Effects of sediment characteristics on the sediment transport capacity of overland flow

Abstract

The transport of sediments is a crucial part of soil erosion. Accurately calculating the sediment transport capacity is key to the construction of soil erosion process models. Research on Tc has focused mainly on the dynamics of a single particle of sediment and hydraulic variables. There have been few studies of the impact of soil aggregates on the Tc. To clarify how sediment characteristics, including those for single particles and aggregates, affect the Tc of overland flow with no raindrop import, flume experiments were implemented at slope gradients varying from 5.24% to 26.80% and flow discharges ranging from 0.68 to 5.41 × 10−3 m2 s−1. The experimental materials were five typical soils in China. The results indicated that the correlation between the measured Tc and sediment mechanical composition indexes of the five soils was indistinctive in this study. The sediment settling velocity with aggregates has a significant correlation with the measured Tc. New equations, including for the sediment settling velocity with aggregates ωud75, were established to calculate the Tc. The empirical equation that included ωud75, slope gradient and unit discharge performed greatly in predicting Tc (R2 = 0.93, NSE = 0.90). ωud75 can effectively improve the calculation accuracy of Tc. The new equation including flow and sediment properties obtained through dimensional analysis performed well in predicting Tc (R2 = 0.99, NSE = 0.91), and the calculation accuracy was better than that of the empirical model derived in this study. These findings indicate that the sediment settling velocity is an important variable in the equation for predicting sediment transport capacity of overland flow.