Effects of grass vegetation coverage and position on runoff and sediment yields on the slope of Loess Plateau, China

Soil erosion poses serious challenge to the sustainable utilization of soil and water resources worldwide. Vegetation restoration can sufficiently improve the environment and reduce soil erosion. It is important to evaluate the effects of vegetation coverage and position on surface runoff and sediment yield. Therefore, this study simulated four vegetation coverage rates (0%, 20%, 40%, and 60%) and two vegetation distribution positions (downslope and upslope) to study the runoff and sediment yield under three rain intensities (60, 90, and 120 mm h(-1)). The results showed that the runoff decreased as vegetation coverage increased: 0% > 20% > 40% > 60%. The minimum total runoff occurred at 60% vegetation coverage rate under 60 mm h(-1)- rain intensity (57.5 L), and the maximum at 0% vegetation coverage rate under 120 mm h(-1) rain intensity (172.2 L). The process of sedimentation was similar to that of runoff. As the rate of vegetation coverage increased, the sediment yield decreased. The total sediment yields under 40% and 60% vegetation coverage rates were significantly lower than that under 0%. In addition, the runoff volume and sediment yield of the upslope vegetation pattern were considerably higher than those of the downslope pattern. Under 60 mm h(-1) rainfall intensity, the total runoff volume and sediment yield of upslope pattern were 70.6 L and 261.1 g, as opposed to 61.6 L and 174.9 g of downslope pattern, respectively. By analyzing the correlations of runoff and sediment yield with vegetation coverage, the interception effect on runoff and sediment yield increased with the increase in vegetation coverage. Moreover, the downslope pattern contributed more in reducing runoff and sediment yield than the upslope pattern. The results can provide scientific basis for vegetation restoration on the Loess Plateau.