| Reservoir is one of the strongest flood control project with flood control and flood regulation,which plays an important role in electricity generation,water supply,irrigation and ecological environment improvement.As time goes on,lots of reservoirs become weak or serious inevitably.Once the reservoirs were broken,the downstream life and property would be threatened seriously.Therefore,the research of vulnerability assessment is valuable to develop disaster prevention and mitigation strategy of dam-break flood scientifically.However,the vulnerability of dam-break flood disaster is characterized by the damage or loss rate of the bearing body.Due to the complexity and the multi-sources of the influence factors of the vulnerability assessment,many problems exist in the process of the vulnerability assessment such as information deficiency,low accuracy of data,unclear assessment criterion and the human cognitive limitation,which result in lots of uncertainties.The necessary hydraulic factor is provided for vulnerability assessment from the numerical simulation of dam-break flood.Due to the huge social influences caused by the cascade reservoirs and urban reservoir dam-break,there is a tremendous need to study the vulnerability assessment of the dam-break flood disaster of the cascade reservoirs and urban reservoir.However,on the one hand,the research of the numerical simulation of cascade reservoirs is still in the initial stage.The empirical formulas or one-dimensional shallow water equations were used in the previous studies with the lack of the three-dimensional dam-break flood numerical simulation of cascade reservoirs.On the other hand,the fine modeling of complex underlying surface is the main difficulty of urban dam-break flood numerical simulation.In the previous studies,the one-or two-dimension model were used,by which the three-dimensional dam-break flood routing rules were difficult to be revealed under the condition of complex underlying surface.Therefore,combined with realistic demand and study hotspot and taking the cascade reservoirs and the urban reservoir as study objects,how to simulate the dam-break flood of cascade reservoirs and urban reservoir accurately in order to provide hydraulic factors for vulnerability assessment,how to consider the influence of uncertainty on the vulnerability of dam-break flood comprehensively,are the vital problems to be solved urgently in the vulnerability assessment of dam-break flood disaster.In this paper,the above problems have been deeply studied and analyzed,and the following research results are achieved:(1)Focused on the lack of systematic uncertainty analysis on the vulnerability assessment,a vulnerability assessment framework for dam-break flood disaster was proposed considering uncertainty influence.Firstly,the vulnerability assessment of dam-break flood disaster was analyzed,which mainly involved random,fuzzy and grey.Secondly,based on the summary of the domestic and foreign related studies on vulnerability,the connotation of vulnerability was discussed.Combined with the characteristics of dam-break flood disaster vulnerability,the dam-break flood disaster vulnerability was defined.The difference between vulnerability and risk of dam-break flood disaster was analyzed.Thirdly,according to the representation of the vulnerability of dam-break flood disaster,the vulnerability assessment of dam-break flood disaster can be divided into the index system-based method and the stage-damage curve-based method.Finally,a vulnerability assessment framework for dam flood disaster was established considering the influence of uncertainty,which could be used to guide the vulnerability assessment of dam-break flood disaster.(2)Focused on the situation of the dam-break flood of the cascade reservoirs simulated by the empirical and one-dimensional model and the lack of the urban dam-break flood simulation with three-dimensional fine modeling of complex underlying surface in the previous studies,the three-dimensional numerical model of the dam-break flood of cascade reservoirs and urban reservoir were developed.In the numerical simulation of the dam-break flood of cascade reservoirs,compared with the single dam-break flood,the differences were the superposition between different dam-break floods from cascade reservoirs,which caused the strong three-dimensional turbulence characteristics of dam-break flood.In addition,the initial boundary condition with the dry river bed was defined in the general numerical simulation of the dam-break flood without considering the initial flow rate of the river.Therefore,to reproduce the superposition phenomenon between the floods from cascade reservoirs,the three-dimensional numerical model of dam-break flood of cascade reservoirs were proposed on the basis of existing studies,in which the momentum and mass exchange between dam-break floods were realized by the inner boundary.The model was verified from the water depth and surface distribution compared with the experimental data by the dam-break experiment of cascade reservoirs.In the numerical simulation of urban dam-break flood,the one-and two-dimensional models of dam-break flood were adopted in the existing studies and the flood routing law couldn't be simulated accurately due to the complex topography and geomorphology.In addition,due to the impacts of secondary circulation,one-and two-dimensional model were limited in the dam-break flood simulation of complex underlying surface of dense urban.Aiming at the above problems,the threedimensional numerical model of urban dam-break flood based on the fine modeling of complex underlying surface was developed in the paper.Firstly,the three-dimensional high-precision digital modeling method was put forward.The polyhedral meshing technology was adopted to divide the digital model with the advantages of complex boundary adaptability of tetrahedrons and the numerical stability of hexahedrons.Then,the three-dimensional standard k-? turbulent mathematical model coupled with VOF method was developed.Finally,the proposed model was verified by comparing with the classical experiment of urban dam-break conducted by Italian and Belgian.(3)Focused on the index system-based method,in which the fuzzy uncertainty of the index was considered with the gray uncertainty ignored,the vulnerability assessment model coupled with grey relational grade-variable fuzzy set-improved set pair analysis was proposed for dam-break flood disaster.Focused on the stage-damage curve-based method without considering the random uncertainty,a vulnerability assessment method for the dam-break flood was proposed considering the random uncertainty.The index system-based method was less applied to dam-break flood disaster vulnerability assessment with the lack of comprehensive index system of vulnerability assessment.In addition,the fuzzy uncertainty of the index was considered,while the gray uncertainty was ignored in previous studies.Therefore,the dam-break of cascade reservoirs was taken as the study object.Firstly,based on the PSR(Pressure-State-Response)model,the vulnerability assessment index system of dam-break flood disaster was established.Then,considering the grey-fuzzy uncertainty,the vulnerability assessment model coupled with grey relational grade-variable fuzzy set-improved set pair analysis was put forward for dam-break flood disaster.Finally,the combination weighting based on game theory was proposed to reduce the subjectivity and improve the scientific nature of the weighting.In the vulnerability assessment study of urban dam-break flood disaster,due to the influence of disaster information,data precision and statistical method,the random uncertainty was introduced into the vulnerability assessment process.In order to solve the above problems,the longitudinal distributions of type use lands were studied and the existing flood stage-damage curves were corrected.Then,the vulnerability assessment model of dam-break flood disaster was established based on three-dimensional numerical simulation.Finally,the vulnerability assessment method of dam-break flood disaster was put forward considering the random uncertainty of land use types and stage-damage curves.(4)Based on the three-dimensional numerical model and vulnerability assessment method for dam-break flood disaster,the vulnerability assessment of the dam-break flood disaster was studied considering the influence of uncertainty.Based on the uncertainty analysis,the index system-based method and the stage-damage curve-based method were applied to the vulnerability assessment respectively.Firstly,the numerical simulation of the dam-break flood of the cascade reservoirs and the urban reservoir were conducted.The routing law of the dam-break flood was studied and the flood risk map was drawn.Secondly,the vulnerability of the dam-break flood of the cascade reservoirs was assessed considering gray-fuzzy uncertainty and the assessment results were compared with that of the other assessment methods.Finally,the vulnerability assessment of the urban dam-break flood disaster was conducted considering the random uncertainty.The bearing body exposure,vulnerability and uncertainty of the urban dam-break flood were analyzed.With the consideration of uncertainty of the dam-break flood disaster,the assessment results showed more vulnerability information,which provided theoretical basis and technical support for dam-break flood vulnerability management. |
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