering in that cabled trees are not live.)
SKETCH. • See Next Page
IMPACTS: Public Safety issues when structures dislodge and move down
river in mass. Positive impacts to habitat.
IMPLEMENTATION.•
Design Requirements: Site survey (including horizontal and vertical locations of
existing rocks and trees), design drawings.
Materials: Coniferous trees, 3/8" min. diameter cable, iron rods.
Equipment Needs: Track excavator with bucket thumb, front end loader, haul
trucks.
Typical Permits: Yakima County Critical Areas or Shoreline Permit, DOE
Stormwater Permit, Temporary Modification of Water Quality
Criteria, SEPA Checklist, WDFW and/or Yakima Nation HPA,
COE Individual Permit, Floodplain Permit.
MONITORING/ Monitor stability of structure, maintain if cables break or pull
MAINTENANCE: out, rocks move, or trees move.
160
Lower Cowiche Comprehensive Flood Hazard Management Plan
STRUCTURAL ALTERNATIVES
Im
Lower Cowiche Comprehensive Flood Hazard Management Plan
STRUCTURAL ALTERNATIVES
GROUP: BANK/IN-STREAM STRUCTURE PROTECTION
PURPOSE: Confine flow to a single channel, improve distribution across the
waterway opening, control angle of attack on piers, break up
meander patterns, and/or prevent erosion of approach ends.
DESCRIPTION. • Upstream and/or downstream banks adjacent to bridge
abutments are rip -rapped at the base and covered with concrete
on the upper bank, directing flow smoothly through the
waterway opening.
SKETCH.•
See Next Page
IMPACTS: Fish, wildlife, scenic/ aesthetic/historic resources, navigation,
water quality, hydrology and recreation. Well-designed
structures can improve the above.
IMPLEMENTATION.•
Design Requirements: Hydraulic/Hydrologic analysis (may include numerical
modeling) of change in channel cross section and effect of
structure length, plan shape, and height on upstream and
downstream channel hydraulics, as built drawings of existing
bridge and site survey, design drawings, historical aerial
photographs of the site.
Materials: Concrete and concrete forms, pump trucks, rock rip -rap, steel
rebar.
Equipment Needs: Excavator, haul trucks, concrete pump truck, concrete truck.
Typical Permits: Yakima County Critical Areas or Shoreline Permit, DOE
Stormwater Permit, Temporary Modification of Water Quality
Criteria, SEPA Checklist, WDFW and/or Yakima Nation HPA,
COE Individual Permit, Floodplain Permit.
MONITORING/ Monitor for structural integrity, modify the design if necessary.
MAINTENANCE: Survey structure following completion for as -built drawings.
Lower Cowiche Comprehensive Flood Hazard Management Plan
STRUCTURAL ALTERNATIVES
IIIII�III�IIIII,II�III� I�������IIIIIGII�II�9�I�� III 111iililillllll�lplllllll ���I
162
163
Lower Cowiche Comprehensive Flood Hazard Management Plan
STRUCTURAL ALTERNATIVES
GROUP: BANK/IN-STREAM STRUCTURE PROTECTION
PURPOSE: Provide protection of banks, bridges, or other in -stream
structures.
DESCRIPTION. • Gabions are wire mesh boxes constructed on site and filled with
relatively small stones (i.e., less than 8 inches in diameter).
Gabions provide an additional measure of structural support over
riprap using similar diameter stone. They act as large heavy
porous masses to protect banks and structures, and have a
measure of flexibility. A filter fabric or filter cloth may be used
to prevent leaching of base materials or undermining of the
baskets.
SKETCH. • See Next Page
IMPACTS: Fish, wildlife, scenic/ aesthetic/historic resources, navigation,
water quality, hydrology and recreation.
IMPLEMENTATION.•
Design Requirements: Site survey, design drawings.
Materials: Gabion cage, rock (slightly larger than wire mesh, maximum
available density, able to withstand abrasion, and resistant to
weathering).
Equipment Needs: Excavator, front end loader, haul trucks.
Typical Permits: Yakima County Critical Areas or Shoreline Permit, DOE
Stormwater Permit, Temporary Modification of Water Quality
Criteria, SEPA Checklist, WDFW and/or Yakima Nation HPA,
COE Individual Permit, Floodplain Permit.
MONITORING/ Monitor for structural integrity, place additional gabions or
MAINTENANCE: replace existing gabions as necessary.
Lower Cowiche Comprehensive Flood Hazard Management Plan
STRUCTURAL ALTERNATIVES
Typical g
164
165
Lower Cowiche Comprehensive Flood Hazard Management Plan
STRUCTURAL ALTERNATIVES
GROUP: BANK/IN-STREAM STRUCTURE PROTECTION
PURPOSE: Protect stream banks from erosion due to high velocity waters.
DESCRIPTION. • Fencing constructed of various types of new or used materials is
used to reduce local velocities, trap debris, and facilitate
sediment deposition and the establishment of native vegetation.
Fencing can be constructed as revetment parallel to the bank, or
as dikes at an angle to the flow.
SKETCH. • See Next Page
IMPACTS: Fish resources, wildlife and safety. Improves water quality.
IMPLEMENTATION.•
Design Requirements: Site survey, design drawings
Materials: Posts: treated or untreated wood, used rails, pipe, steel beams,
concrete; Fencing material: wood, wire; fill soil; rock.
Equipment Needs: Excavator with pile driver attachment, haul trucks.
Typical Permits: Yakima County Critical Areas or Shoreline Permit, DOE
Stormwater Permit, Temporary Modification of Water Quality
Criteria, SEPA Checklist, WDFW and/or Yakima Nation HPA,
COE Individual Permit, Floodplain Permit.
MONITORING/ Monitor for structural integrity, replace posts or boards as
MAINTENANCE: necessary.
IM
Lower Cowiche Comprehensive Flood Hazard Management Plan
STRUCTURAL ALTERNATIVES
Typical tranaverse beadfence
n
n
'� • ux : WY/YIYYVVVVVIIIIVVVfIf�
&'� � /�//�� ///ii�'�• �/VI�I//IYYIV/VYYIIi//l
�
//���r _
///
���
Typical tranaverse beadfence
167
Lower Cowiche Comprehensive Flood Hazard Management Plan
STRUCTURAL ALTERNATIVES
GROUP: BANK/IN-STREAM STRUCTURE PROTECTION
PURPOSE: Provide protection of banks, bridges, or other in -stream
structures.
DESCRIPTION. • Windrow revetment consists of a line of stone placed along the
top of an eroding bank, either on the ground surface or partially
buried. The stone fill is undercut as the adjacent stream bank is
eroded and is launched down the bank, moving into the
underwater bank area and protecting the bank from additional
erosion. Stone fill may be interplanted with saplings, providing
an additional vegetative component to long-term protection.
SKETCH.•
IMPACTS:
IMPLEMENTATION.•
See Next Page
Positive for water quality.
Design Requirements: Analysis of the volume of stone necessary (depending on
channel depth, bank height, material size, and estimated
maximum bed scour), design drawings, site survey.
Materials: Rock.
Equipment Needs: Haul tricks, excavator, backhoe.
Typical Permits: Yakima County Critical Areas or Shoreline Permit, DOE
Stormwater Permit, Temporary Modification of Water Quality
Criteria, SEPA Checklist, WDFW and/or Yakima Nation HPA,
COE Individual Permit, Floodplain Permit.
MONITORING/ Monitor to verify that launched stone is sufficient to protect the
MAINTENANCE: bank. Add rock as necessary. Alternative or supplementary
structural control may be necessary if resulting protection is
inadequate.
168
Lower Cowiche Comprehensive Flood Hazard Management Plan
STRUCTURAL ALTERNATIVES
Im
Lower Cowiche Comprehensive Flood Hazard Management Plan
STRUCTURAL ALTERNATIVES
GROUP: BANK/IN-STREAM STRUCTURE PROTECTION
PURPOSE: Protect bank along river reaches with steep slopes that may be
subject to failure due to undercutting, debris slides or sloughing.
DESCRIPTION. • Bank slopes are reduced by cutting the highest portion of the
bank back away from the channel, then stabilizing the bank
using bioengineering techniques, riprap, or other methods.
SKETCH. • See Next Page
IMPACTS: None.
IMPLEMENTATION.•
Design Requirements: Site survey, design drawings.
Materials: Materials required contingent on structural alternative(s) used
with bank slope reduction.
Equipment Needs: Excavator, haul trucks, grader.
