HomeMy WebLinkAbout04/24/2012 02 Gap-to-Gap Floodplain Restoration Project Presentation , r .,,
BUSINESS OF THE CITY COUNCIL
YAKIMA, WASHINGTON
AGENDA STATEMENT
Item No.
For Meeting of: April 24, 2012
ITEM TITLE: Gap -to -Gap Floodplain Restoration Project presention by
Wastewater Manager Scott Schafer
SUBMITTED BY:
CONTACT
PERSON /TELEPHONE:
SUMMARY EXPLANATION:
Resolution Ordinance Other
(specify)
Contract: Mail to:
Contract Term: Amount: Expiration Date:
Insurance Required? No
Funding Phone:
Source:
APPROVED FOR
SUBMITTAL: C Manager
STAFF RECOMMENDATION:
BOARD /COMMISSION RECOMMENDATION:
ATTACHMENTS:
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El Gap to Gap presentation
City of Yakima
Floodplain Restoration
Outfall Alternative *OS j.
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Incorporating Wastewater Treatment Infrastructure
and the "Gap to Gap" levee removals in the Yakima River
Yakima Regional Wastewater Treatment Facility:
Currently allowed to discharge treated wastewater to
Yakima River under the conditions of a mixing zone
described in its National Pollutant Discharge
Elimination System (NPDES) Permit:
B. Mixing Zone Descriptions
The maximum boundaries of the mixing zones are defined as follows:
The length of the chronic and acute mixing zones shall extend downstream no greater
than 310 feet and 31 feet, respectively. The width of the chronic and acute mixing
zones shall be no more than 50 feet wide. The aquatic life -based dilution factors for the
chronic and acute mixing zones were determined to be 10.12 and 1.86, respectively.
Mixing zone available because the river is held
in place by the Sportsman's State Park Levee
and the City of Yakima WWTP levee .. •
for now.
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Gap to Gap
• Gap to Gap: multi- agency effort to
set back levees in the Gap to Gap
reach since the late 1990s
• 10's of millions of dollars have been
spent
— US Bureau of Reclamation- "Reaches r`
Study" and land purchases "
— WSDOT- Longer bridge span on HWY
24
— Yakima County- Flood Control Zone
District and Boise Pond work
— Army Corps of Engineers- decision to
not repair Sportsman's State Park
Levee, but to build set -back at old
KOA campground City of Yakima Levee and Greenway- Spring 2011
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Gap to Gap and the Regional
Wastewater Treatment Facility
• City of Yakima has requested for Gap to Gap
activities to undergo sufficient environmental
review in order to identify mitigation measures
for loss of outfall /mixing zone.
• An EIS /EA that evaluates impact of Gap to Gap on
outfall has not been done.
• Most recent activity was a major levee setback
that was conducted without review because it
was declared an emergency.
Now, the river will eventually flow through the old levee
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October 2011 March 2012
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April 2012
City of Yakima Regional WWTP outfall
Alternative
• Move outfall to a series of restored fish
bearing habitat features compatible with goals
of gap to gap.
— Phase 1: Restore Billy's Pond- Funded with State
Salmon Recovery Funding Board
— Phase 2: Re -route Greenway trail past restored
pond site and out of floodway
— Get Ecology approval for extended mixing zone
— Phase 3: Discharge effluent diagonally into
restored flood channels
Funding and Timeline
• Phase 1- Funded with SRFB money
• Phase 2- Started application for SRFB money
• Working with Ecology- putting together
engineering report
• Phase 3- Presently un- funded
City Property Restoration Costs •Apply and receive Salmon
$275,400 SRFB Recovery Funding Board Grant for
Phase 1
$ 15,000 ytahp •YTAHP Project Funding /Match
.Hire Ridolfi Engineers for
$802,000 SRFB 2012* restoration design and
engineering report
$250,000 ECY 2012' .
Sub Total $1,682,000
Complete conceptual design for
project.
•Complete Engineering Report for
Department of Ecology Review
*Start permitting
Moving Outfall Distribution
$1,500,000
•Begin design of Phase 1
Engineering Costs $ 500,000 •DRAFT facility plan for WWTP
•Apply for Phase 2 Funding from SRFB
and Ecology
•Complete design work
Complete permitting
•Go to bid in late
Estimated project cost $ 4 Million to $5 Million winter /spring 2013
Summary
• Gap to Gap
— Lowers flood damage risk
— Improves fish habitat
— Improves water quality
— Affects City Wastewater Infrastructure
• Wastewater supports Gap to Gap so long as
impact on ratepayers is minimal
J:/01/ ed 11 4) - '
_ d-b/ i
EXECUTIVE SUMMARY
The Comprehensive Flood Hazard Management Plan (CFHMP) for the Ahtanum and
Wide Hollow basins covers two urbanizing flood -prone basins in the cities of Yakima
and Union Gap, and Yakima County to the north of the Yakama Nation boundary. The
Ahtanum -Wide Hollow Comprehensive Flood Hazard Management Plan is the third
flood hazard plan to be developed in Yakima County by the County -wide Flood Control
Zone District (FCZD). The FCZD develops flood hazard management plans to prioritize
flood hazard mitigation actions, support County and City staff in the floodplain
communities, and develop partnerships across the various agencies and jurisdictions on
projects within floodplains.
The purpose of a CFHMP is to propose a suite of actions that will reduce identified flood
hazards over both the short and the long term. A CFHMP is a policy document which
contains recommended policy changes and flood actions, including projects that reduce
flood hazard. Answers to the questions "What types of actions will be effective ?" and
"Why will these actions be effective ?" are the critical components of an implementation
strategy contained in the plan. The Plan provides a basis for flood hazard risk
management by the jurisdictions in the Ahtanum and Wide Hollow basins. Flooding is
a natural phenomenon, frequently exacerbated by human practices, that cannot be
entirely prevented. There are many approaches to protect lives and property while
protecting the environment and natural resources of the community. The
recommendations of this Plan sought to find the greatest public benefit at the least cost over
the short and long term.
A citizen and agency Advisory Committee was formed and 48 meetings held to assess
hazards, develop the CFHMP goals and objectives, and to develop the CFHMP
alternatives and recommendations. In addition, there were four public workshops,
providing extensive local contribution to the flood knowledge, potential solutions and
plan development by citizens, the two cities, Yakama Nation and all affected public
agencies.
Approval by the Washington State Department of Ecology and endorsement by FEMA
will allow local jurisdictions who adopt the plan to become eligible for state and federal
funds for flood emergency response and non - emergency activities to reduce property
loss and threats to human life. Infrastructure modification or replacement projects
identified within a CFHMP are eligible for funding through disaster grants. Without a
plan, infrastructure is normally replaced or repaired to pre -flood conditions and may fail
again. With the plan, infrastructure can be modified or replaced in a manner that
produces overall reduction in flood hazards to the structure and surrounding area.
The plan contains twelve chapters and supporting appendices. The chapters are divided
into four sections; Chapters 1 and 2 delineate plan process and community involvement,
Chapters 3 through 6 provide the physical and regulatory setting, Chapters 7 and 8
concentrate on flooding characteristics and Chapters 9 through 12 provide the plan
alternatives, recommendations, funding and strategy.
I
II Ahtanum -Wide Hollow Draft CFHMP
Basin Flood Impacts
In 1974 the Ahtanum and Wide Hollow basins experienced a 200 -year flood, as
estimated from Ahtanum Creek stream records. In 1996, the Ahtanum basin
experienced an 80 -year flood while the flooding on Wide Hollow Creek was less severe.
These two major flood events, only twenty -two years apart, may turn out to be more
frequent than the above probability estimates would indicate.
The flood damages in 1996 were more severe than in 1974 since the basin and
floodplains had undergone more urban development. Total County -wide damages in
1996 were $18 million with severe public and private damages in these basins. In
response the County engineer designated these basins as flood prone and requires
higher drainage standards that the cities have also adopted. The continued conversion of
land use from rural to urban during the intervening period has increased flood risk
exposure. This has been demonstrated in recent economic analyses for federal flood
hazard grants that are noted in the plan.
Floodplain Land Use and Channel Conversion Impacts
The communities of Yakima, Union Gap, Ahtanum, Wiley City, and Gromore were
located near these creeks due to productive soils available for agricultural and easy
access to groundwater. These areas were settled before extensive flood experience had
been accumulated. The City of Union Gap is located at the Yakima River confluence of
these two creeks and encountered historic flooding and related development constraints.
