Sediment transport capacity equation for soils from the Loess Plateau and northeast China

Sediment transport capacity (T-c) is a relevant component in physical-process-based soil erosion models. At present, the sediment transport capacity prediction model for soils with a low median grain diameter is not fully understood. In this study, the T-c values of three different soils (median grain diameter d(50) = 0.015, 0.040, and 0.095 mm) were investigated by conducting indoor experiments at unit flow discharges of 0.19 - 1.89 x 10(-3) m(2)center dot s(-1) and slopes of 0.07-0.21. In addition, data describing the overland flow sediment transport capacity of black soil (d(50) = 0.01 mm) were obtained from Yu et al. (2018). First, the performance of seven shear stress, unit stream power, stream power, and mean flow velocity concept-based T-c equations were evaluated based on the measurements. The results confirmed that none of the existing formulas performed well over the entire experimental range. T-c equations derived using soils with a large particle size generally underestimate the T-c of soils containing small particles. The Zhang equation, when calibrated based on the data in this study, can predict overland flow T-c with a PoP of 66 % (PoP refers to the percentage of predictions in which the discrepancy ratio falls between 0.5 and 2.0, whilst the discrepancy ratio is the ratio of the predicted and measured T-c). Based on the general flow parameter concept, a more accurate T-c equation was developed for the four types of soils, which was characterized by a PoP of 83 %. When these equations are beyond the scope of their development conditions, they should be verified further.

Automated summary

In this study, the sediment transport capacity of three different soils was investigated through indoor experiments. The existing prediction models for sediment transport capacity were found to be inaccurate. However, more accurate equations were developed based on the data, improving the prediction accuracy.