Topography factor is one of the main components for soil loss prediction in soil erosion model. Here topography factor includes slope length factor and slope gradient factor, which have been the emphasis and difficulty in related research. Although many of LS factor algorithms have been proposed in literatures, it is not yet clear for the differences between them. In this article, L factor is calculated based on the algorithm of Desmet,which evolved from the unit contributing catchment area. With S factor v...