Exploring rainfall kinetic energy induced erosion behavior and sediment sorting for a coarse-textured granite derived soil of south China

Screen covering is a widely used soil conservation practice to control water erosion in coarse-textured soil areas. A better understanding of the effects of screen covers at reducing rainfall kinetic energy (KE) on the erosion behavior will improve erosion prediction and control measures development. The objective of this study was to investigate and quantify the effects of rainfall KE on the soil loss and sediment sorting for developing a prediction model in a coarse-textured soil. A series of rainfall simulation experiments were conducted in three horizons of a coarse-textured soil under five rainfall KEs (628, 443, 324, 231, and 110 J m−2 h-1) which were obtained by covering the soil surface with wire screens of different apertures at a coincident intensity of 90 mm h-1. The results showed that the increase in rainfall KE increased runoff rate and soil erosion rate. The soil erosion rate also increased with depth of the soil layer exposed to the soil surface. Based on the soil clay content, a power relationship could describe the relationships between soil erosion rate and geometric mean diameter of sediment and stream power. With increasing rainfall KE and runoff duration, although the percentage of clay- and silt-sized particles in the sediment decreased, both were still higher than the content in the original soil. The enrichment of fine particles in runoff produced a coarsening layer on the slope surface, which might restrain the subsequent erosion in situ. The observed large preferential loss of clay- and silt-sized particles by erosion emphasizes the importance of sediment sorting for subsequent erosion in these coarse-textured soils. These results suggest that the relationship of rainfall KE to erosion should be considered for practical and effective estimation and prediction of the potential erosiveness of rainstorms.