Risk assessment on geological hazards in urban areas of lower reaches of Hanjiang River from perspective of monthly prevention and control
The geological environment conditions in the mountainous areas of South China are complex,and geological disasters occur frequently.It is urgent to carry out regional geological hazard risk assessment and solve the problem of"where geological disasters are most likely to occur on a monthly basis and corresponding high-risk areas",and deploy corresponding prevention and control measures in a targeted and phased manner to effectively reduce the losses.Liuhuang Town,Meizhou City,Guangdong Province,located downstream of the Hanjianh River,was selected as the research area.Eight evaluation indicators were selected,including slope gradient,slope shape,elevation,engineering geological rock group,soil thickness,distance from the fault,vegeta-tion NDVI value,and land type.The indicators were graded and assigned values using the disaster frequency ratio(FR)model,and the weight of indicators was calculated by the grey correlation method.The geological hazard susceptibility in the study area was evaluated with an information quantity model,and the results were verified through ROC curves.Based on the susceptibility e-valuation,a month was used as the minimum time evaluation scale,and the maximum monthly average rainfall in historical disaster records was used as the excitation extremum to optimize the rainfall assumption model.The occurrence probability of geological hazards from January to December was calculated,and the risk assessment and zoning of geological hazards in each month were completed.The results showed that:①Overall,the geological hazards in Liuhuang Town were divided into four types of prone ar-eas,namely low prone area,medium prone area,high prone area,and extremely high prone area.The area proportions of each area were 58.60%,22.99%,13.39%,and 5.02%,respectively.The accuracy of the ROC curve test evaluation reached 0.81,indica-ting that the evaluation results were objective and effective.②The monthly geological hazard assessment results showed the prob-ability of geological disasters occurring in Liuhuang Town was the highest from May to August.This period was recommended to be a key defense period for the whole year.Spatially the disasters were concentrated in the northern,central,and southern parts of Li-uhuang Town,which should be assigned as key defense areas.The research results can provide a reference for the dynamic adjust-ment of disaster prevention and control work arrangements and measures in different months in the research area.
geological hazardsmonthly hazard assessmentdisaster frequency ratiogrey correlation degreeweighted infor-mation contentassumption of extreme rainfalllower reaches of Hanjiang River
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