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Grid‐based distribution model for simulating runoff and soil erosion from a large‐scale river basin

Grid‐based modelling is an effective approach for handling the spatial heterogeneity of basin characteristics, such as land use, soil, rainfall and topographical information. In this study, the grid‐based block‐wise use of TOPMODEL together with the Muskingum–Cunge (BTOPMC) model (block‐wise use of TOPMODEL together with the Muskingum–Cunge) was improved by using an erosion module to estimate soil erosion and sediment outflow during storm events. Instead of representing a grid using a single erosion type, the model accounts for the erosion caused by both raindrop detachment in the sheet area as well as concentrated flow detachment in the channel area. The sediment transport process is simulated at the assumed river channel networks, which avoids the problems that are caused by the difference between the channel widths in the upstream and downstream areas. This also enables the model to be applicable in simulating soil erosion and sediment outflow from a large river basin. Geographic information system (GIS) techniques have been utilized in the model to delineate the river network and extract the basin information from the digital elevation model (DEM) data. Through a case study in China's Lushi basin, the improved BTOPMC model got an average Nash–Sutcliffe (NS) efficiency of about 86·1% in discharge simulations and an average NS efficiency of about 75% in sediment outflow simulations. Overall, the results show a satisfactory accuracy for all of the selected events. Moreover, by analysing the spatial distribution of soil erosion or deposition, the erosion‐prone areas can be identified and prioritized. Copyright © 2009 John Wiley & Sons, Ltd.