基于Copula函数的设计洪水地区组成研究

Regional design flood composition based on Copula function

洪水地区组成具有较强的随机性,最科学的分析方法是给出各地区洪水的联合分布,本文应用Copula函数构造了上游断面与区间洪水的联合分布,提出和推导了两种有代表性的设计洪水地区组成:条件期望组成和最可能组成。由条件期望地区组成分析了同频率组成所处的水平,应用实例表明,同频率组成保证率偏低,低于期望水平。本文所推导的条件期望组成还包含了置信区间等信息,为决策人员明晰决策风险提供了依据;推求的最可能组成考虑了地区间洪水的空间相关性,更加符合客观实际,为设计洪水地区组成分析计算提供了一条新的途径。

Regional flood composition is in general a spatially stochastic problem,and the most scientific analysis method is to construct a joint distribution for the composition regions.In this paper,Copula function was used to establish the joint distribution of upper-station flood and interval-basin flood.The conditional expectation composition and most likely composition were proposed and derived.The guarantee level of equivalent frequency composition was analyzed by comparing with conditional expectation composition.A case study suggests that conditional expectation composition is at a low guarantee level.The derived equivalent frequency composition contains confidence interval and other information that is useful to decision-making.The derived most likely composition that considers the spatial correlation of regional flood is more practical.The proposed method provides a new approach for analysis of regional flood composition.