Parameters
Flowpath Length – The length of the Sheet flow path.
Land Slope – The slope of the hydraulic gradient line.
Catchment Retardance – Retardance roughness.
Calculation
where:
L = Length of overland flow (ft)
S = Average catchment slope (ft/ft)
n = Retardance Coefficient
Smooth pavement 0.02
Poor grass, bare soil 0.30
Average grass 0.40
Dense grass 0.80
tc = time of concentration (mins)