This is my second attempt since the last release on February 16, 2025, when only Type II rainfall distribution was available. The tool has now been enhanced with graphs, a map, and the ability to view all curves (for Types I, IA, II, and III) simultaneously.
Unit Peak Discharge (qu) for NRCS (SCS) Rainfall Distribution Types I, IA, II, III Calculator
December 26, 2025
Unit Peak Discharge (qu) Calculator
Unit Peak Discharge (qu)
Tip: hover an area to see Type; click to select.
Rainfall Type
Source: NRCS TR-55, Second Edition, June 1986
Show curves
Active Ia/P (for readout)
Time of Concentration (Tc)
60 min
(1.00 hours)
qu at Tc = 1.00 hr (Ia/P = 0.3)
292
csm/in