Effects of Up-slope Runoff and Sediment on Rill Erosive Sediment Particle Size Distribution

The fine particle loss in the soil is an important issue of soil quality degradation. A dualbox system, consisting of a feeder box located at upslope and a test box located at down_slope, was used to analyze characteristics of rill erosive sediment particle size distribution with 150 gradients under different rainfall intensities and sediment concentrations in the upslope runoff. Effects of rainfall intensity, upslope runoff with variable sediment concentrations, and rill flow velocity on the rill erosive sediment particle size distribution and the mechanisms were discussed. The results have shown that the upslope runoff discharging into the rill box caused the particles (clay) less than 0001 mm in erosive sediments increase, and 0.05-0.001 mm particles (silt) decrease. Impact of rainfall intensity on rill erosive sediment size distribution was not significant. Meanwhile, the clay content in the rill erosion sediment increases with the rill flow velocity and rill sediment delivery.