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

Identifying areas of the landscape that are most sensitive or susceptible to 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 on the availability of measurements able to establish the link between eroded soil leaving an area and the patterns of erosion and deposition occurring along the hydraulic path from the considered area to the nearest stream reach. In this paper, the tracer technique using the radionuclide Cs-137 and its employment in sediment yield studies at basin scale are briefly reviewed. Then Cs-137 data available from an Australian and a Sicilian basin are used for validating a sediment delivery distributed model based on Revised Universal Soil Loss Equation and the sediment delivery ratio of each morphological unit into which the basin is divided. For each basin, the predictive ability of the sediment delivery distributed model is positively tested, comparing the calculated sediment yield values with the measured ones obtained by the caesiographic map and the proportional method. (C) 1999 Silsoe Research Institute.