The City of Yakima, protected by levees from the Naches and Yakima rivers built after
World War II, has more recently expanded into flood prone areas as a result of
westward annexations. Prior to the expansion, much of Yakima was located west of 16th
Avenue on high ground. A high proportion of the remaining developable land within
the Urban Growth Areas of Yakima and Union Gap is low lying former agricultural land
with high groundwater, in or near the floodplains.
Agriculture is very productive in the flat valley bottoms of these basins. With the
advent of large scale irrigation systems many channels were moved to the higher valley
side slopes. In this location, channels and ditches could be used to irrigate the adjacent
lower farmland. In other cases creeks were covered over or directly converted to
ditches. The designers of early irrigation systems took advantage of the geologic tilting
of these flat valleys to create irrigation systems extending across broad expanses of the
valley in both basins. These systems designed for irrigation also route flood waters. This
increased the number of flow paths and extent of shallow flooding over natural
conditions. These flood paths are only rarely active, and therefore the flood risks
associated with these areas are not easily recognized by the public, private institutions,
and public agencies, until after a flood occurs. Where flood paths remain in agricultural
use, only minimal damage occurs. When land is converted to higher density urban use
significant damage can, and has, occurred.
The use of the creeks to convey irrigation flows has led to "artificial hydrographs" and
the proliferation of vegetation in the channels that obstruct flow, trap sediment and
reduce channel capacity. Management of the irrigation systems themselves is also
EXECUTIVE SUMMARY I III
increasingly difficult as large parcels are broken up through the urbanization process.
This change reduces the frequency of maintenance and types of maintenance approaches
for irrigation channels. Both the increases in vegetation and changes in the level of
maintenance tend to reduce the capacity of irrigation channels, which include both
artificial channels and highly modified "natural" channels such as Wide Hollow,
Bachelor and Hatton Creeks. This increases the frequency and severity of "nuisance
flooding" in these drainages.
Urban road infrastructure also tends to exacerbate flooding, especially when located
across relocated channels that promote flood overflow paths. Flood waters may be
dammed or routed by roads or along roads. As the density of the road system has
increased to meet urban needs, more bridges have been required. There are the over 80
public bridges plus a larger number of private bridges in the basins that have the
capacity to deflect flow. Most of the road infrastructure was constructed and sized prior
to the 1974 flood.
Because of the above conditions, minor changes to the topography (road, fence, large
buildings, fill, and beaver dams) can, and often do, change how flood waters are routed
across the floodplains. The 100 -yr flood maps and history of flooding show the
redirection of flood flows across extensive tracts of land, that present a large flood
hazard. These channel flow redirection concerns were addressed in the development of
alternatives and recommendations. Economic implications of this progressive land use
change are also considered in the plan.
A compilation of flood location data is presented in Chapter 2.
Plan Scope and Process
The plan is comprehensive as it incorporates the entire watershed, as much community
input as possible and practical, and because it aims at short and long term solutions that
have been prioritized.. The structural flood hazard solutions frequently chosen in the
past to protect current development have constrained the river at great community
expense and exacerbate the extent of flooding over the long term, or have impacted
development downstream. Through a comprehensive plan these effects are well
understood before flood control actions are taken that could worsen the situation
through redirection of flows.
The CFHMP is guided by a Department of Ecology process that identifies flood
vulnerabilities and risk, and provides recommendations to mitigate community flood
impacts. The CFHMP process seeks to involve a broad spectrum of local people and
interests in the development of a plan and allows the community to carefully consider
and prioritize alternatives for flood hazard management. Recommendations include
both traditional structural solutions, such as channel realignment, and non - structural
solutions, such as regulations or elevation of homes, to reduce flood exposure. CFHMPs
address flood hazard only and review the current community GMA and related
mechanisms effecting flood management and regulation within the plan geographic
extent (see Chapter 8). The non - structural CFHMP recommendations can be
IV I Ahtanum -Wide Hollow Draft CFHMP
incorporated in the Growth Management Act (GMA) Comprehensive Plans, including
capital facilities plans, through inclusion of Hazard goals (see Table 1.1 in Chapter 1)
and through modification of planning requirements and ordinances for development
within floodplains.
CFHMP Goals and Objectives
Defining goals and objectives provides the framework for carrying out the CFHMP.
The goals and objectives were generated by the Advisory Committee following the
inventory of physical conditions, are provided in Table ES -1 below.
Goals reflect the broadest expression of the community's desires in preparing the plan;
objectives target specific results that fulfill the intent of the goals.
Table ES -1. GOALS AND OBJECTIVES FOR AHTANUM -WIDE HOLLOW CFHMP
Goals (to be achieved Objectives
through objectives)
• Identify the location of critical conveyance channel locations
• Identify stream reaches which have lost flood conveyance capacity due to
changes in streamside vegetation or by human activities
• Assess existing roads, bridges and culverts for barriers to flow- through and
1. Identify flood areas potential abatement of flood damage
and flood processes • Identify past erosion and stream migration processes and monitor after
storm events
• Understand and protect the natural function of the system to reduce flood
hazard
• Determine risks and potential mitigations for hollows
• Identify structural and non - structural actions for reducing flood hazards that
recognize the corridor as a resource and are consistent with long -term river
corridor functioning
• Develop flood hazard management alternatives and strategies to reduce
long -term damages
• Develop short-term flood hazard reduction alternatives consistent with long-
term strategies
2. Reduce flood • Prefer mitigation recommendations that provide benefit for multiple problems
damages to citizens, and /or locations or enhance the value of the stream corridor as an asset to
property and the community
infrastructure while • Improve predictability of channel response to flood events
maintaining natural
functions of stream • Evaluate impacts of present management of flood control and irrigation
and floodplain diversion structures during flood events, such as the flood gate on Spring
systems Creek in Union Gap
• Create inundation maps for flood evacuation preparedness
• Conduct training at first responder and jurisdiction level using Flood
Response Plan
• Facilitate coordination with Emergency Management and Public Works
Agencies before, during and after floods (Flood Response Plan)
• Complete flood forecasting and warning projects in the basin and integrate
with Emergency Response
EXECUTIVE SUMMARY I V
Table ES -1. GOALS AND OBJECTIVES FOR AHTANUM -WIDE HOLLOW CFHMP
Goals (to be achieved Objectives
through objectives)
• Protect existing, or enhance where possible, fish and wildlife habitat
• Protect the natural function of the system to reduce flood hazard
3 Work within the • Evaluate the use of setback dikes to allow for a more naturally functioning
physical and floodplain
biological processes • Restore creeks to more natural channel (i.e. instream projects to address 90
in the floodplain degree angle corners and channels "perched" high on landscape)
• Consider mitigation at watershed level or at a minimum reach level across
jurisdictional boundaries
• Use best available flood hazard data for regulation of land development and
permitting
• Show critical areas and floodplain areas on plat maps corresponding to
short/long plat developments (see City of Yakima regulations)
• Conduct restudies of FEMA floodplain maps
• Ensure that land use plans and regulations protect floodplain functions
• Evaluate and ensure County /City enforcement of land use regulations
4 Achieve land use • Coordinate with Yakama Nation on enforcement of land use regulations
practices that • Evaluate other development requirements that may impact flood hazard
respect floodplain management, such as septic systems and water well siting
functions • Ensure consistency of floodplain regulations within jurisdictions and
investigate increasing the consistency between jurisdictions.
• Identify and implement incentive program for bioengineered structural
solutions to flood hazard mitigation
• Work with existing permitting agencies (such as, Fish and Wildlife, USAGE,
Yakima County Shoreline, Ecology, and the Yakama Nation Water Code
Administration) on identifying ways to streamline project permitting process
• Encourage coordination and cooperation among all regulatory agencies
• Work in creative ways to streamline the regulatory process
• Encourage innovative development techniques where natural systems and
floodplain function exists
5 Emphasize the value
of stream corridors • Educate the public and development community on the value of allowing
as an asset to the floodplain and stream function to properties- investigate Smart Growth
community concepts
• Encourage open space planning and acquisition, through incentives such as
leases, easements, acquisition, etc.
