Inputs
m
m (along L)
ha
for NRCS lag
m (≤ ≈ 365 m)
Methods
- Kirpich (1940) — natural channels: tc = 0.0195·L0.77·S−0.385 (min, m, m/m).
- Bransby-Williams: tc = 14.6·L·A−0.1·S−0.2 (min, km, km², m/km) → SI converted.
- NRCS lag (TR-55): tL = L0.8·(S+1)0.7/(1900·Y0.5); tc ≈ tL/0.6 (US units; converted internally).
- Kerby (1959) — overland: tc = 1.44·(Lo·N/√S)0.467 (min, m, m/m).
- SCS Travel Time: tc from sheet + shallow concentrated + channel; this tool reports a simple V·L approximation if you fill area & slope only.
Results
Slope S = ΔH/L—
Recommended tc—
| Method | tc (min) | Notes |
|---|