Bank Stability and Toe Erosion Model (BSTEM) Analysis of Arroyo de la Laguna Associated with Zone 7’s Stream. WISE Program Virginia Mahacek Valley & Mountain Consulting for West Yost Associates Alameda Creek Watershed Sediment Forum April 23, 2008
Introduction • Study Context – Stream. WISE program • Initial Geomorphic Investigation – Spring 2007 • Preliminary Concepts – Summer 2007 • BSTEM Modeling and Refinement – Fall 2007 • Potential ADLL Project Areas 18 -Mar-18 2
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 18 -Mar-18 3
Bed and Bank Problems § § Conceptual Projects § Locations § Treatment Types Bed Incision Toe Erosion Bank Failures Debris Jams 4
BSTEM Sites Location River Station Sub-Reach Description Average Local Bed Slope Channel Status ft/ft 47115 US of Bernal 0. 0008 Constructed 42069 Bernal to B-2 -1 0. 0045 Degrading 35895 B-2 -1 to Castlewood 0. 0025 Degrading/Widening 32424 Castlewood to Verona 0. 0022 Degrading/Widening 29893 Castlewood to Verona 0. 0029 Degrading/Widening 22845 DS of Verona; SFPUC 0. 0014 Aggrading/Widening
River Station 47115 Left (East) Bank Clear Lake clay soils q Holocene basin deposits q
River Station 42069 Left (East) Bank Sycamore silt loam q Holocene stream terrace q Latest Holocene alluvial fan q
River Station 35895 Right (West) Bank Zamora silt loam q Holocene stream terrace q Early Quaternary or older bedrock q
River Station 32424 Left (East) Bank Yolo Loam q Latest Holocene stream terrace q
River Station 29893 Right (West) Bank Yolo loam q Holocene stream terrace q
River Station 22845 Left (East) Bank Yolo loam q Latest Holocene stream terrace q
BSTEM Version 4. 1 • Quantitative, predictive tests of… – Hydraulic Scour – Geotechnical Failure • Surface water • Water-table • Vegetation • Bank height • Bank composition • Bank angle Layer 1 Layer 2 Layer 3 Toe material http: //www. ars. usda. gov National Sedimentation Laboratory
Model Inputs • • Topography/Geometry Stratigraphy Bed and Bank Materials Groundwater Vegetation Hydrograph Duration Water Stage 18 -Mar-18 13
Modeled Treatments Treatment Category Treatment Type Placed Rock Bank Protection Placed Rock Toe-of-Bank Protection Geoweb Toe-of-Bank Protection Reduced Bank Height and Angle Bank Strengthening 18 -Mar-18 Bank Drainage Vegetative Bank Strengthening 14
Model Output • Toe Erosion – occurrences – retreat distances – eroded volumes • Bank Failure – occurrences – eroded volumes – peak or drawdown conditions 18 -Mar-18 15
POTENTIAL ADLL PROJECT AREAS Initial Geomorphic Inventory + BSTEM Modeling = Potential Project Areas to be considered by Stream. WISE 16
Questions? 18 -Mar-18 17
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