Study On The Refined Risk Assessment And Zoning Of Landslide And Collapse At Township Level

Geological disaster is a kind of destructive and harmful natural disaster.The occurrence of collapse and landslide accounts for more than 80 %.It has the characteristics of wide distribution and high frequency in the world.China is located in the eastern margin of the Asian continent,with active tectonic movement,complex geological environment conditions and strong human engineering activities.It is a country with frequent geological disasters such as collapses and landslides.In recent years,the number of deaths caused by collapse and landslide disasters in China has been nearly 100 people every year,which shows that collapse and landslide disasters have caused serious casualties and major economic losses.People are aware of the necessity of risk prevention and control of geological disasters such as collapse and landslide.At present,the risk assessment of geological disasters is mainly carried out in large-scale areas such as countries and provinces.The evaluation results are relatively rough and cannot meet the needs of control and prevention of geological disasters.The prevention and control of geological disasters mainly depends on local governments,especially the management of geological disasters by county and township governments can greatly reduce the losses caused by geological disasters.Therefore,it is urgent to carry out refined risk assessment of collapse and landslide disasters at the township level,so as to effectively control and warn potential collapse and landslide disasters.This paper takes Changxing County as the mesoscale research area and some areas of Meishan Town as the small-scale research area.The refined risk assessment of collapse and landslide disasters under different rainfall conditions in two regions was completed.The main results are as follows.(1)A spatial scale segmentation model is established.Considering the demand of risk management for risk assessment of collapse and landslide disasters and the influence of the autocorrelation of evaluation factors on the risk assessment of collapse and landslide disasters,a spatial scale segmentation model is established based on the geographically weighted regression model.Geographically weighted regression was carried out on the impact factors of collapse and landslide disasters in Changxing County,and the two regional divisions for landslide disasters and collapse disasters were obtained.Combined with the distribution of disaster points and administrative divisions,some areas of Meishan Town are selected as township-level small-scale areas,that is,areas with low spatial autocorrelation between evaluation factors of collapse and landslide.(2)The risk assessment method is determined.The advantages and disadvantages of each evaluation method in the previous risk assessment are summarized and analyzed.Based on the basic geological environment conditions of the study area,the collapse,landslide disaster hidden danger,historical disaster data and detailed information of the disaster-bearing body,the risk assessment of the two scale areas is carried out based on the weighted information model,the risk assessment method of the rainfall extreme value hypothesis and the vulnerability assignment method of the disaster-bearing body.(3)Risk assessment and analysis of different degrees of refinement were carried out.In view of the different scales,the risk assessment results play different roles in the actual management and control work.For different scales,the risk assessment indicators and vulnerability assessment indicators with different degrees of fineness are selected.In the study of susceptibility evaluation,the susceptibility evaluation of distinguishing disaster types was carried out.Based on the comprehensive susceptibility evaluation results of collapse and landslide disasters,rainfall is further used as the main inducing factor of collapse and landslide disasters,and the risk zoning distribution under different rainfall conditions is analyzed.Based on the results of risk assessment,the distribution and variation characteristics of risk zoning of collapse and landslide disasters are analyzed.According to the daily rainfall data collected by the rainfall station,the rainfall conditions of the maximum daily rainfall in each month are judged,and the risk control suggestions for collapse and landslide disasters are put forward in a month.(4)The risk assessment of collapse and landslide disasters at different spatial scales was carried out.The risk assessment of collapse and landslide disasters is realized from large to small in spatial scale,and the evaluation results are from rough to fine.The differences and commonalities of risk zoning in the two scale study areas under the frequent heavy rainstorm conditions were compared and analyzed,and the reasons for the differences were analyzed.