Typical Permits: Yakima County Critical Areas or Shoreline Permit, DOE
Stormwater Permit, Temporary Modification of Water Quality
Criteria, SEPA Checklist, WDFW and/or Yakima Nation HPA,
COE Individual Permit, Floodplain Permit.
MONITORING/ Monitor stability of new slope after construction. Maintain as
MAINTENANCE: appropriate, depending on alternative(s) used.
170
Lower Cowiche Comprehensive Flood Hazard Management Plan
STRUCTURAL ALTERNATIVES
171
Lower Cowiche Comprehensive Flood Hazard Management Plan
STRUCTURAL ALTERNATIVES
GROUP:
PURPOSE:
DESCRIPTION.•
SKETCH.•
IMPACTS:
IMPLEMENTATION.•
BANK/IN-STREAM STRUCTURE PROTECTION
Provide bank protection along stream reaches where bank
erosion mitigation or prevention is necessary.
The stream bank is "paved" with riprap and a large mass of
stone is placed into a trench on the riverward edge of the
revetment. As the bank erodes and the toe of the bank is scoured,
the riprap in the trench falls and paves the newly eroded lower
slope, while the upper slopes remain stable.
See Next Page
Fish resources; wildlife, scenic/ aesthetic/ historic resources;
navigation.
Design Requirements: Analysis of shape, size, and weight of stone required to meet
stability requirements, analysis of thickness, length, and location
requirements, estimates of low and high flow stages, site survey,
design drawings.
Materials: Rock, gravel or porous filter material (placed directly over
graded bank to allow seepage), filter fabric.
Equipment Needs: Bulldozer to grade slope as necessary, haul trucks, excavator,
front end loader.
Typical Permits: Yakima County Critical Areas or Shoreline Permit, DOE
Stormwater Permit, Temporary Modification of Water Quality
Criteria, SEPA Checklist, WDFW and/or Yakima Nation HPA,
COE Individual Permit, Floodplain Permit.
MONITORING/ Monitor stability of riprapped slope and replace rock as
MAINTENANCE: necessary, monitor downstream effects.
Lower Cowiche Comprehensive Flood Hazard Management Plan
STRUCTURAL ALTERNATIVES
IUI 1� iia
Top aScognorn of Bl]ank
172
173
Lower Cowiche Comprehensive Flood Hazard Management Plan
STRUCTURAL ALTERNATIVES
GROUP: CONVEYANCE CAPACITY
PURPOSE: Increase cross-sectional area, resulting in lower flood stage,
increased conveyance capacity and reduced flooding potential.
DESCRIPTION. • Heavy equipment is used to remove the upper portions of gravel
bars and haul the material out of the river channel. Gravel bar
scalping may be considered as an interim measure or as required
maintenance. Persistent development of gravel bars and
associated loss of conveyance capacity may require use of
alternatives that are more effective in the long term. Special care
must be taken not to disturb low flow channel stream bed and/or
spawning gravels when implementing this alternative.
SKETCH. • See Next Page
IMPACTS: Fish resources; wildlife, water quality.
IMPLEMENTATION.•
Design Requirements: Identification of location that will receive gravel.
Materials: None.
Equipment Needs: Bulldozer, front end loader, haul trucks.
Typical Permits: Yakima County Critical Areas or Shoreline Permit, DOE
Stormwater Permit, Temporary Modification of Water Quality
Criteria, SEPA Checklist, WDFW and/or Yakima Nation HPA,
COE Individual Permit, Floodplain Permit.
MONITORING/ Monitor sediment transport regime and channel hydraulics
MAINTENANCE: following gravel removal to detect any resulting changes.
174
Lower Cowiche Comprehensive Flood Hazard Management Plan
STRUCTURAL ALTERNATIVES
175
Lower Cowiche Comprehensive Flood Hazard Management Plan
STRUCTURAL ALTERNATIVES
GROUP: CONVEYANCE CAPACITY
PURPOSE: Reduce localized velocities to decrease erosion associated with
high energy reaches. Decrease local overbank flooding.
DESCRIPTION. • A separate channel is constructed adjacent to the main channel
to which flood flows are routed, resulting in an increase in total
channel capacity and a reduction in overbank flood stages and
areas of flooding. Banks of the overflow channel may be
stabilized with rock riprap or bioengineering techniques.
SKETCH.•
See Next Page
IMPACTS: Well-designed structures can improve fish resources; scenic,
aesthetic, and historic resources; navigation, water quality,
hydrology and recreation.
IMPLEMENTATION.•
Design Requirements: Hydrologic and hydraulic analysis, site survey, design drawings
(including fish passage considerations).
Materials: Inlet and outlet control structures (concrete, etc.), upstream and
downstream fish screens, topsoil, vegetation.
Equipment Needs: Bulldozer, excavator, haul trucks.
Typical Permits: Yakima County Critical Areas or Shoreline Permit, DOE
Stormwater Permit, Temporary Modification of Water Quality
Criteria, SEPA Checklist, WDFW and/or Yakima Nation HPA,
COE Individual Permit, Floodplain Permit.
MONITORING/ Maintain inlet and outlet control structures, remove debris, and
MAINTENANCE: revegetate as needed. Monitor flows in and out of overflow
channel.
Lower Cowiche Comprehensive Flood Hazard Management Plan
STRUCTURAL ALTERNATIVES
176
177
Lower Cowiche Comprehensive Flood Hazard Management Plan
STRUCTURAL ALTERNATIVES
GROUP:
CONVEYANCE CAPACITY
PURPOSE: Increase conveyance capacity and decrease roughness, thereby
reducing flood stages, the extent of flooding, and potential for
damage to bridges.
DESCRIPTION. • Bank vegetation is removed by mechanical and/or chemical
means. Mechanical harvesting of bank vegetation would target
larger shrubs and smaller trees, leaving as much understory
vegetation as possible, while the use of chemical herbicides
would remove vegetation without size discrimination.
Submerged or emergent plants can be removed by manual
cutting, automated cutting by boat, use of herbicides, or grazing
by fish such as carp. Fallen trees and debris jams are removed
from the channel through mechanical means. Removal of
vegetation will decrease roughness, resulting in increased
velocities, which may increase erosion downstream. Vegetation
removal may also result in habitat loss.
SKETCH. • See Next Page
IMPACTS: Fish, wildlife, scenic/ aesthetic/historic resources, water quality,
hydrology and recreation.
IMPLEMENTATION.•
Design Requirements: None.
Materials: None.
Equipment Needs: Bulldozer with trash blade, haul trucks, drag line.
Typical Permits: Yakima County Critical Areas or Shoreline Permit, DOE
Stormwater Permit, Temporary Modification of Water Quality
Criteria, SEPA Checklist, WDFW and/or Yakima Nation HPA,
COE Individual Permit, Floodplain Permit.
MONITORING/ Visually observe channel/bank erosion after removal of
MAINTENANCE: vegetation or debris. Monitor accumulation of new debris or new
vegetation growth.
178
Lower Cowiche Comprehensive Flood Hazard Management Plan
STRUCTURAL ALTERNATIVES
179
Lower Cowiche Comprehensive Flood Hazard Management Plan
STRUCTURAL ALTERNATIVES
GROUP:
CONVEYANCE CAPACITY
PURPOSE: Enlarge a channel cross-sectional area to contain more
floodwaters within the channel banks and reduce overbank
flooding.
DESCRIPTION. • A channel is excavated to a new depth and/or width to contain a
specific design discharge. Channel cross-section shape and
dimensions are determined by the stability of bank materials,
porosity of the streambed, and adjacent structures. This
alternative is typically used in conjunction with other structural
alternatives. Revegetation of bioengineering techniques are
strongly recommended for use in conjunction with channel
widening or deepening to ensure long-term stability in the
affected reach. Special care must be taken to replace any lost
spawning gravels.
SKETCH. • See Next Page
IMPACTS: Fish, wildlife, scenic/ aesthetic/historic resources, water quality,
hydrology and recreation.
IMPLEMENTATION.•
Design Requirements: Hydraulic and hydrologic analysis, analysis of sediment
transport regime (i.e., determining whether there is an upstream
sediment source), site survey (multiple cross sections), design
drawings, estimates of quantities to be removed.
Materials: Vegetation and other materials contingent on structural
alternatives used in conjunction with channel widening or
deepening.
Equipment Needs: Backhoe, drag line, haul trucks.
Typical Permits: Yakima County Critical Areas or Shoreline Permit, DOE
Stormwater Permit, Temporary Modification of Water Quality
Criteria, SEPA Checklist, WDFW and/or Yakima Nation HPA,
COE Individual Permit, Floodplain Permit.
