Through analyzing of physical factors that most infl uence the degradation processes of subaerial rock (lithology, drainage density, slope steepness and exposure), biological and anthropogenic (land use and vegetation cover), could be identifi ed in the Rio San Girolamo basin (Capoterra, SW Sardinia), areas with different degrees of susceptibility to erosion and geological instability and, consequently, assess the main production areas of the solid load handled during extreme events from surface waters and those channeled. For this evaluation we applied a conceptual model that uses the method of the overlay data in raster format developed in GIS environment