Monitoring Soil Erosion In Lizixi Drainage Area By Remote Sensing

The Jialing River Basin is one of the main source areas of the sediments in the Yangtze River Basin. As an area with poor agricultural condition and degraded ecological environment, it was considered as a main area of soil conservation in China in 1987. The changes in soil erosion and sediment delivery after ten years' construction of the Control Project of the Yangtze River Basin are of important issues the government and the public concern about. In this dissertation, taking the representative areas, Lizixi drainage area of Sichuan province, of the middle reach of Jialing River as an example, using the "GPS" , "RS" and "GIS" technology, the author discussed on the method of speedy monitoring and evaluation on the changes of the soil erosion. The research result could help the decision making for further water and soil conversation work in Lizixi drainage area, and it also offers reference for monitoring, evaluating and predicting soil erosion in other drainage areas.Dynamical changes of soil erosion in Lizixi drainage area in 1986 and 1999 are monitored by SPOT and TM. Remote sensing images were basical information. Land use information was gained from merged images of SPOT and Landsat TM. The coverage information of vegetation was extracted from Landsat TM images. Slope gradient maps were created from digital elevation model (DEM). GPS was used for Position in field work. The area of soil erosion was classified by an integration of slope gradients, land use types and vegetation cover rates, and their changes were calculated in a grid-based analysis using ERDAS GIS. These analyses were done: dynamical changes of soil erosion in Lizixi drainage area, the relation between the change of soil erosion and the change of land use, the relation between the change of soil erosion and hill slop.It is shown that compared to 1986, in 1999, the erosion area reduced, especially for the area of moderate intensity and more intense, and the intensity of erosion decreased. The change of soil erosion is related with land use in this area. The technology and method obtaining some factors related with soil erosion was discussed. It is shown that the change of soil erosion can be known quickly and nicely by "3S" technology. This method is scientific and potent for monitoring to soil erosion.