Application Of RS, GIS&GNSS Technology In The Potential Risk Assessment Of Debris Flow In Baoxing County

Unexpected and destructive debris flow which develops in the valley region can pose a serious threat to people's lives and property safety. There are fiercely rolling terrains, crisscross faults and derivative geological hazards of collapse in the transition zone between Qinghai-Xizang Plateau and Chengdu Plain, so its geological environment is particularly complex. Especially after the earthquake in Wenchuan and Lushan, there are more broken stratum and increasing loose deposits, that can greatly increase the probability of occurrence of debris flows in the region. For the purpose of responsing to the western development strategy, promoting social development and improving the abilities of geological disaster prevention and mitigation in the west, so, it is paticularly urgent for us to clear debris flow hazards in the local situation and divide potential hazard level of debris flow at the regional scale. However, the western region has complex terrains, bumpy roads and harsh environments, thus using the conventional method to research geological information is not only time-consuming but also difficult to obtain satisfactory results. "3S" technology is a rising technology which can collect, sort, analyze, count and deposit geographic datas. It can overcome the the deficiencies of the traditional methods in related field of geography, that has been widely used and achieved good results.Baoxing County of Sichuan Province is located in the transition zone between Qinghai-Xizang Plateau and Chengdu Plain, so its terrains rolling fiercely and cause frequently-occurring debris flow. The paper applied deeply the advantages of "3S" technology to the analysis and evaluation of potential hazard of debris flow in Baoxing County and also analyze and research comprehensively the space information such as the geological data, DEM data, remote sensing data, rainfall data and so on. The paper's main research results are as follows:(1) Through researching the source condition, sliding dynamic conditons and trigger conditions that can affect debris flow's emergence and combining with human activities, this study selected thirteen impact factors such as geological structure, lithology, seismic intensity, slope types, gradient, slope direction,terrain information entropy, elevation, river, vegetation cover, the maxinum precipitation of 24 hours, population density and roads. Based on "3S" technology, a geographic database which can assess potential hazard of debris flow in the research area was established analyzing related data and archiving them.(2) By the concept of terrain information entropy to evaluate development degree of debris flow valley was selected and the information of sub-catchments in the research area was also extracted. The study shows that the watershed information is closest to the actual situation when the catchment threshold is set to 20000, and divided 87 sub-catchments based on it. Each sub-catchment's terrain information entropy valuse between 0.099~0.486.(3) The analytic hierarchy process model which can assess debris flow's potential risk in the study area was established, that is able to assort and divide eleven impact factors from four aspects including geology, topography and geomorphology, meteorology and hydrology and human activity. The four factors are the rule layer of the hierarchical model and the thirteen impact factors are the measure layer of the hierarchical model.(4) Through weighted stack all impact factors, the assessment quantitative results of debris flow's potential risk in the study area was obtained. By field reconnaissance, the assessment quantitative results was divided into five hazard grades including extra high, high, sub-high, low, extra low. Southeast of the study area's debris flow risk was extremely high and its overall risk was the highest in the study area. And the overall risk in the eastern region and south region was second-highest. The third-highest was in the western region. And the lowest was in the northern region.In the recent years, "3S" technology is booming and getting a lot of research results in the analysis and evaluation of geological disasters. Based on it, the debris flow's potential risk was evaluated and analysed from the regional scale in this study. And it was aimed at providing reference for assessing debris flow's potential risk of Baoxing County and giving decisive advice for the debris flow disaster's prevention and mitigation work.