Research On Risk Assessment System Of Secondary Mountain Hazard Induced By The Wenchuan Earthquake

Wenchuan Ms8.0Earthquak trigged large numbers of collapses,landslides, debris flows. The secondary mountain hazards induced by theearthquake caused even bigger loss than itself. Earthquakes causedmountain breakages, and change the geological landscape features, whichgreatly changed the geological disaster forming environment. After theearthquake, there will still be high incidence of secondary mountaindisasters, and they are group-occurring in chains. Facing the complicatedpost-earthquake relief situation, conducting secondary mountain hazard riskevaluation research will lay a foundation for various disaster preventionand relief works and rebuilding planning. To meet the needs of secondarymountain disaster prevention and rebuilding planning in the earthquakezone, this paper first made a summary discussion on domestic andinternational geological disaster risk assessment, and then presented acomprehensive secondary mountain disaster risk assessment system thatsuits the disaster hit areas. We picked Yingxiu town, a2km wide zone alongthe Dujiangyan-Wenchuan Highway and32heavily hit counties as ourresearch zones, collected data through remote sensing interpretation,on-site survey, field monitoring and material collection, using3Stechnology for quantification and grading to study secondary mountaindisaster risk assessment methods at points, lines and zones at differentscales. Following results were achieved:In Yingxiu town, a preliminary exploration was done on debris flowhazard assessment using the small watershed unit and landslide hazardevaluation using high resolution grid collapse on a large scale area after the earthquake, and based on that, we presented a comprehensive hazardassessment method that suits the features of the town, which has a certainreference value for post-quake area; under a comprehensive considerationof the natural attributes of the object to cause disaster and thesocio-economic attributes of disaster bearing body, we applied graycorrelation analysis to obtain regional vulnerability, further accomplishedregional risk assessment and grading division.Taking zone along Dujiangyan-Wenchuan Highway as study area,conduct research on secondary mountain hazard assessment in linear projectareas. The effectiveness of disaster prevention projects were introduced,and then establish the hazard assessment index system based on five majorfactors that influence secondary hazards, including formation conditions,activity features, triggering conditions, destruction characteristics andstructural measures.86.65%of the research zone is above moderate level,among which,16.52%are distributed at the river banks within1.5km to theroad, between1,100m and1,800m above sea level, and high steep slopezone between35°and51°, those are the important areas for roadrebuilding, prevention and relief; low risk areas are mainly at gully area andbeaches, gentle slopes, terraces and areas that are1.5km away from the road.The evaluation results are comparatively consistent with field surveys andremote sensing monitoring results.Taking32heavily hit counties as study area, we discussed the principalsand methods of secondary mountain disaster risk evaluation in large regions,providing a reference for post-quake secondary mountain disaster riskevaluation in large region. The results show, regional risk degree isdetermined by both disaster risk and regional vulnerability degree, disasterand vulnerability both are the necessary prerequisites for the existing risks.More than40%of the research area is above high risk level, mostly affectedby both disaster risks and vulnerabilities, becoming the important areas for secondary mountain disaster prevention; low risk area takes less than20%of the research zone, among which, more than50%is at highly vulnerablearea, appropriate for economy developing activities, scale economy can bedeveloped based on prevention to promote regional post-disaster rebuilding.With GIS strong storage space and spatial analysis functions,object-oriented technologies, ArcGIS Engine and ADO developmentcomponents were applied to conduct research on secondary mountaindisaster comprehensive database building. Based on that, we accomplishedthe secondary mountain disaster risk assessment system design anddevelopment, realized the standardized data collection, management,statistical mapping and semi-automated risk assessment on secondarymountain disaster in heavily hit areas.