Estimating rill erosion process from eroded morphology in flume experiments by volume replacement method

Abstract

Rills are commonly found on the sloped farm fields in the loess regions worldwide, especially on Chinese Loess Plateau. The erosion process along a rill provides information for understanding the rill erosion mechanism. This study uses a volume replacement method to estimate the rill erosion processes by refilling the eroded rill segments. The sediment concentration was calculated by summering the eroded soil mass and divided by the total water volume during the erosion period. A flume that was 0.6 wide and 12m long was subdivided into strips of 0.1m wide and 12m long to imitate eroding rills. A typical silty-loam soil from the Loess Plateau of China was used for the experiments. The commutative eroded rill volumes along the rills under five slopes and three flow rates were measured at 11 rill segments. All the sediment-laden runoff was harvested at the rill outlet to measure the average sediment concentration. The sediment concentrations at locations higher than that at the outlet were caused by sediment deposition and removed from the data set. The computed sediment concentration processes increased with slope gradient and flow rate. They also increase with rill length exponentially, with all the coefficients of determination above 0.95. The results were about the same of the previous studies, with sampling method. This demonstrates that the proposed method is a feasible approach to estimate rill erosion distribution. The data set is applicable to the estimation of rill erosion model parameters. This study will provide a basis for estimating rill erosion model parameters.