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Stormwater Runoff Hydrograph Simulator

SCS Curve Number runoff · Triangular unit hydrograph · Peak flow & timing

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Peak Flow Qp = 70.9 cfs at Tp = 0.67 hr
Runoff depth 1.25 in · Time base 1.78 hr · Volume 5.21 ac-ft

🌧️ Storm & Basin Inputs

Rainfall Depth (P)3 in
Curve Number (CN)80
Drainage Area (A)50 ac
Time of Concentration (Tc)1 hr

📊 Results

Runoff depth Q1.25 in
Peak flow Qp70.9 cfs
Time to peak Tp0.67 hr
Time base Tb1.78 hr
Composite S2.50 in
Curve Number80
Runoff volume5.21 ac-ft
SCS / NRCS Method: Runoff depth Q = (P − 0.2S)² / (P + 0.8S) with S = 1000/CN − 10 and initial abstraction Ia = 0.2S. The triangular unit hydrograph uses Tp = D/2 + 0.6·Tc and Tb = 8/3·Tp, with peak Qp = 484·A·Q/Tp (A in sq mi, Q in inches, Tp in hours).
SCS Triangular Unit Hydrograph · Linear Scale
0.00.30.71.01.31.72.001631476278Time (hours)Flow (cfs)Tp = 0.67 hr
Runoff hydrograph
Time to peak (Tp)