MONITORING AND PREDICTING SEDIMENT YIELD IN A SMALL SICILIAN BASIN

Abstract

Identifying areas of a basin that are most sensitive to erosion have stimulated the study of withinbasin variabilityof the sedimentdelivery processes and the use of spatially distributed models. To verify the reliability of a sedimentdeliverydistributed model applicable at the morphological unit scale (i.e., the area of clearly defined aspect, length, and steepness),experiments were carried out at mean annual and event scales in a small Sicilian basin. A Geographical Information Systemis briefly presented into which the measurements carried out at the basin outlet (runoff, sediment yield, etc.) and other pointand areal information (soil erodibility, digital terrain model, etc.) were entered.For validating the model at mean annual temporal scale, the sediment yield spatial distribution calculated by the modelwas compared with the net soil erosion spatial distribution obtained by cesium137 activity measurements. At morphologicalunit scale, the agreement between measured and calculated sediment yield values showed a good predictive ability of themodel at mean annual temporal scale.Finally, the model was calibrated and tested using five rainfallrunoff events measured at the outlet of the experimentalbasin. The analysis showed that the coefficient
, appearing in the expression of the sediment delivery ratio of eachmorphological unit, is independent of subdivision criterion and can be estimated by the hydrological characteristics of therainfallrunoff event. The comparison between measured and calculated sediment yield values showed that the sedimentdelivery distributed approach has a good predictive ability at event scale, too.