Abstract:Vegetation restoration is one of the important reasons for the decrease of sediment yield in the Loess Plateau. To explore the effect of vegetation coverage on sediment transport, the relationship between vegetation coverage and sediment transport rate was analyzed by combining the theoretical analysis and the field plot experiment. Based on the Einstein’s theory of sediment movement, the movement process of sediment particles on slope surface was analyzed theoretically from the perspective of sediment movement, and the relationship between slope relative sediment transport rate and vegetation coverage was established. The field runoff scour experiments were carried out to verify the formula. Six flow levels (flow range 0.14～1.40 L·s^–1, including 0.14, 0.28, 0.56, 0.83, 1.11 and 1.40 L·s^–1) and eight vegetation coverage levels (0, 20%, 30%, 40%, 50%, 60%, 80%, 100%) were set for 48 groups of experiments. The results showed that the calculated value was larger than the measured value; under the condition of large flow, the calculated value was in good agreement with the measured value; there was a certain deviation between the calculated value and the measured value under the condition of small flow. Based on the analyses of theory and test, the influence of vegetation on sediment transport capacity was related to vegetation coverage, plant diameter and sediment particle size. Under the same slope topography and vegetation coverage, the vegetation with smaller plant diameter was more beneficial to sediment reduction than the vegetation with larger plant diameter. In the area with coarser sediment particle size, the effect of slope vegetation on sediment reduction was more obvious, and the same planting only needed to reach a small coverage, then it could start to play an effective effect on sediment reduction. When the vegetation coverage was low, the coverage threshold for the effective effect of sediment reduction was determined by the particle size of sediment and the plant diameter of vegetation.