Snoqualmie at Fall City Reach Restoration Assessment Prepared by Dan Eastman, Project Manager and Fish Biologist Todd Hurley L.E.G, Geologist Will Mansfield P.E., Supervising Engineer Josh Latterell, Ph.D, Floodplain Ecologist Chase Barton P.E., L.G., Senior Engineer and Geologist Tenzing Thinley P.E., Project Engineer Mary Maier, Basin Steward Water and Land Resources Division Department of Natural Resources King County August 2011 Table of Contents Table of Reference Figures .......................................................................................................... ii Table of Reference Tables .......................................................................................................... iii I. Executive Summary ................................................................................................................... 1 II. Introduction ........................................................................................................................... 2 A. Study Goals and Objectives .................................................................................................... 2 B. Restoration Approach .............................................................................................................. 3 C. Feasibility Process Overview .................................................................................................. 3 III. Stage 1 – Investigation .......................................................................................................... 5 A. Data Collection and Compilation ............................................................................................ 5 1. Ground Surface Model and Imagery ........................................................................................5 2. Oxbow Assessment ..................................................................................................................8 3. Reach Hydrology, Flooding and Hydraulics ............................................................................8 4. Flood Protection Facilities ......................................................................................................10 5. Infrastructure Assessment ......................................................................................................13 6. Cultural Resources Assessment ..............................................................................................14 7. Landowner Outreach #1 .........................................................................................................14 B. Historic and Existing Conditions Analysis ........................................................................... 16 1. Approach ................................................................................................................................16 2. Geography and Land Use .......................................................................................................16 3. Hydraulics and Sediment Transport .......................................................................................19 4. River and Floodplain Geomorphology ...................................................................................20 5. Habitat 21 6. Impact Analysis and Summary ...............................................................................................24 C. Development and Application of an Ecofluvial Benefit Ranking Matrix ............................. 24 1. Establishing values and developing a scoring approach ........................................................24 2. Application of the Benefit Matrix ..........................................................................................31 D. Development of Alternatives Analysis Matrix ...................................................................... 31 1. Benefit Criteria .......................................................................................................................32 2. Feasibility Criteria ..................................................................................................................32 3. Cost Criteria ...........................................................................................................................32 E. Action Identification and Prioritization ................................................................................. 33 1. Primary 33 2. Secondary ...............................................................................................................................33 3. Tertiary 33 F. Prediction of Unconstrained Fluvial Response to Primary Actions ...................................... 34 1. Barfuse Levee Removal .........................................................................................................34 2. Hafner Revetment Removal ...................................................................................................36 3. Carlson Upper Levee Removal ..............................................................................................38 4. Aldair Levee Removal ............................................................................................................41 G. Other Secondary and Tertiary Actions Considered ............................................................... 41 1. Oxbow Assessment ................................................................................................................41 2. Reach-Wide Riparian Corridor Enhancement ........................................................................42 3. Huschle Oxbow ......................................................................................................................42 4. Lein Levee ..............................................................................................................................43 5. Keller Meander .......................................................................................................................43 IV. Stage 2 – Generation ........................................................................................................... 44 A. Site Alternatives Development .............................................................................................. 44 1. Barfuse Alternatives 1- 4 ........................................................................................................45 i 2. Hafner Alternatives 1- 2 .........................................................................................................57 3. Aldair Alternatives 1-3 ...........................................................................................................66 4. Carlson Upper Alternatives 1-2 ..............................................................................................76 B. Richmond Response Reach Alternatives 1-3 .........................................................................83 V. Stage 3 – Synthesis and Development ................................................................................ 88 A. Alternatives Analysis ............................................................................................................ 88 1. Ecofluvial benefit analysis .....................................................................................................88 2. Overall benefit analysis ..........................................................................................................89 3. Feasibility analysis .................................................................................................................91 4. Benefit and feasibility analysis ...............................................................................................92 5. Cost and benefit analysis ........................................................................................................93 B. Landowner Outreach #2 ........................................................................................................ 95 Rescoring Landowner Willingness .............................................................................................95 C. The Corridor Project –Opening Doors to Process ................................................................ 95 Reach-Scale, Project & Action Sequencing................................................................................98 D. Conclusion ........................................................................................................................... 103 References .................................................................................................................................. 104 Appendix A: Aerial oblique images collected @ ~ 26,000 CFS on December 2010. .......... 105 Appendix B - Criteria from Palmer et. al. .............................................................................. 114 Appendix C. Ecofluvial Benefit Scoring Data and Charts .................................................. 115 Appendix D. Results of initial cultural resources screening of the SAFC reach............... 119 Table of Reference Figures Figure 1: Vicinity Map with 2009 aerial photo showing study area. 2 Figure 2: Flow chart showing the feasibility process followed during this assessment. 4 Figure 3: Aerial photo (2009) showing the primary areas of assessment within the reach. 5 Figure 4: Digital Elevation Model (DEM) of the project reach generated from 2009 Lidar and 2004 flood study data. 6 Figure 5: Historic USGS Quadrangle Mapping (late 1800‟s) 6 Figure 6: 1936 photo of the project reach. 7 Figure