MONITORING/ Resurvey channel cross sections following construction and one
MAINTENANCE: year after construction to assess changes in channel cross
section/alignment. Provide additional bank and channel
stabilization as necessary.
180
Lower Cowiche Comprehensive Flood Hazard Management Plan
STRUCTURAL ALTERNATIVES
Lower Cowiche Comprehensive Flood Hazard Management Plan
STRUCTURAL ALTERNATIVES
GROUP:
CONVEYANCE CAPACITY
PURPOSE: Reduce volume of water conveyed downstream (infiltration
basin) or reduce peak flows during flood events (detention
basin). Reduction of volumes and/or peak flows will decrease
the extent and duration of downstream flooding.
DESCRIPTION.•
SKETCH.•
IMPACTS:
IMPLEMENTATION.•
181
An off -stream basin is excavated, with inflow and outflow
channels and control structures installed to regulate flows to and
from the main channel of the river. Water in infiltration basins
will be recharged to groundwater, resulting in a reduction in
volumes received by downstream river reaches. Temporary
storage of water in a detention basin during high discharge
periods will reduce peak flows and flood -related damages at
downstream locations.
See Next Page
Positive impact for water quality, hydrology.
Design Requirements: Hydraulic and hydrologic analysis, site survey and design
drawings (including fish passage considerations), identification
of areas where sufficient infiltration capacity is available.
Materials: Inlet and outlet control structures (concrete, etc.), upstream and
downstream fish screens, topsoil, vegetation, fencing, material
for dikes (if included in design).
Equipment Needs: Bulldozer, front end loader, backhoe, excavator, haul trucks.
Typical Permits: Yakima County Critical Areas or Shoreline Permit, DOE
Stormwater Permit, Temporary Modification of Water Quality
Criteria, SEPA Checklist, WDFW and/or Yakima Nation HPA,
COE Individual Permit, Floodplain Permit.
MONITORING/ Maintain inlet and outlet control structures, remove debris, and
MAINTENANCE: revegetate as needed. Monitor flows in and out of basin, adjust
inlet and outlet control structures as necessary.
182
Lower Cowiche Comprehensive Flood Hazard Management Plan
STRUCTURAL ALTERNATIVES
Lower Cowiche Comprehensive Flood Hazard Management Plan
STRUCTURAL ALTERNATIVES
GROUP:
CONVEYANCE CAPACITY
183
PURPOSE: Reduce the volume of water conveyed in the main channel or the
peak flows during flood events by constructing a detention basin
along a tributary system or storm sewer system. Reduction of
volumes and/or peak flows will abate the extent and duration of
downstream flooding.
DESCRIPTION. • Detention basins are constructed in creeks or storm sewer
conveyance systems to detain excess flow from the river during
peak periods of storm runoff. Stormwater is detained in the basin
until peak flows have passed on the main river channel.
Stormwater is then released at a rate that can be accommodated
by the river. (Because of the significant natural flood storage
provided by wetlands, this alternative also includes wetlands
preservation and constructed wetlands.)
SKETCH. • See Next Page
IMPACTS: Positive impact Fish resources, water quality, hydrology.
IMPLEMENTATION.•
Design Requirements: Site survey, design drawings, hydraulic and hydrologic analysis.
Materials: Inlet and outlet control structures (concrete, etc.), upstream and
downstream fish screens, topsoil, vegetation, fencing, material
for dikes (if included in design.)
Equipment Needs: Bulldozer, front end loader, excavator, backhoe, haul trucks.
Typical Permits: Yakima County Critical Areas or Shoreline Permit, DOE
Stormwater Permit, Temporary Modification of Water Quality
Criteria, SEPA Checklist, WDFW and/or Yakima Nation HPA,
COE Individual Permit, Floodplain Permit.
MONITORING/ Maintain inlet and outlet control structures, remove debris, and
MAINTENANCE: revegetate as needed. Monitor flows in an out of basin. Adjust
inlet and outlet control structures as necessary.
184
Lower Cowiche Comprehensive Flood Hazard Management Plan
STRUCTURAL ALTERNATIVES
185
Lower Cowiche Comprehensive Flood Hazard Management Plan
STRUCTURAL ALTERNATIVES
GROUP:
CONVEYANCE CAPACITY
PURPOSE: To provide the basis for reasonable permanence in designs
through the incorporation of sediment scour, deposition and
transfer in the design reach.
DESCRIPTION. • The success of the long-term goals for infrastructure designs in
the channel and floodplain require not only scour and deposition
calculations but their locations coupled with the sediment transfer
and budget through the design reach, Channels and floodplains
that have been confined laterally will respond through floods to
the designs and must be ensure success.
SKETCH See Next page
IMPACTS Positive Impact to Fisheries, Wildlife, Scenic/ Aesthetic, Water
Quality and Recreation if designed to establish benefits.
IMPLEMENTATION.•
Design Requirements: Hydraulic and hydrologic analysis, analysis of sediment transport
regime (i.e., determining whether there is an upstream sediment
source), site survey (multiple cross sections), design drawings,
estimates of quantities to be removed.
Materials: Removal of channel/floodplain materials. Vegetation and other
materials contingent on structural alternatives used.
Equipment Needs: Bulldozer, front end loader, haul trucks.
Typical Permits: Yakima County or City Critical Areas or Shoreline Permit, DOE
Stormwater Permit, Temporary Modification of Water Quality
Criteria, SEPA Checklist, WDFW and/or Yakima Nation HPA,
COE Individual Permit, Floodplain Permit.
MONITORING/ Yakima County Flood Control Zone District or proponent.
MAINTENANCE:
186
Lower Cowiche Comprehensive Flood Hazard Management Plan
STRUCTURAL ALTERNATIVES
GROUP: CONVEYANCE CAPACITY
PURPOSE: Techniques required where aggradation is a problem.
DESCRIPTION. • Removal of materials is usually part of the solution but must be
accompanied by other methods that address the cause. Once this
is identified designs that address the cause through other
alternatives on a reach basis are required.
SKETCH See Next page
IMPACTS Positive Impact to Fisheries, Wildlife, Scenic/Aesthetic, Water
Quality and Recreation if designed to establish benefits.
IMPLEMENTATION.•
Design Requirements: Hydraulic and hydrologic analysis, analysis of sediment transport
regime (i.e., determining whether there is an upstream sediment
source), site survey (multiple cross sections), design drawings,
estimates of quantities to be removed.
Materials: Removal of channel/floodplain materials. Vegetation and other
materials contingent on structural alternatives used.
Equipment Needs: Bulldozer, front end loader, haul trucks.
Typical Permits: Yakima County or City Critical Areas or Shoreline Permit, DOE
Stormwater Permit, Temporary Modification of Water Quality
Criteria, SEPA Checklist, WDFW and/or Yakima Nation HPA,
COE Individual Permit, Floodplain Permit.
MONITORING/ Yakima County Flood Control Zone District or proponent.
MAINTENANCE:
187
Lower Cowiche Comprehensive Flood Hazard Management Plan
STRUCTURAL ALTERNATIVES
GROUP: CONVEYANCE CAPACITY
PURPOSE: To return river flooding behind levees to the river, minimizing
damage.
DESCRIPTION. • Floodwaters can find routes into developed areas behind levees
through failures or capacity exceedance. Such waters can create
significant residential and commercial damage if not directed
back to the river quickly through structures designed to relieve
pressure.
SKETCH See Next page
IMPACTS Neutral impact to Fisheries, Wildlife, Scenic, Water Quality and
Recreation.
IMPLEMENTATION.•
Design Requirements: Hydraulic and hydrologic analysis, analysis of sediment transport
regime (i.e., determining whether there is an upstream sediment
source), site survey (multiple cross sections), design drawings,
estimates of quantities to be removed.
Materials: Removal of channel/floodplain materials. Vegetation and other
materials contingent on structural alternatives used.
Equipment Needs: Bulldozer, front end loader, haul trucks.
Typical Permits: Yakima County or City Critical Areas or Shoreline Permit, DOE
Stormwater Permit, Temporary Modification of Water Quality
Criteria, SEPA Checklist, WDFW and/or Yakima Nation HPA,
COE Individual Permit, Floodplain Permit.
MONITORING/ Yakima County Flood Control Zone District or proponent.
MAINTENANCE:
188
Lower Cowiche Comprehensive Flood Hazard Management Plan
STRUCTURAL ALTERNATIVES
GROUP: FLOODPLAIN PROTECTION
PURPOSE: Protect land and property from floodwaters while maintaining all
or part of the natural floodplain.
DESCRIPTION. • A levee is installed away from the channel bank to contain flood
waters. The height of the levee depends on the level of flood
protection to be provided. (The levee may be constructed using
bioengineering methods.)
