Response of interrill erosion to flow parameters of sand loess in regions with high and coarse sediment yields

Abstract

In the Loess Plateau, regions with high and coarse sediment yields are the main sources of the Yellow River sediments. The responses of the interrill erosion rate of the soil in this area (Shenmu soil) to flow intensity parameters were systematically investigated through indoor artificially simulated rainfall experiments considering five slope gradients (0.1564, 0.2079, 0.2588, 0.309, and 0.3584) and five rainfall intensities (60, 80, 100, 120 and 140 mm·h−1). Thereafter, an interrill erosion model was established based on two types of soil: Shenmu soil and Ansai soil. The experimental data of Ansai soil were obtained from a study by Wu et al. (2017). The results showed that for Shenmu soil, the interrill erosion mechanism can be classified into two types. The first type was detachment-limited interrill erosion in the initial rainfall phase and transport-limited interrill erosion in the subsequent rainfall. The other type was transport-limited interrill erosion during the entire rainfall duration. Among the flow intensity parameters (i.e., mean flow velocity (R2 = 0.92), shear stress (R2 = 0.84), stream power (R2 = 0.96), and unit stream power (R2 = 0.82)), stream power was found to be satisfactory for predicting the interrill erosion rate of Shenmu soil in terms of the coefficient of determination (R2). However, the interrill erosion rate model based on the stream power for the two types of soil exhibited low prediction accuracy. Furthermore, a general flow intensity parameter was derived to predict the interrill erosion rate of overland flow. Based on this parameter, an interrill erosion rate model for the two types of soil was formulated by multiple regression analysis with an R2 value of 0.96, a relative root mean square error of 18.9%, and a model efficiency of 0.94. Overall, this general flow intensity parameter was shown to be the preferred predictor for estimating the interrill erosion rate for steep slopes in the regions with high and coarse sediment yields.