June 2007 Upper Yakima River Update

Title
Page Number
Acknowledgments (PDF)
i
Table of Contents (This Page)
ii
List of Tables
vii
List of Figures
ix
List of Abbreviations
xi
Executive Summary
ES-1
Comprehensive Flood Hazard Management Planning
ES-2
1998 Upper Yakima CFHMP
ES-3
CFHMP Goals and Objectives ES-3
2007 Upper Yakima CFHMP Update
ES-5
Recommended Actions
ES-7
Project Implementation Strategy
ES-13
1. Introduction (PDF)
1-1
Background
1-1
Flooding Issues in Study Area
1-1
Principles of Flood Hazard Management
1-2
Authority and Scope for Yakima County CFHMP
1-2
Plan Development Process
1-4
Involving the Public and Affected Agencies
1-4
Defining Goals and Objectives
1-8
Collecting Data
1-8
Related Programs or Actions
1-11
Plan 2015 - Yakima Countys Comprehensive Plan
1-11
Yakima County Revised Flood Insurance Study
1-11
Flood Control Assistance Account Program
1-11
Funding
1-12
Requirements for CFHMPs
1-12
Applicant Eligibility
1-13
Maintenance Project Eligibility
1-13
Emergency Projects
1-14
Required Consultation with Other Agencies
1-14
2. Study Area Characteristics (PDF)
2-1
Yakima River Basin
2-1
Study Area Limits
2-2
Upper Reach - Yakima Canyon to Selah Gap
2-2
Middle Reach - Selah Gap to SR 24 Bridge
2-4
Lower Reach - SR 24 Bridge to Union Gap
2-5
Physical Characteristics
2-5
Climate
2-5
Hydrology
2-5
Geology
2-8
Soils
2-10
Wetlands
2-11
Fisheries and Wildlife
2-11
Vegetation
2-12
Water Quality
2-13
Socioeconomic Characteristics
2-15
Jurisdictional Boundaries
2-15
Population
2-15
Land Use
2-16
3. Previous Studies (PDF)
3-2
Revised Preliminary Yakima County Flood Insurance Study
3-2
Estimated Flood Flows
3-2
Hydraulic Computer Modeling
3-7
Flood Insurance Rate Maps, Floodway Maps, and Flood Boundary Maps
3-8
1970 Floodplain Information; Yakima and Naches Rivers
3-9
1973 Floodplain Information; City of Selah and Vicinity
3-9
1978 Yakima-Union Gap Flood Damage Reduction Report
3-10
Alternative 1 - No Action
3-10
Alternative 2 - Floodplain Management Alone
3-10
Alternative 3 - Floodplain Management with Additional Flood
Control Storage

3-10
Alternative 4 - Floodplain Management with Levees
3-12
Alternative 5 - Floodplain Management with Channel Modification
3-12
Alternative 6 - Purchase of Development Rights
3-12
Alternative 7 - Purchase of Floodway
3-12
Recommended Plan
3-13
1986 Yakima-Union Gap Flood Control Project
3-14
1991 Yakima River Flood Evaluation for Yakima County Diking District No. 1
3-14
Estimated Flood Flows
3-15
Review of Historical Floods
3-15
Issues Identified as Affecting Flood Risks
3-16
Assessment of Previous Studies
3-16
Key Results from Previous Studies
3-17
Recent Related Studies
3-18
1998 Department of Natural Resources Flood Plains, Salmon Habitat,
and Sand and Gravel Mining

3-19
1998 Department of Natural Resources Reclamation of
Flood-Plain Sand and Gravel Pits and Off-Channel Salmon Habitat

