不同二变量重现期在水利工程防洪设计中的应用对比——以桂平航运枢纽为例

Comparison of Different Bivariate Return Periods in Flood Control Design of Hydraulic Structure: A Case Study on Guiping Shipping Hub

针对多变量洪水共同作用下的水利工程,已有的多变量重现期计算所得的防洪参数仍存在防洪能力不一致导致的风险,多变量重现期的定义与计算也成为洪水频率分析中的重难点。介绍了一种新的多变量重现期定义——防洪重现期,并与传统二变量重现期在定义及危险域划分方面进行对比,再以桂平航运枢纽为例,利用Copula函数构造干支流洪水的联合分布,计算分析防洪重现期与传统二变量重现期在防洪设计中的差异,验证防洪重现期在洪水风险分析中的合理性与可靠性。研究表明,防洪重现期考虑了洪水组合与调洪耦合的关系,利用防洪重现期计算得到的防洪设计参数,防洪能力与防洪标准一致,能避免高估洪水风险,增加工程费用或低估洪水风险,增加工程防洪破坏风险的问题。

Under the combined action of multiple variables of flood,hydraulic projects are subjected to risks of inconsistent flood control capaciy caused by flood control parameters calculated from existing multivariate return periods.Hence,the definition and calculation of multivariate return period has become a difficulty in flood frequency analysis.In view of this,a new definition for multivariate return period is proposed in this paper,that is,flood control return period.Flood control return period is defined as the average time between two successive events(event is defined as the flood control design parameter being exceeded).The coupling relationship between flood combinations and flood regulation are taken into consideration.The proposed return period is compared with traditional bivariate return periods in terms of definition and risk area delimitation.With Guiping shipping hub as a case study,the differences between the proposed flood control return period and the traditional bivariate return periods in flood control design are calculated and examined by constructing the joint distribution of floods in the mainstream and tributary using the Copula function.The rationality and reliability of flood control return period are verified.The results manifest that flood control capacity can be consistent with flood control standard by using the proposed return period.Overestimating flood risks and increasing of engineering cost,or underestimating flood risks and increasing of flood damage can both be avoided.