Lower Skykomish River Reach-Scale Plan
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July 2017 Sustainable Lands Strategy Lower Skykomish River Reach-scale Plan Snohomish County Department of Public Works, Surface Water Management and the Executive Committee of the Sustainable Lands Strategy July 2017 Sustainable Lands Strategy Lower Skykomish River Reach-scale Plan Prepared for Prepared by Snohomish County Anchor QEA, LLC Department of Public Works 720 Olive Way, Suite 1900 Surface Water Management Seattle, Washington 98101 3000 Rockefeller Ave., M/S 607 Everett, Washington 98201 and The Executive Committee of the Sustainable Lands Strategy Recommended Citation Snohomish County Surface Water Management and the SLS Executive Committee, 2017. Lower Skykomish River Reach-scale Plan. Snohomish County Department of Public Works and the Executive Committee of the Sustainable Lands Strategy. Everett, Washington. Project Number: 160723-03.01 ACKNOWLEDGEMENTS Project Team Snohomish County Staff Consultants Steve Britsch Aaron Kopp Anchor QEA, LLC, Lynn Turner Zach Brown Frank Leonetti Carlstad Consulting, Cynthia Carlstad Ann Bylin Beth Liddell Dan Evans Consulting, Dan Evans Chien Chang Dave Lucas Donald “Kit” Crump Mike Rustay Brett Gaddis Erik Stockdale Jessica Hamill Lauren Tracy Mary Hurner David Wilson Linda Neunzig Reviewers The Nature Conservancy Tulalip Tribes Jenn Baker Julie Morse Kurt Nelson Morgan Ruff Heather Cole NOAA Restoration Center Snohomish Conservation District Paul Cereghino Cindy Dittbrenner Kate Riley Ducks Unlimited C.K. Eidem SLS Executive Committee Klesick Family Farm Ducks Unlimited Tristan Klesick, Co-Chair C.K. Eidem Tulalip Tribes Snohomish Conservation District Terry Williams, Co-Chair Monte Marte Pilchuck Audubon Society Lord Hill Farms Kristin Kelly, Secretary-Treasurer Dave Remlinger Cherry Lane Farms Stillaguamish Tribe Brian Bookey Shawn Yanity Cover photo courtesy of the Washington State Recreation & Conservation Office SLS Lower Skykomish River Reach-scale Plan i July 2017 TABLE OF CONTENTS Executive Summary ..................................................................................................................... ES-1 Purpose and Background ...................................................................................................................................... ES-1 Summary of Conditions in the Lower Skykomish River Reach ................................................................ ES-1 Concerns for Agriculture, Salmon Habitat, and Flood Damage Reduction ........................................ ES-2 F3 Multi-benefit Projects ........................................................................................................................................ ES-4 Collaboration in the Reach .................................................................................................................................... ES-5 Measuring Success and Next Steps ................................................................................................................... ES-5 1 Background ................................................................................................................................. 1 1.1 Plan Focus .............................................................................................................................................................. 2 1.2 Plan Purpose and Goals .................................................................................................................................... 3 1.3 How the Plan Will be Used .............................................................................................................................. 3 1.4 Integrated, Multi-benefit Approach to Planning .................................................................................... 4 1.4.1 Sustainable Lands Strategy .............................................................................................................. 5 1.4.2 Collaboration in the Reach .............................................................................................................. 6 1.4.3 Progress in the Reach ........................................................................................................................ 7 2 Conditions in the Lower Skykomish River Reach .............................................................. 9 2.1 Geographic Overview of the Reach ........................................................................................................... 10 2.1.1 River Subreaches .............................................................................................................................. 10 2.2 Property Ownership and Land Use ............................................................................................................ 16 2.2.1 Zoning ................................................................................................................................................... 16 2.2.2 Land Use .............................................................................................................................................. 18 2.2.3 Land Cover Changes ....................................................................................................................... 21 2.3 Geomorphic Conditions ................................................................................................................................. 22 2.3.1 Channel Migration ........................................................................................................................... 24 2.3.2 Side Channels ..................................................................................................................................... 27 2.3.3 Avulsion Risks .................................................................................................................................... 27 2.3.4 Summary of Geomorphic Conditions and Future Assessment Needs ......................... 29 2.4 Hydrologic and Hydraulic Conditions and Flood Profile .................................................................. 29 2.4.1 Hydrologic Conditions .................................................................................................................... 30 2.4.2 Major Runoff Inputs and Controls ............................................................................................. 31 2.4.3 Historic Flood Events ....................................................................................................................... 35 2.4.4 Flood Studies...................................................................................................................................... 38 2.4.5 Expectations Associated with Climate Change ..................................................................... 40 SLS Lower Skykomish River Reach-scale Plan i July 2017 2.5 Water Quality Conditions .............................................................................................................................. 42 2.5.1 Washington State Water Quality Standards .......................................................................... 42 2.5.2 Existing Water Quality Impairments .......................................................................................... 42 2.5.3 Ecology’s River and Stream Water Quality Monitoring ..................................................... 44 2.5.4 Continuous Temperature Monitoring ...................................................................................... 45 2.5.5 Expectations Associated with Climate Change ..................................................................... 49 2.6 Habitat Conditions ........................................................................................................................................... 52 2.6.1 Existing Habitat Conditions .......................................................................................................... 53 2.6.2 Expectations Associated with Climate Change ..................................................................... 55 3 Farm, Fish, and Flood Related Considerations ................................................................ 57 3.1 Considerations for Agriculture .................................................................................................................... 57 3.1.1 Current Agricultural Operations ................................................................................................. 57 3.1.2 Challenges for Current Agricultural Operators ..................................................................... 63 3.1.3 Opportunities to Strengthen and Support Agricultural Viability ................................... 69 3.2 Considerations for Salmon Habitat and Water Quality ..................................................................... 77 3.2.1 Opportunities for Habitat Improvement ................................................................................. 78 3.2.2 Opportunities for Restoration and Protection of Water Quality .................................... 81 3.3 Considerations for Flood Risk Reduction ................................................................................................ 82 3.3.1 Sultan to Monroe Flood Risk/Repetitive Loss Areas (Subreaches 2, 3, and 4) ......... 83 3.3.2 Tualco Valley Flood Risk/Repetitive Loss Areas (Subreach 1) ......................................... 84 3.3.3 Opportunities for Flood Risk Mitigation .................................................................................. 84 3.4 Actions