Prediction of Soil Erosion at Small Watershed Level Based on GIS and Universal Soil Loss Equation(USLE)

Xiazhuang watershed,sub-watershed of Jiulong river watershed,is chosen as the typical study area.Desktop GIS software,i.e.MapInfo and ArcView,is used to establish the spatial database,including boundary of sub-watershed,water course,land-use,soil category,plant,etc.Based on the GIS's function of raster spatial analysis,the watershed is discreted into uniform grids with the cell of 10×10 m,and USLE is integrated with ArcView and ARC/INFO to predicted soil erosion in the Xiazhuang sub-watershed after selecting reasonable USLE factor values.The soil erosion is estimated and the critical areas of soil erosion in the Xiazhuang sub-watershed are finally identified.Results show that annual average soil erosion amount is 2730.3 t/km~2,which falls into the category of moderate erosion.High erosion category(sediment yield is higher than 5000 t/km~2·a) occupied 11.17% of the total watershed areas.After changing the controlling measures of soil erosion in the Xiazhuang sub-watershed,the soil erosion is further simulated and predicted by integrating USLE with ArcView.As a result,annual average soil erosion amount declines to 1570.89 t/km~2 which falls into the category of low-grade erosion.The proportion of highly eroded area is only 3.75% of total,and the extreme erosion area disappears.The simulation result reveals that the critical areas of soil erosion play a key role in regional soil erosion,which makes a good suggestion for management and control of the soil erosion in the Xiazhuang sub-watershed.