________________Dungeness River Comprehensive Flood Hazard Management Plan 2009 Dungeness River Comprehensive Flood Hazard Management Plan 2009 Clallam County, WA Prepared for Clallam County by the Dungeness Flood Hazard Advisory Committee, a subcommittee of the Dungeness River Management Team ________________Dungeness River Comprehensive Flood Hazard Management Plan 2009 Dungeness River Comprehensive Flood Hazard Management Plan 2009 Clallam County, WA This report should be cited as: Clallam County, 2009. Dungeness River Comprehensive Flood Hazard Management Plan. Clallam County, WA. Report available from: Hannah Merrill, Project Manager Clallam County Department of Community Development 223 East Fourth Street; Port Angeles, WA 98382 Report prepared by: Ann Seiter Technical Writing and Editing; Sequim, WA Pam Edens, GIS Specialist, Jamestown S’Klallam Tribe Dungeness Flood Hazard Advisory Committee: Robert Brown, Dungeness Beach Association Welden Clark, Dungeness River Audubon Center Al Moore, Dungeness riverside property owner Gary Dougherty, Clallam Conservation District Joe Holtrop, Clallam Conservation District Byron Rot, Jamestown S’Klallam Tribe Randy Johnson, Jamestown S’Klallam Tribe Michael Blanton, WA Department of Fish and Wildlife Hannah Merrill, Clallam County Dept. of Community Development Cathy Lear, Clallam County Dept. of Community Development Bob Martin, Clallam County Emergency Management Department Ross Tyler, Clallam County Roads Department Steve Tharinger, Clallam County Commissioner John Miller, Clallam County Dept. of Community Development Public outreach during the preparation of this document was provided by: Sam Gibboney, ISE Consultants; Port Townsend, WA The preparers would like to thank the contributions of data, reports, and photos from Clallam County staff, the Jamestown S’Klallam Tribe, Clallam Conservation District, and Dungeness River Audubon Center during the preparation of this document. Map Acknowledgements: Unless otherwise noted, map diagrams in this document were produced using the Jamestown S’Klallam Tribal GIS with data from the Tribe, Clallam County, and the Bureau of Reclamation. Cover Drawing and Figure 4-3 by: Amanda Kingsley, Port Townsend, WA ________________Dungeness River Comprehensive Flood Hazard Management Plan 2009 Table of Contents 1. EXECUTIVE SUMMARY .........................................................................................................1 2. WATERSHED CHARACTERISTICS AND PLANNING HISTORY............................................8 2.1 Description of the Watershed...............................................................................8 2.2 Watershed Planning and Implementation History ..........................................10 2.3 Other Key Plans and Related Studies................................................................12 3. GOALS AND PRINCIPLES FOR FLOOD HAZARD MANAGEMENT.................................14 3.1 Goals and Objectives for Flood Hazard Management in the Dungeness River.........................................................................................................................14 3.2 Principles of Comprehensive Flood Hazard Management Planning ..........15 4. FLOOD HISTORY AND IDENTIFICATION OF FLOOD HAZARDS .....................................17 4.1 Flood History and High Flow Events....................................................................17 4.2 Flood Damage History .........................................................................................21 4.3 Levees, Bridges, and other Modifications to the Dungeness River ..............23 4.4 Identification of Flood Hazard Areas.................................................................29 5. STRATEGIES AND RECOMMENDATIONS FOR FLOOD HAZARD REDUCTION .............41 5.1 General recommendations ................................................................................44 5.2 Analysis of alternatives and Reach-by-Reach Recommendations.............51 5.3 Summary of estimated costs for recommended actions..............................60 6. RELATIONSHIP TO REGULATORY AND SPECIES RECOVERY PROGRAMS ...................65 6.1 Clallam County Critical Areas Code.................................................................67 6.2 Clallam County Shoreline Master Program ......................................................73 6.3 Relationship to other County Ordinances........................................................74 6.4 Relationship to the Federal Endangered Species Act ...................................75 6.5 Dungeness River Reports .....................................................................................79 7. EMERGENCY MANAGEMENT...........................................................................................82 7.1 Preparing for a Flood............................................................................................83 7.2 During a Flood .......................................................................................................84 7.3 After a Flood ..........................................................................................................86 7.4 Tsunami Hazard Areas..........................................................................................87 7.5 Certification of Comprehensive Emergency Operations Plan .....................88 8. GLOSSARY AND ACRONYMS...........................................................................................89 APPENDICES .......................................................................................................................93 A. Plans and Studies in the Dungeness Watershed 1989-2008 B. Description of Structural Flood Control Options (from Tetra-Tech 2003 Draft Dungeness River Flood Hazard Management Plan) C. Delineation of the Dungeness Channel Migration Zone (Rot & Edens, 2008) (electronic) D. Recommended Land Protection Strategies for the Dungeness River Riparian Area (Hals and Dungeness River Restoration Work Group, 2003) (electronic) E. State Environmental Policy Act (SEPA) Checklist F. Public Outreach & Newspaper Articles G. Public Hearing Process H. Resolution for Plan Adoption ________________Dungeness River Comprehensive Flood Hazard Management Plan 2009 List of Figures Figure 2-1: General Location of the Dungeness Watershed ................................................10 Figure 4-1: Variation of mainstem channels of the Dungeness River near Taylor Cutoff Road..............................................................................................................................17 Figure 4-2: Major infrastructure on the Dungeness River .......................................................22 Figure 4-3: Illustrated risk of development in the Channel Migration Zone........................30 Figure 4-4: Kinkade Island ...........................................................................................................33 Figure 4-5: River reaches with CMZ, 100-yr flood plain, & identified hazards (4 reaches) ..34 Figure 6-1: Differences in protection standards among three types of critical areas under the Clallam County Critical Areas Code. ...................................................72 Figure 6-2: Example of how a structure may become a non-conforming use under the Critical Areas Code over time ..................................................................................81 Figure 7-1: Tsunami Hazard Zones in the Sequim-Dungeness area .....................................87 List of Tables Table 1-1: Summary of Flood Hazards by Reach ......................................................................4 Table 4-1: Flood Discharge and Probability.............................................................................18 Table 4-2: Top 20 flood events of record on the Dungeness River by total volume, peak flow, and daily mean flow, 1924-2008.....................................................................19 Table 4-3: Major levees and bank protection structures in the Dungeness River .............23 Table 4-4: Bridges spanning the lower Dungeness River .......................................................26 Table 4-5: Dungeness River reaches without riparian vegetation in 2003..........................27 Table 5-1: Summary of general recommendations ...............................................................43 Table 5-2: Analysis of alternatives and reach-by-reach recommendations .....................52 Table 5-3: Summary of estimated costs at 2009 levels...........................................................60 Table 5-4: Estimated Dungeness River Riparian Land Values ................................................63 Table 5-5: Additional breakout of land value estimates for selected portions of the Dungeness River riparian area..................................................................................64 Table 6-1: Regulations affecting flood plain and riparian management in the Dungeness River area ................................................................................................65 Table 6-2: Regulation of Dungeness River flood hazard areas in the Clallam County Critical Areas Ordinance...........................................................................................68 Table 6-3: Examples of policies and requirements of the Clallam County Shoreline Master Program for Dungeness River Shorelines....................................................73 Table 6-4: Excerpts from the three-year salmon recovery list for the Dungeness watershed