Study On Regional Composition Of Design Flood And Flood Control Dispatch Under Changing Environment

Current studies on the composition of design flood areas are based on the hypothesis of hydrological consistency.For the design of reservoir flood control and flood control level and planning rules based on the assumption of consistency should make the corresponding change.In this paper,an inconsistent method for calculating the composition of design flood area was established.Taking it as input,which is applied to the formulation of reservoir flood limit water level and flood control dispatching research.In order to take inconsistency into account in regional composition,firstly,the mutation recognition of sequences was carried out according to the mutation diagnosis system.Inconsistent sequences were divided into two subsequences bounded by mutation points,then the conditional probability distribution model based on P-III distribution was coupled with the calculation method of regional composition and the calculation method,which is used to calculate the design flood region composition of inconsistency condition,was formed.Then,according to the results,the flood control regulation and flood limit water level of the design section were redrawn,and the risk and benefit were analyzed.The results of application examples are as follows:(1)It was comprehensivly analyzed the inconsistency of flood peak sequence in upper Shiquan,Shi-An region and downstream Ankang design sections by using the mutation diagnosis system.After preliminary diagnosis,detailed diagnosis and comprehensive diagnosis,the consistency of flood peaks in all three regions was destroyed.The results show that all three regions are jumping variation.And variation years are 1990,1987 and 1985.(2)The conditional probability distribution model based on P-III distribution was the best one in the goodness test of 4 linear types in P-III distribution,Weibull-3 distribution,LN-3 distribution and Gev distribution.By estimating the parameters of conditional probability distribution model and calculting,we obtained the natural design flood in Shiquan,Shi-An and Ankang zones at different frequencies.(3)It was proposed a calculation method considering the composition of inconsistent design flood area and obtained one typical combination,two same frequency combinations,two conditional expectation combinations and one most probable combination.There are altogether six regional combinations.the application example shows that:(a)The most probable combination is the most probable value in statistical sense.The area in which interval flood inflow is relatively large,the typical combination was closed to the most possible combination.There is a high probability that the occurring flood will be a type of disadvantage to flood control.(b)In the same frequency combination between upstream and the design section of this area,the corresponding value of interval exceeded its expected value,and it was given more consideration about the uncontrollable amount of water in the interval.(c)Coupling about inconsistency calculation method and regional composition calculation method is a new way to calculate design flood region composition of inconsistency condition.(4)This paper established Ankang Reservoir Simulated Reservoir Regulation Model.Ankang reservoir inflow flood affected by regulation and storage of Shiquan Reservoir under different combination forms as input,through trial calculation and comparison,the new flood limit water level of Ankang Reservoir is 324.8m and the risk rate is 0.0123%o,which is lower than 0.1‰ for checking risk rate of Ankang Reservoir.