Flood Hazard Assessment Based On Spatially Explicit Multi-criteria Decision Analysis Under Uncertainty

Floods is the most frequent and the most serious natural disaster in human society,which profoundly affects the existence and development of mankind and is a major challenge faced by the whole world.China has a large population and an uneven distribution of water resources in time and space,which is one of the few countries suffered the most severe flood disaster in the world and faces arduous tasks in water control.In the new century,global warming is increasing the frequency of extreme precipitation events,which leads to a significant increase in suddenness,abnormality and uncertainty of the flood.In the face of frequent flooding and increasing loss,how to effectively cope with floods and reduce the adverse impact of disasters is a major challenge in the field of flood risk management.Flood risk assessment is an important means and foundation for flood risk management.It is helpful to improve the cognition level of the inherent law and spatial distribution pattern of flood risk,and then to promote the scientific level of decision-making on flood control and disaster reduction.Based on geographic information system,multi-criteria decision analysis,probability statistics and other theoretical knowledge,this paper studies the model and method of spatial multi-criteria decision analysis in flood risk assessment,which will be the basis for policy formulation and decision-making in the case of uncertainty.The main research work and innovations of the dissertation are as follows:(1)This paper sorts out the characteristics of the flood disasters and the research status quo of flood risk assessment,and systematically researches the basic theory and technical methods of spatial multi-criteria decision analysis,as well as the spatial multi-criteria decision analysis framework for flood risk assessment,thus laying a foundation for further research of flooding risk assessment.(2)For the uncertainty in the spatial multi-criteria flood risk assessment,this paper expoundes the classification of uncertainty,the sources of the uncertainty and how to cope with the uncertainty,then the theory of probability and statistics is utilized to quantify the uncertainty of criteria weights.Based on Monte Carlo simulation,a probabilistic space multi-criteria flood risk evaluation method is proposed,and then flood hazard evaluation for Gucheng County of Hubei province is selected as a case study to validate the efficiency of the proposed method.The experiment results show that the proposed method has realized the measurement and expression of the uncertainty of the evaluation results and has the actual feasibility and necessity.Therefore,the proposed method provides more information support for the accuracy and scientificity of flood risk management in uncertain circumstances.(3)For the lack of considering the effects of decision makers' risk attitude in spatial multi-criteria flood risk evaluation process,the ordered weighted averaging method is applied to incorporate the decision-maker's risk perception into the evaluation process,and thus taking into full account the influence of different risk preference or different decisionmaking strategies on the evaluation results.The experiment results show that the decisionmaker's risk attitude has a significant impact on the evaluation result: the higher the level of optimism of the decision-maker,the higher the risk degree of the evaluation result;and even a small change of the risk attitude can lead to huge differences in evaluation results.By comprehensively analyzing the impact of different risk attitudes,the results of flood risk evaluation can be as objective and accurate as possible,thus reducing or avoiding the decision-making risks caused by subjective factors.(4)For failing to consider the influence of the spatial heterogeneity of flood disaster system in the process of flood disaster risk evaluation,this paper expounds the differences between the conventional multi-criteria decision analysis and spatial explicit multi-criteria decision analysis,analyzes the spatial heterogeneity of flood risk and utilizes the ordered weighted averaging method which based on range sensitive principle and neighborhood model to carry out flood risk evaluation under spatial heterogeneity.The experiment results show that compared with the conventional multi-criteria decision analysis method,the spatially explicit multi-criteria method which based on the premise of spatial heterogeneity can better approximate the nature of the flood risk.And the revealed space distribution pattern of the flood risk is closer to the objective reality,this is helpful to better locate the serious flood disaster area and make flood control and disaster reduction more efficient and targeted.(5)For the robustness of spatial multi-criteria flood risk evaluation model and the sensitivity of the parameters of the model,this paper discusses the contents,the relationship and the common methods of the uncertainty analysis and sensitivity analyses.A spatially explicit uncertainty and sensitivity analyses method which based on Monte Carlo simulation is proposed,and the proposed method is used to compare the conventional multi-criteria decision analysis model and spatially explicit multi-criteria decision analysis model.The experiment results show that the proposed method can measure the robustness of the evaluation results and analyze the main sources that lead to the uncertainty of evaluation results,so as to ensure the evaluation results meets the required confidence level and improve the reliability of comprehensive decision-making for flood control and disaster reduction.