Modeling the sediment transport capacity of rill flow using a soil-rock mixture on steep slopes

Study region: Yangkeng watershed (E118°03 ', N24°57 '), one of the typical representative areas where Benggang occurs in southern China. Study focus: Sediment transport capacity (Tc) plays a key role in the construction of models of soil process-based erosion, and is closely related to sediment particle properties. However, few studies have been conducted on Tc using soilrock mixtures along steep slopes. This study investigated the impacts of gravel content and gravel composition on Tc using soilrock colluvial deposits in a steep flume. New hydrological insights for the region: Tc increases with the increase of gravel content and proportion of large gravel (5–10 mm), and can be simulated by slope steepness, unit flow discharge, gravel mass content and gravel composition (R2 =0.904; NSE=0.911). The mean weight diameter (MWD) can be used as a sediment characteristic parameter to simulate Tc, and the flow velocity, Reynolds number and stream power are suitable hydrodynamic parameters for predicting Tc. The new equation obtained by dimensionless analysis includes flow properties (unit flow discharge, stream power and Reynolds number) and sediment characteristics (MWD) has a good prediction effect on Tc (R2 =0.991, NSE=0.990), and the simulation accuracy is greater than that of other Tc equations deduced in this study. These results promote understanding of the relationship between Tc and sediment characteristics and contribute to further elucidating the erosion process of soilrock mixtures