Susceptibility Assessment Of Debris Flow After The Earthquake In Yingxiu Area,Wenchuan County

Since the 2008 "5.12" Wenchuan earthquake, Yingxiu as the epicenter of Wenchuan County and the whole southwest region has undergone a major geological changes, in addition to the heavy casualties and property losses directly caused by the earthquake, but also gives the surface environment and the surrounding ecosystems unprecedented damage. In fact, in addition to the direct damage caused by the earthquake, more local residents trapped in a large number of secondary disasters caused by the earthquake. Especially in the annual rainy season, heavy rainfall prompted lack of vegetation and human engineering protection of unstable slope to further landslides, debris flow and other disasters after the earthquake, which made the houses buried, the roads and bridges broke off, rivers clogged. In short, during several years after the earthquake in Wenchuan County has been in the disaster-prone period, especially the area around Yingxiu where was the epicenter.In this regard, the paper took Yingxiu area as an example, by means of Geological Survey Project of the China Geological Survey- "major geological disaster investigation and assessment and early warning comprehensive study of the Southwest," with the principle of geological disasters, and based on remote sensing interpretation of the study zone, combining various types of geographic information technology to acpuire the collapse, landslide disaster point information, analyze its spatial distribution, comparative analysis of the current models of common hazards susceptibility evaluation method, and using the logistic regression model and the information model to evaluate the susceptibility of the material source in the study area, namely, the quantity of the change of the landslide body, then compared the two model of evaluation results, and regarded the results that were more accurate as the source factors of debris flow susceptibility evaluation main factors in the study area, combined with the other two kinds of evaluation factors as landform factors and predisposing factors, using the analytic hierarchy process(AHP) susceptibility evaluation of study area within 38 pieces of debris flow gully. The main results are as follows:1.Discussed the spatial feature extraction method and Spatial distribution characteristics of study area disasters.Based on the high resolution image and field survey in the study area, interpretation and information extraction solution of collapse and landslide, and on this basis, this paper will map not included in the whole area of debris flow basin the expansion, and also the interpretation and extraction of the disaster area on the point, finally get the 38 debris flow in the study area complete basin, landslide disaster point total of 6203, of which the number of landslides is 1385, the number is 4818 then the landslide landslides in elevation, slope, slope, lithology, fault distance, the distance from the river and peak quake acceleration(PGA) of these seven factors, analyzed the spatial distribution characteristics, different spatial factors have different effects on the distribution of collapse slide disaster, especially Slope factor and PGA factor, with the increase of factor level, the density ratio of disaster distribution is linear increasing.2?Study area collapse and landslide disaster susceptibility assessment.According to the study area, this paper choose Logistic regression model and information model two kinds of collapse landslide susceptibility evaluation. Information model, wide application field, the evaluation unit information used expert knowledge; Logistic regression model has the advantages of flexible evaluation data selection variable can be continuous but also discrete selection. The spatial distribution characteristics of the seven factors, according to the principle and technical route evaluation method research area landslide disaster classification map susceptibility evaluation, two kinds of model evaluation results, and verified the results with the ROC curve, found that the evaluation results of the two models are more reliable, but the assessment results from Logistic regression model more accurate.3?Debris flow susceptibility assessment.Introduced Analytic Hierarchy Process calculation of the evaluation factors weight values, and verify their accuracy. Based on the evaluation index system that it established, put the predisposing factors, topography factors and source factors as the main index, and the group Index were annual rainfall, elevation, basin slope, gully density, Longitudinal slope, fault distance and disaster points susceptibility. Each index based on different weight value for overlay analysis to give a final evaluation of the debris flow susceptibility of the study area.According to the reliable model of debris flow gully identification, the results of the 38 channel of the study area are judged, and the result is corresponding to the classification of the debris flow susceptibility. Provide a reference to local government for disaster prevention and reconstruction project.