CHECKING GENERALIZATION OF THE USLE-MM IN CENTRAL AND SOUTH ITALY

Abstract

The USLE-MM estimates event normalized plot soil loss, Ae,N, by an erosivity term given by the runoff coefficient, QR, times the single-storm erosion index, EI30, raised to an exponent b1 > 1. In this investigation, carried out at the three experi-mental sites of Bagnara, Masse and Sparacia, in Italy, the soundness of the USLE-MM scheme with a single exponent for the three sites was tested. The model was parameterized both locally and considering all sites simultaneously. The performances of the fitted models were established by considering all erosive events and also by distinguishing between events of different severity. The b1 exponent varied widely among the three sites (1.05 - 1.44) but using a common exponent (1.18) for these sites was possible. The Ae,N prediction accuracy increased in the passage from the smallest erosion events (Ae,N < 1 Mg ha-1, median error = 3.35) to the largest ones (Ae,N > 10 Mg ha-1, median error = 1.72). The QREI30 term was usable to both predict Ae,N and the expected maximum uncertainty of this prediction. Development of a single USLE-MM model appears possible.