bank stability and toe erosion model (bstem) analysis of arroyo de la laguna associated with zone...
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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
forWest Yost Associates
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Introduction
• Study Context– StreamWISE program
• Initial Geomorphic Investigation– Spring 2007
• Preliminary Concepts– Summer 2007
• BSTEM Modeling and Refinement– Fall 2007
• Potential ADLL Project Areas
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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
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Bed and Bank Problems
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Conceptual Projects
Bed Incision Toe Erosion Bank Failures Debris Jams
Locations Treatment
Types
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BSTEM Sites
LocationSub-Reach Description
Average Local Bed
Slope Channel StatusRiver
Station ft/ft
47115 US of Bernal 0.0008 Constructed
42069 Bernal to B-2-1 0.0045 Degrading
35895B-2-1 to Castlewood 0.0025 Degrading/Widening
32424Castlewood to Verona 0.0022 Degrading/Widening
29893Castlewood to Verona 0.0029 Degrading/Widening
22845DS of Verona; SFPUC 0.0014 Aggrading/Widening
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River Station 47115 Left (East) Bank
Clear Lake clay soils Holocene basin deposits
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River Station 42069 Left (East) Bank
Sycamore silt loam Holocene stream terrace Latest Holocene alluvial fan
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River Station 35895 Right (West) Bank
Zamora silt loam Holocene stream terrace Early Quaternary or older bedrock
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River Station 32424 Left (East) Bank
Yolo Loam Latest Holocene stream terrace
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River Station 29893 Right (West) Bank
Yolo loam Holocene stream terrace
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River Station 22845 Left (East) Bank
Yolo loam Latest Holocene stream terrace
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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 3Toe material
http://www.ars.usda.gov
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Model Inputs
• Topography/Geometry• Stratigraphy • Bed and Bank Materials• Groundwater• Vegetation• Hydrograph Duration• Water Stage
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Modeled Treatments
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Treatment Category Treatment 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
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Model Output
• Toe Erosion – occurrences– retreat distances– eroded volumes
• Bank Failure – occurrences– eroded volumes– peak or drawdown conditions
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Initial Geomorphic Inventory
+
BSTEM Modeling
=
Potential Project Areas to be considered by
StreamWISE
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POTENTIAL ADLL PROJECT
AREAS
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Questions?
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