• Identify erosion and stream migration hazards and evaluate mitigation
options as necessary
• Create and submit FEMA floodplain map for Shaw Creek
• Sustain the mapping program
• Compile varied available mapping data into a comprehensive
database /library resource that can be used to address future assessments
6. Quantify hazards in • Identify changing flood condition areas to support new floodplain mapping
our floodplain work
• Identify draws that are prone to flash flooding
• Avoid contaminating land uses in the floodplain
• When designing a flood overflow area, make sure it is not a contaminated
area
• Minimize impacts of septic systems and other critical facilities on water
quality
VI Ahtanum -Wide Hollow Draft CFHMP
Table ES -1. GOALS AND OBJECTIVES FOR AHTANUM -WIDE HOLLOW CFHMP
Goals (to be achieved Objectives
through objectives)
• Communicate and coordinate with local governments and community groups
on flood issues /hazards
• Provide documented examples of positive steps being taken
• Highlight projects that will educate the public on sustainable flood hazard
7 Ensure a sustainable mitigation
flood plan through • Ensure an ongoing educational program that keeps up with current
public and agency understanding, science, and changes in the watershed
awareness,
acceptance, • Participate in the CRS (Community Rating System) program
involvement, and • Flood safety preparedness education
education • Determine where large numbers of animals may be kept during a flood event
and distribute information to the public
• Develop a stream corridor improvement program consistent with this plan
• Increase public awareness and understanding of flooding issues and
floodplain functions
• Seek grant funding
• Investigate possible cost savings through coordination with other multiple
objective projects
• Determine possible areas for flood control sub -zones
8 Ensure the • Address the causes of problems as opposed to the symptoms
implementation of
the flood plan in a • Identify and utilize complementary Plans
timely manner for • Consider flood related recommendations from large scale plans such as the
both the short and Ahtanum Watershed Assessment
long term • Integrate flood hazard reduction into ongoing planning, management
programs, and capital facilities plans
• Understanding how the landscape is managed
• Create and implement educational efforts to inform other organizations
about flood risks, plans, and possible mitigation approaches
These flood hazard goals and objectives are achieved by the plan development process
and subsequent implementation of the plan recommendations.
FEMA 100 -Yr Floodplain Remapping
During the development of the CFHMP the FEMA Flood Insurance Study (FIS) revised
the flood insurance rate maps (FIRMs). The accuracy of the old FIRMs for Ahtanum and
Wide Hollow Creeks had been under question following the 1996 flood. The previous
FIRMs were generated in the late 1970's and published in 1985. Remapping of these two
creeks was initiated under the nation -wide FEMA Map Modernization program starting
in 2004.
As part of the CFHMP the combined Steering and Citizens Advisory Committee, along
with the FCZD, municipalities and citizens, came forward to contribute to the accuracy
of the new FIRMs flood maps through direct input on historic flooding. A major focus
was the identification of overland flow paths.
This process also assisted in the development of the CFHMP. The flooding impact of
various factors such as vegetation, bridge sizing, sediment buildup at bridges and
agricultural infrastructure could be evaluated using the FEMA hydraulic models. The
EXECUTIVE SUMMARY I VII
draft CFHMP was initially delayed to allow the Advisory Committee to view the
preliminary FIRMs in order to refine CFHMP alternatives and recommendations.
The FIS Preliminary Maps for the new Wide Hollow Creek FIRMs were released to the
cities of Yakima and Union Gap in October 2010, followed by Ahtanum Creek FIRMS in
October 2011. The maps will be finalized in 2011 or 2012, respectively, depending on the
appeals process. The hydraulic models for both basins are available from the FCZD and
can be used for future studies and proposed or revised infrastructure.
Use of the FEMA models to evaluate sediment management at bridges revealed that
modifying the existing bridges would not resolve the overflow path problems for 100 -yr
floods, as originally hoped. A stronger non - structural approach than originally
envisioned during goals and objectives formulation, and one that addresses more
frequent floods at, or less than, the 25 -year flood, would be required in order to protect
future development.
Flood Hazard Management Recommendations
The plan recommendations focus on damage prevention to future and existing
development in order to reduce costs, including flood insurance fees. Many of the
recommendations will provide relief for both future and existing development. The plan
recommendations contained in Tables ES -2 and ES -3 were designed to incorporate
parallel objectives of multiple parties to facilitate implementation and maximize
benefits.
Partners have been added to the recommendations as a separate column in recognition
of the need to coordinate ongoing activities across agencies, to leverage funding, and
conduct long term planning of new and replacement infrastructure.
Priorities provided in the tables were based on issues of flood benefits, threat and
expediency. The jurisdictions and agencies will determine their final priorities in this
regard.
As priority does not fully convey the capability to implement, an onset timeline for
implementation was designated and added to the recommendations. The use of this
designation also provides an initial strategy for community implementation of the plan.
Actions completed by the FZCD are denoted "C" for "completed" and contained in
Chapter 10 and the Appendices. Actions already underway, usually by the FCZD (see
Chapter 10), are denoted IP for "in progress ". Actions recommended to be initiated
shortly after Plan adoption are denoted S for "short term ", while L is for "long term ",
again referring to start date. Actions recommended within the next cycle of regulatory
update, such as Comprehensive Plan or Ordinance updates are denoted as AU for
"awaiting update ". Actions recommended to be initiated as part of upcoming projects
or opportunities are denoted 0 for "opportunity ".
To guide implementation, recommendations were grouped into categories.
Recommendation categories indicate the work nature and main partners required for
VIII I Ahtanum -Wide Hollow Draft CFHMP
implementation. The categories are: Inventory and Study, Planning and Regulatory,
Maintenance and Management, Structural, Public Outreach, and Flood Response. For
example, the FCZD cannot take the lead for Planning and Regulatory, a role that belongs
to the jurisdictions. The FCZD can facilitate Maintenance and Management for facilities
and lands that belong to landowners and jurisdictions. The FCZD has already taken a
major role in Public Outreach and Flood Response. Implementation of Public Outreach
recommendations will require an ongoing, coordinated approach to planning,
regulatory, structural, and maintenance actions and programs over the long term.
The flood hazard definition and mitigation recommendations are summarized in tables
ES -2 and ES -3, respectively. Inventory and Study recommendations within Table ES -2
will fill information gaps and may refine flood hazard mitigation recommendations
within Table ES -3. Many of these Inventory and Study recommendations are currently
in progress, and those complete are noted and included in the appendices. Additional
details on these recommendations and estimated costs are provided in Chapters 9 and
10, respectively. The largest proportion of costs is for structural recommendations; the
high priority structural recommendations are estimated at approximately $5 million
dollars.
ES -2 Recommendations for Further Flood Hazard Definition
INVENTORY AND STUDY
Description Onset Priority Partners
IS - Establish technical work groups and pilot programs on IP H FCZD/WDFW Irrigation
a reach by reach basis for channel, vegetation and sediment Districts, Landowners,
maintenance (including Wide Hollow coarse sediment Jurisdictions
budget), to develop criteria and enable appropriate larger
scale maintenance programs which meets flood and habitat
needs. (See Appendix J)
IS - Establish cleanout guidelines and a pilot program C H FCZD/ Roads, Plan
bridge sediment removal & maintenance. (See Appendices Depts
G &H)
IS - Inventory problematic bridges, roads and infrastructure IP H FCZD/ Roads Depts
impacts and sediment buildup to generate action plan for
removals, etc. This includes areas of ponding.
IS - Inventory flooding impacts for existing and abandoned IP H FCZD/
irrigation structures. Irrigation
IS - Modify bridge crossing design to reduce flooding and IP H Roads/ Plan Depts
maintenance on case to case basis — wider spans, wider
easements upstream and downstream for channel design
and cleanout, deeper footings, to enable for scour, etc. (See
Appendix G)
IS - Wapato dam impact assessment for Union Gap IP H FCZD
IS - Provide 10 and 25 year flood extent maps to show C H FCZD
chronic flooding areas where actions such as infrastructure
sizing and siting, proposed development and
redevelopment can be designed to guide flood hazard
reduction. (See Appendix J)
IS - Provide 10 and 25 year flood damage estimates using IP H FCZD
established federal methods to guide economic and
environmental decisions.
EXECUTIVE SUMMARY I IX
INVENTORY AND STUDY (cont)
Description Onset Priority Partners
IS - Study to identify Ahtanum avulsion scenarios and S H FCZD
existing flood issues at Mission.
IS -10 Establish historical flooding areas —e.g. Wiley City & S H FCZD /Plan Depts
Ahtanum -as special study areas to include all infrastructure.
IS -11 Establish historical map and identity flood risks in S H FCZD
Hollows.
IS - 12 Identify & prioritize emergency response access S H City & County
routes during 10, 25 and 100 year floods to incorporate into Roads/YVOEM
emergency transportation and planning.
