Effects of grass strips distribution on soil erosion and its optimal configuration on hillslopes

The mechanism by which vegetation regulates the water erosion process of a hillslope and the optimal vegetation configuration have become a focus of soil erosion research. A physical model of a hillslope was established to systematically analyze the regulation mechanism of five grass strips on soil erosion processes through simulated intermittent rainfall, and proposed optimal configuration of grass strip under low coverage for erosion regulation. The results showed that the grass strip placed at 60% of the upslope could reduce runoff and sediment by 7.35% and 62.93%, respectively, and consequently the grass strips were better at direct sediment interception than water storage and sediment reduction. The scope and strength of grass strip's effect in regulating erosion processes were closely correlated with the position of the grass strip. The most effective position of grass strips for decreasing hillslope erosion was placed at the middle-lower part of the upslope, as it could better perform dual functions on runoff sediment and erosion energy. A quadratic function described the relationship between the relative position of vegetation and the sediment yield of the hillslope. An optimal configuration of vegetation for regulating erosion exists when the grass strips plant within the vertex region of the quadratic function, as it could effectively slow runoff and intercept sediment above their locations while retaining runoff and eliminating energy below their locations. The results provide an understanding of how the grass configuration affects sediment transportation processes and hydrodynamics processes on a hillslope.