SKETCH. • See Next Page
IMPACTS: Well-designed structures can improve fish, wildlife, scenic/
aesthetic/historic resources, navigation, water quality, hydrology
and recreation.
IMPLEMENTATION.•
Design Requirements: Site survey, design drawings, analysis to determine design flood
stage, geotechnical work to determine foundation soil
parameters.
Materials: Rock, fill soil, topsoil, vegetation.
Equipment Needs: Haul trucks, bulldozer, grader.
Typical Permits: Yakima County Critical Areas or Shoreline Permit, DOE
Stormwater Permit, Temporary Modification of Water Quality
Criteria, SEPA Checklist, WDFW and/or Yakima Nation HPA,
COE Individual Permit, Floodplain Permit.
MONITORING/ Check condition of levee annually and after major flood events,
MAINTENANCE: replace/repair damaged sections, revegetate as necessary, inspect
for animal burrows.
189
Lower Cowiche Comprehensive Flood Hazard Management Plan
STRUCTURAL ALTERNATIVES
um
Lower Cowiche Comprehensive Flood Hazard Management Plan
STRUCTURAL ALTERNATIVES
GROUP:
PURPOSE:
DESCRIPTION.•
SKETCH.•
IMPACTS:
IMPLEMENTATION.•
FLOODPLAIN PROTECTION
Protect floodplain areas from flooding.
A rock or rock/earth embankment is constructed on the river
bank to protect floodplain areas from flood waters. The height of
the levee depends on the level of flood protection to be provided.
See Next Page
Fish resources; scenic, aesthetic, and historic resources; wildlife
resources; recreation.
Design Requirements: Site survey, design drawings, analysis to determine design flood
stage, geotechnical work to determine foundation soil
parameters.
Materials: Rock, fill soil, topsoil, vegetation.
Equipment Needs: Haul trucks, bulldozer, grader.
Typical Permits: Yakima County Critical Areas or Shoreline Permit, DOE
Stormwater Permit, Temporary Modification of Water Quality
Criteria, SEPA Checklist, WDFW and/or Yakima Nation HPA,
COE Individual Permit, Floodplain Permit.
MONITORING/ Check condition of levee annually and after major flood events.
MAINTENANCE: Specifically, investigate areas of erosion upstream of the levee
that may result in damage to the levee, and areas of erosion
downstream of the levee that may be caused by the levee.
Replace/repair damaged levee sections, revegetate as necessary,
inspect for animal burrows.
191
Lower Cowiche Comprehensive Flood Hazard Management Plan
STRUCTURAL ALTERNATIVES
192
Lower Cowiche Comprehensive Flood Hazard Management Plan
STRUCTURAL ALTERNATIVES
GROUP:
PURPOSE:
DESCRIPTION.•
SKETCH.•
IMPACTS:
IMPLEMENTATION.•
FLOODPLAIN PROTECTION
Protect a critical structure or parcel of public or private land by
encircling it with a levee.
A rock or rock/earth embankment is constructed to surround
critical structures or parcels of land located in the floodplain.
Protection from damages due to the design flood is limited to the
critical structure or parcel encircled by the ring levee.
See Next Page
Water Quality.
Design Requirements: Site survey, design drawings, analysis to determine design flood
stage, geotechnical work to determine foundation soil
parameters.
Materials: Rock, fill soil, topsoil, vegetation.
Equipment Needs: Haul trucks, bulldozer, grader.
Typical Permits: Yakima County Critical Areas or Shoreline Permit, DOE
Stormwater Permit, Temporary Modification of Water Quality
Criteria, SEPA Checklist, WDFW and/or Yakima Nation HPA,
COE Individual Permit, Floodplain Permit.
MONITORING/ Check condition of levee every 1 to 2 years or after major flood
MAINTENANCE: events. Replace/repair damaged sections, revegetate as
necessary, inspect for animal burrows.
193
Lower Cowiche Comprehensive Flood Hazard Management Plan
STRUCTURAL ALTERNATIVES
Lower Cowiche Comprehensive Flood Hazard Management Plan
STRUCTURAL ALTERNATIVES
GROUP:
FLOODPLAIN PROTECTION
194
PURPOSE: Protect a critical parcel of public or private land and existing or
new riverbank levees. Prevent floodplain flow behind an
otherwise adequate levee.
DESCRIPTION. • A rock or rock/earth embankment is constructed perpendicular
to the stream channel to prevent movement of water along the
floodplain. The cutoff levee will also prevent degradation of
downstream streambank levees due to erosion and undercutting
of the landward slide.
SKETCH. • See Next Page
IMPACTS: Fish, wildlife, Scenic, aesthetic, and historic resources.
IMPLEMENTATION.•
Design Requirements: Site survey, design drawings, analysis to determine design flood
stage, geotechnical work to determine foundation soil
parameters.
Materials: Rock, fill soil, topsoil, vegetation.
Equipment Needs: Haul trucks, bulldozer, grader.
Typical Permits: Yakima County Critical Areas or Shoreline Permit, DOE
Stormwater Permit, Temporary Modification of Water Quality
Criteria, SEPA Checklist, WDFW and/or Yakima Nation HPA,
COE Individual Permit, Floodplain Permit.
MONITORING/ Check condition of levee annually and after major flood events.
MAINTENANCE: Replace/repair damaged sections, revegetate as necessary,
inspect for animal burrows.
195
Lower Cowiche Comprehensive Flood Hazard Management Plan
STRUCTURAL ALTERNATIVES
Im
Lower Cowiche Comprehensive Flood Hazard Management Plan
STRUCTURAL ALTERNATIVES
GROUP: FLOODPLAIN PROTECTION
PURPOSE: Reduce or eliminate flood damages through use of structural (or non-
structural) changes or adjustments incorporated in the design,
construction, or alteration of individual buildings or properties.
DESCRIPTION. • Floodproofing is accomplished through one or more of the following
measures (see summaries below for additional information):
• Elevating structures on fill, pilings, or slabs to elevations
above the 100 -year flood stage base (base flood level).
• Constructing berms or floodwalls around structures.
• Waterproofing structures; sealing all openings (with provision
for watertight closures around windows and doors.
• Elevating valuables and other contents within the structure
above the base flood level, including service facilities such as
electrical, heating, ventilation, and plumbing facilities.
• Anchoring buildings and associated structures (above ground
tanks, sheds, etc.) to prevent flotation, collapse, or lateral
movement.
• Relocating buildings to locations outside the floodplain.
SKETCH. • See Next Page
SUMMARIES OF FLOODPROOFING APPROACHES:
Raising or Moving the Structure:
Raising or moving the structure is a permanent floodproofing technique since it removes the damageable portions
or the entire structure from risk. Raising the structure involves jacking up the structure and setting it on a new or
extended foundation. The lowest habitable floor of the raised structure should be located above the predicted 100 -
year flood stage. Moving the structure involves relocating the structure to a portion of the building lot outside the
floodplain or to a nearby lot entirely outside the floodplain. While relocation is costly, it is particularly
appropriate where continued occupancy in high hazard areas is unsafe.
Construction of Barriers:
Barriers stop floodwaters from reaching damageable portions of structures. They canbe free-standing barriers not
attached to the structure or involve sealing a building so that floodwaters cannot enter (called "dry
floodproofing"). Free-standing barriers include berms, levees, and floodwalls. Berms are typically earthen
structures constructed close to the structure, while levees are typically constructed along the riverbank (see river
bank levee alternative). Dry floodproofing is accomplished by making all areas below the flood protection level
(100 year flood stage) water tight. Openings such as doors, windows, sewer lines, and vents are closed with
permanent closures or removable shields, sandbags, valves, or other materials.
Wet Floodproofing:
This approach involves modifying the structure to allow floodwaters inside but ensuring that there is minimal
damage to the building and contents. This approach is generally appropriate when areas are available above flood
levels to which damageable items can be relocated or temporarily stored. Utilities and furnaces are protected or
relocated to an area above the predicted 100 -year flood stage. Special caution should be used in employing this
alternative where safety hazards may result from flooding areas containing sources of electricity or hazardous
materials.
197
Lower Cowiche Comprehensive Flood Hazard Management Plan
STRUCTURAL ALTERNATIVES
198
Lower Cowiche Comprehensive Flood Hazard Management Plan
STRUCTURAL ALTERNATIVES
��� iu�!�IIIIICCI��llllllllllllllillllllll lul�l�l�lllllllllllllill��l�l��lll���
WO DSOOMM
f
a
um
Lower Cowiche Comprehensive Flood Hazard Management Plan
STRUCTURAL ALTERNATIVES
GROUP:
PURPOSE:
DESCRIPTION.•
SKETCH.•
IMPACTS:
IMPLEMENTATION.•
STREAMBED CONTROL
Limit channel scour and degradation.
