Modeling sediment concentration of rill flow

Accurate estimation of sediment concentration is essential to establish physically-based erosion models. The objectives of this study were to evaluate the effects of flow discharge (Q), slope gradient (S), flow velocity (V), shear stress (tau), stream power (omega) and unit stream power (U) on sediment concentration. Laboratory experiments were conducted using a 10 x 0.1 m rill flume under four flow discharges (2, 4, 8 and 16 L min(-1)), and five slope gradients (5 degrees, 10 degrees, 15 degrees, 20 degrees and 25 degrees). The results showed that the measured sediment concentration varied from 87.08 to 620.80 kg m(-3) with a mean value of 343.13 kg m(-3). Sediment concentration increased as a power function with flow discharge and slope gradient, with R-2 = 0.975 and NSE = 0.945. The sediment concentration was more sensitive to slope gradient than to flow discharge. The sediment concentration was well predicted by unit stream power (R-2 = 0.937, NSE = 0.865), whereas less satisfactorily by flow velocity (R-2 = 0.470, NSE = 0.539) and stream power (R-2 = 0.773, NSE = 0.732). In addition, using the equations to simulate the measured sediment concentration of other studies, the result further indicated that slope gradient, flow discharge and unit stream power were good predictors of sediment concentration. In general, slope gradient, flow discharge and unit stream power seem to be the preferred predictors for estimating sediment concentration.