Rainfall erosivity over the Calabrian region

Following the results of a study carried out for the neighbouring Sicilian region, this paper reports a study of the applicability of the annual value, F-aj, of the Arnouldus index to represent the erosion risk in Calabrian region. Firstly, by using 214 values of the mean annual value of the erosivity index, F-F, and a Kriging interpolation method, an isoerosivity map is plotted. Then, in order to predict the erosion risk for an event of any return period, the probability distribution of the F-aj index is studied. An in situ statistical analysis, carried out by using candidate distributions with two parameters (Gauss, LN2, EV1 and Weibull distribution), showed that the EV1 and LN2 laws were characterized by the best fit to the empirical Cumulative Distribution Function (CDF) In order to establish the theoretical CDF to use as a regional parent distribution, the descriptive ability of the LN2 and EV1 distributions was also studied by a hierarchical regional procedure. Finally, the analysis showed that for each Calabrian sub-region, characterized by a constant value of the coefficient of variation, the erosion risk index was constant.