We consider here an example where there is a single record of precipitation at time \(i=5\) of duration \(n=4\) time steps (on top). The IUH is represented instead in the central figure. It is given over four time intervals, each one of 3 time steps. The total rainfall of the catchment is \(A\ \) times the volume of total rainfall \(p_i\ \Delta t\ =\ p_i\ n\ \delta t\) where \(n=4\) is the number of intervals over which the rainfall duration spans. \(A=7\ h\ =21\) being \(h=3\) the number of intervals in which each IUH column is subdivided.  On bottom there is the s-function resulting. The whole mass of the rainfall is then \(84\ p_i\). The concentration time of the example is \(t_c=12\)