Modeling feedback processes between soil detachment and sediment transport along hillslopes on the Loess Plateau of China.

ABSTRACT

A dynamic model of soil erosion along hillslopes considering soil detachment and sediment transport is still a major challenge in terms of its applicability to field conditions. Data availability for model calibration and validation is very limited for physically process models. An improved hillslope erosion dynamic model (HED) with a simple structure and strong application on field plots was established based on the sediment feedback mechanism in this study. Observed runoff and sediment data from field plots with slope gradients of 14.1 %-62.5 % and slope lengths of 7.9-64.7 m within runoff events for the Chagagou catchment on the Loess Plateau of China were used to evaluate the HED. We confirmed that the power function can reproduce the soil detachment capacity (Φ) and sediment transport capacity (Tc) under varying field slope conditions (gradients and lengths). The two parameters associated with the power function of Φ or Tc are consistent across the variable conditions. When the HED model simulates the process and event sediment discharge, the unified model parameters could be obtained. The simulation precision of above results ranged from 0.44 to 0.95 for Nash-Sutcliffe simulation efficiency (NSE), from 0.65 to 0.96 for R2 and from -32.37 % to 31.61 % for relative error (RE). The feedback term of HED was close to one as the slope length approached zero. Decreasing of sediment yield as slope length increased was quite consistent with the measured data due to the reasonable sediment feedback term. The critical slope lengths were more easily reached, and the feedback term value along the slope decreased more rapidly at steeper slopes and higher runoff events. HED can be further integrated into distributed watershed models for predicting sediment discharge within runoff events.