Sandy - Salmon River Confluence Fish Habitat Restoration Project (River Mile 37.3-38.4) Hydraulic Analysis and Design Alternative Assessment BAIR L.L.C. and Associates For Sandy River Basin Watershed Council Sandy-Salmon River Confluence Fish Habitat Restoration Project March 2018 Prepared by: Brian Bair Principal BAIR L.L.C. Hydraulic Analysis Amanda Jones P.E. Rowan Cooper-Caroselli Marjorie Wolfe P.E. Wolfe Water Resources I Sandy-Salmon River Confluence Fish Habitat Restoration Project Table of Contents Introduction .................................................................................................................................................. 1 Rehabilitation Design Approach ................................................................................................................... 4 Aerial Photo Analysis ................................................................................................................................ 4 LIDAR Topographic and Bathymetric Mapping ......................................................................................... 4 Flood Frequency Analysis .......................................................................................................................... 5 Hydraulic Analysis ..................................................................................................................................... 5 Results, Discussion and Design Alternatives ................................................................................................. 5 Geology and Geomorphology ................................................................................................................... 5 Aquatic Habitat Restoration Goals and Objectives ................................................................................... 5 Restoration Alternatives ........................................................................................................................... 7 Project Action Goals ................................................................................................................................ 10 Hydrology and Hydraulics ....................................................................................................................... 11 Aerial Photo Analysis .............................................................................................................................. 11 HEC-RAS Modeling .................................................................................................................................. 11 Model Setup and Parameterization .................................................................................................... 12 Results ................................................................................................................................................. 12 Preferred Design Alternative ...................................................................................................................... 21 Project and Structure Risk and Durability Assessment ............................................................................... 23 Potential Failure Mechanisms ................................................................................................................. 26 Stream Bed Scour ................................................................................................................................ 26 Increased Surface Area: Debris Loading ............................................................................................. 27 Buoyancy ............................................................................................................................................. 27 Burial and Abandonment .................................................................................................................... 27 Stream Channel Capture – Channel Avulsion ..................................................................................... 27 Water Elevation Response .................................................................................................................. 28 Structure Risk Summary ...................................................................................................................... 28 Project Cost Estimates ............................................................................................................................ 28 References .................................................................................................................................................. 31 Appendix A .................................................................................................................................................. 35 Appendix B .................................................................................................................................................. 37 Appendix C .................................................................................................................................................. 38 I Sandy-Salmon River Confluence Fish Habitat Restoration Project List of Figures Figure 1. Locator map for the Sandy River Basin, Clackamas County, Oregon. ............................................ 3 Figure 2. Locator map for the Sandy River Fish Habitat Restoration Project Area, river mile 35.6 to 36.5, Clackamas County, Oregon. .......................................................................................................................... 4 Figure 3. Alternative D Proposed Restoration Actions, Sandy-Salmon River Confluence Area. .................. 8 Figure 4. Alternative E Proposed Actions, Sandy-Salmon River Confluence Project Area. .......................... 9 Figure 5. Alternative F Proposed Actions, Sandy-Salmon River Confluence Project Area. ........................ 10 Figure 6. Existing condition modeled 2-year recurrence interval discharge overlain on LIDAR imagery show the extent of area occupied by flowing water Sandy River, Clackamas County, Oregon, river mile 37.3-38.4. .................................................................................................................................................... 13 Figure 7. Alternative D modeled 2-year recurrence interval discharge overlain on LIDAR imagery show the extent of area occupied by flowing water Sandy River, Clackamas County, Oregon, river mile 37.3- 38.4. ............................................................................................................................................................ 13 Figure 8. Alternative E modeled 2-year recurrence interval discharge overlain on LIDAR imagery show the extent of area occupied by flowing water Sandy River, Clackamas County, Oregon, river mile 37.3- 38.4. ............................................................................................................................................................ 14 Figure 9. Alternative F modeled 2-year recurrence interval discharge overlain on LIDAR imagery show the extent of area occupied by flowing water Sandy River, Clackamas County, Oregon, river mile 37.3- 38.4. ............................................................................................................................................................ 14 Figure 10. Existing condition modeled 5-year recurrence interval discharge overlain on LIDAR imagery show the extent of area occupied by flowing water Sandy River, Clackamas County, Oregon, river mile 37.3-38.4. .................................................................................................................................................... 15 Figure 11. Alternative D modeled 5-year recurrence interval discharge overlain on LIDAR imagery show the extent of area occupied by flowing water Sandy River, Clackamas County, Oregon, river mile 37.3- 38.4. ............................................................................................................................................................ 15 Figure 12. Alternative E modeled 5-year recurrence interval discharge overlain on LIDAR imagery show the extent of area occupied by flowing water Sandy River, Clackamas County, Oregon, river mile 37.3- 38.4. ............................................................................................................................................................ 16 Figure 13. Alternative F modeled 5-year recurrence interval discharge overlain on LIDAR imagery show the extent of area occupied by flowing water Sandy River, Clackamas County, Oregon, river mile 37.3- 38.4. ............................................................................................................................................................ 16 Figure 14. Existing condition modeled 100-year recurrence interval discharge overlain on LIDAR imagery show the extent of area occupied by flowing water Sandy River, Clackamas County, Oregon, river mile 37.3-38.4. .................................................................................................................................................... 17 Figure 15. Alternative D modeled 100-year recurrence interval discharge overlain on LIDAR imagery show the extent of area occupied by flowing water Sandy River, Clackamas County, Oregon, river mile 37.3-38.4. .................................................................................................................................................... 17 Figure 16. Alternative E