The Quantitative Assessment Of Soil Erosion In Small Watershed On Loess Plateau Based On GIS

Loess Plateau of China is one of the most serious soil erosion areas in the world. Severe soil erosion not only destroys the ecosystem environment roughly, affects the economic and social sustainable development, but also produces large quantities sediments that silt up the downstream riverbed, and endangers flood control of the yellow river. Therefore, the assessment of soil erosion, as the basis of the comprehensive control and land use planning on Loess plateau, must be done actively. But till now, there has been no unanimous conclusion on the quantitative assessment indexes and their thresholds for the small watershed on Loess Plateau.The study area is located in WangDongGou, a small watershed in ChangWu county, ShaanXi province. With the principles of combination of qualitative and quantitative analysis, macroscopic and microscopic analysis, the assessment indexes of soil erosion are selected through a series processes such as field investigation, soil sampling, physical and chemical properties analysis of soil, analysis of relations between the influencing indexes and soil erosion, statistics method, and so on. Every index is divided into five grades according to the specific criterion, and its weight is drawn by AHP method. The soil erosion intensity of the whole watershed is assessed with the quantitative method of GIS and RS.The results of the study are followed:1. The quantitative assessment system of soil erosion is established. It includes slope gradient , length of slope, land use, vegetation cover density, soil porosity, non-waterstable aggregate of soil above 0.25mm,total P of soil,CaCO3 of soil, and the weight of these indexes is 0.184, 0.088, 0.417, 0.188, 0.023, 0.051, 0.016, 0.033 respectively. The Samples verifying shows that the accurate of the assessment system is 85% above.2. The intensity of soil erosion in the watershed is the insignificant and slight. Comparing with other gully watershed on Loess Plateau, the intensity of soil erosion in WandDongGou is lower and it's land use is more reasonable.Generally, the paper makes progress in understanding the law of soil erosion by selecting some microscopic indexes about physical and chemical properties of soil. Moreover, the paper discusses the processes of the establishment of soil erosion assessment indexes system and the application of GIS, RS in the soil erosion assessment in details. So it can be references to the related studies. The study result of the paper can directly provide science ground for more reasonable comprehensive control and use of land in WandDongGou watershed.