Geomorphology and GIS analysis for mapping gully erosion susceptibility in the Turbolo catchment (Northern Calabria, Italy)

This work summarizes the results of a geomorphological and bivariate statisticalapproach to gully erosion susceptibility mapping in the Turbolo stream catchment(northern Calabria, Italy). An inventory map of gully erosion landforms of the area hasbeen obtained by detailed field survey and air photograph interpretation. Lithology, landuse, slope, aspect, plan curvature, stream power index, topographical wetness index andlength-slope factor were assumed as gully erosion predisposing factors. In order to estimateand validate gully erosion susceptibility, the mapped gully areas were divided in twogroups using a random partitions strategy. One group (training set) was used to prepare thesusceptibility map, using a bivariate statistical analysis (Information Value method) in GISenvironment, while the second group (validation set) to validate the susceptibility map,using the success and prediction rate curves. The validation results showed satisfactoryagreement between the susceptibility map and the existing data on gully areas locations;therefore, over 88% of the gullies of the validation set are correctly classified falling inhigh and very high susceptibility areas. The susceptibility map, produced using a methodologythat is easy to apply and to update, represents a useful tool for sustainableplanning, conservation and protection of land from gully processes. Therefore, thismethodology can be used to assess gully erosion susceptibility in other areas of Calabria, aswell as in other regions, especially in the Mediterranean area, that have similar morphoclimaticfeatures and sensitivity to concentrated erosion.