基于Copula函数的感潮河段洪潮遭遇组合风险分析研究

Research on Encounter Risks of Floods and Tides in Tidal River Based on Copula Function

感潮河段的水位受上游河道洪水与下游河口潮位共同影响,故其河段整治规划中洪潮遭遇分析尤为重要。以瓯江感潮河段为研究区,提出从实测洪潮遭遇数据的频率结构特性出发,选取对上尾部更敏感的Gumbel Copula函数建立洪水和潮位的联合分布,推求各种洪潮组合的重现期,进而建立风险模型。从治涝风险、同现风险和组合风险多角度评估设计组合值的合理性。结果表明:基于Gumbel Copula函数构建的联合分布能够较好的反映瓯江感潮河段的洪潮组合特性。瓯江感潮河段部分现役工程所采用的20a一遇的设计洪水与较不利潮位(5.8m)这一设计组合型的同现重现期为29a,同现风险率为3.46%、组合风险率为11.52%、治涝风险率为15.94%,其防洪涝能力稍显不足。同时基于Copula函数所建立的风险模型集能够较好地对感潮河段防洪设计标准进行风险评估,为感潮河段整治规划提供决策支持。

The water stages of tidal reaches are affected by upstream flood and downstream tide, thus, the analysis of the encounters of tide and flood in harnessing and planning for tidal reaches is indispensable. This paper took the tidal reaches of Oujiang as study area, and Gumbel Copula function was choosen to construct the joint probability distribution of flood and tide based on the structure of the ob served data, which is sensitive to the upper tail area. Then, the return periods were calculated and the risk models were established. And the rationality of different design standards was evaluated from the indexes of waterlogging prevention risk, simultaneous risk and joint risk. The results show that Gumbel Copula function works well in showing the characteristics of Oujiang’s tidal reaches. The simultaneous return period, which combined twenty-year return period of the design standard and the typical harmful tidal level(5.8 m), is twenty-nine-year. And the rates of simultaneous risk, joint risk and waterlogging control risk are 3.46%, 11.52% and 15.94% respectively. Risk models based on Copula function can provide decision support and risk assessment for the design standard of waterlogging prevention in tidal reaches.