Distributed Sediment Delivery at Masse Experimental Basin (Central Italy)

The use of appropriate models for environmental decision-making is crucial for supporting soil conservation strategies, particularly in erosion-prone systems such as Mediterranean basins. In this study, the suitability of the Sediment Delivery Distributed (SEDD) model at the event scale was evaluated in a 231 ha basin in Central Italy, where rainfall–runoff–sediment yield data from four erosive events were available. The model was applied by subdividing the basin into morphological units, defined as areas with uniform aspect, length, and slope steepness. Model parameterization involved the estimation of a single coefficient, βe, embedded in the sediment delivery ratio of each morphological unit. The variability of βe with rainfall–runoff event intensity was analysed. The resulting relationship reflects the physical mechanism whereby sediment transport along hillslopes becomes more efficient as event intensity increases, as represented by the runoff coefficient QR. Analysis of the empirical cumulative frequency distribution of the sediment delivery ratio for each morphological unit suggests that the influence of the runoff coefficient on βe may vanish during the most erosive events. Under this hypothesis, for QR > 0.15, the variability of sediment delivery processes is governed solely by the structural component of sediment connectivity, while the functional component becomes invariant and characteristic of the investigated basin.