Linking sediment yield and caesium-137 spatial distribution at basin scale

Identifying areas of the landscape that are most sensitive or susceptible t o erosion stimulated the study of within-basin variability of the sediment delivery processes and the use of spatially distributed models coupled with Geographic Information Systems. The progress of sediment delivery distributed modelling is also dependent o n the availability of measurements able to establish the link between erode d soil leaving an area and the patterns of erosion and deposition occurring along the hydraulic path from the considered area to the nearest stream re ach. In this paper, the tracer technique using the radionuclide Cs-137 and its e mployment in sediment yield studies at basin scale are briefly reviewed. Th en Cs-137 data available from an Australian and a Sicilian basin are used f or validating a sediment delivery distributed model based on Revised Univer sal Soil Loss Equation and the sediment delivery ratio of each morphologica l unit into which the basin is divided. For each basin, the predictive abil ity of the sediment delivery distributed model is positively tested, compar ing the calculated sediment yield values with the measured ones obtained by the caesiographic map and the proportional method. (C) 1999 Silsoe Researc h Institute.