Stabilizers are essentially buried weirs which extend laterally
across the channel. They channel invert upstream and
downstream of the structure is about the same and coincides
with the crest of the weir. Stabilizers limit channel scour and
degradation and are applicable primarily in higher energy
systems in which channel scour and degradation are excessive.
See Next Page
Fish, wildlife, scenic/ aesthetic/historic resources.
Design Requirements: Analysis of historical channel bed -slope changes, hydraulic
analysis of proposed structure, site survey, design drawings,
geotechnical work to determine streambed foundation
parameters.
Materials: Stabilizer may be constructed of grouted or ungrouted rock,
sheet piling, concrete sills, and gabions, or a combination of
materials; also requires fill material appropriate for use in
channel bed.
Equipment Needs: Haul trucks, excavator, concrete pump, concrete trucks, forms.
Typical Permits: Yakima County -City Critical Areas or Shoreline Permit, DOE
Stormwater Construction Permit with Temporary Modification
of Water Quality Criteria, SEPA Checklist, JARPA,WDFW
HPA, Yakima Nation Code (where applicable), COE Individual
Permit, Floodplain Permit.
MONITORING/ Check condition of structure annually and after major flood
MAINTENANCE: events. Inspect channel bed upstream and downstream for
excessive scour or other detrimental changes in channel
characteristics.
N
Lower Cowiche Comprehensive Flood Hazard Management Plan
STRUCTURAL ALTERNATIVES
StabilizerGrouted Stone
F /— CharAM Owed
3
Sheet P [lire` Stabilizer
chamo
flaw
M
Lower Cowiche Comprehensive Flood Hazard Management Plan
STRUCTURAL ALTERNATIVES
GROUP: STREAMBED CONTROL
PURPOSE: To increase conveyance and reduce flood stage through
excavation.
DESCRIPTION. • Stages are reduced across all flows including floods through
direct excavation. The changes can be reversed by deposition
along the reach over time. Best used where a constriction is being
removed downstream.
SKETCH See Next page
IMPACTS Negative impact to Fisheries and short term Water Quality.
Neutral impact to Wildlife, Scenic/ Aesthetic, Hydrology and
Recreation.
IMPLEMENTATION.•
Design Requirements: Hydraulic and hydrologic analysis, analysis of sediment transport
regime (i.e., determining whether there is an upstream sediment
source), site survey (multiple cross sections), design drawings,
estimates of quantities to be removed.
Materials: Removal of channel/floodplain materials. Vegetation and other
materials contingent on structural alternatives used.
Equipment Needs: Bulldozer, front end loader, haul trucks.
Typical Permits: Yakima County or City Critical Areas or Shoreline Permit, DOE
Stormwater Permit, Temporary Modification of Water Quality
Criteria, SEPA Checklist, WDFW and/or Yakima Nation HPA,
COE Individual Permit, Floodplain Permit.
MONITORING/ Yakima County Flood Control Zone District or proponent.
MAINTENANCE:
202
Appendix C
2018 Advisory Committee
Voting Results
APPENDIX C April 13, 2018
2018 Advisory Committee Members Voting Results on Flood Hazard Reduction Alternatives
Flood Issue / Proposed Alternatives
Acceptable
Not
Leads*
Acceptable
Inadequate facilities in floodplain, and hydraulic capacity of Lower Cowiche Creek to prevent flood overflows to City (LC1)
a. Construct new Powerhouse Rd Bridge that will pass the 100 -year flood event
S12
10
0
City
with three feet of freeboard
b. Widen US 12 bridge, allowing 100- ear levees to connect to the road prism.
S6
12
0
City, W SDOT
c. Remove City storage pond for floodplain/bridge space
S7
10
0
City
d. Provide minimum 100 -yr flow capacity channel between Powerhouse road
PL8
12
0
City
and US 12 bridge, while allowing FEMA freeboard and width for channel
floodplain capacity and natural habitat functions.
e. Minimum 500 -yr flow capacity floodplain system downstream of US 12
PL10
10
2
FCZD
bridge that is unarmored and deformable, and accesses the floodplain at the 2-
r flow, or more often.
f. Seek and secure local, state and federal funding to make improvements to this
PL7
10
0
City, FCZD
reach of Cowiche Creek
g. Downstream of US 12, widen the active floodplain to minimize need for
PL10
10
2
FCZD
ongoing sediment removal and large woody material management, and ensure
that the low -flow channel supports typical flow conditions that are beneficial
for fish and water quality.
h. Coordinated design all items from d/sto u/s to reduce overflows in risk area
PL13
10
0
FCZD, City
and meet 100- ear accreditation
i. Action Plan: Any Flood Facilities for Interim Period be coordinated between
PL6
10
0
FCZD, City,
agencies in design and implementation
YVOEM
j. Design channel and floodplains to minimize the need for gravel and debris
S4
9
0
City, FCZD
removal while still allowing for unplanned removals
k. Continue to explore, then construct interim action to alleviate flood east of
S9
12
0
City, WSDOT
40m Ave.
1. Design channel and floodplain systems which allow self -building and
PL10
11
0
City, FCZD
self-sustaining habitat characteristics, while minimizing armoring and
a. Adopt new FEMA regulated maps
PL3
10
0
maintenance.
b. Review and consider interim combined Naches River and Cowiche Creek
flood of record under FFA for building restrictions
PL5
9
1
Flood Issue / Proposed Alternatives
Acceptable
Not
Acceptable
Leads
Floodplain and Flood Risk Mapping not reflective of risk. (LC2)
a. Adopt new FEMA regulated maps
PL3
10
0
City, Count
b. Review and consider interim combined Naches River and Cowiche Creek
flood of record under FFA for building restrictions
PL5
9
1
City
c. Review risk map for planning restrictions
PL5
10
0
Cit
d. FCZD provide comment regarding mapped and estimated flooding inundation
areas during SEPA comment period.
PL17
12
0
FCZD
e. Regulate to extent allowed by CAO and Shorelines, also using flood of record.
PL17
11
0
City, Count
f Task Force to resolve planning/regulatory interim measures
PL4
PL6
PLI8
9
1
City
g. Flood information provided by County/FEMA for facility siting and design
PL17
10
0
FCZD
Flood Issue / Proposed Alternatives
Acceptable
Not
Leads
Acceptable
Improve Public Awareness and Flood Insurance knowledge. (M)
a. Inform Public of new FEMA and flood risk map early to allow lower cost
PAI
10
0
City, FCZD
insurance
PA5
b. Advise property owners of potential for flooding and encourage flood
PA2
11
0
City, FCZD
insurance
c. Assist public with preparation planning that minimizes flood damages
PA4
10
0
City, FCZD
d. Garner public support for capital measures to remove flood areas through
PA7
10
0
City, FCZD
capital expenditures
e. Site and design of facilities to avoid overall flood damages
FP4
11
0
City
Improve Formal Interagency coordination. LC4
FP8
PL2
12
0
Flood Issue / Proposed Alternatives
Acceptable
Not
Acceptable
Leads
Improve Formal Interagency coordination. LC4
a. Extend Interagency coordination between all appropriate agencies during all
Cowiche phases
PL2
12
0
City, FCZD
b. Seek upper management and elected official support for Cowiche flood mitigation
PA6
12
0
City, FCZD
Flood Issue / Proposed Alternatives
Acceptable
Not
Acceptable
Leads
Revision and Consistency of Flood Hazard, Critical Areas & Shoreline Ordinances for this location. (LC5)
a. Ordinances must coordinate for interim measures in this area (CAC), SMA,
SEPA, Zoning)
P`L18
12
0
City, County
b. Create Task Force with public involvement for purpose of reviewing
ordinances
PL18
7
0
City, County
c. Establish a channel migration zone to the edge of the levees on the Cowiche.
