A Study On Mechanism And Prediction Model Of Hillslope Water And Soil Loss In Three Gorges Area

The hillslope erosion processes include soil separation, sediment transport and sediment precipitate, which these three process result from the rainfall splash erosion and runoff erosion. To study and analyze the happening and developing conditions of hydraulic, soil and terrain, and the mechanisms of transitions and influences of these processes each other is the prerequisite to set up physical model of soil erosion. Study on the processes and relationships of soil erosion separation and sediment transport and precipitate of slope cultivated land according to Chinese practical status have a very important theory and production significance to built Chinese specific soil erosion model and further instruct the water and soil conservation practice. Studies on Ilillslope erosion concentrate mainly on three aspects now, first, the study method of hillslope soil erosion including experiment research method and evaluation method of soil erosion; secondly, the researches of hillslope erosion mechanism; thirdly, the researches and evaluations of measure to reduce the hillslope erosion. The inland hillslope research methods are dominated by qualitative analysis and statistic analysis, therefore, much more studies need to be made to the hillslope water and soil mechanisms and processes, the prediction and evaluation of plane source pollutionresulting from nutrient loss, the quantitative prediction model of hillslope water and soil loss and the interaction between the control measures and hillslops. There are only researches about the slope loss's soil particle characteristics and the temporal process of hillslope agro-forestry compound system nutrient loss in the Yangtze river watershed, and deficient to the mechanism and process parameters of hillslope sediment and nutrient loss of three gorges area, and there is not a preferable systematic prediction model of sediment runoff and nutrient loss also, let alone forming benefits evaluation model of hillslope harnessing measures.The area and intensity of soil and water conservation in the Yangtze River watershed have been increased for past nearly 40 years by many irrational land use patterns. The eminent three gorges engineering's make soil and water conservation in the regions nearby three gorges area and the uppers of Yangtze River are more important significantly. After the completion of three gorges dam, the area of three gorges regions will add up to 54200km2 divide by divide, and the mountain area will make up of 74% of total area of this region. With the people's transporting of three gorges area the reclamation ratio of steep slope sloping plantation has increased to 43.7%, however, it is a unquestionable fact that the three gorges region's slope cultivated land is the major material resource of water and soil loss. Therefore, nowadays major problem is how to reduce the slope cultivated land's soil erosion and sediment concentration transporting to three gorges reservoir in order to prolong the three gorges engineering's use time and protect the safety of the middle and lower reaches channel of Yangtze river. In addition, if the soil average thickness is calculated as 78cm, then the total soil interspaced in the uppers of Yangtze River about 1,000,000km2 areas adds up to 197,300,000,000m3, but this total soil reservoir carrying capacity (total interspaced carry capacity) is decreasing with aggravating of soil erosion. Soil is the base of agriculture production, the key measure to prevent water and soil loss is to conserve soil, but most soil nutrient is lost with the sediment loss, and serious water and soil loss make the soil thickness degrease, the soil nutrient be deficient and lean, the land quality degrade and the yield of plant decrease, all this results is going to threaten the people's transplanting and the agriculture sustainable development, and restrict the economy development of three gorges regions. Therefore, there is a whole significance to study the soil erosion mechanism and to explore methods and measures to reduce the soil loss of hillslo...