Average Several UHG’s
It is recommend that several unit hydrographs be derived and averaged.
The unit hydrographs must be of the same duration in order to be properly averaged.
It is often not sufficient to simply average the ordinates of the unit hydrographs in order to obtain the final unit hydrograph. A numerical average of several unit hydrographs which are different “shapes” may result in an “unrepresentative” unit hydrograph.
It is often recommended to plot the unit hydrographs that are to be averaged. Then an average or representative unit hydrograph should be sketched or fitted to the plotted unit hydrographs.
Finally, the average unit hydrograph must have a volume of 1 inch of runoff for the basin.