Landslide Risk Analysis In Ningqiang County

The landslide process is a natural geological phenomenon, but its consequences is a social and economic problem which not only causes harm to human’s safety but also causes damage to property, environment and so on.In May12,2008, Wenchuan in Sichuan Province occurred a devastating Ms8.0class earthquake. This earthquake has large magnitude and shallow source and thereby very destructive. In this paper, Ningqiang in Shaanxi Province, one of the most severely affected areas in the earthquake is chosen as study area, with the support of Shaanxi Province "13115" scientific and technological innovation projects of major scientific and techno logical special projects (2008ZDKG-75), the distribution law of landslide hazard in the region after the earthquake is studied, the regional landslide risk is estimated and partitioned and thus provides basic information for post-earthquake reconstruction and planning of Ningqiang. Through field survey and remote sensing interpretation,333landslide hazard points are found after the strong earthquake. Combined with the actual situation of the study area, impact factors such as surface lithology, rock hardness, elevation, slope, disaster point density, distance to fracture zone, distance to river system, and distance to road as well as rainfall are selected as landslide hazard control factors. Results found that the disaster point density has the largest influence on landslide risk; terrain slope has the controlling influence on landslide hazard, the slope range for the majority of the Slump disaster is9.25-36.17; in the none-disaster area, fault zone has little influence on landslide hazard, no obvious feature of the hazard distribution along fault zone is found, and different lithology and hardness has no significant correspondence between the distribution and development of the landslide hazard; landslide hazard point mainly distributes along the banks of the river, it is more concentrated along the river within600m; rainfall is not an obvious factor for the landslide hazard in large area.Combined with the GIS spatial analysis model, the Information model and the analytic hierarchy process are used to analyze the impact factors. Landslide hazard risks in Ningqiang are divided into very low danger (stable), low, moderate, high and very high. The study area is thus divided into low, medium and high region after a comprehensive evaluation for the five risk level. The high risk area features for its poor geological environment, full development of landslide disasters, concentrated disasters points and high density, which mainly locates in Anlehe, Yanzibian, Gongjiahe, Donghuanggou, Nanping, and part of Maoba; Zigui; medium risk area locates in Cangshe, Taiyangling, Huangbayi, Juting and so on; low risk area locates in Yangpingguan, Shujiaba, Hanyuan, Gaozhaizi, Qingmuchuan and so on.