| Soil Erosion is an important way of eco-environment degradation in a region, and has been the chief environment problem in China. Soil Erosion has produced large negative effects on ecological environment, human existence and social economic development, so it's an urgent need to control and monitor soil erosion, especially in the Yangtze River, which is attached strategic importance to the development of socio economic in China.Based on USLE, RS, GIS and image data, this paper carried out vegetation fraction and spatial overlay analysis by five factors of USLE, and got five soil erosion maps. And then it estimated soil erosion in more than 20 years, and analyzed soil erosion dynamics in the Region of Daoshuihe basin in Hongan County, Hubei Province and especially in the forest area. This study gave a certain technical demonstration of evaluation of cost-effect in soil erosion control and monitoring. The results indicated that:1. The remote sensing image of Landsat MSS in 1979, Landsat TM in 1987 and 1993, Landsat ETM in 2001, and SPOT-5 in 2007 were used as information source. And the method of supervised classification combined with the expert knowledge was used for the classification. At last, five classification maps of remote sensing images were gotten. Their accuracy arrived at 84.82%, 92.57%, 92.09%, 85.68%, and 90.44% respectively.2. Five periods' forest coverage rate in the studied region (years of 1979, 1987, 1993, 2001, and 2007) were obtained, and arrived at 20.84%, 28.04%, 32.29%, 37.26%, and 37.15% respectively.3. Based on the atmospheric correction on the FLAASH Model by using ENVI software, the inversion accuracy of NDVI was improved. And then Vegetation Coverage factor was obtained by setting up the relation between NDVI and Vegetation Coverage.4. Five periods' soil erosion maps were obtained by carrying out spatial overlay analysis by five factors of USLE based on ArcGis9.2 software. And according to the criterion of soil erosion classes, five period s' maps of soil erosion intensity were obtained by classifying the soil erosion maps.5. The Statistical Analysis of land use type in studied region by area showed that:Area of farmland decreased gradually with the change of time. And the areapercentage of farmland in the region was decreased from 63.67% in 1979 to 40.85% in 2007. The plant percentage was increased from 20.84% in 1979 to 37.26% in 2001, and had little change from 2001 to 2007. Area of construction land increased rapidly from 1979 to 1993, and decreased gradually from 1993 to 2007. It was showed that the increase of forestland area benefited from Forest Protection Project at Middle Yangtze River, by analyzing dynamics of five period's land use in the whole studied region.6. By estimating five periods' soil erosion, some significant research results were gotten as below:Soil erosion area in the studied region was decreased from 75736. 1hm~2 in 1979 to 68528.5hm~2 in 2007. And soil erosion had been remarkably controlled.The area without obvious erosion was increased from 60444.2hm~2 in 1979 to 69682.1hm~2 in 1987. Fluctuating within a narrow range after 1987, but it was larger in 2007 than in 1979. Light erosion area was increased from 45140.8hm~2 in 1979 to58714.9hm~2 in 2007. And the main feature of light erosion was "light I >lightIII> light II" in 1979 and "light I >light II >lightIII" in 1987,1993,2001 and 2007. The increase of light erosion area and the structural optimization of light erosion showed that soil erosion had been controlled gradually. The area above middle degree erosion was gradually decreased from 1979 to 2007, and was keeping "middle degree erosion> intensive erosion>very intensive erosion>the most severe erosion".7. By analyzing the soil erosion dynamics in forest area, some results were also gotten below:With increasing forest coverage rate, the area without obvious erosion in forest area was increased from 1928.6hm~2 in 1979 to 11387.0hm~2 in 2007, and the area percentage of light erosion in studied region was increased from 8.41% in 1979 to 28.75% in 2007.By Surveying, it was showed that: even though in middle and northern mountain Area with a great slope, the Protection Forest appeared the better soil conservation benefit, which was without the most severe erosion. At the same time, the area above middle degree erosion was decreased gradually with the increase of the plant percentage. And light erosion was the main erosion way in forest area.Research showed that quantitative remote sensing inversion of soil and water loss could be achieved in the region of Daoshuihe basin. Because of the increase of the plant percentage, soil erosion had been remarkably controlled. And the protection forest for the Yangtze River was Source Power to increase the plant percentage.
|
PDF Full Text Request