PL13
10
0
City, Count
Flood Issue / Proposed Alternatives
Acceptable
Not
Leads
Acceptable
Inadequate flood forecasting system. (LC6) „
a. Improve and add to climate and surface water monitoring technologies to
PL11
11
0
FCZD, City
improve flooding response time, including additional snow, rain, temperature,
streamflow data and quicker retrieval. New_' gages and telemetry.
b. Evaluate flood forecasting system after new components are added
PL11
10
0
FCZD
Flood Issue / Proposed Alternatives
Acceptable
Not
Leads
Acceptable
Define Clear Action Points to Initiate Emergency Response Activities for Cowiche Creek overflows. (LC7)
a. Identify response thresholds for notifications and actions in Near and Short-
FP2
11
0
City, County
Term Action Plans prior to removal of areas from flood threat, updated as
FP7
WSDOT,
needed
PA7
YVOEM
b. Improve flood forecasting to update Near and Short -Term Action Plans
FP2
12
0
City, FCZD
funding mechanism
FP7
c. Develop City of Yakima Public Works Emergency Response Plan with
FP2
12
0
City, County
specific flood elements.
FP7
WSDOT,
d. Preparation of flood hazard mitigation measures, consistent with the CFHMP,
PL7
11
0
YVOEM
Flood Issue / Proposed Alternatives
Acceptable
Not
Leads
Acceptable
Funding for Flood Control Works and Restoration Project elements. (LC8)
a. Seek local political support
PL7
11
0
City, FCZD
PA6
PA7
b. Seek property owners' support to enable local measures may need local
PL7
11
0
City
funding mechanism
PA7
c. Seek local support to garner Federal, State and WSDOT funding
PL7
11
0
City, FCZD
PA7
d. Preparation of flood hazard mitigation measures, consistent with the CFHMP,
PL7
11
0
City, FCZD
to receive funding from grant or disaster programs
e. To the extent possible, flood hazardmitigation measures should be consistent
PL7
11
0
City, FCZD
with, or implement, basin plans
Flood Issue / Proposed Alternatives
Acceptable
Not
Leads
Acceptable
Extensive Short -Term Emergency Flood Routing in (and outside of) the City of Yakima. (LC9)
a. Evaluate drainage and plan for improvements within the CFHMP planning
PL14
10
0
City
area to mitigate short-term damages from overflows
b. Construct short-term routes and structures to direct waters back to Naches
PL14
11
0
City
River or more appropriate watercourses
FP5
c. During emergencies, plan to minimize fish stranding with flood hazard
FP8
11
0
City, WSDOT
mitigation measures, and fish salvage from existing infrastructure. Design
S 10
structures for safe up- and downstream fish passage especially during known
S9
11
0
City
spawning runs.
d. Encourage local protections to protect individual infrastructure such as ring
PL15
11
0
City
dikes around homes, barns, shops; rather than entirely prohibiting floodplain
PA4
flow on a property.
Flood Issue / Proposed Alternatives
Acceptable
Not
Leads
Acceptable
Stability of berms on Lake Aspen/Myron/Willow & drainage of Aspen Lake. (LC10)
a. Provide comprehensive' drainage study to assess capacity of drainage from
PL14
10
0
City
Myron Lake back to Naches River at 6th Ave
b. Establish ownership of drainage facilities and identify additional drainage
PL14
10
0
City, Owners
options as needed
c. Have Myron and Willow Lake dam owners consider spillway improvements
PL14
11
0
Landowners
and long-term management
S 10
d. Consider Constructing Aspen Lake outflows under 16m Avenue and route
S9
11
0
City
adjacent to US 12
Flood Issue / Proposed Alternatives Acceptable Not Leads
Acceptable
Risk to US12 During Major Flood Events. (LC11)
a. Design a new bridge using WDFW's stream crossing design guidelines with S1 10 0 WSDOT
more flow conveyance capacity to reduce overtopping and closure of US 12 S6
and ramps.
Flood Issue / Proposed Alternatives
Acceptable
Not
Leads
Availability of centralized GIS data & modeling impacts in planning and inventory. (LC14)
a. Continue collection of Flood of record FFA: Frequently flooded areas PL5 11 0 FCZD
Acceptable
Threat of flooding to State, County, and City Roads. (LC12)
a. Plan preferential road closures and detour routes to mitigate impactsFP2
11
0
City, County
FCZD, City
accurately estimate flood, flows.
WSDOT,
b. Secure funding to install, monitor and maintain additional stream, rain and
YVOEM
b. Reduce City Road damages from overflows by culvert _ placement S 11
11
0
Cit
Flood Issue / Proposed Alternatives
Acceptable
Not
Leads
Availability of centralized GIS data & modeling impacts in planning and inventory. (LC14)
a. Continue collection of Flood of record FFA: Frequently flooded areas PL5 11 0 FCZD
Acceptable
Lack of Cowiche Creek historical flow data. (LC13)
a. Identify key locations for additional stream, rain and snow gages to more
FP6
10
0
FCZD, City
accurately estimate flood, flows.
b. Secure funding to install, monitor and maintain additional stream, rain and
FP6
10
0
City
snow gages, and to incorporate data into flood estimates and flood forecasting.
Flood Issue / Proposed Alternatives
Acceptable
Not
Acceptable
Leads
Availability of centralized GIS data & modeling impacts in planning and inventory. (LC14)
a. Continue collection of Flood of record FFA: Frequently flooded areas PL5 11 0 FCZD
Flood Issue / Proposed Alternatives Acceptable Not Leads
Acceptable
Operation and Standards for new/upgraded Flood Control Facilities. LC15
a. Develop design and maintenance standards, procedures and funding to ensure PL6 11 0 City, FCZD
enhanced hvdraulic and habitat performance
Flood Issue / Proposed Alternatives Acceptable Not Leads
Acceptable
Development pressures in affected overflow areas/potential additional harm... (LC16)
a. Design development in the overflow area during interim (before secure 100- PL3 11 0 City
year facilities) to minimize damages to proposed and existing development PL5
PL18
Flood Issue / Proposed Alternatives Acceptable Not Leads
Acceptable
Lack of Space for Cowiche Creek low flow Channel Migration. (LC17)
W,
Flood Issue / Proposed Alternatives
Acceptable
Not
Leads
Acceptable
Operation and Maintenance of Proposed Flood Control Facilities. (LC18)
a. Secure dedicated Funding to maintain operational standards, enrollment in
S5
11
0
City
PL84-99 or accreditation to ensure continuing attention and repair
b. Organize community -level funding districts or local funding that construct and
PL12
11
0
City
maintain approved risk -reduction features.
Flood Issue / Proposed Alternatives
Acceptable
Not
Leads
Acceptable
Acquisition/Preservation of Floodplain Open Space. (LC19)
a. Expand Greenway Overlay, where appropriate
PL19
10
1
City, County,
channel capacity.
Greenway
b. Acquire or manage land use to create sufficient open space downstream of
PL10
11
0
FCZD
US 12 to allow for riverine processes.
c. Develop an implementation and funding plan to acquire/preserve parcels to
PL10
11
0
City, FCZD
increase floodplain extent and minimize the need for sediment removal.
d. Preserve open space land uses (ex: wildlife reserve, park, orchard, and pasture
PL9
I1
0
City, County
land) in this area through zoning.
PL21
Flood Issue / Proposed Alternatives
Acceptable
Not
Leads
Acceptable
Loss of Channel Capacity due to Sediment Accumulation and lateralconfinement. LC20
a. Upstream of US 12, design for minimal periodic gravel removals to maintain
PL20
11
0
City, FCZD
channel capacity.
b. Downstream of US 12, widen the active floodplain to minimize need for
PL20
11
0
FCZD
ongoing sediment removal and large woody material management, and assure
that the low -flow channel supports typical flow conditions that are beneficial
for fish and water quality.
c. Include in channel/floodplain design processes for gravel storage, erosion
PL20
11
0
City, FCZD
deform ravel transport; and sustainable vegetation stands.
Flood Issue / Proposed Alternatives
Acceptable
Not
Leads
Acceptable
Sediment accumulates in reach, reducing flood capacity. (LC21)
a. Identify location for sediment removal and sediment monitoring, and removal
PL22
11
0
City, FCZD,
of identified sediment, especially upstream of US 12
PL21
b. During Upper Cowiche C171 -EMP, consider effects of sediment releases or
PL23
10
0
FCZD
pulses on the reach.
Flood Issue / Proposed Alternatives Acceptable Not Leads
Acceptable
Nelson Dam and Fruitvale infrastructure reducing hydraulic capacity downstream of US12. (LC22)"
a. Design Naches floodplain infrastructure removals resulting from the combined I S3 1 10 0 City, FCZD
diversions to maximize Cowiche Creek cabaci
Flood Issue / Proposed Alternatives
Acceptable
Not
Leads
Acceptable
Erosion/Loss of Agricultural Land. (LC23)
a. Downstream of Powerhouse Road and upstream of US 12, acquire land to
PL10
10
0
City, FCZD
accommodate/confine flood flows within a corridor. >
PL21
b. Downstream of US 12, maintain Agricultural land uses to reduce flood risk vs
PL21
9
0
FCZD
higher risk development
* First party named in Leads column has primary responsibility
212
The recommendations were created by combining the accepted (voting) alternatives from
Appendix B. and then separated into functional implementation categories: Planning, Flood
Preparedness, Public awareness and Structural Recommendations. The long-term Structural
recommendations are contained in Table 7-1. The short-term recommendations, which bridge the
gap prior to full implementation of the Structural alternatives are in Tables 7-2, 7-3 and 7-4
separated by their functional category, such as Planning. Each table is ordered by approximate
implementation priority.