IS - 13 Resolve run -off issues presented by DIDs. S M Jurisdictions
IS - 14 Document floods including aerial photos, high water S M FCZD
marks, etc.
IS - 15 Identify high flood risk stream reaches where man- S M FCZD/ WDFW
made changes or proposed projects effect channel processes
or flooding including roads, perched channels and other
alterations
IS - 16 Design bridges and irrigation infrastructure to reduce L M Roads/FCZD Plan
potential for accumulation of debris and sediment and Depts, WDFW
creation of un- natural overflow channels /paths.
IS - 17 Study use of ring dikes to protect St. Joseph's Mission IP L Landowners
property
IS - 18 Consider major levee construction on Mission IP L FCZD
property to alleviate headcuts, this may not be needed if
Recommendations A & B in Hatton section are successfully
implemented.
IS - 19 Perform an Emma Lane flood study, and develop IP L FCZD
design guidance on acceptable flood protection levels. (3 -2).
Address Ahtanum Creek flood conveyance downstream of
42" and Ahtanum Rd.
IS - 20 Develop a Coordinated Resource Management Group L L NYCD/WDFW
to develop joint priorities for resource management (e.g.
Wenas working group).
IS - 21 Investigate and recommend increased maintenance L L Roads
and debris cleanout of culverts and ditches on public roads
(coordinate with road maintenance crews to optimize ditch
cleaning for flood purposes)
IS - 22 Monitor effects of urbanization and land use L L FCZD
intensifications to the characteristics (runoff, time of
concentration, water quality) of the watershed over time.
Take action to mitigate for negative watershed scale effects.
IS - 23 Map non — mapped Channel Migration Zones (and 0 L FCZD/ plan Depts
other hazards) (15G -4, 15D -3). Identify areas that are at risk
for channel migration in addition to identified CMZ, i.e. N.F.
Ahtanum, below the Narrows, at the Mission, Shaw Creek,
etc.
IS - 24 Alter drainage systems and easements, based on 0 L FCZD
Emma Lane floodplain remap study.
IS - 25 Inventory of private roads acting as levees. 0 L FCZD
IS - 26 Private road culvert inventory. 0 L FCZD
I5 Investigate funding sources or incentives for private 0 L FCZD
drainage infrastructure.
X I Ahtanum -Wide Hollow Draft CFHMP
ES -3 Recommendations for Flood Hazard Mitigation
PLANNING & REGULATORY
Policy Development
To be implemented in the policy processes associated with the broad scale Growth Management Act processes such as
County -Wide Planning Policies, Comprehensive Plans, Capital Facilities Plan Elements, and UGA expansion.
Description Onset Priority Partners
PR - Ensure drainage infrastructure is properly sited, sized IP H RSPG /Stormwater
and designed to minimize flood effects from stormwater Utilities
run -off. This includes establishing the relationship between
flooding and stormwater and determining
detention /retention and other stormwater standards.
PR - Petition State Noxious Weed Control Board to list IP H FCZD
hybrid willows as invasive species as designated in other
states.
PR - Incorporate floodplain and economic impacts into S H Plan Depts /FCZD
SEPA for subdivision layouts floodplain development
(losses, damages, safety, insurance, response and recovery)
from the planning to the project level, especially in urban
and urbanizing areas.
PR - Establish policies, such as a flood hazard audit and AU H Plan Depts/FCZD
hazard element using the flood problem inventory in this
plan, within County -wide planning policies and
comprehensive plans in flood hazard areas to direct
preferred locations for new infrastructure such as arterials,
water and wastewater distribution mainlines, regional
stormwater facilities, parks and greenbelts.
o New major arterials should be located outside of
floodplains where possible. If in floodplain, design to
minimize flood impacts.
PR - Retain and provide Open Space land use in all AU H Plan Depts/ FCZD
jurisdictions using zoning easements, acquisitions and
incentives within floodplains to provide multiple public
benefits such as preserving space for flooding, greenbelts
and trails.
PR - Provide open space incentives that target general AU H Jurisdictions /Plan
floodplain function, riparian and storage recommendations. Depts., Interest
Groups, FCZD
PR - Decide upon, designate (in flood response, S H Roads/YVOEM
transportation and capital facilities plans) and maintain
critical access routes at 10, 25 and 100 year events.
PR - 19 Develop flood abatement policies for high risk flood 0 M Plan Depts/ FCZD
prone areas of existing dense development in the floodplain.
o Design drainage to meet multiple objectives FCZD/Plan
including flood alleviation, in flood -prone areas, esp. Depts
in Wiley City and Ahtanum. L
PR - 20 Identify areas that are "islands" surrounded by L M FCZD /Plan
floodplain and develop standards to limit density, provide Depts
emergency access and consider transportation networks
within the context of surrounding area.
PR - 21 Seek land use examples for flood -prone areas from L M FCZD /Plan
other similar communities. Depts
EXECUTIVE SUMMARY I XI
PLANNING & REGULATORY (cont)
Description Onset Priority Partners
PR - 24 Preserve natural drainage including draws and S M Plan Depts
mitigate identified hollows that provide natural flood flow
paths but are not identified as FEMA floodplains.
Implementation is through drainage requirements within
stormwater, County /City drainage, grading, and long and
short subdivision ordinances.
PR - 25 Consider development moratoriums or high 0 M Plan Depts
standards of proof in place where development is outpacing
flood knowledge or tools available to keep the public safe
(i.e. the area has not been mapped, or conditions have
changed since the last mapping).
PR - 26 Maintain open areas near the mouth of Ahtanum 0 M Plan Depts
Creek for flooding such as Fulbright Park.
PR - 30 Take larger scale effects to the watershed into account AU L Roads / Plan Depts
when designing new transportation systems: Minimize
number of roads — maximize efficiency and design roads in
a manner to minimize flooding.
PR - 31 Assess the cumulative effect of road policies and AU L Roads /Plan Depts
standards for new roads within the transportation element
of the comprehensive plan that act as dams or conveyances.
PR - 32 Limit future development in the Emma Lane AU L Plan Depts
floodplain area if structural alternatives not implemented.
PR - 33 Place controls on building in the flood -prone areas in AU L County Plan Dept
and around Emma Lane (e.g. using zoning, utility hook -ups,
etc.)
PR - 34 Investigate geologic hazard area standards for L L FCZD/ Plan Depts, Bldg
applicability to high flood risk hazard categories such as Officials
channel migration zones and alluvial fans to address
potential regulatory gaps.
Standards and Ordinance Development - To be implemented in association with the development and approval
processes for ordinances that implement the Comprehensive Plan, and in some cases modifications to the building
codes. Some of these recommendations (work group) would need to begin well before modifications to existing
ordinances are proposed.
PR - Ensure all new development and redevelopment AU H Plans Depts/
within identified FEMA floodplains are adequately FCZD
reviewed for NFIP compliance and overall environmental
(SEPA) impacts through the use of additional review
procedures which may include; at minimum a public notice
(type 2 for the County), a signed checklist for all floodplain
items; a floodplain development permit independent of
other required permits; or establishing a floodplain overlay
zone covering the above concerns.
PR - Establish work groups to formalize regulatory S H Plans Depts/
applicability of man -made and natural courses. FCZD
PR - 10 Ordinance increase for residential to at least one foot AU H Bldg Officials/ Plan Depts
above BFE for future development to reduce community
costs and damage.
PR - 27 Work for consistency in zoning and development AU M Plan Depts
standards across jurisdictions for developments and
buildings within floodplains. Determine gaps in the
regulatory scheme.
XII Ahtanum -Wide Hollow Draft CFHMP
PLANNING & REGULATORY (cont)
Standards and Ordinance Development - To be implemented in association with the development and approval
processes for ordinances that implement the Comprehensive Plan, and in some cases modifications to the building
codes. Some of these recommendations (work group) would need to begin well before modifications to existing
ordinances are proposed.
Description Onset Priority Partners
PR - 28 Reduce risks through subdivision development M
standards to minimize new structures in harm's way
o Integrate protection of floodplain functions
improvement /flood hazard reduction into 0 Plan Depts
subdivision platting process.
o At a minimum, require a buildable area outside of
the floodplain including standards for lot size and 0 Plan Depts
housing location.
PR - 29 This includes special land use standards for industrial SU M Plan Depts/
uses relating to hazardous materials, storage, use, disposal Bldg Officials
and flood - proofing for non - residential structures, including
elevating to make existing structures less flood damage
prone. Jurisdictions should adopt Appendix G of IBC.
