Kinematic Wave Equation is often used to calculate the time of concentration for overland flow. This equation has the rainfall intensity as a dependent variable, which is a function of the time of concentration. Therefore it's an iterative process to determine the time of concentration.
Where,
tc = time of concentration (minutes)
i = rainfall intensity (in/hr)
L = overland flow length (ft)
n = manning's roughness coefficient
S = slope of the surface (ft/ft or m/m)
Pulldown Menu Location: Watershed -> Time of
Concentration > Kinematic
Wave Method
Keyboard Command: flowtc5
Prerequisite: None