Research On Soil Erosion And Sediment Delivery Of Laohahe River Basin In Liaoning Province

The land is the important fundament for human's living, but the gradually increasing problems of land degradation are becoming serious constraint in human development. Soil erosion causes the destruction of land resources, decrease in grain production, disasters and declines in soil fertility. The sand caused by soil erosion fills up in the river or reservoirs year after year, and result in floods. Liaoning province is famous for serious soil erosion in China. Soil erosion happens nearly all over the province, especially in the west.The Laohahe river basin in the western Liaoning is chosen as topics in the thesis, the remote sensing and geographic information technology is used as major tools, and six factors, i.e., land use, vegetation, slope gradient, soil, lithology and geological disasters derived from TM and ETM+ images and other data are selected. The spatial distribution of soil erosion and sediment delivery of the basin in 1990 and 2000 are calculated by weighted overlay method. The main contents and achivements of the thesis are as follows:1.Based on the hydrology model in ArcGIS, the boundline of the study area is obtained via analyzing the hydrologic characteristics of the Liaoning digital elevation model (DEM). The TM and ETM+ images in the study area are rectified by RS processing software ERDAS8.7. Land use and vegetation coverage are gotten from the images, and slope, soil, lithology and geologic disaster information are derived from other maps separately.2. Soil erosion intensity and its change from 1990 to 2000 are evaluated by weighted overlay method which chooses the land use, vegetation coverage, slope gradient, soil, lithology and geological disaster as factors according to the study models of soil erosion and the facts in the study area. The weights of various factors are determined by AHP.The result shows that the acreage of intensive erosion reduced, but the total area of erosion increased. In the spatial distribution, soil erosion was meliorated obviously in the area from south of Changlong town to Zhangjiayingzi town, and also in Laoguandi, Shaoguoyingzi, Beiershijiazi, while deteriorated in Heishui, south of Machang and Sanjia.3.The SDR of the basin based on grids is obtained by calculating the sediment travel time. This model is firstly used in the sediment delivery study of drainage basin in Liaoning province.4. The spatial distribution model of sediment delivery is established:Mi=SDRi×Si. The charts of sediment delivery distribution of Laohahe river basin in 1990 and 2000 are gotten, which indicate that the northern part of the area is the major sediment source, also the both sides of rivers contribute much more to the sediment yields because of high SDRs in these areas.5.The analysis on spatial distribution of sediment delivery indicares that the sediment delivery intensity enhances with the increasing soil erosion intensity and slope. In different types of land, the sediment delivery intensity increases in the following order:resident< water