Study On The Collapsing Hills And Gullies Of Survey And Evaluation Based On RS/GIS

Collapsing hills and gullies is a serious erosion phenomenon. Once occurred, it will bring serious harm to the ecological environment. Wuzhou City, the east gate of Guangxi Province and the focus of Xijiang River economic belt, is one of the country’s main inland ports. The study found that the Cangwu County of Wuzhou City is a sensitive area for the development of collapsing hill sand gullies. The collapsing hills and gullies brings serious soil erosion, which not only influence the river channel, but also destruct the village and the road. In addition, it may change the use of land, and the ecological environment. Therefore, this paper used the method of RS and GIS technology, selecting Cangwu County and Wuzhou City as research objects, using High-resolution Remote Sensing Image of Word View-3 data as the data source, combined with field investigation of perceptual knowledge, according to collapsing hills and gullies type building collapse post remote sensing information map, through man-machine interactive visual solution translation gets the collapse process data to do the research. Using the collapsing hills and gullies data obtained from the interpretation of the soil erosion classification and classification criteria, two indexes, vegetation coverage and slope gradient, were selected to evaluate the risk of collapse of the study area. At the same time, using the interpretation of collapsing hills and gullies data as the basis of the data, referring the ecological sensitivity evaluation theory system, combined with four data of study area, which concluded the DEM data, soil data, geological data and land use data, and selected seven evaluation indicators to do the research. The seven evaluation indicators contains five natural factors(gradient, slope direction, soil, geology, elevation) and two human activities factors(vegetation coverage and land use).Using the Analytic Hierarchy Process(AHP)decision analysis method to construct the sensitivity evaluation system of the collapse and calculating the weight of the evaluation index of collapse sensitivity. The research could provide policy recommendations for the prevention of collapsing hill area. The main conclusions of this paper are as follow:(1)This paper used RS technology and High-resolution Remote Sensing Image. Created the remote sensing information map of Collapsing hills and gullies. Obtained 737 collapsing hills and gullies through the man-machine interactive visual interpretation. Most of them are in large and medium scale collapsing hills and gullies. There are 440 large scale collapsing hills and gullies, 265 medium sized and 32 small sized. In addition, through the interpretation of the collapsing hills and gullies of the data, this paper constructed the catalogue database of collapsing hills and gullies. The database can help prevent and manage the collapsing hills and gullies.(2)The risk assessment of individual is to study the size of the risk of collapsing hills and gullies. This paper selected two indicators, vegetation coverage and slope, to evaluate the risk of post collapse. According to the result, there are 11 seats extreme dangerous collapsing, 161 seats highly dangerous collapsing, 482 seats moderate risk collapsing and 83 seats mild risk collapsing. On the basis of the risk rank size of collapsing hills and gullies, this paper proposed corresponding management measures and suggestions.(3)According to the interpretation of the collapsing hills and gullies, using Analytic Hierarchy Process(AHP) decision analysis method, this paper built the collapse of the sensitivity of the evaluation index hierarchy. Selected five natural factors, which contains slope factor, aspect factor, soil factor, geological factor and the elevation factor, and two personal factors, which concludes land use factor and vegetation coverage factor, to assess collapsed gully sensitivity results in study area. In the result, there are94.414km2 extremely sensitive area, 637.111km2 highly sensitive area, 1706.184km2 moderately sensitive area and 1529.451km2 light sensitive area. Based on the evaluation results of sensitivity of collapsing hills and gullies, this paper analyzed some natural factors of collapsing hills and gullies sensitivity distribution, such as slope, aspect, soil, geology, elevation and other natural factors. At last, this paper proposed collapsing hills and gullies prevention countermeasures and suggestions from the regional scale.