| Bailongjiang River Basin is high geo-hazards susceptibility area in China. Strictly control by the regional tectonic and dynamic environment, the tectonically active and earthquakes frequently occurred, soft rocks distributed widely, and the geo-hazards developed extremely in the Bailongjiang River Basin. The geo-hazards threaten seriously the towns in the basin. Therefore, the geo-hazards risk assessment for the mountain towns should be accomplish timely to provide the scientific basis for town planning, prevention and reduction of geo-hazards. This article took the zone from Wudu to Hanwang along the Bailongjiang River as the study area, where human life and property concentrately distributed and the geo-hazards developed intensively. Based on the comprehensive review of risk assessment and in-depth analysis of the geo-hazards distribution, the assessment model and index system were established through the data collection, field geological investigation and data processing. And then the geo-hazards risk assessment was completed (1:50000). The main results are as followed:(1) The geo-hazards distribution was analyzed deeply by using GIS. Geo-hazards include collapses, landslides and debris flows, which were mainly distributed on both sides of the Bailongjiang River. The geo-hazards were occurred mainly in the area where the loess, phyllite and slate distributed, and the slope from20to40°and the elevation from1200to1780m. The seismic action, rainfall and human activities are the major predisposing factors to geo-hazards.(2) Combined with the geological condition of the study area, the geo-hazards risk assessment model and index system were established by analytic hierarchy process (AHP). Took the geo-hazards damaging scope, lithology, gradient, relative elevation and river as the index, the hazard assessment was accomplished. The study area was divided into high-hazard, medium-hazard and low-hazard area, the proportion was15.4%,42.4%and42.2%. High-hazard area included the damaging scope of collapses and landslides, and the alluvial fan of debris flows, such as Beiyuhe, etc. Took the population density and land cover as the index, the vulnerability assessment was accomplished. The proportion of high-vulnerability, medium-vulnerability and low-vulnerability area was18%,23.8%and58.2%. High-vulnerability area included high buildings, general residential, infrastructure and significant land, such as school, hydropower station, gas station etc.(3) The geo-hazards risk assessment was completed by geo-hazards hazard and vulnerability assessment for the zone from Wudu to Hanwang along the Bailongjiang River. Thereinto, the proportion of high-risk, medium-risk and low-risk area was2.4%,6.4%and91.2%. High-risk areas included important buildings and residential housings in the damaging scope of the landslides and debris flows; medium-risk areas included main road, public green space and farmland on the piedmont areas and the damaging scope of the geo-hazards; low-risk areas included the wider area outside the high and medium-risk areas. |
