A project for regional analysis of floods in Italy

Abstract

Regional methods for flood estimation are examined and discussed in a companion paper (Rossi and Villani, this volume). The results of the application of a three-level regionalization scheme based on the TCEV distribution to a case study, Italy, are here referred as work in progress. These results are part of the special VAPI project, a large-scale research program being conducted by the National Group for the Prevention of Hydrogeological Disasters (CNR-GNDCI). The whole of Italy is subdivided into three homogeneous regions at the first regionalization level to identify the shape distribution parameters. Several homogeneous subregions in the Apennine Region are identified at the second level through behavior analysis of the skewness and variation coefficients of the maximum daily rainfalls. This is achieved by means of clustering techniques and decision criteria for the optimal value of a number of subregions. Sampling interstation correlation and theoretical spatial variability are taken into account by considering synthetic generation mechanisms with incorporated sampling interstation autocorrelation structure and by means of geo-statistical analysis. Empirical relationships between rainfall and flood scale parameters are proposed. At the third level of analysis, the mean annual flood is derived using multiregressive relationships that are either purely empirical or have a structure identified by a rational approach or by a geomorphoclimatic model.