Experiment Study On Soil Erosion Process And Regulation On Loess Slope Under Simulting Rainfall

Soil erosion on slope was one of the main types of water erosion. Its development and progression was the core content for soil erosion dynamic studies, and also was the key for setting up soil erosion model on the basis of physical process. Effect of rainfall and runoff on surface soil erosion mainly included three continious process:particle detachment, sediment trasportation, and deposition. Further studies on soil erosion dynamics and its monitoring emchnics (including slope, topography and vegetation) were most important for the establishment of soil erosion prediction model. In this study, indoor and field simulation study were adopted to ananlyze changes of surface roughness in the rainfall, reveal temporal and spatial changes of runoff and sediment yield from different underlyings, especilly the influence of vegetation cover and position on runoff and sediment yield. Following conclusions can be reaced.(1) Relations between surface roughness and runoff yield were analyzedResults indicated that surface roughness can extend time of producing runoff, the bigger the roughness, the longer the time of producing runoff was; surface roughness increased with slope and rainfall intensity. The existence of vegetation increased surface roughness, but changes of surface roughness was decreased, which indicated that vegetation improved surface resistance to rainfall erosion.(2) Changes of runoff and sediment yield under different rainfall intensity were analyzed.Genrally, the declining runoff yield order was slope farmland, waste land, grassland and grassland under forest, while the declining sediment yield order was waste land, slope farmland, grassland and grassland under fores. Compared to grassland, vegetative cover on grassland on was effective in reducing sediment yield, which was up to 70%, but less effective in reducing runoff. To the grassland under forest, it was more effective in reducing runoff and sediment yield, which was up to 80% and 95% respectively, and this trend was more obvious when the rainfall intensity was smaller.(3) Changes of runoff and sediment yield on bare slope was stated by indoor simulating rainfall, and the equation for accumulative runoff and sediment was set uo respectively. In the expeirment condition, time of producing runoff decreased with the increase of slope, while runoff and sediment concentration increased with it, but its increase amplitude was slowdown. Based on the indoor experiment analysis, equation for accumulative runoff and sediment was set uo respectively, which was listed as y=atb, further analysis indicated that the constant parameter a increased with rainfall intensity.(4) Monitoring effect of vegetation arrangement on soil and water loss was revealed.Results indicated that to the same vegatation cover, vegetation arrangement had profound effect on soil and water loss, and the cover with vegetation at the bottom of the slope showed the best effect in reducing runoff and sediment yield. In the experiment, under 25% vegetative cover, maximum difference of amout in reducing runoff and sediment among vegetation arrangements was 41% and 85% respectievly, while it was 23% and 126% under 50% cover, and was 13% and 277% under 75 cover respectively, which indicated that the difference of effect in reducing runoff due to vegetation arrangement decreased with vegetation cover, but its difference in reducing sediment increased.