Grass coverage and the runoff path length decreased by sedimentation have synergistic effects on runoff and sediment yields in a slope-gully system, revealed by rainfall simulation experiments

Abstract

Slope-gully systems on the Loess Plateau, China cause severe soil erosion. Planting vegetation and the construction of check dams are the most effective measures utilized for the mitigation of soil erosion in this region. Among them, due to the sedimentation behind the dam, the erosion basis was lifted, resulting in a decrease of the runoff path length (Runoff Path Length Decrease; RPLD) of the slope-gully system. However, the synergistic effects of vegetation and check dams to reduce the runoff and sediment yields of the slope-gully system has not been addressed often. In the present study, 10 physical models of slope-gully systems, including grass coverage on a slope (0% and 33%) and the RPLD (0, 1, 2, 3, and 4 m), were constructed to evaluate the synergistic effects of these measures. The results indicated that grass coverage reduced runoff and sediment yields by 42.63% and 25.66%, respectively. The combination of grass coverage and RPLD could control water erosion of slope-gully systems more effectively than the independent measures. With increasing RPLD, the runoff and sediment yield reduced significantly. Grass coverage and RPLD exhibited a synergistic effect on the erosion caused by water, which increased with RPLD as follows: 4 m (19.83%) > 3 m (18.68%) > 2 m (17.39%) > 1 m (16.70%). These results demonstrate that grass coverage on slopes and the RPLD synergistically influence hydrological processes. The synergistic effects not only should be incorporated to develop soil and water conservation regulations, but also should be considered in soil erosion models.