Demonstration Research On Risk Management Of Geological Disasters In Typical Small Watersheds

This paper focuses on the challenging issues about the understanding and systematic overview of debris flow control in typical small watersheds in Guizhou Karst area.It selects the Ertang River small watershed in Bijie,Guizhou as a study area and uses field surveys,on-site interviews,questionnaires,system analysis,and field review methods to analyze the distribution characteristics of geological hazards and recognize the risk awareness of residents’ geological disasters(based on debris flow)in small watersheds and the current disaster prevention capabilities;investigates whether the disaster reduction and prevention of communities in study area is lacking and what the people’s needs are.The risk analysis of 17 debris flow gullies in the typical area was carried out,and the analysis results were reviewed on the field.Based on this,the risk management model for small watershed in typical karst areas was proposed,including the overall model for risk management of geological hazards in typical small watersheds,typical community geological disaster risk management models two different scales management and control models.1.Distribution characteristics of geological hazards in a typical small watershedThrough field investigations,all the hazards hidden points in the study area were visited,including a total of 17 debris flow gullies,44 landslides,and 26 collapses.The debris flow gullies accounted for more than 90% of the entire study area,and the population in the area was distributed in the debris flow within the basin.All of the hazards are small landslides and artificially caused small collapses,and are within the debris flow basin.Because their threat is far less than that of debris flow,they are categorized as sources of debris flow and are not analyzed and discussed separately.2.Questionnaire survey on the risk consciousness of people in typical areasThrough the questionnaire survey combining household visits and site surveys,the risk awareness of residents in typical districts was obtained,about four aspects: the risk awareness of geological disasters,the recognition of protective measures,monitoring and early warning,and preventive measures.In the form of Level 5 Likert items,and using SPSS to process and analyze the data obtained by EXCEL,it is found that the risk consciousness of residents in typical areas is not optimistic,and the awareness of disaster prevention among the respondent groups,their knowledge of basic theory and emergency response are limited,more than half of them lack knowledge of relevant and are constrained by their own professional knowledge(respondents think themselves)that few people will not actively learn about disaster reduction and disaster prevention.Respondents confirm the main impact of geological disasters,including destruction of farmland and forests(85.1%),damage to buildings(74.5%),burial of major roads(63.8%),loss of life(52.5%).Local residents are optimistic about the possibility of geological disasters in the environment they live in for the next five years,and they are not concerned about the surrounding environment.3.Two kinds of risk control modes of geological disasters in typical small watershed are extractedAfter reviewing the results of a large number of documents,field surveys and questionnaire surveys,analyzing the current mainstream risk management framework in the world,considering with the geography,topography,geology,and economic characteristics of typical regions,a reasonable risk management framework for typical small watersheds in karst areas was proposed.Then two typical small watershed risk management models were extracted,a risk management and control model of typical small watershed including the two major measures of engineering measures and non-engineering measures,a debris flow risk management model of typical community including monitoring,early warning,disaster prevention plan,disaster prevention planning,disaster insurance,and community disaster management.4.Risk assessment of geological hazards(mainly debris flow)in typical areasBased on a large amount of literature and actual data obtained,the debris flow hazard model based on the cloud model and the debris flow vulnerability assessment model based on the CD production function,which is focus on the integrated disaster prevention capability of the prevention and control system,were used to carry out debris flow hazards in typical areas and get a map of the corresponding evaluation results.Basing on the above evaluation results,there is one high-risk debris flow gully named Chuangdongcunsanzu,seven middle-risk dangerous debris flow gullies and eight low-risk debris flow gullies and there are three extremely high vulnerable debris flow gullies,seven high-damage debris flow gullies,four middle-damage debris flow gullies,and three low-viability debris flow gullies.Finally,the risk assessment results of debris flow in the study area shows that there are one extremely high-risk debris flow gully named Pingdong gully,four high-risk debris flow gullies,seven middle-risk debris flow gullies and five low-risk debris flow gullies.5.Conducted on-site review and analysis of risk assessment resultsThe survey conducted a detailed on-site review and analysis of the 17 debris flow gullies risk assessment results and zoning in the small watershed,the results showed that Changchong Village No.6 Ditch(DF15)and Changchong Village No.7(DF16)have relatively large difference,and there is a small amount of inconsistency with the evaluation result in Pingdongcungou(DF09),Chudongcungou(DF08),Faiguncungou(DF05),Fushashangcungou(DF02)and Changchong Village #1 Ditch(DF10).The overall risk assessment results are basically consistent with the actual results.It is proved that the risk assessment based on high-precision images and reasonable mathematical models is a reasonable and scientific method,and also verifies the accuracy of the results.6.To propose a model for risk management of mudslides in typical small watershedsCombining with the verification of field risk zoning,household visits,and point-based questionnaire surveys to conduct comprehensive calculations and analysis,the risk management and control measures for the debris flow risk in the town of Hechangchang basin of the Ertang River Basin in the Karst area have been formulated,and a preliminary plan for the risk management of debris flow in small watersheds in the Karst area has been designed.The entire small watershed is divided into four risk management and control units,namely are Pingdong Village,Chudong Village,Suiweisha Village and Shashang Village.For the extremely high-risk area,Pingdong gully,disaster prevention community,key risk early warning detection area and engineering risk management control area was set up.The remaining three risk management units have risk early warning monitoring areas and disaster prevention communities.7.A risk management model and detailed measures on Pingdong village,a key community,is proposed The risk management and control model for debris flow in Pingdong gully,a typical community,has been defined.The risk management and control measures includes: five basic disaster monitoring and warning systems including monitoring and early warning,disaster planning,residential site planning,disaster insurance,and community disaster management;three aspects including forecasts and plans,active disaster mitigation(controlling the factors and processes of disaster occurrence),comprehensive disaster reduction(combined with geotechnical engineering measures,ecological engineering measures,and non-engineering measures).