Applying the time-area method for estimating the flood hydrograph for Sicilian basins

Abstract

The estimate of the runoff coefficient of given return period represents an uncertainty parameter in applying rainfall-runoff models at basin scale.
At first, in this paper, some similarities are recognized between the runoff coefficient estimated for applying the rational formula and the one used in the time-area method. Then, using a calibration procedure of flood hydrographs obtained applying the time-area method to seventeen Sicilian basins with the peak flood discharge estimated through the direct method, two empirical relationships for establishing the runoff coefficient and the flood volume of given return period are proposed. Each relationship allows to estimate the above-mentioned variable (runoff coefficient or flood volume) as the product of the value having a return period of 100 years and a frequency factor only depending on the given return period. In both cases an estimate criterion of the value having a return period of 100 years is also proposed.