Regionalization And Evaluation Of Geological Gazards In Qinzhounarea Based On GIS

Since entering the21st century, due to natural disasters, especially geologicaldisasters cause to personnel casualties and property losses more frequent than before,the phenomenon also attracted more and more attention. This thesis focuses onqinzhou district, located in Tianshui City, Gansu province, and does research on riskzoning of geological hazards in Qinzhou County.This thesis is based on fully collection meteorological, hydrological, physicalgeography and regional geo-environment information of Qinzhou County, andcombined them with the survey information of geological disasters in QinzhouCounty, analyzing the characteristics and formation mechanism of geological hazardtypes in Qinzhou County, my thesis development risk zoning with comprehensiveevaluation method based on GIS and fuzzy comprehensive evaluation and gets resultsof risk zoning map of Qinzhou County, then analysis and contrast the results of thetwo methods. In this thesis the core contents are listed as follows:(1) This thesis analyzes types, distribution characteristics and formationconditions of geological disasters in Qinzhou County. Types of geological disastersincluding landslides, collapses, mudslides and unstable slopes; With the influence ofterrain, meteorological, hydrological conditions and human engineering activities,distribution character in Qinzhou County is different from area to area. Geologicalhazards are very scarce in high and low mountain hazard, while they are richlydeveloped in Low Mountain and valley area and are unbalanced between each town;the developing characteristics are summarized as group character, unplanned propertyand correlated. The forming conditions are containing intrinsic factors and inducedfactors. The induced factors are made up of rainfall, earthquakes and humanengineering activities and so on, while the intrinsic factors are terrain conditions, layerrock character, hydrological conditions, geological structure, and earthquake.(2) Establish a three-level evaluation index system. The system is set up bychoosing seven concrete evaluating indicators, including density of geological hazards,vegetation index (NDVI), geomorphology, catchments, rainfall and humanengineering, engineering geology and rock group. And the weight of each evaluationindex is calculated withAHP. (3) This thesis develops risk zoning of geological hazards with comprehensiveevaluation based on GIS, under the ARCGIS platform, using the basis of the digitalgeological map with a scale of1:100,000and detailed survey data and information ofgeological hazards in Qinzhou County, dividing slopes using DEM data as anevaluation unit, extraction seven layers of evaluation index based on weighted overlayanalysis, finally get to risk zoning map Qinzhou County.(4) Fuzzy comprehensive evaluation is used for developing risk zoning ofgeological hazards based on evaluation units of1km×lkm, using the trapezoidfunction to determine the degree of membership. On the various indicators of riskranking, using fuzzy comprehensive evaluation to calculate seven evaluation ofextraction index layer gets to Qinzhou County geology disaster risk zoning map.(5) Using the reclassification of ARCGIS, the geological disasters in QinzhouCounty are divided into high risk zone, middle risk zone, and low risk zone.Comparing the risk zoning results by two divisions, they are relatively similar to eachother and match the reality. Finally, countermeasures and advice are given to preventand even eliminate geological hazards.