Risk Assessment On The Soil Erosion Of Changwu County Based On GIS Technology

In support of GIS and RS technology, this paper selected Changwu County, a typical gully region of Loess Plateau, as the study area and applied Chinese Soil Loss Equation (CSLE) framework to estimate the amount of soil erosion of Changwu County. Taking into account the gully erosion factors, this paper analyzed the evolution of county-scale soil erosion intensity and the soil erosion variation characteristics. Then this paper took the risk assessment of soil erosion to see how the soil erosion changed and explored effective ways to control soil erosion to provide a scientific and technological support to local ecological environment and sustainable economic development. The main results involved:(1) Based on the data of Changwu County (daily rainfall, soil data, DEM, RS, statistical data of soil and water conservation measures, etc.), this paper established a county-scale quantitative evaluation index system for soil erosion Then, according to the methods of CSLE, this paper calculated the rainfall erosivity and estimated the coefficient of soil erodibility, slope / slope length, soil and water conservation measures, gully erosion and other factors.(2) According to the hydrological observation data of Yaergou catchment (1980-1992), we validated the applicability of CSLE model. The estimated soil erosion modulus of Yaergou catchment was 1365t/(km~2·a) and the measured sediment modulus was 1275t/(km~2·a). The relative error was 7.1% showed the model and parameters adapted to the evaluation of soil erosion in this region.(3) According to the land use map of Changwu County (1983, 1993 and 2005), bringing the validation coefficients of this model in, we got three average county-scale soil erosion modulus which were 4012.0t/(km~2·a), 3204.9t/(km~2·a) and 2554.6t/(km~2·a), showing a gradually decreasing trend. In these three periods, all of these soil erosion areas reduced with the increase of intensity levels. No erosion, micro erosion and slight erosion (erosion modulus < 2500t/(km~2·a)) which were 67.0%, 68.7%, 72.7%, respectively, accounted for the largest.(4) The trend analysis of spatial and temporal characteristics showed that the area of higher soil erosion intensity level transferred to that of 1 or 2 lower levels. From 1983 to 1993, there was 52.8% of severe erosion area transferred to very intensive erosion and intensive erosion area and 50.8% of very intensive erosion area transferred to intensive erosion and moderate intensive erosion area. From 1993 to 2005, there was 43.9% of severe erosion area transferred to very intensive erosion and intensive erosion area and 44.9% of very intensive erosion area transferred to intensive erosion and moderate intensive erosion area.(5) The soil erosion risk assessment showed that all of the soil erosion risk indexes in these three periods (2.05 in 1983, 1.92 in 1993 and 1.79 in 2005) were decreasing. No risk and slight risk were the main types, accounting for above 80%. While, the area of severe risk and damage risk occupied less than 10%.