3-19
1998 Revisions to Yakima County Flood Insurance Study
3-19
Yakima River Floodplain Mining Impact Study (2002)
3-19
The Reaches Project Report (2002)
3-21
SR 24 Project Floodplain Consistency Report (2003)
3-23
Lower Naches River Coordination Project (2005)
3-23
Yakima County Mineral Resource Task Force (2006)
3-26
Conclusions - Additional Ongoing Efforts that Affect Flood Management
3-27
2003 Yakima River Basin Water Storage Feasibility Study
3-28
Subbasin Plan and Salmon Recovery
3-28
4. Yakima River Flooding Characteristics (PDF)
4-1
Common Flood Characteristics
4-1
Flood Magnitude
4-1
Flood Duration
4-2
Channel Migration
4-3
Sediment Transport and Deposition
4-4
Effects of Levees
4-8
Effects of Roads and Bridges
4-8
Effects of Reservoir Storage
4-9
Flood History
4-9
February 9, 1996, Flood
4-10
November 30, 1995, Flood
4-14
February 1995 Floods
4-14
November 26, 1990, Flood
4-15
December 27, 1980, Flood
4-18
December 2, 1977, Flood
4-18
December 4, 1975, Flood
4-19
January 16, 1974, Flood
4-19
March 14, 1972, Flood
4-20
May 29, 1948, Flood
4-20
December 23, 1933, Flood
4-21
Summary of Historical Floods
4-21
Historical Flood Improvement Projects
4-22
5. Flood Control Facilities and Programs (PDF)
5-1
Facilities Inventory
5-1
Yakima Levee Project
5-1
Public Law 84-99 Levees
5-2
Highways
5-4
Other Flood Control Works
5-6
Operation and Maintenance
5-11
Special Districts
5-11
Other Flood-Related Programs
5-11
United States Bureau of Reclamation, Yakima Project
5-12
Yakima Greenway Foundation
5-13
Yakima River Watershed Council
5-20
Yakima River Basin Water Enhancement Project
5-20
Yakima Subbasin Fish and Wildlife Planning Board (YSPB)
5-21
Yakima Basin Salmon Recovery Board Lead Entity
5-21
Yakima Basin Fish & Wildlife Recovery Board
5-21
6. Regulations (PDF)
6-1
Summary of Existing Regulations
6-1
County Regulatory Tools for Flood Hazard Management
6-8
City of Yakima
6-11
City of Union Gap
6-11
City of Selah
6-12
NPDES Phase II Municipal Stormwater Permits
6-13
Permitting Requirements
6-14
SEPA/GMA Integration
6-14
7. Alternative Analysis Approach (PDF)
7-1
Flooding Issue Identification
7-1
Flood Hazard Management Options
7-1
Nonstructural Measures
7-1
Structural Measures
7-3
Alternative Analysis and Selection
7-4
Considerations for Evaluating Alternatives
7-4
Alternative Selection
7-7
8. Analysis of Flood Mitigation Alternatives (PDF)
8-1
LR5 - Aggradation/Reduced Flood Capacity Upstream of SR 24 Bridge;
Flood Damage to SR 24 Bridge, Yakima Regional Wastewater Treatment
Plant Levee, and DID #1 Levee (1)


8-3
MR2 - Yakima Beech Street Gravel Pit Levee (2), and
UR5 - East Selah Gravel Pit Levee (24)

8-25
LR3 - Increased Flood Elevation near Union Gap (3)
8-30
LR7 - Capture of Edler Ponds (4)
8-37
RW1 - Floodplain Mapping (5)
8-38
RW20 - Loss of Channel Capacity due to Sediment Accumulation (6)
8-42
NA1 - Bedload Movement and Channel Instability of Naches River (7)
8-43
RW13 - Funding for Flood Control Work and Restoration Projects (8)
8-44
RW6 - Public Disclosure of Floodplain Status (9)
8-45
RW12 - Protection of State and County Roads (10)
8-46
RW3 - Channel Migration (11), LR1 - Erosion of Agricultural Lands (15), and
UR1 - Erosion of Agricultural Land (22)

8-49
RW9 - Diversity of Opinions Relating to River Management (12), and
RW8 - County Policy on Flood Hazard Management (17)

8-50
RW4 - Flood Hazard Ordinance (13), and
RW5 - Revision and Consistency of Critical Areas Ordinance (25)

8-51
RW2 - Loss of Fisheries Habitat and Riparian Areas (14), and
MR8 - Borrow Pit Levee Upstream of Terrace Heights Bridge (31)

8-61
RW17 - Existing Structures in the Floodplain (16)
8-64
RW16 - Operation and Maintenance of Flood Control Facilities (18)
8-67
RW10 - Acquisition/Preservation of Floodplain Open Space (19)
8-70
RW19 - Flood Warning and Emergency Response (20)
8-73
RW18 - Community Rating System (21), and
RW7 - Flood Insurance and Public Education (28)

8-79
RW15 - Use of Geographic Information (GIS) Data (23)
8-84
OSA1 - Continued Flood Damage Outside the CFHMP Study Area (26)
8-88
MR6 - Flood Damage to Greenway path Near Boise Cascade Pond (32)
8-89
LR6 - Spring Creek Backwater Flooding (29)
8-92
MR7 - Flood Damage to Robertson Landing (30), UR3 - Flood Damage
to Harlan Landing (33), and UR4 - Inundation of Elks Golf Course (34)

8-94
9. Funding Options (PDF)
9-1
Funding Sources
9-2
County Administrative Options
9-2
External Funding Sources
9-10
Funding Source Evaluation
9-23
Evaluation Criteria
9-23
Programs to be Funded
9-24
Large Project Funding Strategy
9-27
References (PDF)
R-1