The time of concentration is the time it takes for a drop of water to travel from the most distant part of the catchment to the catchpit. This calculator allows you to calculate the time of concentration. Two types of flow are taken into account - overland and watercourse.
The overland flow option is used where there is no defined stream or concentration of water. When this option is selected you will be able to specify the roughness factor. The time of concentration is calculated according to the Kerby equation.
Where:
r = Roughness coefficient.
L = Length of the catchment area in km.
S = Slope of the catchment area in m/m.
This option is used when all flows are concentrated into streams or rivers. The time of concentration is calculated according to the US Soil Conservation Services equation.
Where:
L = Length of the catchment area in km.
Savg = Average slope of the catchment area in m/m.
See Also Rational Runoff Data, Time of Concentration Calculator