SCS Unit Hydrograph – Synthetic Flood Hydrograph Tool

Builds a triangular SCS unit hydrograph (peaking factor 484) and event flood hydrograph
from watershed area, direct runoff depth, time of concentration, and storm duration. Units: SI or US customary.

1. Inputs Watershed & Runoff

Use runoff depth from your SCS CN tool as the effective precipitation. The tool constructs a triangular SCS hydrograph with peak factor 484 and reports Q(t) at a chosen time step.
Internal calculations follow standard NRCS relations; results are shown in both m³/s and cfs.
Design hydrograph SCS Unit Hydrograph Peak & timing
Total drainage area contributing to the outlet.
Use the direct runoff depth from SCS CN (Q) or other loss method.
Hydraulic time of concentration of the watershed (e.g. from TR‑55 Tc methods).
If left blank, D is approximated as 0.133 · Tc, a common NRCS choice for SCS UH.
Output hydrograph will be tabulated at this interval (e.g. 5, 10, 15 minutes).
For documentation only – does not affect the hydrograph shape.