Simulation study on effects of slope grade on process of runoff and sediment generation with the Robinia pseudoacacia cover in the Loess Plateau region

The experiment of simulated rainfall was carried out by using the soil under the artificial forest from Caijiachuan of Jixian County of Shanxi Province in the Loess Plateau region. The Robinia pseudoacacia was planted as a vegetation cover for the experiment. The process of runoff and sediment generation was studied in different slope grade with the Robinia pseudoacacia cover on the slope. The results show that, under a given condition of certain rainfall intensity and slope grade, along with the slope grade increasing, the sediment generation starts earlier; the runoff goes faster; the crown interception percentage and the runoff decreases; the erosivity, erosion energy, soil erosion as well as sediment yield increases. The relation between the forest crown interception percentage and the slope grade and the relation between the covered slope and soil erosion was derived. Under the same slope condition, compared with the Robinia pseudoacacia cover slope, the bare soil shows higher amount in terms of the average velocity of runoff (15%-25%), runoff (15%-48%), soil erosion (10%-117%), the average and the maximum sediment concentration (55.5%-133%).