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Module # 13 Understanding the Key Instability Drivers to Inform Design/Decision Matrix

Module # 13 Understanding the Key Instability Drivers to Inform Design/Decision Matrix. Iowa’s River Restoration Toolbox Level 1 / Base Training. Key Design Parameters. Key Drivers. Floodplain Access Bank Height Ratio Entrenchment Bankfull Properties Area Discharge Width Depth

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Module # 13 Understanding the Key Instability Drivers to Inform Design/Decision Matrix

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  1. Module # 13Understanding the Key Instability Drivers to Inform Design/Decision Matrix Iowa’s River Restoration Toolbox Level 1 / Base Training

  2. Key Design Parameters

  3. Key Drivers • Floodplain Access • Bank Height Ratio • Entrenchment • Bankfull Properties • Area • Discharge • Width • Depth • Channel Evolution Stage • Dominant BEHI • Buffer Width

  4. Bank Height Ratio (BHR) BHR= LBH/Dbkf Lowest Bank Height (LBH) Bankfull Depth (Dbkf)

  5. Geomorphic Floodplain Bankfull Width Bankfull Depth Entrenched Channel

  6. Bankfull Geometry

  7. Channel Evolution Models Simon’s Modification of Schumm’s Model

  8. 100-Year Storm D100  Shear Stress = R S 2-Year Storm D2 Shear Stresses in Streams Channelized Stream Shear Stress Natural Stream Channelized Stream Discharge Return Interval 100-Year Storm D100 2-Year Storm D2 Natural Stream

  9. BEHI • Study Bank Height • Bankfull Height • Root Depth • Bank Angle • Surface Protection • Bank Material Adjustment • Stratification Adjustment • Bank Length • Reach Length

  10. Heading for Text Over a Photo Riparian Buffer

  11. Additional Key Drivers • Pattern/Geometry • Radius of Curvature • Meander Width Ratio • Pool to Pool Spacing • Width to Depth Ratio • Channel Length • Channel Slope • Stream Type • Presence of Headcuts/Bed Stability • Geomorphic Region/Geology • Sediment Supply/Bed Materials • Constraints

  12. Pattern/Geometry Wbkf = Bankfull Width Wblt = Belt Width Am = Amplitude Lm = Meander Wavelength Rc = Radius of Curvature

  13. Channel Slope

  14. Stream Type FP width / BKF Width BKF Width / Mean BKF Depth Well-defined point bars Veg. islands Heavy veg. Both banks erode in wide dirt canyon Confined, u-shaped valley VisualCues Gully in soft materials Often bedrock / log controlled Sed. islands Classifications from Rosgen, 1996

  15. Headcuts/Bed Stability • Caused by Excess Shear Stress • Often Triggered by Downstream Straightening of Channel • Will Propagate Upstream • Increases Channel Entrenchment

  16. Sediment Supply/Bed Materials

  17. Constraints

  18. Key Design Parameters

  19. Functional Status

  20. The Assessment Process

  21. Purpose of Decision Matrix Documentation of intuitive knowledge used in stream restoration design Establish logic used to determine appropriate practices & techniques Note that there are multiple “right answers”

  22. Channel Evolution Models Simon’s Modification of Schumm’s Model

  23. Decision Matrix – Channel Evolution

  24. Bank Height Ratio (BHR) BHR= LBH/Dbkf Lowest Bank Height (LBH) Bankfull Depth (Dbkf)

  25. Decision Matrix – Bank Height Ratio

  26. Decision Matrix - Slope

  27. Decision Matrix – Bankfull Width

  28. Design Assessment Tab

  29. Technique Ranking

  30. Module # 13Understanding the Key Instability Drivers to Inform Design/Decision Matrix Iowa’s River Restoration Toolbox Level 1 / Base Training

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