Establishment of a Sediment Transport Capacity Equation on Loessal Slope Via Experimental Investigation

A reliable sediment transport capacity function provides response against challenges of soil erosion prediction on the Loess Plateau of China. The popular sediment transport capacity functions are questionable on loess slopes because the experimental conditions from which they were derived, like bed materials, gentle slopes, and surface roughness, are different from soil erosion processes on the loess slopes. Due to the foregoing uncertainty, a suitable sediment transport capacity function was developed based on a flume experiment investigation. The erodible bed experiment was implemented for five unit width discharges (1.3 x 10-4-3.3 x 10-4 m2/s) and ten slopes (5.2%-57.7%). The selected sediment transport capacity equations were tested in an applicability evaluation. The results of this evaluation found that the Govers (1990) function had the best performance (P.O.0.5-2.0 = 76%, R2= 0.93, RMSE = 0.03 kg/(m center dot s)), followed by the Yalin (1963) function (P.O.0.5-2.0 = 80%, R2 = 0.81, RMSE = 0.05 kg/(m center dot s)), and finally by the Low (1989) function (P.O.0.5-2.0 = 72%, R2 = 0.79, RMSE = 0.04 kg/(m center dot s)), where P.O.0.5-2.0 is the percentage of estimated values with logarithmic discrepancies with the measured value between 0.5 and 2.0; R2 is the coefficient of determination and RMSE is the roof mean squares error. The cohesive sediment incipient motion velocity is introduced into the Govers (1990) function, and the sediment particle parameter is determined from measured experimental data. The developed sediment transport capacity equation has good performance with predicted values corresponding to measured values (P.O.0.5-2.0 = 98%, R2 = 0.98, RMSE = 0.006 kg/(m center dot s)). The research results provide an improved sediment transport capacity function on the basis of experiments for steep loessal slopes.(c) 2022 International Research and Training Centre on Erosion and Sedimentation/the World Association for Sedimentation and Erosion Research. Published by Elsevier B.V. All rights reserved.