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VII. Effects Of Transportation Structures On Fluvial Systems

VII. Effects Of Transportation Structures On Fluvial Systems. A. Riverine Systems 1. Analytical Tools to Evaluate Impacts 2. Single Channel 3. Braided 4. Meandering B. Non-Riverine Systems 1. Alluvial Fans/Distributary Flow 2. Sheet Flow 3. At-Grade Crossings

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VII. Effects Of Transportation Structures On Fluvial Systems

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  1. VII. Effects Of Transportation Structures On Fluvial Systems A. Riverine Systems 1. Analytical Tools to Evaluate Impacts 2. Single Channel 3. Braided 4. Meandering B. Non-Riverine Systems 1. Alluvial Fans/Distributary Flow 2. Sheet Flow 3. At-Grade Crossings C. Recommended Best Management Practices

  2. VII. Effects Of Transportation Structures On Fluvial Systems A. Riverine Systems 1. Analytical Tools to Evaluation Roadway Impacts: • Sediment Transport Function Qs = W n1.77 V4.32 G0.45 Y-0.3 D50-0.61 • Lane’s Relation: Q S  QS D50 • Manning’s Equation V (A) = 1.49 n-1 R0.67 S0.5 (W * d)

  3. Analysis Increase V & D ordecrease upstream Decrease V & D Decrease Qs Change Slope (+/-) VII. Effects Of Transportation Structures On Fluvial Systems A. Riverine Systems 2. Single Channel Streams • Lateral Impacts • Narrow the Floodplain or Channel • Widen the Channel • Prevent Channel Movement • Vertical Impacts • Base Level Adjustments (+/-)

  4. Analysis Same as single channel Increase Q, V & D Increase Qs Upstream impacts Same as single channel VII. Effects Of Transportation Structures On Fluvial Systems A. Riverine Systems 3. Braided Channels • Lateral Impacts • Narrow/Widen Channel • Cut Off Braids • Concentrate Flow • Obstruction • Vertical Impacts • Base Level Adjustments (+/-)

  5. Analysis Roadway approach Channel training VII. Effects Of Transportation Structures On Fluvial Systems A. Riverine Systems 4. Meandering Streams • Lateral Impacts • Prevents Natural Channel Migration

  6. Rivers

  7. Analysis Shift fan location Discharge changes Cross above apex or below avulsions Maintenance Induce degradation VII. Effects Of Transportation Structures On Fluvial Systems B. Non-Riverine Systems 1. Alluvial Fan Impacts • Limit Channel Movement • Upstream Channel Location • Crossing Alignment • Vertical Impacts • Long-Term Aggradation

  8. B. Non-Riverine Systems 2. Sheet Flow Areas: Culverts Concentrate Flow Perpendicular Alignment Identify Flow Paths Vertical Impacts Invert Elevation Analysis Induce degradation Downstream and upstream damages Roadways become drainage paths Too low - headcut VII. Effects Of Transportation Structures On Fluvial Systems

  9. Analysis Lower n, Increase V Decrease S Downstream drop Same as single channel VII. Effects Of Transportation Structures On Fluvial Systems B. Non-Riverine Systems 3. At-Grade Crossings • Paved • Wide and Flat • Widen or Narrow Channel

  10. VII. Effects Of Transportation Structures On Fluvial Systems C. Recommended Best Management Practices 1. Don’t obstruct or narrow main channel 2. Mimic bankfull width and depth 3. Relief culverts 4. Match natural grade 5. Energy dissipation 6. Inspection, maintenance and documentation

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