A NEW VERSION OF THE USLE-MM FOR PREDICTING BARE PLOT SOIL LOSS AT THE SPARACIA (SOUTH ITALY) EXPERIMENTAL SITE

Improving empirical prediction of plot soil erosion at the event temporal scale has both scientific and practical importance. In this investigation, 492 runoff and soil loss data from plots of different length,  (11 <  < 44 m), and steepness, s (14.9 < s < 26.0%), established at the Sparacia experimental station, in Sicily, south Italy, were used to derive a new version of USLE-MM model, by only assuming a value of one for the topographic length, L, and steepness, S, factors for  = 22 m and s = 9%, respectively. An erosivity index equal to (QREI30)b1, QR and EI30 being the runoff coefficient and the event rainfall erosivity index, respectively, with b1 > 1 was found to be an appropriate choice for the Sparacia area. The specifically developed functions for L and S did not differ appreciably from other, more widely accepted relationships (maximum differences by a factor of 1.22 for L and 1.09 for S). The new version of the USLE-MM performed particularly well for highly erosive events, since predicted soil loss differed by not more than a factor of 1.19 from the measured soil loss for measured values of more than 100 Mg ha-1. The choice of the relationships to predict topographic effects on plot soil loss should not represent a point of particular concern in the application of the USLE-MM in other environments. However, tests of the empirical approach should be carried out in other experimental areas in an attempt to develop analytical tools, usable at the event temporal scale, reasonably simple and of wide validity.