Page 1 2/7/2008 McGlinn Island Causeway & Jetty Habitat Restoration Feasibility Phase 1: Establishing the Viability of Hydraulic Connectivity between Skagit & Padilla Bays Puget Sound, Washington January 2008 Contributing authors: Steve R. Hinton W. Gregory Hood Nora E. Kammer Eric Mickelson Skagit River System Cooperative Zhaoqing Yang Tarang Khangaonkar Battelle Pacific Northwest National Laboratory Eric E. Grossman Andrew Stevens Guy Gelfenbaum U.S. Geological Survey Photo Courtesy of Washington State Department of Ecology, 1994 Oblique Photo Series 1 Page 2 2/7/2008 Contents Introduction ............................................................................................................................................ 5 Goals & Objectives ................................................................................................................................. 7 Problem Statement ............................................................................................................................ 7 Problem [1]: Salinity Gradient ........................................................................................................... 7 Problem [2]: Salmonid Rearing Capacity .......................................................................................... 8 Goal Statement .................................................................................................................................. 8 Objectives ........................................................................................................................................... 9 Historic Context .................................................................................................................................... 11 Habitat Effects of ACOE Swinomish Channel Projects ..................................................................... 12 History of ACOE Swinomish Channel Projects ................................................................................. 13 The Navigation Channel ................................................................................................................... 13 North Dike ........................................................................................................................................ 15 McGlinn‐Island‐to‐Mainland Dike (AKA “The Causeway”) .............................................................. 15 South Jetty ...................................................................................................................................... 16 McGlinn‐to‐Goat‐Island Jetty (AKA “The Jetty”) ............................................................................. 16 Present Day Channel Conditions .......................................................................................................... 18 Methods & Data Collection .............................................................................................................. 18 Results & Analysis ................................................................................................................................. 20 Tides ................................................................................................................................................. 20 Currents ............................................................................................................................................ 22 Mooring Site Water Column Properties ........................................................................................... 25 Spatial Patterns in Water Properties ............................................................................................... 26 Hydrodynamic Modeling ...................................................................................................................... 29 Model Set‐up .................................................................................................................................... 29 Model Validation I. (6 to 23 June 2005) .......................................................................................... 32 Model Validation II (1 to 30 May 2006) .......................................................................................... 35 Restoration Alternatives Analysis ......................................................................................................... 44 Summary and Conclusions ................................................................................................................... 51 Conceptual Design ................................................................................................................................ 53 References ............................................................................................................................................ 54 Appendix A ........................................................................................................................................... 56 2 Page 3 2/7/2008 Figures Figure 1. Historic Skagit Geomorphic Delta (Collins, 2001) .................................................................... 5 Figure 2. Location of the Swinomish Channel Causeway to McGlinn Island & Jetty to Goat Island. ........................................................................................................................................................... 7 Figure 3. Project feasibility decision tree. ..................................................................................... 10 Figure 4. Pre- and post-dredge habitat conditions for the Swinomish Channel and environs. .................................................................................................................................................................... 11 Figure 5. US Coast and Geodetic Survey map (1892).. .............................................................. 12 Figure 6. Swinomish Channel project components ..................................................................... 14 Figure 7. Detail of existing (1903) and proposed North Dike. ..................................................... 15 Figure 8. Detail of existing (1903) wattled pile and proposed rock McGlinn-Island-to- Mainland Dike.. ......................................................................................................................................... 16 Figure 9. Dikes and Navigation Channel Chronology. ............................................................... 17 Figure 10. The tripod deployed at the north end of the Swinomish Channel ..................................... 19 Figure 11. Comparison of water levels between the north and south sites (top panel). ......... 21 Figure 12. Time-series of u (positive eastward), v (positive northward), and w (positive up) velocity components, speed and direction for the top 1 m of the water column. ............................ 23 Figure 13. Representative ADP water velocity data. .................................................................... 24 Figure 14. North (left) and south (right) Swinomish Channel time-series of low-pass filtered, along-channel velocity (top panels) for the surface (blue line), depth-averaged (red line) and bottom (black line) portion of the water column. .................................................................................. 24 Figure 15. Salinity time-series at the surface mooring (blue lines) and at the south channel site (red lines). .......................................................................................................................................... 25 Figure 16. Normalized histogram of salinity at the mooring site. ............................................... 26 Figure 17. Cross-sections of salinity between the Rainbow Bridge and station 4B (seaward of the Fish Passage) at two different tidal elevations.. ....................................................................... 28 Figure 18. FVCOM Model Grid for Skagit Bay Including Swinomish Channel. ...................... 30 Figure 19. Hydrodynamic Model Bathymetry for Skagit Bay. ............................................................ 31 Figure 20. Comparison of tidal elevations and velocities at Skagit Bay station. ...................... 32 Figure 21. Comparison of tidal elevations and velocities at North Fork Skagit River station. .................................................................................................................................................................... 33 Figure 22. Salinity comparisons at Skagit Bay and North Fork Skagit River stations. .......... 33 Figure 23. Surface salinity at ebb (top) and flood (bottom) tides. ............................................ 34 Figure 24. Locations of USGS monitoring stations. .................................................................. 35 Figure 25. Skagit River flow at Mount Vernon gage (RM 15.7) .................................................. 36 Figure 26. Leaking jetty at the south end of the Swinomish Channel. ...................................... 37 Figure 27 Comparisons of tidal elevations (MSL) and velocities at Station S1. ....................... 38 Figure 28. Comparisons of tidal elevations (MSL) and velocities at Station S2. ..................... 39 Figure 29. Predicted water surface elevations west and east of the jetty ................................ 40 Figure 30. Estimated leaking flow through the jetty.. .................................................................... 40 Figure 31. Comparisons