Influence Of Topography On Soil Erosion Calculation In Daling River Basin

Topography is one of the key influencing factors of soil erosion.On the one hand,topography affects the distribution of soil erosion by affecting land use types and vegetation coverage.On the other hand,the resolution of DEM(Digital Elevation Model)data has a profound impact on the extraction quality of topographic factors involved in soil erosion calculation.Different departments and researchers used topographic data with different precision to calculate soil erosion and got different calculation results.It seriously affects the accurate judgment of regional soil erosion.The complex relationship between topography and soil erosion has become an important issue to be clarified in theoretical research and practical work.Taking Daling River basin as the research object,this paper used Arc GIS and LS-Tool to extract topographic factors such as slope,slope length and slope direction in the study area,and analyzed the impact of topographic factors on land use,vegetation coverage and soil erosion distribution.At the same time,topographic data with different accuracy were obtained from three large,medium and small slope areas in the basin,and Soil Erosion was calculated by using CSLE(Chinese Soil Loss Equation)model and WEPP(Water Erosion Prediction Project)model.The influence of DEM accuracy on soil erosion calculation in different slope areas was investigated.The results showed that the land use of Daling River basin changed from "arable land--forest land" to "forestland--grassland" with the increase of slope.Agricultural farmland was mainly distributed in the gentle terrain region with slope <6°,and forest and grass land was dominant when the slope was larger than this.The vegetation coverage increased firstly and then decreased with the increase of slope,and reached the maximum value in the range of6-15°.Forestland mainly distributed on the shady slope with relatively high soil moisture content,and vegetation coverage also reached the peak on the shady slope.The dominant position of cultivated land was obvious on the sunny slope.In the areas with high degree of human development and utilization,soil erosion is serious,resulting in slope length truncation and terrain fragmentation,which is manifested as rich land use types on the slope length <200m.In recent years,with the improvement of soil erosion control intensity of forest and grass,it also shows that the vegetation coverage on the previously seriously eroded broken slope is relatively high.From the perspective of terrain gradient,cultivated land,construction and transportation land,rivers,lakes,reservoirs and ponds are mainly concentrated in the low gradient region,while forest and grass land are distributed in the high gradient region.Soil erosion is greatly affected by land use and vegetation coverage,and the high value area of erosion is mainly distributed in the arable land with relatively large slope and low cover forest and grassland area.When DEM data is applied to model calculation,it is found that the lower the resolution is,the stronger the terrain generalization is.The lower the resolution is,the flattening phenomenon occurs in the steep slope area,the slope is concentrated in the middle grade,and the slope length extends from the short slope to the middle and long slope.It is found that the calculated results of soil erosion under the condition of DEM data with 2 m resolution are most close to the actual erosion,indicating that the resolution can basically reflect the topographic features and has a good effect on topographic and geomorphic expression,which is suitable for the extraction of topographic parameters in the calculation of CSLE model.Further improvement of DEM data accuracy has no obvious effect on improvement of erosion calculation accuracy.The WEPP model is more suitable for the relatively gentle slope area with slope <15°,and the results of soil erosion calculation of the WEPP model are relatively poor when slope >15°.This paper elucidates the relationship between topography,land use and vegetation coverage in Daling River basin,and provides theoretical reference for rational land distribution in Daling River basin and other similar basins.The 2 m resolution terrain data proposed in this paper is more conducive to improving the calculation accuracy of soil erosion of CSLE model,and the WEPP model is more suitable for the range of slope <15°,which has important reference value for the selection and application scope of relevant model terrain data.