Experimental Study Of Soil Erosion On Red Soil Under The Interaction Of Rainfall And Scouring Flow

Hilly red soil region is an important grain production area, playing a key role in the development of agricultural economy. It is characterized by gentle climate and plenty rainfall. Yet excessive human activities had destroyed large areas of forest and vegetation with the development of economy, which in turn lead to serious problems such as thinning of soil layer, the naking of bed rock, the reduction of farmland area and the lowering of farmland quality. Therefore, deep understanding mechanisms of soil erosion are an urgent demand to protect red soilresources. Knowledge of hydraulic characteristics of rill flows provides a basis for better understanding and modeling the rill erosion processes and mechanisms, which is also essential for planning the appropriate conversation measures in red soil region.Based on the laboratory flume experiment combining the rainfall and scouring flow, we study the process of soil erosion. The objectives were: to evaluate the effect of rainfall intensity and scouring flow rate on the erosion principle and to reveal the hydrodynamic mechanism of erosion. The main conclusions are as follows:(1) Effects of raindrop impact on slope erosion process.The raindrop impact had a significant effect on the runoff and sediment rate under the simulated rainfall. The stronger rainfall intensity, the faster the rate of runoff and sediment. Runoff, sediment rate and sediment concentration of runoff showed a step change trend with the rainfall time. There was a good linear function between cumulative runoff volume or cumulative sediment mass and runoff time. Slope plays a bigger role on slope erosion, Change of the slope will lead to the change of runoff sediment concentration. Runoff sediment concentration increases in the beginning and then decreases.There was a good power function between cumulative runoff volume and cumulative sediment mass.(2) Effects of flow on slope erosion process.In the same scouring flow condition, flow velicity increases with the distance from the top of slope. The rate of the runoff and sediment yield changes in volatility in the process. Scouring flow play dominant role in the process of slope erosion. The sediment rate displayed different variation under different scouring flow. Sediment rate changed gently at low scouring flow(5 L/min), while it decreased sharply at early 5 min. There was a good linear function between cumulative runoff volume and runoff time. There was a significant power function between cumulative sediment mass and runoff time or cumulative runoff volume..(3) Effects of the interaction of rainfall and scouring flow on slope erosion process.Gradient and scouring flow rate have small influence on the variation of runoff and sediment rate as temporal variation. The sediment yield rate has a periodically change trend with the change of scouring flow and gradient. Scouring flow has little effect on the rate of sediment. The runoff and sediment rate showed an overall decreasing trend. The decay rate of sediment rate was faster than that of runoff rate under the interaction of rainfall and scouring flow. Slope on the effects of flow rate has obvious difference in the same flow. Under the condition of small flow gradient, early runoff sediment concentration rise rapidly, and then continue to fall until the stable over time.The relationship between cumulative runoff volume and runoff time was linear. The relationships between cumulative sediment mass and runoff time or cumulative runoff volume could be fitted in power function significantly. The power function between bromide concentration in runoff and time could well describe the process of bromide concentration with runoff time.The flow regime was mainly laminar and torrent under the interaction of rainfall and scouring flow.