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NRCS DIMENSIONLESS UNIT HYDROGRAPH

NRCS DIMENSIONLESS UNIT HYDROGRAPH. q = Discharge at time 1 q p = Peak Discharge Q a = Accumulated Volume at time 1 Q = Total Volume = A Selected Time T o = Time from Beginning of the rise of the peak. 1.0. t l. q/q peak or Q a /Q. 3/8. 5/8. 0. 1. 0. 5. Time/T peak.

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NRCS DIMENSIONLESS UNIT HYDROGRAPH

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  1. NRCS DIMENSIONLESS UNIT HYDROGRAPH

  2. q = Discharge at time 1 • q p = Peak Discharge • Qa = Accumulated Volume at time 1 • Q = Total Volume • = A Selected Time • To = Time from Beginning of the rise of the peak 1.0 tl q/qpeak or Qa/Q 3/8 5/8 0 1 0 5 Time/Tpeak NRCS DIMENSIONLESS UNIT HYDROGRAPH

  3. PEAK FLOW

  4. Timing Considerations Lag Equation (Regression) Segmental Method (Physically Based)

  5. Lag Equation

  6. Segmental Method • Sheet Flow – Overland Flow • Shallow Concentrated Flow (Rills and Gullies • Open Channel or Pipe Flow (Conveyance System

  7. Precipitation Sheet flow SheetFlow Infiltration Sheet Flow

  8. ??? L Sheet flow SheetFlow Infiltration Sheet Flow

  9. Where: 0 < L < 100 ft S = slope ft/ft P = 2-year 24-hour Precipitation Sheet Flow

  10. Shallow Concentrated Flow

  11. Land Use Curves Slope in ft/ft Velocity in fps Shallow Concentrated Flow

  12. n = 0.07 n = 0.035 n = 0.06 Open Channel Flow

  13. Open Channel Flow Topen channel flow = Length/Velocity

  14. Time of Travel Tt = t1 + t2 + t3 Sheet Flow Shallow Concentrated Flow Open Channel or Pipe Flow

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