Flood Frequency Analysis for Sicily, Italy

Abstract

In this paper a regional flood frequency analysis based on the two-component extreme value (TCEV) distribution is developed using flood data recorded in Sicily. The hierarchical approach, characterized by three investigation levels for estimating the parameters of the theoretical distribution, is discussed first. The highest level of homogeneity hypothesis with regard to the skewness coefficient was verified by using a Monte Carlo technique and taking account of the separation effect proposed by Matalas et al. in 1975. This analysis also showed (1) the inability of the generalized extreme value model to reproduce the empirical cumulative distribution function (CDF) of the skewness coefficients, and (2) the convenience of using annual maximum peak flood data instead of annual maximum mean daily discharge records to estimate the parameters of the TCEV model. At the second level of regionalization, three different methods for identifying hydrologically homogeneous subregions are then performed: the first is based on the