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Retention/Detention Pond Routing - Up to 24 Hour Storm:
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*Referencing Part 630, Hydrology, Chapter 16, Hydrographs, National Engineering Handbook, USDA, NRCS this calculation is to be used to route the flood hydrograph for a watershed and up to a 24 hour SCS design storm through a retention/detention pond. |
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Calculation: |
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Designer/Checker: |
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Input: |
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Time of concentration (tc - hr) |
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Gamma equation shape factor (m) |
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Design Storm: |
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Rainfall (P - in or mm) |
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Drainage area curve number (CN) |
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Drainage area (Am - sq mi or sq km) |
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Pond bottom elevation (ELb - ft or m) |
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Maximum pond stage elevation (ELt - ft or m) |
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Area of pond bottom (SAb - sf or m^2) |
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Max stage water surface area (SAt - sf or m^2) |
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Outlet Structure 1: |
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Outlet Dimension (OD1)
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Structure opening elevation (Eo1 - ft or m)
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Outlet Coeficient (Co1)
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Pipe only: pipe length (L1 - ft or m)
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Outlet Structure 2: |
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Outlet Dimension (OD2)
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Structure opening elevation (Eo2 - ft or m)
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Outlet Coeficient (Co2)
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Pipe only: pipe length (L2 - ft or m)
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Outlet Structure 3: |
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Outlet Dimension (OD3)
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Structure opening elevation (Eo3 - ft or m)
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Outlet Coeficient (Co3)
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Pipe only: pipe length (L3 - ft or m)
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Calculate Pond Infiltration Recovery: |
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Unsaturated vertical hydraulic conductivity (Kvu - ft/day or m/day) |
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Factor of safety, typically 2 (FS) |
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Elevation of ambient water table (Ewt - ft or m) |
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Fillable porosity (f) |
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Equivalent Pond length (L - ft or m) |
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Equivalent Pond width (W - ft or m) |
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Elevation of base of aquifer (Eb - ft or m) |
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Hydraulic conductivity of aquifer (k - ft/day or m/day) |
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Porosity of material in pond (mp) |
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Output: |
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Time to peak, tp = |
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Unit peak discharge, qp = |
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Sum of dimensionless DUH coordinates = |
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Nondimensional time interval of DUH = |
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Peak rate factor, PRF = |
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Volume entering pond = |
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Pond storage volume, Vs = |
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Total Vertical Unsaturated Flow Volume = |
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Vertical Unsaturated Flow Volume Remaining = |
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Vertical Unsaturated Flow Recovery Time = |
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Saturated Lateral Flow Recovery Time = |
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Total Recovery Time = |
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