PR - 35 Adopt and implement stricter building standards in AU L County Plan &
Emma Lane area - flood - proofed homes, buildings. Bldg Officials
PR - 36 New traffic generating developments should be 0 L Jurisdictions, Plan &
located outside of floodplains (see also Bridges & Roads). FCZD
Project and Permit Level — These recommendations should be incorporated as standards of review for development
in floodplains, mostly in relation to new subdivisions, commercial /industrial and public and private infrastructure
projects.
PR - 11 Improve compliance with NFIP on all new and IP H Bldg Officials
replacement bridges and culverts.
PR - 12 Based on the 10 and 25 -year flood mapping, consider S H Plan Depts/WDFW
them, for design requirement of land use designation
decisions in future floodplain development to minimize
frequent damages and economic impact.
PR - 13 Use SEPA and Comprehensive Plan Policies and S H Plan Depts
Goals to address flood issues /impacts associated with larger
scale proposed developments where current zoning,
subdivision or building standards are not sufficient to
mitigate flood risk.
PR - 14 Implement NPDES Regional stormwater to limit run- IP H Local Jurisdictions
off up to 100 -yr flood.
PR - 15 Fully utilize new FEMA models and maps, and S H Plan Depts/
locally developed 10 and 25 -yr map products, including loss Roads
data, for alternative analysis and infrastructure and land use
decision making, by providing models and mapping free of
charge.
PR - 16 Consolidate access for floodplain crossing to AU H Plan Depts/
minimize flood impacts. Roads
EXECUTIVE SUMMARY I XIII
PLANNING & REGULATORY (cont)
Standards and Ordinance Development - To be implemented in association with the development and approval
processes for ordinances that implement the Comprehensive Plan, and in some cases modifications to the building
codes. Some of these recommendations (work group) would need to begin well before modifications to existing
ordinances are proposed.
Description Onset Priority Partners
PR - 17 Ensure floodplains and floodways are identified on AU H Plan Depts
final plat maps — included would be text identifying
effective map date and disclosure regarding fact that the
maps will change over time. Also consider including
identification of riverine Critical Areas buffer on plats.
PR - 18 Increase flood code enforcement through adequate S H Code
funding mechanisms 6.3.A. Enforcement
PR - 37 Improve drainage throughout the entire Emma Lane IP L Roads
area — culverts, roads, etc.
MAINTENANCE & MANAGEMENT
Continuous and stable Channel and Riparian Management
MM - Program for sediment and debris removal, invasive IP H WDFW/FCZD Plan
species control, replacement species in plantings, sediment Depts,
& bank stabilization. NYCD
MM - Beaver management. IP H WDFW/Landowners
MM - Riverine Infrastructure Management — debris and IP H Jurisdictions/
sediment maintenance. Irrigators
MM - Riparian restoration, mitigation and protection to S H FCZD/WDFW
reduce flood impacts. Jurisdictions
MM - Land acquisition in problem areas prior to IP H FCZD/ Jurisdictions
development (Emma Lane /Cottonwood /Shaw Creek/Union Landowners/ Interest
Gap, etc.). groups,
MM - Apply appropriate range management standards to S H WDFW
elk in confined feeding operations near riverine
environment.
MM - Obtain landowner access permission for problem IP H FCZD/ Jurisdictions
bridge channel maintenance.
MM - Coordinate opening irrigation diversion gates for IP H FCZD/Irrigators YVOEM
flood relief, based on forecasts, channel maintenance needs,
and impact to diversion facility.
MM - Separate irrigation conveyances from streams as L H Irrigators/ Jurisdictions
practical and based on priority
MM -10 Consolidate irrigation diversions and remove as L H BOR/BPA/
become obsolete. Irrigators, Jurisdictions
MM -11 Community adoption of Community Rating System L H Jurisdictions
to reduce insurance rates through CRS activities.
MM - 12 Investigate irrigation infrastructure changes such as L M Irrigators
flood gates or siphons to reduce flood routing through
irrigation systems.
MM - 13 Modify drainage standards for existing roads in AU M Roads/FCZD
overflow areas to minimize flood impacts (i.e. Emma Lane
area).
MM - 14 Ensure replacement of damaged infrastructure 0 M Roads
reduces future flood damage risks.
MM - 15 Explore additional funding methods for mitigation 0 M Roads
or reduce environmental effects (including flooding) from
existing roads or other infrastructure.
XIV I Ahtanum -Wide Hollow Draft CFHMP
MAINTENANCE & MANAGEMENT (cont)
Continuous and stable Channel and Riparian Management
Description Onset Priority Partners
MM - 16 The Spring Creek floodgate should generally be IP L Union Gap/FCZD
closed except for habitat or flow enhancement for a limited
time period (see alternative F below also).
MM - 17 Review DID management in relation to flood hazard L L DIDs (County)
over the long term as land use changes.
MM - 18 Investigate funding for enforcement and cleanup of 0 L SW, DOE &
illegal dumps on private ground. Health Dist
MM - 19 Improve stormwater system on Ahtanum Road to 0 L City of Yakima
limit Emma Lane overflows into the airport area, and
downstream to 16th (which floods the intersection at
Ahtanum Road).
MM - 20 Investigate methods for the following: 0 L SW, FCZD, Jurisdictions
- Research how other communities deal with
dumping in floodplains, particularly concrete, fill,
etc.
- Research measures to deal with
illegal /contaminated dumps (meth labs, etc.)
- Examine statewide laws relating to dumping and
streams to establish authorities.
MM - 21 Utilize fence designs that prevent floodwaters from 0 L NYCD/FCZD Bldg
backing up on fences, such as: Officials, Plan Depts
o Breakaway fence panels in locations that flood
frequently.
o Suspension fences, which consist of steel pipe or
cable hung high above the creek, and hanging
lighter materials down from the cable. This works
as a fence, but is not lost during floods.
Fence setbacks — hold fences back some distance from the
creek (loss of traditional land usage).
STRUCTURAL
Projects in Urban Growth Areas
ST - Property acquisitions and home elevations for IP H FCZD/
repetitive loss properties. Jurisdictions
ST - Emma Lane channel improvements. IP H FCZD/
Jurisdictions
ST - Bachelor Bridge at Ahtanum Rd. & Ahtanum Creek & 0 H County Roads/ Plan Depts
16th Avenue bridge replacements
ST - Wide Hollow flooding between 64th and 101st— channel IP H FCZD/
improvements and acquisitions — recommendations include Jurisdictions
those for Shaw Creek, plus regional retention
ST - Resolve Shaw Creek relocation /overflow to remove S H FCZD/ Jurisdictions, Plan
community damages and insurance Depts.
ST - Wide Hollow relocation or overflow channel 0 H DOT/
incorporated in future development and proposed Jurisdictions
infrastructure design in Union Gap
ST - Improve grade for Spring Creek East to reduce 0 H DOT/
flooding in Union Gap Jurisdictions
ST - Mill structure — Develop shelf ready open channel 0 H FCZD/
bypass design for grant application on, lower channel Jurisdictions
EXECUTIVE SUMMARY I XV
STRUCTURAL (cont)
Projects in City of Union Gap
Description 'Onset 'Priority Partners
Projects in areas which route floodwaters overland
ST - Reduce catastrophic flow captures at Mission S H FCD/Irrigators
(infrastructure and town impacts — Rutherford Road) and landowners, Plan Depts
preventing avulsions into Hatton and capacity issues
ST - 10 Flood design for John Cox diversion (new) L H FCZD/Irrigators
ST - 11 Make infrastructure improvements in Emma Lane M
area: IP FCZD/
o Remove abandoned fill and infrastructure in Emma Landowners
Lane area to increase flood capacity and reduce
redirection of flood flows
o Widen bridge at 42" Ave. IP Roads
ST - 12 Evaluate not filling in the existing Ahtanum channel IP M FCZD/
so it can be used for habitat if the creek is relocated near Landowners
Emma Lane
ST - 13 Perform a cost - benefit analysis for stream relocation IP M FCZD
near Emma Lane
ST - 14 Improve flood conveyance and predictability by L M FCZD
reconfiguring modified or "perched" streams and
establishing overflow channels if relocation is not feasible
such as Shaw, and Emma Lane
ST - 15 Maintain Wide Hollow flood mitigation methods in 0 M City of Union
Union Gap by retaining an overflow path along railroad Gap
right of way and encouraging development of an 0 & M
agreement among appropriate parties for flood and fish
structures the Mill
ST - 16 Consider the following structural alternatives where L L FCZD/ Plan Depts
changes in the channel threaten homes, businesses,
agricultural land, or infrastructure.
o Levees, armor, buffers, CMZ (channel migration zones)
o Structural flood control measures either by individuals
or government
o Utilize "softer" solutions for bank stabilization, bio-
engineering.
o Levees constructed along perched channels (i.e.
