Analysis On Geological Disasters Occurred In The Reconstructed Settlements After The Earthquake In Beichuan

All kinds of urban and rural buildings in Beichuan Qiang Autonomous County, which was one of the hardest destroyed areas of the 2008’s earthquake, were greatly damaged. The region’s settlements have been rapidly reconstructed after the post-disaster reconstruction of three years. Because the natural environment is not yet stable, coupled with the frequency of extreme weather events in recent years, a number of potential threats gradually were exposed. That caused a number of catastrophic events in the settlements of reconstruction after the earthquake. Particularly, the geological disasters broke out in Beichuan after the 7.9 floods in 2013, which caused serious security threat to the settlements of reconstruction. In this paper, using the nearest neighbor method and principal component analysis method to analyze and evaluate the characteristics and disaster situation of geological hazard of the settlements in Beichuan based on the census data of disaster after the 7.9 floods in 2013, the land use data, seismotectonic maps and DEM of Beichuan. Therefore, it can provide the fundamental basis for the local government to develop a scientific decision-making of disaster prevention and mitigation.The main research results are as follows:(1) Analyzed these geological disasters, characteristics around the reconstruction settlements of Beichuan Qiang Autonomous County found that they have these characteristics of large quantities,many types, distributed clustering, high density, small-scale and large-harm. Concentrated in the eastern part of the county, contain Badi, Dunshang, Xiaoba, Chenjiaba, and Qushan. The region of lower elevations and gentler slopes is prone to occur debris flows, and the region of between 1000-2000m elevation and slope area of 25°-35° is prone to occur collapse and landslides.81% of disaster points locate within 1km buffer zone of the river, and the distance from 57% of disaster points to the river is less than 0.5km.42% of geological disasters are located within 5km buffer zone of the fault, and the closer the more disaster-point.(2) Using the nearest neighbor method to extract the affected settlements by the geological disaster points, the total of 1016 plaques, accounting for 5.702 percent of the total of residential plaques, mainly in the central and eastern regions of the county. Distribution trends of affected settlements is positively related to that of entire settlements, they are less affected by the terrain of elevation and slope, but a greater impact by the fault.(3) Depending on the disaster index value of each residential plaque, the disaster of affected settlements will be divided into four grades of minor, a little serious, serious and very serious. The results of the evaluation showed that the worst affected settlements mainly concentrated in Chenjiaba which in the east of the county and extending southwest to Qushan and Leigu, and other villages and towns, contain Piankou, Kaiping, Badi, Yuli. There are 45 settlements which be very seriously destroyed by geological disasters, there are 64 settlements which be seriously destroyed by geological disasters, there are 775 settlements which be heavily destroyed by geological disasters, there are 132 settlements which be slightly destroyed by geological disasters.(4) According to the results of the evaluation of the disaster, for the geological disaster prevention and control work of the reconstruction residential of Beichuan County to make the following recommendations:1. For very serious disaster settlements, the Government may directly make residents to avoid and move.2. For serious disaster settlements, if there is a possibility that geological disasters point can be completely governed, the government implements the policy of project management. If there is no possibility, the Government makes residents to avoid and move.3. For minor and a little serious disaster settlements, the policy of project management can be implemented to protect the settlements.4. To strengthen the construction of geological disaster warning and monitoring system, under government guidance, mobilize the masses to monitoring and prevention, and constantly improve the level of early warning of disasters, ensure the safety of settlements.