Response of soil detachment rate by raindrop-affected sediment-laden sheet flow to sediment load and hydraulic parameters within a detachment-limited sheet erosion system on steep slopes on Loess Plateau, China

The response of soil detachment rate by raindrop-affected sediment-laden sheet flow to sediment load and hydraulic parameters was investigated within a detachment-limited sheet erosion system on steep slopes to understand sheet erosion processes fully and derive an accurate experimental model. An experiment was conducted at slopes of 12.23%, 17.63%, 26.8%, 36.4%, 40.4% and 46.63% under rainfall intensities of 48, 60, 90, 120, 138 and 150 mm h(-1), respectively, by using simulated rainfall. Results showed that the soil detachment rate by raindrop-affected sediment-laden sheet flow decreased as the sediment load by sheet flow increased, and the decrease was a power function of sediment load by sheet flow with NSE = 0.58, MSE = 0.0099 and R-2 = 0.58. In addition, the soil detachment rate by raindrop-affected sediment-laden sheet flow increased as a linear function of shear stress, stream power and unit stream power. Shear stress and stream power could be used to predict the soil detachment rate by raindrop-affected sediment-laden sheet flow accurately through a linear equation. Stream power (R-2 = 0.87, MSE = 0.003 and NSE = 0.87) was a better predictor of soil detachment rate by raindrop-affected sediment-laden sheet flow than shear stress (NSE = 0.83, MSE = 0.004 and R-2 = 0.83). However, prediction based on unit stream power (NSE = 0.43, MSE = 0.01 and R-2 = 0.43) was poor. These findings can improve our understanding and modelling of sheet erosion processes on steep slopes in the loess region of China.