Cottonwood Grove)
ST - 17 Expand diking along Shaw Creek to protect new and L L Add Insurance
existing development Costs
ST - 18 In some locations, add wood to stream to "catch" 0 L FCZD
wood debris — this accomplishes multiple objectives — would
benefit habitat as well as reduce the volume of woody debris
that accumulates on bridges, diversions, and other
structures.
ST - 19 Armoring: 0 L FCZD
- Provide armoring of roads with act as levees
(Ahtanum /Cottonwood Canyon Rd., etc.).
- Armor road ditches where road fill is going to
contribute to excess bedload and to protect road prism.
XVI I Ahtanum -Wide Hollow Draft CFHMP
STRUCTURAL (cont)
Projects in City of Union Gap
Description Onset Priority Partners
ST - 20 Culverts: 0 L FCZD & Jurisdictions
- Recognize the limitations of culverts as flood Roads
conveyance structures
- Replace old culverts with higher capacity culverts based
on flood risk
ST - 21 Identify sources of funding for removal of abandoned 0 L FCZD & Agencies
irrigation structures
ST - 22 Preserve and restore natural floodplain in places that 0 L FCZD
retain some of the floodplain function. Prioritization - allow
for flexibility while identifying critical locations, based on
CFHMP and mapping. -
ST - 23 Install a remote control floodgate that could be 0 L City of UG
opened some times of year, closed at others (on Spring
Creek floodgate)
ST - 24 Protect natural floodplain functions in Shaw Creek's 0 L FCZD
watershed, especially before it is mapped.
•
PUBLIC OUTREACH
P0 Information to public and local governments on New IP H FCZD/
FEMA Maps Jurisdictions
P0 Outreach to public regarding flood hazard related to IP H FCZD/ plan Depts
regulatory changes
P0 Provide flood risk & regulatory constraints at S H Plan Depts
beginning of development process
P0 Outreach to Realtors, lenders, etc. about flood risks S H FCZD
P0 Provide information to the general public and L H FCZD/Plan
property owners to enhance their understanding of: specific Depts
flood risks, beneficial functions of floodplain, and aesthetic
values of streams and floodplains for development
P0 Work with landowner assistance programs to improve S M FCZD
appropriate streamside vegetation and provide information
about flood resistant fencing
P0 Utilize meetings and other methods of notification to IP M FCZD
inform developers and current and prospective residents
about flood risks for Shaw Creek
P0 Encourage residents and property owners who are at IP M Jurisdictions
high risk for flooding to purchase flood insurance even if
they are not in a mapped floodplain
P0 Provide public notice /disclosure /consultation about 0 M Jurisdictions/
planned flood projects FCZD
P0 Provide information for the public about culvert S M FCZD/Roads
maintenance and sizing
P0 Yakima County Flood Control Zone District to IP M FCZD
provide technical assistance and comments regarding flood
hazards and infrastructure design
P0 Encourage volunteer flood - watchers program to S M FCZD
provide information
P0 Cooperate with other agencies to support or develop IP L FCZD
public education programs, such as stream cleanup
programs and volunteer monitoring.
P0 Encourage citizens to report dumping in streams L L FCZD
(public outreach).
EXECUTIVE SUMMARY I XVII
FLOOD RESPONSE
Description Onset Priority Partners
FR -1 Designation of evacuation routes and notification of S H YVOEM /Roads
the public and first responders
FR -2 Implement and participate in activities for the Flood S H YVOEM/
Response Plan Jurisdictions
FR -3 EOC environmental coordination L H EOC/WDFW
FR -4 Determine where large numbers of animals may be L H Conservation
kept during a flood event and distribute information to the Authorities
public. Work with Emergency Management and Red Cross
to establish animal food and shelter contingencies —
discussions may include Central Washington State
Fairgrounds, farm feed stores,
FR -5 Coordination between Emergency Management and 0 H YVOEM /AID
the Irrigation Districts such as AID and Yakima Valley YVCCo
Canal, for management during floods. Include Irrigation
Districts in communications with the EOC
FR -6 Public and agencies coordinate flood fight and post S M YVOEM
flood actions with recommendations identified in the
Ahtanum -Wide Hollow CFHMP to provide a good basis for
decision whether to take emergency action
FR -7 Install gages on North Fork Ahtanum and Wide 0 M FCZD
Hollow Creeks, including telemetry
FR-8 Develop warning systems including mass media L M YVOEM
FR -9 Identify known problem locations so information is S M YVOEM/ FCZD
available for first responders and include in the Flood
Response Plan (if appropriate)
FR -10 Provide special flood phone line for public to call in L M YVOEM/ FCZD
and provide information about current flooding — EOC &
FCZD cooperate /coordinate
FR -11 Improve access to Bachelor diversion during floods L M Irrigators/ BOR
without diverting flood waters or making flood problems
worse
FR -12 Improve communication, coordination and IP M YVOEM
information dissemination between various agencies and
emergency management office during flood emergencies
FR -13 Coordinate between jurisdiction procedures in place 0 L OEM, Jurisdictions,
for expedited permit issuance during and period after a Agencies, FCZD
flood event under State and County regulations.
FR -14 Outline emergency response to ice jams in the Flood 0 L FCZD /Agencies
Response Plan.
- Alert residences at risk. (new)
- Blast ice jams — (normally only done on very stable
ice jams)
Facilitate regulatory approval by Ecology and Fish &
Wildlife and local jurisdictions due to short time frame.
(new)
XVIII I Ahtanum -Wide Hollow Draft CFHMP
Mapping Tools
The recently released (2011) Preliminary FIS maps for the 100 year flood increase
awareness of flood hazard. From the extent and nature of the flooding portrayed on the
FEMA maps it is evident that, despite the implementation of this plan, infrequent flood
events such as the 100 year event will continue to affect large areas, causing substantial
damage and economic disruption. Frequent floods, from a five year interval up to the 25
year flood, produce the majority of property damage and economic disruption to the
community over time. As part of this plan, 10 and 25 year flood maps are provided that
can serve as guidelines for future infrastructure planning.
Preferred Implementation Order for Recommendation Categories
The Inventory and Study recommendation category should be implemented first as the
topics they cover increase awareness of flooding problems, problem causes and
locations, and may amend other recommendations. In particular the high priority
recommendations have been pursued by the FCZD to facilitate other recommendations.
The inventory results may change the focus of, or add to, some of the Planning and
Regulatory, Maintenance, and Structural recommendations, so that maximum public
benefit can be attained at reduced costs. Several of these inventories, including problem
bridges, and the effects of Drainage Improvement District facilities (DIDs) will improve
management of floods and allow tracking of changes to the basin into the future.
Recommendations to minimize future damages for new development require Planning
and Regulatory recommendations due to the widespread flooding nature (generally
shallow) of major floods (i.e., in the order of the 100 year), the general inability of
structural measures to remove such large affected areas from flooding, the relative effect
of minor changes to the landscape (fences, roads, emergency flood berms) on flood
routing and potential flood damage, and the impracticality of halting development or re-
development on large tracts of land.
For existing development floods between the 10 and 25 -year return period frequency
will cause the majority of long term property damage and economic disruption to the
community. For these floods, which are more frequent than the 100 -year flood, which
generally occur in the areas adjacent to stream and river channels, versus the overflow
paths, the Maintenance and Management plus the Structural recommendations will
provide the highest return. The plan has developed and provided flood maps for 10
and 25 year flood levels in Appendix J and sediment removal guidelines in appendix G
to enable the communities to guide these recommendations.
Reducing future and current damages across the range of flood events will require a
combination of modified design guidelines and standards, land use zoning, related
planning methods, flood response and channel maintenance.
Cornerstone to these mitigation recommendations is community involvement and a
cooperative approach involving agencies and the public. Recommendations for this
element are contained in the Public Outreach.
EXECUTIVE SUMMARY I XIX
Implementation Strategy
The purpose of a CFHMP is to propose a suite of actions that will reduce flood hazards
over both the short and long term. In order to develop a long term strategy it was
necessary to understand the underlying causes and obstacles to overcome. The most
relevant new understanding attained during development of this plan, apart from the
large extent of flooding, was the pervasive and historic nature of floodplain and channel
modifications to suit agricultural practices and the legacy that alteration presents for
future urbanization of the floodplains.
