Regional scale modelling of hillslope sediment delivery with SRTM elevation data

A spatially distributed soil erosion and sediment delivery model (WATEM/SEDEM) was applied to the Scheldt River Basin (19,000 km2) using SRTM elevation data with a 3″ resolution, and CORINE Land Cover data which are available at a resolution of 100 m. Transport capacity coefficients in the model were first calibrated using observed sediment yield data and WATEM/SEDEM predictions made with a higher resolution DEM derived from contour maps. When optimal transport capacity values are used, the calibrated model with SRTM data has an overall model efficiency of 0.79 for area-specific sediment yield and 0.95 for total sediment yield. R-square values between observed and predicted sediment yields are > 0.8. Optimal calibration values are much smaller than those obtained from a higher resolution model, illustrating the need for recalibrating distributed models when input data with different accuracies or resolution are used. Application of the calibrated model to the Scheldt River Basin estimated the total sediment supply from hillslopes to the river channels in the basin at 1.9 × 106 t year− 1. Model results indicate a large spatial variability in hillslope sediment delivery, with the major sediment sources situated in the upper parts of the river basin. It is shown that the decrease in area-specific sediment yield with increasing catchment area can already be explained by the increasing importance of lower slope gradients in the lower parts of the river basin, without taking into account of floodplain sediment storage.