1. Bank Stability and Toe Erosion Model (BSTEM) Analysis of Arroyo de la Laguna Associated with Zone 7’s StreamWISE Program Alameda Creek Watershed Sediment Forum April 23, 2008 Virginia Mahacek Valley & Mountain Consulting for West Yost Associates

2. Introduction Study Context –StreamWISE program Initial Geomorphic Investigation –Spring 2007 Preliminary Concepts –Summer 2007 BSTEM Modeling and Refinement –Fall 2007 Potential ADLL Project Areas 9-May-152

3. Approach Representative Sites on ADLL –Initial Investigation Results Existing Geomorphic Conditions –Estimates of Parameters Future Stormwater Flows –Hydrographs with COL (provided by WYA) Alternative Treatments –BSTEM Scenarios 9-May-153

4. Bed and Bank Problems 4 Conceptual Projects  Bed Incision  Toe Erosion  Bank Failures  Debris Jams  Locations  Treatment Types

5. BSTEM Sites Location Sub-Reach Description Average Local Bed SlopeChannel Status River Station ft/ft 47115US of Bernal0.0008Constructed 42069Bernal to B-2-10.0045Degrading 35895 B-2-1 to Castlewood0.0025Degrading/Widening 32424 Castlewood to Verona0.0022Degrading/Widening 29893 Castlewood to Verona0.0029Degrading/Widening 22845 DS of Verona; SFPUC0.0014Aggrading/Widening

6. River Station 47115 Left (East) Bank  Clear Lake clay soils  Holocene basin deposits

7. River Station 42069 Left (East) Bank  Sycamore silt loam  Holocene stream terrace  Latest Holocene alluvial fan

8. River Station 35895 Right (West) Bank  Zamora silt loam  Holocene stream terrace  Early Quaternary or older bedrock

9. River Station 32424 Left (East) Bank  Yolo Loam  Latest Holocene stream terrace

10. River Station 29893 Right (West) Bank  Yolo loam  Holocene stream terrace

11. River Station 22845 Left (East) Bank  Yolo loam  Latest Holocene stream terrace

12. BSTEM Version 4.1 Quantitative, predictive tests of… –Hydraulic Scour –Geotechnical Failure Surface water Water-table Vegetation Bank height Bank composition Bank angle National Sedimentation Laboratory Layer 1 Layer 2 Layer 3 Toe material http://www.ars.usda.gov

13. Model Inputs Topography/Geometry Stratigraphy Bed and Bank Materials Groundwater Vegetation Hydrograph Duration Water Stage 9-May-1513

14. Modeled Treatments 9-May-1514 Treatment CategoryTreatment Type Bank Protection Placed Rock Bank Protection Placed Rock Toe-of-Bank Protection Geoweb Bank Protection Geoweb Toe-of-Bank Protection Reduced Bank Height and Angle Bank Strengthening Bank Drainage Vegetative Bank Strengthening

15. Model Output Toe Erosion –occurrences –retreat distances –eroded volumes Bank Failure –occurrences –eroded volumes – peak or drawdown conditions 9-May-1515

16. Initial Geomorphic Inventory + BSTEM Modeling = Potential Project Areas to be considered by StreamWISE 16 P OTENTIAL ADLL P ROJECT A REAS

17. Questions? 9-May-1517