Synthesis of flood hydrograph in Tiber River basin of Italy

A dimensionless instantaneous unit hydrograph (IUH) is derived for the Upper Tiber River basin in Central Italy by assuming basin linearity and time-invariance. The derivation contains parameters which can be determined from basin geomorphology and may therefore be potentially applicable to data-scarce watersheds. The IUH and the effective rainfall are convoluted to produce the flood hydrograph for a given rainfall event. A determination of the effective rainfall assumes an a priori knowledge of the volume of direct runoff. The two-term Philip infiltration equation is employed to determine it by satisfying the equality between the volume of effective rainfall and that of direct runoff obtained by hydrograph separation of streamflow. The applicability of the dimensionless IUH is verified by comparing its results with streamflow data observed for a number of rainfall events on tour watersheds in the Upper Tiber River basin.