Testing a spatially distributed sediment delivery model (SEDD) in a forested basin by cesium-137 technique

The aim of the paper is to validate the sediment delivery distributed (SEDD) model for estimating hillslope sediment yield estimates using net soil erosion values obtained by the cesium-137 technique. The cesium-137 technique provides spatially-distributed measurements useful to verify the predictive capability of a distributed sediment yield model. The application of the cesium-137 technique requires a calibration procedure to convert measurements of 137Cs inventories to estimates of net soil erosion rates. Rainfall and sediment yield data from 1978 to 1994 in a small Calabrian basin forested with eucalyptus trees, were initially used to calibrate, at mean annual temporal scale, the SEDD model applicable both at the morphological unit and basin scale. Then, estimates of net soil erosion were obtained using a mass balance model and the spatial distribution of cesium-137 inventories. The reliability of the mass balance model was verified by comparing the basin net soil erosion value obtained by 137Cs measurements against the mean annual value of sediment yield measured at the basin outlet. Finally a good concordance between calculated mean annual hillslope sediment yield and the corresponding net soil erosion values was proved at the scale of both the single morphological unit and the entire basin. In conclusion, the cesium-137 technique and the mass balance model confirmed the validity of the internal functioning of SEDD model.