TABLE 7-1 PLANNING RECOMMENDATIONS - SHORT-TERM
ID
Recommendation
Estimated
Lead
Cost in $
Entities
PL1
Provide a new Cowiche Creek riverine infrastructure corridor
between Powerhouse Road and the Naches River to eliminate
See below
City,
Cowiche overflows into the City.
WSDOT,
FCZD
PL2
Maintain interagency coordination, necessary flood fight ILAs and
information exchange until existing Lower Cowiche corridor
10,000/yr
City, FCZD,
replaced.
YVOEM,
WSDOT
PL3
Adopt the new Cowiche Creek FEMA preliminary maps for new
development and use overflow scenario map as guidance. Early
10/000/yr
City, County
community adoption of the FEMA maps reduces community risk,
PL4
Appoint a Planning Task Force to minimize Community risk from
Cowiche Creek overflows to ensure planning and building
10/000/yr
City, County
measures are in step with structural measures over all phases of
exposure. The Task Force should provide corridor replacement
timelines and sunsets for the measures.
PL5
Incorporate the 2017 flood extent map during the interim period for
flood protection on development for drainage, stormwater,
5,000
City
building design, siting, and layout. Regulatory use of the actual
2017 flood extent and development guidance using the hypothetical
100 -year overflow maps presented herein will reduce risk exposure
within the City for the interim period prior to lower Cowiche
Corridor replacement.
PL6
Provide Contingency Planning across jurisdictions & agencies as a
living document for the following overflow scenarios: current day,
5,000/yr
City,
the intervening period when individual corridor elements are
YVOEM,
replaced, and upon completion of rehabilitated corridor.
FCZD
Contingency Plans must reflect changed conditions for all newly
introduced infrastructure in addition to current lower capacity
infrastructure. This coordination will require emergency
preparedness, including action planning, and require supplemental
basin data collection specifically for rain on snow storms, drainages
studies for the vulnerable City areas, use of new flood risk maps and
213
TABLE 7-1 PLANNING RECOMMENDATIONS - SHORT-TERM
ID
Recommendation
Estimated
Lead
Cost in $
Entities
formation of a Planning Task forces to use the information and
studies for decision making on interim measures.
PL7
Provide an ILA or MOU to locate funding sources (local, state and
federal) and secure funding to replace the Lower Cowiche stream
10,000
City,
and stream crossing corridor and increase reliability of flood
County,
warning. Funding (local, private, state, and federal), needs to be
WSDOT
established to permit the land acquisition and infrastructure
replacement and be cooperative across agencies, including basin
proponents, to ensure maximum support and effective utilization of
public funds. Infrastructure leads should seek and secure local, state
and federal funding to make improvements to this reach of Cowiche
Creek. The CFHMP, and an overall hydraulic design study outlining
benefits and common goals should be used and developed as a
planning document to justify funding requirements.
PL8
Provide a rehabilitation design that is hydraulically coordinated to
replace the existing channel and crossings between Powerhouse
60,000
City, FCZD,
Road and the confluence with the Naches River (Lower Cowiche).
WSDOT
The channel's capacity will be increased to pass the 100 -year
discharge with adequate freeboard to meet FEMA flood mapping
requirements. Jurisdictions and owners will coordinate the overall
design. The model would be provided by the FCZD and designs of
individual elements must fit within the agreed overall design that
ensures removal of the City of Yakima from the extended 100 -year
floodplain from Cowiche Creek overflows, minimize design and
operational risk failures from the features and interfaces of features.
Due to the Yakima and Cowiche basin recovery value provided by
this reach the overall and component designs will allow for habitat
enhancement requirements outlined in the goals and objectives and
for the planned removal of Fruitvale irrigation infrastructure at the
Cowiche-Naches confluence. The new channel inverts made possible
will result in a channel bed reduction of up to 3 feet along most of the
channel length. The design will be sensitive to capital, operating and
life cycle costs and provide costing numbers necessary for funding.
Sediment passage elements required in this design are expected at
Powerhouse and US 12 bridges, and sediment removal locations at
channel segments upstream and downstream of US 12. The new trail
,bridge may require an extension.
PL9
Incorporate multi benefit considerations with the coordinated
corridor design such as trails, open space, agricultural and habitat.
5,000
City, County
Preserve and/or expand open space and land uses including
agricultural and recreational that not only reduce flood risk but
enhance other preservation, nature benefits. Trail location options
should be investigated.
214
TABLE 7-1 PLANNING RECOMMENDATIONS - SHORT-TERM
ID
Recommendation
Estimated
Lead
Cost in $
Entities
PL10
Acquire required land to increase the current Lower Cowiche
corridor in accordance with goals and design standards (noted in
200,000
City, FCZD
Recommendation PL 8). In order to reduce risk to an appropriate
level the current corridor must be expanded to allow for the
expansion of stream bed and stream crossing footprints and the
necessary operational maintenance and access required to sustain
and respond to the natural processes. The width of the corridor
should also be designed to minimize need for ongoing sediment
removal and large woody material management, and ensure that the
low -flow channel supports typical flow conditions that are beneficial
for fish and water quality. The variety of ownership requires
coordination in accordance with design to promote adequate real
property interests transfer and satisfactory incorporation of
landowner concerns.
PL11
Assess Cowiche basin need for new snow, precipitation and stream
gages to reduce risk and seek partners for regional small basin
100,000
FCZD, City
needs on the west slopes of Naches and Upper Yakima region
(Cowiche, Wide Hollow and Ahtanum). Partners should include
basin data collection agencies: USGS, Ecology and BOR
PL12
Organize community -level funding districts of local funding that
construct and maintain approved protective risk -reduction
N/A
City
features.
PL13
Install the coordinated Cowiche corridor channel elements from
downstream to upstream order to maximize upstream function,
N/A
FCZD, City
minimize cost and reduce transitory impacts. Pursuit in this order
lowers the channel bed bottlenecks by as much as three feet and
increases hydraulic and habitat capacities for all components. This
will require some existing infrastructure adjustments and retirements
(existing City waterline and soon to be retired Fruitvale canal intake
structure). It provides overall cost reductions to all replacement
infrastructure noted in Recommendation PL1.
PL14
Provide a Cowiche Creek overflow drainage study through the
City. This study will provide Contingency Planning guidance
60,000
City,
required in Recommendation PL6, identify problematic areas from
Landowners
Cowiche Creek overflows through town such as Cowiche drainage of
Aspen Lake across 1611, Avenue, routing through Myron and Willow
lakes, and overflow drainage between 1611' and 61" Avenues plus
drainage options back to Naches River at or west of 61" Avenue,
along with alternate drainage scenarios and preferences. Identify and
retain routes to Naches River.
PL15
Review safety and drainage of Myron and Willow lake dams in
response to Cowiche Creek overflow drainage for current day,
60,000
Landowners,
interim and rehabilitated condition. The dam owners need to assess
215
TABLE 7-1 PLANNING RECOMMENDATIONS - SHORT-TERM
ID
Recommendation
Estimated
Lead
Cost in $
Entities
dam safety issues related to Cowiche Creek overflows due to
consequences of low-lying development and limited drainage
PL16
Ensure all owners of critical infrastructure (defined by
consequences of failure) develop operational plans and funding to
5,000
City,
sustain structure integrity. These operational plans should be
WSDOT
incorporated in overall and individual project and life cycle costs and
ensure enhanced hydraulic and habitat performance with regard to
potential overflows over structure life.
PL17
Provide during SEPA or Shorelines comment period comment to
City on development proposals in the overflow area regarding
5,000 yr
FCZD, City
facility siting and layout based on mapping, inundation areas. The
FCZD does not have a regulatory role but can provide relevant flood
specific information. This information transfer would be enhanced
should the City provide a drainage study under Recommendation 14
with proposed measures and timelines.
PL18
Coordinate existing ordinances to establish ability to provide
interim and long-term protection from Cowiche creek overflows
20,000
City
and/or dam failures. Development in the overflow area should be
designed to reduce incurred interim damages. The ordinance
revision should be one of the topics of the Task Force in
recommendation PL4.
