Estimating sediment transport capacity on sloping farmland on the Loess Plateau considering soil particle size characteristics

The sediment transport capacity (T-c) is essential for understanding soil erosion and creating soil erosion prediction models. Although many T-c equations exist, they are not universally applicable to sloping farmland on the Loess Plateau. To tailor T-c equations for this region, T-c for four soils (Shenmu Inceptisol (SMI), Shenmu Entisol (SME), Ansai Inceptisol (AS), and Yongshou Alfisol (YS)) from sloping farmland on the Loess Plateau was determined through flume tests with slopes ranging from 15.84 % to 38.39 % and flow discharges of 0.05 to 0.11 m(2) min(-1). Additionally, appropriate particle size characteristics were selected to distinguish the soil types. The results revealed that the T-c of SME exceeded that of YS, followed by SMI and AS in descending order. The T-c of the four individual soils increased exponentially with flow discharge (Q) and slope (S). T-c for individual soils could be satisfactorily predicted using power functions of mean velocity, shear stress (tau), stream power (omega), or effective stream power (R-2: 0.661-0.950, MAE: 0.020-0.110, RMSE: 0.023-0.151), with omega being identified as an optimal hydraulic parameter for simulating T-c. In contrast, the unit stream power was a poor predictor of T-c for individual soils (R-2: 0.403-0.700, MAE: 0.035-0.123, RMSE: 0.040-0.161). The median particle size (D-50), sorting coefficient, and kurtosis (K-g) exhibited highly significant positive correlations with T-c (P < 0.01). Finally, a quadratic power equation for Q, S, D-50, and K-g, along with two ternary power equations for omega (or tau), D-50, and K-g were newly constructed, all with satisfactory accuracies (R-2: 0.808-0.826, MAE: 0.061-0.063, RMSE: 0.086-0.090). The inclusion of sigma and K-g rectified the inaccuracies in predicting T-c for all four soils using Q and S equations or omega (or tau). The results of this study offer valuable insights into the construction of the T-c equations.