The Risk Evaluation On The Geological Hazards In Zhashui County

Zhashui County, Shangluo, Shaanxi, is a region that slopes are steep and soils are thin. Rocks there are fractured; large-scale fault are widespread; geological structures are complex. Combined humans engineering activities, made Shangluo one of the county that suffered geological hazards most. Landslides, collapse and mud-rock flows happened frequently and widespreadly, which are fatal threat to local citizen and their properties. Geological hazard has become one of the most limited factors of Zhashui’s development.This paper takes Zhashui as the research target, through the study of current researches in this area all over the world, and based on the particular geological hazard investigation of Zhashui, combines the Yahhp hierarchical analysis and fuzzy comprehensive judgment, utilizes the ArcGIS to get the final result. And the research achievements are as follow:1. Based on the filed investigation and collection of materials, this paper analyzes deeply about the Zhashui geological hazard characteristics. Spatially,geological hazards happens more in the coasts of Qianyou River, Jinqian River and Shechuan River and the way sides of 307 provincial road; most of them happen in the rainy months. Hazards also happen frequently in the regions that fracture developed,in where stratums are weak, rocks are broken, slopes are steep, rains heavily and human activities are centralized.2. Combined the Yahhp analytical hierarchical process, weight got by the adding method and factor data extracted by ArcGIS, the author divides this county as three levels: respectively are high, medium and low; Using fuzzy comprehensive evaluation,the author takes each villages as evaluation unit and selects lower semi trapezoid to establish unitary membership function. Comprehensive considers population,resources, materials and economy, etc. processes vulnerability evaluation, also divided to three levels: high, medium and low.3. The author utilizes ArcGIS Raster Calculator, through the model that risk equals dangerousness multiply with vulnerability, processes the risk assessmentthrough dangerousness and vulnerability. The assessment result is: high risk zones are653.06km2, which are about 27.60% of the county’s whole area; medium risk zones are 625.18km2, which are about 26.42% and the low risk zones are 1087.93km2,which are about 45.98% of whole county area.