基于二次重现期的多变量洪水风险评估

由于洪水是一种具有多个特征属性的随机事件,频率分析成为洪水风险评估的一种有效手段,多变量重现期与设计值的定义与计算则是洪水频率分析中的重点和难点.本文通过构造洪水历时、洪峰与洪量的联合分布,介绍了一种新的多变量重现期定义——二次重现期,并探讨了"或"重现期、"且"重现期和二次重现期对安全与危险域识别的差异性,以及在洪水风险管理与工程设计中的合理性与可靠性.传统的"或"和"且"多变量重现期对安全与危险域的识别存在局限性,利用Kendall函数定义的二次重现期则提供了更加合理的安全与风险域识别,避免了对安全事件与危险事件的错误判定,更有利于指导洪水风险的管理.在给定的二次重现期条件下,依据出现概率最大原则推算的历时、洪峰与洪量设计值组合可以满足工程设计以较低成本承受较大风险的追求,相比于单变量设计值,考虑了洪水多个属性联合特征的多变量设计值提供了更加全面和可靠的参考信息.

Multivariate flood risk assessment based on the secondary return period

Frequency analysis is a useful tool for flood risk assessment, but the definition and calculation of return periods and design values in a multivariate framework are difficult tasks. In this paper, by constructing the joint distribution of flood duration, peak discharge and volume, we introduced the definitions of multivariate "OR", "AND" and secondary return periods and discuss their differences in identifying the safe and dangerous regions in a critical level. The rationality and reliability of information provided from them in flood risk management and engineering design were then analyzed, respectively. The traditional "OR-AND" approach in multivariate return periods definition is limited in the identification of safe and dangerous regions, while the secondary return period based on the Kendall measure would be more rational. Consequently, mistakes in the recognition of safe and dangerous event can be avoided by the use of second return period, which, obviously, is better for the flood risk management. For a given second return period, the combination of flood duration, peak discharge and volume design values calculated from the most-likely approach, may have an advantage to meet the requirement that with low cost to bear greater risks in engineering design. Furthermore, the information provided from multivariate design values would be more considerate and reliable than the univariate ones.