PL19
Allow within the planning and design process of structural
elements for the insertion of trails and future Greenway overlay to
10,000
WSDOT,
connect Naches and Cowiche trails. The feasibility of success of this
City,
measure is dependent on early discussions with all parties including
County,
landowners and trail groups. Various routes need to be investigated
Greenway,
as noted in Recommendation PL9.
WO Douglas
PL20
Establish a gravel management plan in the Lower Cowiche corridor
to reduce flood and habitat risk over the short and long-term.
20,000 &
City, FCZD
Gravel removals are expected to be more critical upstream of US 12
1,000/yr
due to the confinement above Powerhouse Road. Design of the
entire reach should result in minimal gravel removals and vegetation
preventing removals. There will be preferred areas for removals
noted above. Lower frequency floods should not overly disrupt
design elements requiring excessive disturbance.
PL21
Emphasize more natural riverine processes downstream of US 12 to
maximize habitat enhancement for current and future species. This
100,000
FCZD
reach is important for ESA species- steelhead and bull trout and
habitat enhancement would be enhanced by the retention of
agriculture/pastoral uses versus development and the emphasis on
gravel and sediment transport and deposition through this reach.
Specific zoning should be pursued.
M
TABLE 7-1 PLANNING RECOMMENDATIONS - SHORT-TERM
ID
Recommendation
Estimated
Lead
Cost in $
Entities
PL22
Identify location for sediment removal and monitoring, and
removal of identified sediment, especially upstream of US 12. As
See PL20
City, FCZD
per recommendation PL20 to limit disturbances
County,
PL23
Provide a future Cowiche Upper Basin CFHMP from the siphon
WSDOT
FP2
upstream to South and North Cascade branches including
100,000
FCZD
hydrological effects including sediment releases or pulses on the
Ongoing-
City, FCZD,
reach
Near -Term
YVOEM
TABLE 7-2 FLOOD PREPAREDNESS RECOMMENDATIONS - SHORT-TERM
ID
Recommendation
Estimated
Lead
Cost in $
Entities
FP1
Form ILAs or MOUS to allow cross coordinated flood response
measures. This enables multiple parties to assist City during
completed
City, FCZD,
Cowiche overflows.
County,
WSDOT
FP2
Provide a Cowiche Creek Overflows Flood Response Plan that
includes a public Notification Plan. The response plan should
Ongoing-
City, FCZD,
assign preferential road closures and evacuation routes.
Near -Term
YVOEM
action plan
FP3
Provide flood fight locations on Cowiche Creek levee to minimize
overflows. City should affect arrangements with landowner to allow
10,000
City,
flood fighting at this most upstream section in order to improve
Landowners
public safety, based on PL20.
FP4
Provide emergency flood fight facilities to intercept overflows and
reroute west of 401h interchange. This requires coordination across
Completed
City,
landowners, WSDOT and resource agencies by the City
& ongoing
WSDOT,
YVOEM
FP5
Emphasize short-term flood routes, maximizing Cowiche Creek
overflows returns back to the Naches as far east as practical and
10,000
City
identified in City Drainage study. Based on PL20
FP6
Increase the gaging stations in the upper watershed to increase
flood response time at Lower Cowiche levee. This requires funds
30,000/yr
City, FCZD,
and basin hydrologic assessment.
Ecology,
USGS,
USBOR
FP7
Provide timely public notice of flood threat status to allow for
timely private mitigation response.
N/A
YVOEM
FP8
Design emergency facilities to minimize fish stranding. This
requires discussion between City and WDFW This requires
N/A
City, WDFW
coordination across landowners, and resource agencies by the Cit
217
TABLE 7-3 PUBLIC AWARENESS RECOMMENDATIONS - SHORT-TERM
ID
Recommendation
Estimated
Lead
Cost in $
Entities
PA1
Increase general Public Awareness of current risk and measures.
Include landowners with large risk in specific discussions, including
5,000
City, FCZD
flood insurance implications.
WSDOT
PA2
Advise landowners on interim and long-term potential for
flooding. Landowners and developers need to know risk and the
5,000
City
goals of the CFHMP to gage their response
PA3
Share Action Plans. City developed action plans need to be publicly
available on web and other means, including permitting
5,000
City, FCZD,
OEM
PA4
Encourage local protections for individual infrastructure such as
ring dikes around homes, barns, shops. This allows specific structure
5,000
City
related protections versus protection of entire property which would
not be allowed because of impacts on others.
PA5
Awareness of new FEMA Maps and limitations. The new maps are
not representative of the large failure consequences as evidence by
10,000
City, FCZD
the condition of Cowiche levees during the 2017 flood and will
require further restrictions. FEMA map replacement will be made
once new infrastructure are completed.
PA6
Engage upper management and politicians in plan for flood hazard
mitigation. Funding for the new interim and long-term infrastructure
N/A
City, FCZD
will not be attainable without political support by local jurisdictions
PA7
Garner public support for capital measures to remove flood risk
areas through capital expenditures.
10,000
City, FCZD
PA8
Locate best Web sites(s) for public notification and use YVOEM
response abilities as emergency declared.
5,000
FCZD,
YVOEM
PA9
Notify public of flood threat status to allow private mitigation
response.
5,000
City,
YVOEM
TABLE 7-4 STRUCTURAL RECOMMENDATIONS - LONG-TERM
ID
Recommendation
Estimated
Lead
Cost in $
Entities
S1
Design and Implementation of all structural recommendations will
be coordinated with the overall design in Recommendation PL8
20,000
City, FCZD,
and updated during implementation of each structural element.
WSDOT
The designs for each element will support habitat and sediment goals
and objectives and incorporate sediment management and other
operational issues. Develop design and maintenance standards,
218
TABLE 7-4 STRUCTURAL RECOMMENDATIONS - LONG-TERM
ID
Recommendation
Estimated
Lead
Cost in $
Entities
procedures and funding to ensure enhanced hydraulic and habitat
performance.
S2
Replace Cowiche channel between US 12 and the Naches
confluence with capacity to pass 100 -yr flood and remove Cowiche
800,000
FCZD
overflows into City from 100 -yr flood maps. Widen the active
floodplain to minimize need for ongoing sediment removal and large
woody material management, and ensure that the low -flow channel
supports typical flow conditions that are beneficial for fish and water
quality. Lower the channel by 3 feet to allow upstream capacity.
S3
Coordinate removal of Fruitvale infrastructure at Cowiche-Naches
confluence with downstream channel design. This measure will
10,000
City, FCZD
maximize flood and habitat benefits for the Naches and Cowiche
floodplain confluence.
S4
Replace Cowiche channel between Powerhouse Road and US 12
with capacity to pass 100 -yr flood and remove Cowiche overflows
2,000,000
City
into City from 100 -yr flood maps. Design channel and floodplains to
minimize the need for gravel and debris removal while still allowing
for unplanned removals, as outlined in Recommendation PL8.
S5
Provide levees in the reach between Powerhouse Road and US 12
that prevent Cowiche overflows into the City and allow for
700,000
City
enrollment in PL84-99 program, certification and accreditation, as
well as connection to a new US 12 bridge. FCZD can provide
guidance on standards.
S6
Replace US 12 bridge capacity to pass 100 -yr flood and remove
Cowiche overflows into City from 100 -yr flood maps. This design
10,000,000
WSDOT
must match all other replacement infrastructure at this point.
S7
Remove city storage pond to increase hydraulic capacity for
Recommendations S4, S5 & S6.
100,000
City
Sg
Improve Naches Trail Bridge downstream of US 12 as necessary to
pass 100 -yr flood with planned wider channel.
100,000
County,
FCZD
S9
Interim structural elements will be required east of 401h Avenue
based on the Cowiche overflow drainage study.
50,000
City,
W SDOT
S10
Spillway and drainage improvements for Myron and Willow dams.
Landowners will establish safe drainage of these lakes to minimize
60,000
Landowners
downstream consequences.
S11
City culvert improvements to route City overflows from Cowiche
Creek The means to move water downstream with the least damage
10,000
City
should be established along with any event specific actions.
S12
Replace Powerhouse bridge with capacity to pass 100 -yr flood and
remove Cowiche overflows into City from 100 -yr flood maps.
12,000,000
City
99
TABLE 7-4 STRUCTURAL RECOMMENDATIONS - LONG-TERM
ID
Recommendation
Estimated
Lead
Cost in $
Entities
Design will accommodate adjacent infrastructure and prevent
overflows down Powerhouse Road to the City and to the north into
Warehouse District.