Soil erosion assessment using USLE in the GIS environment: a case study in the Danjiangkou Reservoir Region, China

The purpose of this study was to investigate the spatial distribution of annual soil loss in the Danjiangkou Reservoir Region, China. Soil erosion was estimated by integrating the universal soil loss equation (USLE) model with GIS. The main factors affecting soil erosion including rainfall erosivity, soil erodibility, slope length and steepness, cover and management factor, and conservation supporting practice factor were determined from precipitation data, soil sample analysis, digital elevation model, land use and land cover, and empirical assessment, respectively. The results showed that the average annual soil erosion was 31.18 t hm(-2) year(-1), far above the soil loss tolerance maximum of 5.0 t hm(-2) year(-1) in the region. Regional soil erosion risk (SER) was estimated and categorized into five classes in terms of intensity (minimal, low, moderate, high, and intense), and 70.3 % of the total area was classified as minimal or low erosion risk. The soil erosion map was linked to land use and soil depth maps to explore the relationship between soil erosion and environmental factors and identify the areas of SER. The results can be used to advise the local people to prioritize critical areas for soil erosion prevention measures. The study also indicated that the USLE-GIS methodology allowed for relatively easy and cost-effective evaluation of SER with explicit spatial input.