Remote sensing and GIS as tools for the hydrogeomorphological modeling of soil erosion in semi-arid Mediterranean regions

This contribution highlights the advantages of using a multidisciplinary modelling approach to the characterisation of the environmental dynamics of a typical semi-arid Mediterranean region, the Flumendosa river basin located in central Sardinia (Italy). Here, the widespread presence of geomorphological active processes interacts with the consequences of intense human activities on crop cultivation and forest management to produce a fragile environment the equilibrium of which must be carefully surveyed and maintained. To this end, an hydro-geomorphological soil erosion hazard model was devised and applied using remote sensing and G.I.S. techniques as support tools. Radiometric enhancement and supervised classification processing of multitemporal Landsat TM images were used to derive land cover information, allowing to understand the seasonal evolution of the area and to monitor the presence and movement of organic materials. These data were then combined with those derived from ground truth and ground survey campaigns concerning geology and geomorphology. At the same time, rainfall simulations were carried out in order to evaluate the principal parameters involved in the soil erosion processes. On these data a hydro-geomorphological model based on the spatial prevalence of the different erosion processes, was applied. Six main parameters (i.e. soil erosivity, land use, hillslope gradient and curvature, contributing area and soil infiltration capacity) were used and combined with a matrix linear combination. Results show that the model could represent, if routinely applied at a local administrative level, a valuable tool for forecasting the relative risk of soil erosion in the framework of a correct environmental management.