Research On Theory And Method In Cascade Reservoirs Flood Risk Analyze

Along with the cascade reservoirs group successively built in our country, it is particularly important to research the flood risk problem of river basin security as a whole.There are many different risk sources in the operation of cascade reservoirs group, risk source complex, disaster chain length, influence degree big. At present, the research level of risk analysis needs to be improved.The cascade reservoirs group constitutes by a series of unite in space. The series of unite connect with each other, the upstream reservoir failure will impact the adjacent downstream reservoir. The safety of whole system will be impacted too. This research will use this problem as breakthrough point and take the Dadu river as an example, research the identify and evaluation problem of flood risk. The main research work is described as follows:(1) Construct the cascade reservoirs group multi-source risk source identify and evaluation framework, on the basis of the basic flows of the risk analysis, the theoretical system contain risk identify, quantification, evaluation. In the risk identify respect, through analysis the structural feature of cascade reservoirs, consider the nature and engineering risk are influence the operation of cascade reservoirs. This research analyzes the system flood risk under the two risk source. The weak engineering of system will be distinguished from the physical cause and probability statistics concentrations. In the risk quantity respect, the research use the failure risk model to analyze reservoirs venture ratio of invalidation, establishment the cascade reservoirs group system failure risk model by the theoretical basis of Bayes network, quantification the reservoirs and system posterior probability in the case of original design parameters and recommended design parameters. In the risk evaluation respect, through analysis the risk of life loss under the two conditions, evaluation the system risk whether or not in an acceptable range. The theoretical system will support the full research.(2) Analysis the design parameters such as, engineering quality demands, flood control criterion and the calculation method of design flood. The design flood of reservoirs calculated used the achievement of control hydrological station calculated by the method of area weighted interpolation. The weak engineering of system can't be determined only by design parameters. In order to consider the reservoirs design parameters through the integrated river basin, and the dam-break flow from upstream influence the security of downstream reservoirs. According to the physiographic characteristics of basin and hydro logic climate feature, divide the rainfall scenarios into Luding-Pubogou (A7) section and above Luding (B7) section. Take advantage of hydrometeorology calculated the Dadu river cascade reservoirs PMP and PMF.(3) In the angle of the physical causes, identify the structural failure reservoir and the functional failure reservoir under the two rainfall situation. In the angle of the mathematical statistics, judgement the two failure state reservoir, on the basis of reservoirs venture ratio of invalidation. The identify results will be contrast analysis and then confirmed the weak engineering finally. In consideration of the earth-rock dam is easily breaking when overtopping, make use of the dam failure analysis software analysis the dam-break, and then analysis the reservoir state in thesituation.On the purpose of river basin security, the results will put forward reasonable suggestions for reservoir design parameters. In the cascade reservoirs group, the weak engineering is risk trigger, once dam-break occurred in the system, the security of dominant engineering must be ensured. The dominant engineering could play a certain function in interdict risk.(4) In allusion to reservoir risk quantity and evaluation, this research includes the random distribution characteristics of excess flood peak standard serie, the random distribution characteristics of the highest flood water level and reservoirs venture ratio of invalidation respects. Based on the extreme value theory, use the check flood flow, check flood level, crest heights as threshold, research the random distribution characteristics of the excess flood peak serie and highest flood water level. The results show that:The excess flood peak match well with P-III curve, this result conform to flood element distribution regularity of most region, the highest flood water level match well with the logarithm function.(5) In the reservoirs venture ratio of invalidation respect, divide the reservoirs into three parts according to developing order of each reservoir. The Monte Carlo Simulation Method will be used to caculte reservoirs venture ratio of invalidation. Comparative analysis the result and the weak engineering, the results indicate that:in order to ensure the onger-term security of basin, the reservoirs need to be constructed in the basin by different batchs. At the same time, the result will offer data support for the bayes network model.(6) On account of the structural physical feature of cascade reservoirs group, the certain of correlation exist between each reservoirs, the reservoir failure is conditional probability events.The Bayes network has some advantages in uncertain knowledges expression and causal reasoning. The resreach establish the Bayes network model of cascade reservoirs venture ratio of invalidation. On the basis of dominant engineering, the basin is devided into Bala-Shuangjiangkou, Houziyan-Pubugou two parts(D1?D2). The modle analyzes the venture ratio of invalidation underoriginal design parameters and recommended design parameters. Meanwhile, this charpter builds up the Bayes network model of each reservoir action to system. Result proves that:the venture ratio of invalidation from recommended design parameters significantly reduce. The result of each part system is similar with the dominant engineering. This paper used the risk control criterion of the special grade and the acceptable level of risk of life loss to evalution the invalidation ratio. It turned out that the recommended design parameters can significant reduction the risk.