Elements-at-Risk As A Framework For Modeling The Complex Disaster Scenario Of Hazard-Affected Regions

Recent years,all kinds of major disasters are taking place frequently.These disasters show a tendency of obvious secondary or derivative characteristics and usually lead to the formation of disaster chains,which make the disaster scenarios more complicated and severe.Especially for those unconventional emergencies,the probability of occurrence is always unable to be predicted,the influence scope of disaster consequences is broad,and it is difficult to deal with effectively using conventional emergency countermeasures.Therefore,the paradigm of emergency decision-making is changing from "prediction-response" to "scenario-response.”Modeling and evolution deducing of disaster scenario is a kind of strategic risk management approach,which is based on the understanding of the formation and evolution mechanism of disasters,to prepare for uncertain future disasters according to "bottom line thinking." It emphasizes "prepare for the worst-case," and the results can be used as the basis for identifying disaster risk and realizing emergency decision-making of "scenario-response" which directly aims at coping with the states and trends of disaster consequence.The scenario-based approach can contribute to the transition of emergency management from focusing on post-disaster relief to pre-disaster preparedness and prevention,from taking consideration of single disaster type separately to comprehensive disaster reduction,and from reducing disaster losses to mitigating disaster risk.Taking the nature of the discrepancy in disaster loss risk among different disaster-affected regions into consideration,this work focuses on the research of problems about disaster scenario modeling and disaster scenario evolution deducing,which can not only reflect the characteristics of the hazard-affected regions but also adapt to multi-disaster risk assessment.Hence,this paper proceeded from the formation mechanism of disaster consequence with the elements-at-risk(EARs)as the core,which is beneficial to cross the limits of single disaster as well.We hope that our research can provide some valuable suggestions for realizing the paradigm of"scenario-response" in emergency management.The main work in this dissertation was organized as follows:(1)The spatial distribution characteristics of EARs.Firstly,this paper analyzed the basic disaster characteristics of EARs that may influence the risk level of disaster loss and prosose a hierarchical distribution model of EARs.And then based on land-use patterns,the analysis method of the spatial distribution characteristics of some critical EARs was proposed.For the built environment,the map relations between bulidings and land-use patterns were determined in the functional dimension;a vulnerability index system was developed in the structural dimension.For the population,human activities that contribute to spatial distribution variance were considered to establish the correlation between human types and land-use patterns at a regional scale.In this basis,this paper proposed a spatial-temporal human exposure model which was applied to the analysis of potential human exposure in the built district of Dalian City.(2)The topological interrelation of impact between EARs.The states of EARs directly reflect the disaster consequence and the complicated interrelations between EARs lead to the diversity of evolution trends.Firstly,the concept of disaster evolution attribute of EARs was defined based on the chain reaction mechanism of emergencies.This paper studied the divided ways of the states of EARs and summarized the evolution modes of the EARs’ states into four types.On these bases,the method to determine the evolution paths of the EARs’ states was proposed.Secondly,the "egg-yolk" representation of EARs was put forward considering the disaster evolution attribute and a kind of topological interrelation of impact was defined to describe the interrelations among EARs based on region connection calculus theory.Through typical case analysis,the practicability of the "egg-yolk" representation of EARs and topological interrelation of impact between EARs were illustrated.(3)Hazard-affected region modeling based on EARs and topological interrelations of impact between EARs.Based on system theory and the requirmmts of disaster scenario deducing,EARs and topological interrelations of impact between EARs were chosen as the core to model the hazard-affected regions.Further,this paper studies the modeling method and process.Firstly,based on the mapping relation between hazards and EARs,a bipartite graph of hazards and EARs was obtained,and by means of turning the bipartite graph to a unipartite network of EARs,the logical relationship network of EARs was bulit.After concreted the EARs according to the target region,it is the network of all potential impact relations between EARs in the specific region.Finally,the network of topological interrelations of impact between EARs to represent the target region was obtained,according to the judgment of the type of topological interrelation of impact between EARs based on "the most dangerous rule".What’s more,a hypothetical region was designed to illustrate the modeling method,and a relative risk analysis idea was given along with this method.(4)A dynamic model of regional disaster scenario evolution was built considering the phenomenon of multiple disasters coupling.The core thought of the dynamic model of regional disaster scenario evolution is that the occurrence and development of the event can be characterized by the change of the EARs’ states,and the purpose of risk identification and scenario response can be accomplished meanwhile.Firstly,the disaster scenario was divided into three stages,i.e.,initial scenario,evolutionary scenario and terminal scenario.By analyzing the factors that might motivate the change in the states of the EARs,the disaster spreading dynamic model on the network model of the region was developed.Secondly,the simulation process of the core segment of the model was designed.Then this paper implemented multi-group simulations under the disaster situation of the earthquake and conducted comparative analysis from different angles:the change trends of the EARs’ states,the release degree of the dangerousness in the region,zoning of the secondary risk and the evolution paths of disaster consequence.The strategies for achieving "scenario-response" were suggested following the principles of risk control and disaster loss minimizing.