The Geological Hazard Assessment And Mapping Study Of Wenchuan In Meizoseismal Area

Wenchuan is located in the center of 5.12 earthquake. During the earthquake, a large number of earthquake landslide happened, a lot of loose rock mass deposited in valleys, and the superficial and ecological environment suffered a devastating damage. Few years after the earthquake, the environment recovery slowly, especially for vegetation and in the mountains. Combined with the influence of the aftershocks, the heavy rainfall and human engineering activities, many potential instability slope and original landslides induce landslides again, and the loose material in valleys along with flow scour become debris flow. In recent years, especially in the flood season, multiple debris flow often outbreak together in Wenchuan, blocked rivers, destroyed homes and bridges, buried roads, caused unimaginable damage to local residents. In conclusion, after a long period of time, many landslides and debris flows will outbreak frequently. Base on this, this article take Wenchuan county as example, relying on the China geological survey geological survey project- "major geological hazard investigation in southwest comprehensive evaluation and early warning research", with the interpretation of landslide and debris flow disasters, the author use GIS, mathematical models and numerical simulation to overcome geological disasters hazard assessment research with different areas and different spatial scales, such as landslide hazard assessment in Wenchuan county and Yingxiu, debris flow hazard assessment in Wenchuan county and Weizhou. The purpose of this article is give the appropriate advice about construction and disaster prevention and mitigation planning to local government, the main results are the following:1, the statistical analysis of the present distribution of landslidesBased on remote sensing images and aerial photographs in recent years, with the help of field investigation, the author use dots and polygon to describe landslide in Wenchuan or Yingxiu. The article take these interpretation as statistical sample, respectively statistic and analyze landslides’ distribution on lithology, seismic intensity, drainage, slope, elevation and other factors. The distribution not only provides the basis for the landslide hazard assessment, but gives a good basis for landslide development research after earthquake.2, discusses the various evaluation unitsIn the evaluation of regional analysis, the most basic job is to choose a reasonable evaluation unit. The article take the spatial scale and nature of the disaster into account, select the grid unit, the slope unit and the catchment unit as the basic evaluation units. On the basis of their respective characteristics, the author use them overcome landslide and debris flow hazard assessment and mapping in Wenchuan. Thus, the research gives the beneficial reference to the selection of units for hazard assessment.3, try a variety of hazard assessment methodsThis article defines hazard as the product of susceptibility and time frequency, hazard=susceptibility × time frequency. This define break the domestic scholars’ idea: susceptibility is equal to hazard. The author think hazard is a kind of dynamic attribute which will be changed over time. For landslide disaster, this paper introduce landslide point nuclear density and rainfall distribution into susceptibility to describe the landslides’ time frequency. Among them, landslide point nuclear density is the quantitative description of the intensity of landslides activities. Its basic theory is frequent landslides areas, the environmental damage should be more serious, the possibility of landslides’ happen should be higher than other area in the shorter time. At last, we get regional landslide hazard by the combination of time frequency and susceptibility.For debris flow, this article make an exploratory study by using topography, loose materials and time frequency to describe the hazards. Finally, we use the catchment basin to analyze the regional debris flow hazard. In addition, we take the numerical simulation to overcome debris flow hazard assessment in Weizhou.4, hazard zoningThe paper take Wenchuan, Yingxiu and Weizhou as study area, we make landslides and debris flow hazard zoning from the different spatial scales, such as landslide and debris flow hazard zoning in Wenchuan, landslide hazard zoning in Yingxiu and debris flow hazard zoning in Weizhou. The zoning will provide the beneficial reference for the disaster prevention and engineering construction in local area.