Impacts of climate change and human activities may lead to changes in the spatiotemporal composition of the design flood as well as its size. Previous studies mainly focused on changes in design flood size, while there has been relatively little research on changes in its regional composition. In this study, a nonstationary multi-site design flood estimation method is developed, which is useful for the design flood regional composition analysis under nonstationary conditions. Dynamic copula models are first constructed to analyze the change in the joint distribution of the nonstationary multi-site flood variables with the consideration of the nonstationarity of the marginal distribution and copula structure parameters. Then the design flood combinations in multi-site for a specified design standard are calculated by comprehensively applying the equivalent reliability method, the expectation conditional and the most-likely conditional combination strategies, which considers the future precipitation change and design lifespan length impacts on the design flood. Finally, the uncertainty of the multi-site design flood estimation caused by the model parameters uncertainty is evaluated. A case study, based on the annual maximum 7-day (AM7) flood volume in the Yichang (YC) and Cuntan (CT) sites, is conducted to illustrate this method. Results show that flood quantiles in the YC and CT sites exhibit an increasing trend as the precipitation projections will increase in the future, but the flood quantiles in the YC site are less compared to the historical period because of the huge regulation and storage effect of the Three Gorges Reservoir. In addition, the design flood combination in the CT and YC sites are calculated and the CT design floods from the expectation combination strategy are bigger than those provided by the most-likely combination strategy.

中文翻译：

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非平稳多站点设计洪水估算及其在设计洪水区域构成分析中的应用


气候变化和人类活动的影响可能导致设计洪水的时空组成及其规模发生变化。以往的研究主要集中在设计洪水规模的变化上，而对其区域构成变化的研究相对较少。本研究开发了一种非平稳多站点设计洪水估算方法，可用于非平稳条件下的设计洪水区域成分分析。首先构建动态Copula模型，考虑边缘分布和Copula结构参数的非平稳性，分析非平稳多点洪水变量联合分布的变化。综合运用等效可靠度法、期望条件和最可能条件组合策略，计算指定设计标准下的多场地设计洪水组合，考虑未来降水变化和设计寿命长度对设计的影响洪水。最后，评估了模型参数不确定性导致的多站点设计洪水估算的不确定性。以宜昌 (YC) 和寸滩 (CT) 站点年度最大 7 天 (AM7) 洪水量为基础进行案例研究来说明该方法。结果表明，随着未来降水量的增加，YC和CT站点的洪水分位数呈现增加趋势，但YC站点由于巨大的调节和调蓄作用，洪水分位数较历史时期减少。三峡水库。 此外，还计算了CT和YC站点的设计洪水组合，并且期望组合策略提供的CT设计洪水大于最可能组合策略提供的设计洪水。