Testing USLE-MB for Plots Subjected to Rilling Over a Rainfall Season at the Sparacia Station (South Italy)

The Universal Soil Loss Equation - MB (USLE-MB) is a specific application of the USLE approach for event-based erosion modeling. It was recently calibrated using data collected in the Sparacia (South Italy) area from plots where rills originated starting from an initial planar surface. The aims of the present investigation are to (i) test the reliability of the previously parameterized USLE-MB against soil loss measurements collected on four plots with pre-existent rill channels due to a sequence of three erosion events after that of rill formation, and (ii) assess the erosive response of these plots and the rill network evolution to explain the applicability of USLE-MB to data from plots with pre-existing rills. The measured and estimated soil loss values exhibited a good agreement, characterized by a mean absolute error of 43.5%. Pre-existent rill channels have not generally favored further erosion processes. After each event, the surface of a single plot was surveyed by terrestrial photogrammetry. The analysis of rill characteristics demonstrated that the growth of the rill network across events was limited even because of no-tillage, thereby explaining why erosion processes did not intensify.