Abstract:In order to investigate the effects of herbaceous roots on soil detachment in alluvial fan of benggang, Paspalumwettsteinii and Pennisetum sp. were chosen as the research objects, and an experiment was carried out using flow flumes with adjustable slope gradients to analyze the changing characteristics of soil detachment and their influencing factors. The results showed that the soil detachment rates of each soil layer were as follows:Bare land (69.93 g/(s·m2)) > Paspalumwettsteinii(57.42 g/(s·m2)) > Pennisetum sp.(43.28 g/(s·m2)), and the soil detachment rates increased with the increase of soil depth as a power function. The most important factor to characterize soil detachment was root length density, and the soil detachment rates of Paspalumwettsteinii plot declined as a logarithmic function with all root indexes, while a power function decline was observed for Pennisetum sp. plot, indicating the difference effects of root system configurations on soil detachment. Soil detachment of two kinds of grasslands could be estimated using flow shear stress, soil shear strength, and root length density (NSE ≥ 0.90). The results of this study could provide scientific evidences for the disposition of collapse management measures.