RS And GIS Based Soil Erosion Assessment In Weihe Basin

Weihe is the biggest tributary of the Yellow River, which crosses Gansu, Shaanxi and Ningxia provinces. It plays a very important part in the living and production conditions of the people who live along the river. For a long time, soil erosion in Weihe Basin worsens unceasingly because of the effects of natural and man-made factors. Conducting soil erosion assessment at regional scale using the RS/GIS techniques, the theories and the methods to the soil and water conservation is very significant for the task of ecosystem management.In this paper, taking Weihe basin as study area and monthly rainfall, SPOT-VGT S10 NDVI, SRTM-DEM and landuse data in 2006 as main data sources, applying RS and GIS technology, the methods to extract the impact factors of soil erosion were studied, and soil loss of Weihe Basin in 2006 was calculated based on SL190-2007,USLE and CSLE model; Furthermore, spatial distribution and relationships between soil erosion and environmental factors were analyzed. Following are main results:1. To establish the spatial database of Weihe Basin. According to the requirement of regional soil erosion evaluation, main soil erosion factors were extracted and database was established. After that, the spatial distribution and statistical characteriatics of the factors were analyzed, The factors included soil erodibility, rainfall erosivity, vegetation cover management factor, slope length and slope steepness factors and tillage measure factor.2. To evaluate the situation of soil erosion in 2006. The soil loss of Weihe Basin was calculated based on Standards for classification and gradation of soil erosion.SL190-2007, USLE and CSLE model. The results by the three methods were compared in terms of spatial distribution and statistical analysis. It showed that:the mean value of the soil loss calculated by USLE model and CSLE model are 5158.18 t·km-2·a-1 and 3107.43 t·km-2·a-1 respectively. The result from SL190-2007 is the smallest and from the USLE model is the largest.3. To expound the spatial distribution of soil erosion about Weihe Basin. In the loess plateau in LongDong district, the loess hilly area in LongZhong district and sparse forest grasslands in Liupan Mountains, Soil loss is the most servious, Areas of soil loss is smaller are in Weibei Plateau, gullied rillong loess region in northern Shaanxi province and desertization grasslands district. The soil erosion in Weihe plain and earth and rock mountains is the slightest.4. To reveal the relationship between the environmental factors and soil erosion.(1)Soil erosion and slope is not as simple proportional relationship. In this paper it indicated that the erosion index value is the biggest when the slope is 15°-25°, in other words, the soil erosion intensity is the strongest.(2) The relationship between soil erosion and vegetation coverage is much closely. Slight erosion and mild erosion mainly corresponds to high coverage, serious erosion and extremely erosion mainly corresponds to low coverage.(3) The way of landuse effects soil erosion.The most serious erosion mainly distributes in the cultivated land on slopes. The slightest erosion mainly distributes in the regions of woodland and the towns.The sequence according to descending order beginning with the highest degree of erosion is:cultivated land on slopes>grassland> flat farmland> shrubs> paddy field> woodland> town.