The Study Of Flood Safety Risk Rate Model And Flood Control Standard Of Reservoirs (Group)

Reservoir is one of primary structural measures to alleviate flood hazard, and the new flood damage reduction strategy is represented by reservoir risk management etc. The flood safety risk analysis of reservoir and reservoir group system may provide a quantitative and consistent probability standard for comparison and selection of panning design schemes and determination of flood control operation rules. It provides a criteria for judging whether the dam is safe. So there are some significant meanings both in theory and in practice on research of reservoirs risk which meets current technique requirements. With single reservoir and series reservoirs as study objects, and computation methods of risk rate as the leading line, the paper has analyzed the problem of flood control safety of single reservoir itself, the protected zone and cascade reservoirs, the determination problem of flood control standard of reservoirs in series, the coordination problem of reservoir system safety, and the determination problem of dam flood control safety risk standard, etc. The main contributions are as follows:(1) The risk sources existing in flood safety design and conventional flood control operation were identified and analyzed, and the primary risk factors were presented explicitly in this paper, which are the loading factors, (i.e. reservoir inflow and wind waves), initial condition factor, (i.e. starting reservoir water level), boundary condition factors, (i.e. storage curve and water surface area curve), resistance factors, (i.e. the discharging capacity of flood releasing structure, dam crest elevation or wave protection wall crest elevation) , respectively. The probability distributions and methods used to determine distribution parameters of risk factors above were also analyzed and given.(2) On the basis of the definition of the reliability of designed discharging capacity, the optimization model to calculate the flood releasing structures'designed discharging capacity reliability or risk rate was established, and the corresponding PSO solution algorithm was presented. The model doesn't directly give the discharging capacity variable's distribution form and parameters, but by analyzing combination action of basic risk elements to calculate the risk, avoids the randomicity of assuming distribution subjectively and the partial differential operation required in solving the complex nonlinear limit state equations, it is relatively simple and precision is improved.(3) The risk transfer mechanism of reservoir flood routing was analyzed in this paper. The probability distribution of the highest reservoir water level behind dam is demonstrated by combining the stochastic simulation flood routing with Maximum Entropy Distribution. The conclusion is that the highest reservoir water level behind dam don't always follow the normal distribution for certain frequency's design flood, it was suggested to treat different reservoirs with different ways according to specific situation, and to adopt theMaximum Entropy Distribution as the distribution of the highest reservoir water level behind dam when calculating the risk.(4) The overtopping risk model under floods and wind wave jointly action was established.There are two differences between the established model and conventional model, they areâ‘ Using the Maximum Entropy Distribution as the distribution form of the highest reservoir water level behind dam , by means of the advantage that the Maximum Entropy Distribution is minimal bias distribution.â‘¡Transforming combination probability formula and considering the impact by various flood hydrograph modes in calculating the overtopping risk, respectively. With better overall and rational risk factors included in the established, the precision of risk is further improved.(5) According to the similarity, the problem of studying out the flood spatial pattern schemes is abstracted as the limit state problem in structure reliability theory, the design points correspond to the regional composition scheme, and risk corresponds to the occurrence likelihood. The method may better overcome the difficult of studying out the most probable flood spatial pattern scheme. In order to ensure the project safety further, it was suggested to consider the most probable flood spatial pattern in deriving the design flood, in terms of the principle of using many various methods, implementing comprehensive compare and selecting rational scheme.(6) By means of the advantages of JC method and reliability theory in solving the risk rate, the revised frequency model of combining flood at downstream control section was established. The flood risk rate is obtained by interpolating the revised frequency curve. The model can better deal with the correlation of regional flood, and it is simple and convenient relatively.(7) The paper has analyzed the computation method of risk rate of cascade reservoirs, defined the system risk rate and presented the relation formula between system risk rate and individual reservoir's risk rate. From planning design to operation management, many methods and measures to coordinate and improve the cascade reservoir flood control standard in various steps were presented.(8) The"risk-as-feeling"theory and"prospect theory"in new economics were introduced in this paper, by which, the problem on people's aversion to dam risk was interpreted. It is pointed out that people should attach enough importance to the perceived feeling to risk. The determination procedure and principle of dam safety risk standard were presented in this paper, and the conversion formula between dam safety risk standard and flood safety risk rate were also given.