『Abstract
　A grid-based erosion model is developed by integrating the distributed hydrological model, TOPMC, with the modified USLE to estimate soil erosion and sediment outflow during single storms. The possible sheet, rill, channel erosion types, and sediment transport processes are considered within each grid under the model structure. Instead of representing the sheet erosion and rill erosion separately, the classic USLE model is modified to simulate the lumped sheet-rill erosion during storms. In the modification, the runoff ratio and a relevant correction coefficient are brought into the R-factor which improves the model's applicability in predicting erosion during single storms. Instead of representing a grid with a unique erosion type, a channel component is assumed to exist in each grid, and its width varies with the upstream contributing area of the grid. This assumption avoids the problems that are caused by the difference between the channel widths in the upstream area and the downstream area if the grid is simply recognized as a channel grid. It also enables the model to be applicable in simulating soil erosion and sediment outflow from a large catchment. Through a case study in the Lushi catchment, China, the results show an overall satisfactory for the selected events. Moreover, by analyzing the spatial distribution of soil erosion or deposition, the erosion-prone areas are identified for the prioritization purpose.

Keywords: BTOPMC; Infiltration; Erosion; Sediment concentration; USLE』

Introduction
Simulation of the rainfall-runoff process
Simulation of lumped sheet and rill erosion
Simulation of channel erosion
Channel sediment transport
The study area and data
Validation of the modified USLE
Results and discussion
Assessment of the influence of grid resolution
Identification of the area prone to erosion
Conclusions
References