The greatest return on investment is to increase flood hazard awareness. Public
Outreach recommendations, including distribution of this Plan, will extend the
awareness of past and future floodplain changes. Development of the Plan increased
awareness of information needs to fill data gaps, therefore, the Inventory
recommendations received the highest implementation priority.
Answering what and why certain actions will be effective are the critical components of
an implementation strategy for the plan. The answers to these questions differ for new
and existing development. For new development, a higher priority is placed on
Planning and Regulatory recommendations. For existing development, a significant
specific issue is channel sediment and invasive vegetation, and the need for a
maintenance program to manage their effects. Studies to quantify the impacts of
sediment at bridges and in the channels have been initiated as a result of this Plan
(Appendix G) so that Maintenance recommendations can be more effective.
Recommendations for structural alternatives primarily act to route more water into the
main channels and transfer flow capacity issues from one location to another, where
channel capacity should be higher and impacts less. Many of the recommended
structural projects are located in the Urban Growth Areas and should be implemented
sooner rather than later — before development precludes the opportunity for these
structural alternatives and flood hazard conditions are fixed in place. Some of the
structural recommendations in the plan address critical locations in these watersheds
where overflow paths for large floods originate. These overflow points are usually
activated during frequent floods. Once identified, the projects focus on these locations
to reduce the frequent chronic, wide spread flooding.
Other structural recommendations are located in already urbanized areas, and will be
implemented in conjunction with planned infrastructure or redevelopment activities as
the opportunity arises.
The most economic action after the provision of selected Inventory recommendations is
to translate the new awareness into design and planning guidelines and building
restrictions that mitigate flood effects. Jurisdiction planning measures should
acknowledge the legacy of agricultural conversion of floodplains to more flood -prone
development. Building code revisions that reduce future economic burden to the
citizens through flood insurance reduction should be pursued to avoid subsidizing other
more flood prone communities.
XX I Ahtanum -Wide Hollow Draft CFHMP
The next most economical action is to address existing flood issues specific to a cause
through wider actions such as channel maintenance.
The most expensive category is to address existing flood issues specific to a location.
Structural projects are typically very expensive; however, projects should be addressed
as soon as practical before the land is overdeveloped or under urbanization
development pressures. Structural projects, such as levees, also require maintenance
that is a continual commitment of resources, making them the least financially attractive.
In most cases the structural measures are more suited to 10 and 25—yr floods as they
encompass the majority of the community losses, as determined through economic
analysis.
A Funding Strategy is presented in Chapter 12.
Distribute
Meeting iIt
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AHTANUM -WIDE HOLLOW
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COMPREHENSIVE FLOOD HAZARD
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Comprehensive Flood Hazard Management Plan
(CFHMP) Process
Establish Community Participation
1
■ Establish CFHMP Advisory Committee
V
Inventory Physical Conditions
& Public W orkshops
i
Set Goals & Objectives
V
a) Determine the need for
.v flood hazard management measures
v Identify alternate flood hazard management
alternatives - structural & non - structural
-a
Review concurrent
N FEMA restudy flood maps
Evaluate alternative measures with respect to
goals & objectives, cost, benefits & impacts
1
Develop a flood hazard
management strategy
1
► Complete draft plan
Plan reviewed by local jurisdictions
1
Local SEPA review & approval
Submit final plan to local jurisdictions
for public hearing & adoption
4.
Submit plan to Ecology
'.ir:- ' . ,,- . ,.. .
.1. ,
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Historic Stream & Canal Locations VS Current Stream & Channel Locations
LEGEND
1911 stream location N
1911 canal location — — GGG� IN
2011 stream location . .- —= W \ E
2011 canal location '� ,
Contours S Il 1 c 1 1 4 hik . . • Nilio. , 11 i N fi i I wii f i iii r p - - • • • •
\ SUM►�ITVIEW _-
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An example of the progression of willows.
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Wide Hollow Creek Vegetation
Location: - - . # 1
Washington Ave. between 16th Ave & ;I .'. k._ NO lik
24th Ave. City of Yakima. - g
Issue:} I EMI i u _ ; it
Woody debris and other debris has /is '' I• 1 , 1
building up within the streams floodplain. ti• - '' 1 7, During high water events water flows pre - y I • , r .�i
maturely out of the stream channel to the `' - .1�'i }•
South. -
Remedy: II F ' 1106, ■ f _ lit
NM
Remove woody debris and other debris to
reduce flood risk. AI
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Wide Hollow Creek Vegetation
Location: , ` 4' • - . F - t
t: ' .r_ '' 1 L r r T .-
Washington Ave. between 24th Ave & , r ,� _ A .� l , � _ ; - ' ..
'" 1 r. t ,.� ' d
36th Ave. City of Yakima.
10 ,. 1 ! . . ` y +►.t c _ s . ;3 _
ISSUe: ■ ,.c,1 ` 1i - _ ll-' - -
Woody debris and other debris has/is .. ( .
irk N
building up within the streams floodplain. � ' �.' `` ; _! , I
During high water events water flows pre-
g p � — -
maturely out of the stream channel to the _ OF 1 i:
South. - ,., e mrs, t ■
_• W. ,- - �'
NM
Remedy:
Remove woody debris and other debris to .5, { �" R 4 , 1
reduce flood risk.
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. ' '•gy m . - ` 4 - - n ,'
Wide Hollow Creek Vegetation
Location: — I • 1 I .. I -. _. x t 1 .
1
�'
Washington Ave. between 40th Ave & a " $. y 4 - -.
48th Ave. City of Yakima t< I.., �_ ' •
4 Randall Park
Issue: ( - l ' I t
d l f • Woody debris and other debris has /is •. .-
building up within the streams floodplain. { i ri
Beavers have constructed a dam across ar,1 Ll '
the steam. During high water events water :. -'...
flows prematurely out of the stream chan- - ,s ' --
nel to the South an area currently under ,` I Y
development. ,v, .44
Remedy:
Remove woody debris and other debris,
pursue relocation of the beaver and re-
move the dam to reduce flood risk.
1 .- . t 1
�� -+4444 •• 411-..41111
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it
f . :r.. - . - : i : 770 * ,... .... z : 1 / /..7 : :, / '
4 . .%..4,,,ii ,<"*".' , :.,,,.g: .
Y• 11%.44or
t � w _ a ` \ -N --1 a. R w r a l 'y mil. • _ i; � .�.�� .� q - • 1 1zC ws is 'b.
- ...- @" - •A , ' x . •. 1 F 11 -_ •• y C�
sue:' > ?,7 y. -. � { i. + N., 1 „. 4-
J c A i' i a '
. . . bl. , , ` it -<. ,Yi?' .../ad •• L.5 i •
conveyance at this location will make floodwaters travel downstream faster, and with more
quantity, potentially causing higher flood hazards in more densely populated areas
downstream.
Other alternatives, such as lengthening the bridge (i.e. additional span), only improving the
conveyance to allow passage of the 10 year flow, or allowing this road to be impassable during
flood events, should be considered at this location. Also, raising of the road at this location,
without improvements to the bridge is not recommended as the backwater from a raised road
would likely cause water upstream to flow into Hatton Creek, which is even more undersized
for flow conveyance than Bachelor Creek.
Bachelor Creek - Bridge 97 25 Year Flow
Existing 100 yr flood plain water Waal t _
1410 . .17" -bt' fAITI
Md
t
w 1615
1 - ■
�' 6 - ... _ post -excavatlon water level
1610
FA Q`A ' ' • T `e
1406 — -
-- 010 400 600 800 1000 1100
StaIOn 161
10 Year How 100 Year Flow
illik .. .�- . water Waal 4
existing water Waal i
I p. -e avation water level
paatexcaaatlm water level
1610 -
1__
500 000 400 1000 1100 0 400 600 000 1000 T 1100
810044 00 814o0 (p
Figure 9 — Case Study Bridge 97 Profile
Bachelor Creek - Bridge 97
10 Year Floodplain r" b' ? ..r-l?
Existing '
Post excavation Ar
pm x .' •' ,"
"'F.
25 Year Floodplain •
Existing
Post excavation r
sin 4- . t a� t
't
a
.r .
