PREDICTION OF SEDIMENT TRANSPORT PROCESS IN RIVER BASIN FOCUSING ON THE EFFECT OF HILLSLOPE EROSION

Abstract

 In this study, a rainfall-sediment-runoff model is proposed, in which a hillslope erosion model is incorporated into a river basin sediment transport model consisting of a distributed rainfall-runoff model and a unit channel sediment transport model in. In detail, the hillslope erosion model is constructed by applying the convection equation of suspended sediment flow containing the erosion-rate and deposition-rate terms of suspended sediment to the hillslope area, which formulates the sediment supply process from hillslopes to the unit channel induced by the gully erosion. The sediment transport processes in the Abira River basin were simulated by the model for the rainfall events from July 16 to August 23, 2022. The predictions of the grain size distributions of riverbed materials at different locations, suspended sediment concentration, and its grain size distributions over time are close to the observed results. The comparison of two cases with and without hillslope erosion shows that the fine sediment supplied from hillslopes gradually changes the conditions of bedload sediment flow and suspended sediment flow throughout the river basin as the flooding progresses. This suggests that hillslope sediment supply due to hillslope erosion plays an important role in influencing the long-term sediment transport process in river basins.