Time of Concentration (Tc) & Watershed Lag – Multi‑Method Tool

Quick‑check calculator for watershed response time using NRCS lag equation, Kirpich formula,
and simple travel‑time segments. Units: SI (m, s) or US (ft, s) with automatic conversions.

1. Method & Units Tc / Lag Setup

Choose a time of concentration method and then provide the required inputs. Use NRCS lag for rural SCS CN projects, Kirpich for steep small catchments, or travel‑time segments when you already know flow velocities.
Geometry and velocities follow the chosen system; internal calculations use consistent units.
Change method here; the input fields below will update automatically.
Watershed lag Time of concentration Rational / SCS linkage