100 Year Floodplain 9 0- i z
Existing •
Post excavation r
.R.J I
■
1 .1 1 s 5 , . ,......... di g
.
i
Figure 10 - Case Study Bridge 97 Floodplain
Shaw Creek
— ,
- :-1 —
t• i t I.° ,ca
4 • — , -` {
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P t l
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.• j -_ - � � �
• F
•
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Shaw Creek _Shaw Creek
AS Fi ure Al . 100 -Year Flood lain aedHollow Creek
m
9 p — Shaw - Wide Hollow Overflow _ Wide Hollow
0 _ for Existing Conditions
QFee1 g —Shaw Creek Overflow r---1 100 -Year Floodplaln
CONIULswwrafwd:. h ,,,, !
ir 1 ! , *. ,
i
.. ,
—
i• t ,_,_ ... ,„:' r _
•
{[` ? • _ .... J� II r
Li
r .
. * t ies . ■ i
^_at . _ 1
1iY dEaw �rYlMr I' Ii „al w- - - -
11ay F 4 Id Ndo aadYnr — d r , t -S7 • 7 - • ~ -
i I i.
• . . i _ • .
_ "I w
j S
■
Linn of Existing Conditions
\ \
11/0yr Fbodploln on Wade Hollow
s
1
v. - .
ifitiar, WEST Figure A2. 100 -Year Floodplain for Wde creel(
High Flow Bypass Alternative #1 Wde Creek
a 1 ' eel 9 YP Cl 100 -Year Floodplain
CONSULTANTS. INC
When Will It Flood?
Flood Chance % Chance
Frequency in any year Over 30 yr
(years) mortgage
10 10 out of 100 96%
25 4 out of 100 (5%
50 2 out of 100 46%
100 1 out of 100 26%
500 .2 out of 100 6%
FL 001) UA I SCHE_llA TIC
✓
BASE FLOOD 1 o FLOODPLAIN
FLOOD \ \AI - +FLOOD \ \AVFRINGE = BASE FLOOD / 1% FLOODPLAIN
SITRCHARGE NOT TO EX CEED 1.0 FEET
.
Rating Exampks
Type Bldg. Coverage Premium
-1' at BFE +1'
Pre - FIRM $100,000 $6834 $685* $683'
Post- FIRM $100,000 $2546 $816 $451
Mfg. Home $ 60,000 $1.42 $t)65 $410
Ulm A Zotie $100,000 submit submit $1191 r
Commercial $150,000 $6396 $1641 1711
X Zones $100,000 $441''' $441 *' 3 $441'"
'Pre -FIRM: EC not required, but can be elevation rated
'' In Unnumbered A Zone, $536 it ?'> ground; $276 it 3'>
* l`' Can be less with Preferred Risk Policy ;e.g,, $233 tar $100,000 uis,
Estimated Flood Insurance Costs
IN )IIO;, f _i ii i ( ) \,.•_'r 'l<M :tl r .P.-,•r _ill
S I(Nl ( H II 1 ill r<.' _'rY' ∎I \ i,..,ir AIr)!'r:,.I..r, •
J ft c1!i J`l Err — a J( ) I ,O ,1 1 7( 1
fr 1!!)(0': ,' III ,.,. � J _j,"i, 7 {i( )
1 1 fi. abole Err = ':;;"45 S. 3()
0 ft at BFE = S8 < ( $24
-'1 f_ _1 J J 1 = r
�r C f^ r _ � r 7
-.) ft _1JJf_. Err - 7_),. - ': 9 --, (
-5 ft - lbo'Je Err - :)O ; I I ,f _O
Below -Grade Crawlspaces & Insurance
Rating
Floor Joist
r _ BFE
Foundation Wall
L = 4 ft Maximum —T / Flood Vent
-- - Lowest Adjacent
- + :: Exterior Grade (LAG)
"44. __
D = 2 ft Maximum -,____
Crawlspace 'T ?rr -
Interior Grade ?
'
Figure 3 Requirements regarding Mow-grade crawlspace construction.
Flood Insurance Requirements for
Typical Residential Sites in ..,_,--:
L
. ...-..,-,,.. ��/ `
< ,
Example A: ��_ ;�. - � _- % Example E:
Property in SFHA „. se MO • Structure located in SFHA sio \\ I although on high bluff.
but structure is not 1:- =
Insurance apt required. \ ,` , Lender must require insurance
1 ,._ 1 but buyer can request LOMA.
7 :1" -- --
t _ \�. Upon approval of LOMA. buyer
1
` ` may receive insurance refund.
Example B:
I. \� Y .� _. Structure in SFHA but
substantially elevated ■ • i - : Special
on natural knoll. � ,.' .. �; Lu , -
Lender must require f / r ,r %"/�
insurance. Builder can ! � Flood � g
request Letter of Map 11": �' % �
Amendment ILOMAI. %i % / . �
Hazard _�
� A rea
_,_ . \y Structure in SFHA but
� subsla ntially elevated on fill.
.�\ • 111 Insurance initially required but
Structure C: buyer can request LOMA.
ure partially �'
Struct / �� Insurance may be refunded.
located in SFHA. %
Insurance always f i
-'!1
� .
required. -` j `/ i / `` 1
f! / -, �!� - a Example G.
n a 1 Structure in SFHA but
e - - �" �� " elevated through means
%/ ■ \
1 other than fill, e.g. posts.
/.��� • • • 1 pilings. piers. etc
\\ ` Insurance always required
Z� /..
Exam Ip a D: - ,- s
Structure located in 1� : : ::
SFHA but not elevated. „-----------__.,/,---------
`s
Insurance always required. ` ■ _ ` �" /.?� 1
� .. 1 \ '
ft `;
it:.;-- .` � \ \�
Enhanced Flood Risk Assessment
Analyses
. ..._ . , ,
... ...
• Enhancements could include:
• Risk Assessments at site- specific � , `4. r
locations - ! 1
• Incorporation of locally - provided -,
• inventory data (first -floor elevations -
and /or parcel data) Total Losses
W
• Additional sources of flood depth , S1- 4k
g rids •S20-53c
• SS4-
• Supplemental HAZUS analyses or :� p :.g. 8
other types of analyses Z "g -e ail. , I .,
Q : . f. co a s
4:It IP„'-, -
0
Total Losses
SO
S1 -4k
. :$5 -19k
0 S20 - 53k
0 554 -88k
Percent �hance of Floodin over a
30-yr Period Grid
• What is the likelihood that a specific location will flood at least once
duringa 30 -yr period?
• Usingthe PercentAnnual Chance of FloodingGrid as an input, perform
the fol lowing ca lcu lation:
1 — (1-p)
...where "p" = percentannual chance of floodingand "n" = 30
Percent Annual Chance Percent 30yr Chance
i jRi 1 � 1404 I 1
... �
t
' `'' ■ . .• IP,41itf
# - :
� y •20
r
IA ® 30 -
♦ 00.2 -2% X 40 -
�` �� 00
50 -
' : '' '
04 -6%
06 -8% MI 70 -80%
v i - y
•8- 10% •80 -90% •
0,41k _..,1 •,0%+ IM 90°k +
Fl oo d Ri R epor t El emen t s
Estimated Potential Losses for Flood Event Scenarios
Total Inventory 10% (10 2% (N0 -yr) 1% (100 -yr) 0.2% (500-yd Annualized (5 /K)
Estimated Sot Total Dollar Losses' Loss Ratio' - Dollar Loses Loss Ibfio" Dollar Losses' Los Wdot Della Loses" Loss Radial Dollar Losses' Loss Ratioi
Value
Residential
Building/Contents 594,495,000 77% 5:3,439,000 11% 513,571,300 14% 519,273,000 20% $32,925,000 35% 5176,030 0%
Commercial
Building/Contents 515,127,000 12% 52,112,000 14% 53,225,000 21% $4,337,000 29% 54,925,000 33% $109,000 1%
Other Building/Contents 5:3 073000 11% 51,663,000 :3% 2 :95 000 17% 4
r,/C 5 53,620,009 28% 55,430,000 ... 579,000 _-
Total Building/Contents 5122.695.000 100% 514.211.000 12% 5111.991,000 15% 527.230,000 22% 543.2110,000 35% 5364,000 0%
Business Disruption° N/A N/A $760,000 N/A 51.259.000 N/A $2.011.000 N/A 54.074.000 N/A 518,000 N/A
TOTAL* 5122.695A0D N/A 514,971,000 _ N/A _ 520.250,000 N/A 529,241,000 _ N/A 547,354.000 N/A 5332,000 N/A
11111:4".1111/1 41 . , ,
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