1.3.2 Bransby – William’s Formula

In catchments where the runoff coefficient, C, is greater than 0.40, the Bransby Williams formula is a popular choice. The method calculates time of concentration as a function of catchment area, length, and slope as follows:

(1)

where:
= time of concentration (min)
L = catchment length, (m)
= catchment slope (%)
A = catchment area (ha)