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SR 542 MP 33.3 Glacier Creek Preliminary Hydraulic Design Report

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SR 542 MP 33.3 Glacier Creek Preliminary Hydraulic Design Report SR 542 MP 33.3 Glacier Creek Preliminary Hydraulic Design Report Julie Heilman PE, State Hydraulic Engineer WSDOT Headquarters Hydraulics Section Cygnia F. Rapp, LG, LHG, Geomorphologist Hydrology Program, WSDOT Headquarters Hydraulics Section Dave Toften, PE, Hydraulic Engineer WSDOT North Central Region Hydraulics Section Simon Page, PE, Hydrologist Hydrology Program, WSDOT Headquarters Hydraulics Section SR 542 MP 33.3 Glacier Creek Preliminary Hydraulic Design Report June 2019 Americans with Disabilities Act (ADA) Information Materials can be made available in an alternative format by emailing the WSDOT Diversity/ADA Affairs Team at [email protected] or by calling toll free: 855-362-4ADA (4232). Persons who are deaf or hard of hearing may contact that number via the Washington Relay Service at 7-1-1. Title VI Notice to Public It is Washington State Department of Transportation (WSDOT) policy to ensure no person shall, on the grounds of race, color, national origin, or sex, as provided by Title VI of the Civil Rights Act of 1964, be excluded from participation in, be denied the benefits of, or be otherwise discriminated against under any of its federally funded programs and activities. Any person who believes his/her Title VI protection has been violated may file a complaint with WSDOT’s Office of Equal Opportunity (OEO). For Title VI complaint forms and advice, please contact OEO’s Title VI Coordinator at 360-705-7082 or 509-324-6018. Contents Figures .......................................................................................................................................................... iii Tables ........................................................................................................................................................... vi 1.0 Introduction and Purpose ......................................................................................................... 1 2.0 Site Assessment ......................................................................................................................... 3 2.1 Historical Summary of SR 542 Crossing Over Glacier Creek........................................................... 3 2.2 Risks and Impacts of Left Bank Levee on Channel Processes near Glacier Creek Bridge............... 8 3.0 Watershed Assessment ........................................................................................................... 12 3.1 Watershed Overview .................................................................................................................... 12 3.1.1 Flood Hydrology ..................................................................................................................... 15 3.1.2 Vegetation and Land Use Patterns ........................................................................................ 18 3.2 Mapped Floodplains ..................................................................................................................... 21 3.3 Geologic Setting ........................................................................................................................... 21 3.4 Sediment Supply ........................................................................................................................... 24 3.4.1 Large, Deep-Seated Landslides .............................................................................................. 26 3.5 Channel Morphology .................................................................................................................... 29 3.5.1 Channel Geometry and Floodplain Flow Paths ..................................................................... 29 3.5.2 Assessment of Sediment Transport ....................................................................................... 31 3.5.3 Channel Migration and Potential for Aggradation, Incision, and Headcutting ..................... 33 3.5.4 Channel Migration of North Fork Nooksack River ................................................................. 37 3.5.5 Existing LWM and Potential for Recruitment ........................................................................ 38 3.5.6 Sediment Size Distribution .................................................................................................... 39 4.0 Hydrology and Peak Flow Estimates ....................................................................................... 42 4.1 Model Development .................................................................................................................... 42 4.1.1 Model Review............................................................................................................................ 42 4.1.2 Model Update and Revision ...................................................................................................... 43 4.1.3 Literature Review of North Cascades Data ............................................................................... 43 4.1.4 Future Time Series .................................................................................................................... 43 4.2 Peak Flows .................................................................................................................................... 44 5.0 Hydraulic Analysis .................................................................................................................... 46 5.1 Methods ....................................................................................................................................... 46 SR 542 MP 33.3 Glacier Creek – Preliminary Hydraulic Design Report Page i 5.1.1 Model Topography ................................................................................................................ 46 5.1.2 Mesh ...................................................................................................................................... 47 5.1.3 Roughness .............................................................................................................................. 49 5.1.4 Boundary Conditions ............................................................................................................. 49 5.1.5 Limitations ............................................................................................................................. 49 5.2 Calibration Runs ........................................................................................................................... 50 5.3 Model Results ............................................................................................................................... 50 5.3.1 Existing Conditions – 115-Foot Gallup Bridge and 85-Foot Glacier Bridge ........................... 50 5.3.2 Proposed Conditions – 115-Foot Gallup Bridge and 880-Foot Glacier Bridge ...................... 55 5.3.3 Future Conditions – 115-Foot Gallup Bridge and 880-Foot Glacier Bridge without Levee ... 60 6.0 Considerations and Next Steps ............................................................................................... 65 References .................................................................................................................................................. 70 Appendix A Floodplain Transects ............................................................................................................... 74 Appendix B Analyzing Glacier Creek DEM Differences .............................................................................. 80 Appendix C Hydrology Model Results ........................................................................................................ 86 C.1 Gallup Creek ................................................................................................................................ 87 C.2 Glacier Creek ............................................................................................................................... 91 Page ii SR 542 MP 33.3 Glacier Creek – Preliminary Hydraulic Design Report Figures Figure 1 Vicinity map for Glacier Creek, State Route 542 MP 33.3. ........................................................ 2 Figure 2 Rapid bank erosion into Left Bank Levee approximately 1,000 LF upstream of Glacier Bridge in response to the November 26, 2018 flood (looking upstream). Photo taken November 27, 2018. .......................................................................................................................................... 5 Figure 3 Rapid bank erosion into Left Bank Levee approximately 1,000 LF upstream of Glacier Bridge in response to the November 26, 2018 flood (looking upstream). Photo taken November 27, 2018. .......................................................................................................................................... 6 Figure 4 Rapid bank erosion into Left Bank Levee approximately 1,000 LF upstream of Glacier Bridge in response to the November 26, 2018 flood (looking downstream at levee face). Photo taken by Cygnia Rapp on May 7, 2019. ..................................................................................... 6 Figure 5 The inlet of the slot canyon where debris floods originate as surge or dam-break floods located about 8 miles upstream of SR 542. Surge events augment storm-driven floods that worsen flooding and erosion risks of the Left Bank Levee, Glacier Creek Bridge, and SR 542 embankment. Photo taken by Gabe Ng via drone December 3, 2018. .................................... 7 Figure 6 Looking
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