Effects Of Surface Roughness On The Process Of Slope Erosion,Sediment Sorting And Transportation

Soil erosion process is an extremely complex process,affected by many factors.A series of studies have been carried out on the effects of rainfall intensity,slope,slope length,soil properties,soil moisture and other combinations on soil erosion.Surface roughness is also an important factor affecting the soil erosion process.However,due to the difference between the test material,the experimental design and the measurement method,the mechanism of the effect of surface roughness on the erosion process is not clear.Some scholars believe that surface roughness by changing the physical properties of soil,runoff form and path,as well as reducing the crust to weaken the erosion.While the other part of the scholars believe that the impact of surface roughness on the erosion of the slope in the process of rainfall is uncertain,The effect of roughness on the increase of concentrated runoff of soil erosion and the reduction of runoff shear force are coexistent.Only in different rainfall types and erosion stages,these two effects act on the soil at the same time,and the final result depends on the combined effect of the two effects.In addition,the surface roughness will follow its evolution directly affects the slope micro-terrain changes,and thus affect the erosion of the development process.The mechanism of the influence of surface roughness on the erosion process has been studied from the point of view of hydrodynamics,however little research has been studied on the influence mechanism of surface roughness on the erosion process from the angle of separation and transportation of sediment particles.Based on previous research,this study worked on soil surface roughness of slope land which was developed by artificial hoeing.This study chose smooth slope as control group,used indoor artificial simulated rainfall method,combined Soil erosion,pedology,hydrology,close-range photogrammetric technology and GIS,to probe into soil surface roughness and its influence on soil surface erosion of water erosion.Studies involved coupling effect of rainfall and soil surface erosion on slope runoff and sediment yield,responding mechanism of soil surface erosion to rainfall and its influence on slope erosion,and the effect of soil surface erosion to sediment particles sorting and transportation.The main results are as follows:(1)The surface roughness can delay the occurrence of slope runoff to some extent,and reduce the runoff rate,sediment yield,sediment yield and sediment concentration significantly.The results of single factor analysis of variance and cross analysis of two factors showed that the effect of rain intensity on slope runoff and sediment yield is more significant than that of roughness,and the two factors have no obvious interaction.(2)The erosion and siltation of the smooth slope are in the form of flakes,while the erosion and siltation of the rough slope is patchy.And with the accumulation of rainfall,the two kinds of slope of the clay particles from the easy to move into the structure of aggregates easy to move in the form of the original particles.But the agglomeration rate of the coarse slope is slightly larger than that of the smooth slope under the same rain intensity,which shows that the rough slope is more selective than the smooth slope.(3)Under different rain intensity,the enrichment rate of different soil fraction had a significant difference for the response pattern of different surface roughness.When the rain intensity was small,the two kinds of slope forms were in the form of clay enrichment,sand grain dispersion and silt changelessness.And the "runoff through" mechanism of the rough slope affects the enrichment of each grain level greatly,and the clay enrichment of the rough slope was quasi-periodic.When the rain intensity was large,the surface roughness limited the enrichment of coarse particles,and promote the enrichment of clay.(4)As the rain increased,the relative importance of the bed load was becoming increasingly important.Surface roughness restrained coarse particle transportation,and made the relative importance of the suspended-saltatin load more important under the same rain intensity.With the extension of the duration of precipitation,their transportation mechanisms were different,although their sediment erosions were bimodal distribution.With the prolongation of rainfall time,the suspended-saltatin load of the smooth slope became more and more important,and the bed load of the rough slope became more and more important.