Quantifying the Contribution of Sediment Load to Soil Detachment Rate by Sediment-Laden Rill Flow

Sediment load changes with downslope distance during rill erosion process, and thus quantifying the potential contribution of sediment load on soil detachment rate is essential to accurately model the rill erosion process. A standardization-based method was adopted to quantify the contribution for the first time, and the rill flume with a soil-feeding hopper was specifically designed to insulate the effect of sediment load on detachment rate. Loessial soil was quantitatively fed into rill flow to produce different sediment loads. Seven flow discharges were combined with six slopes. Soil detachment rate was measured for each combination under five sediment loads (10, 25, 50, 75, and 90% of the sediment transport capacity, respectively). The results showed that soil detachment rate by sediment-laden rill flow decreased linearly with the increase in sediment load. Stream power is the best hydrodynamic parameter in relation to the detachment rate under different sediment loads compared with shear stress and unit stream power. The comprehensive response relationship of soil detachment rate to sediment load and stream power is a binary linear equation (R-2 = 0.9482). The contribution rate of sediment load to soil detachment rate is 30.43% and that of stream power is 64.39%. The negative effect of sediment load on soil detachment rate accounts for almost one-third of the total contribution. It is important to draw sediment load as a negative factor into process-based rill erosion model. This study can provide a feasible way for researchers to quantify the contribution rate of factors and can help to understand rill erosion process sufficiently.