Parameters

Flowpath Length

The length of the Sheet flow path.

Land Slope

The slope of the hydraulic grade 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

t= time of concentration (mins)