变化环境下珠江河口区复合洪水事件遭遇分析

Analysis of Compound Flood Event Encounters in the Pearl River Estuary under Changing Environments

受全球气候持续变暖影响,沿海城市受到上游洪水、热带气旋、天文潮等海陆要素联合驱动引发的复合洪水事件频发,严重威胁该地区人民生命财产安全。以1986—2018年间影响珠江河口区的135场台风为统计样本,采用Mann-Kendall检验法和Pettitt检验法分析复合洪水事件的发生趋势和变化情况,并通过Vine Copula拟合复合洪水事件潮位、风速、流量三变量的联合分布函数,采用Copula似然比检验法对联合分布函数相关结构进行变点检验。研究结果表明:考虑Vine Copula函数突变的情况下三个变量间的相关性增强,能更好地反映各个变量间随事件变化的相依关系,提高了复合洪水事件重现期评估的准确性。近三十年来热带气旋数量呈现出下降趋势,而风速则呈现显著增强的趋势且风速在2002年发生突变,即热带气旋事件呈现“出现次数下降、等级增强”的特性。在变化环境下“天鸽”“山竹”等极端复合洪水事件联合重现期计算结果相比传统固定参数的Copula重现期计算结果小,即未来极端复合洪水事件发生概率在增大。

Under the influence of continuous global warming,compound flood events triggered by upstream floods,tropical cyclones,astronomical tides,and other sea and land elements driven jointly are frequent in coastal cities,seriously threatening the safety of people′s lives and properties in the region.Based on 135 typhoons affecting the Pearl River Estuary during 1986-2018as statistical samples,this study used Mann-Kendall test and Pettitt test to analyze the occurrence trend and change of composite flood events.Vine Copula was used to fit the joint distribution function of the three variables of tide level,wind speed and discharge of a composite flood event,and Copula likelihood ratio test was used to test the correlation structure of the joint distribution function.Considering the mutation of Vine Copula function,the correlation between the three variables was enhanced,which can better reflect the dependence of each variable with the change of events,and improve the accuracy of the assessment of the recurrence period of complex flood events.In the past 30 years,the number of tropical cyclones has shown a decreasing trend,while the wind speed has shown a significantly increasing trend,and the wind speed has a sudden change in 2002,that is the characteristics of tropical cyclone events have shown a decrease in the number of occurrence and an increase in the grade.Under the changing environment,the calculated results of the combined recurrence period of extreme composite flood events such as "Hato" and "Mangosteen" are smaller than the calculated results of the traditional fixed parameter Copula recurrence period,that is the occurrence probability of extreme composite flood events in the future is increasing.