Over half of the global population and the majority of the cities in coastal zones are at risk of coastal flooding. Changes in the occurrence of individual extremes and the interactions between hydrological and coastal variables can exacerbate flood risks. While extensive research has been conducted to understand and predict different types of flood hazards in isolation, spatial and temporal trends and variability of compound flooding, that is, flooding caused by multiple drivers, remain an open question. This study investigates the individual and joint temporal variations of multiple drivers that can cause compound flooding in Canada's coasts including total water level, storm surge, precipitation, and streamflow. Long‐term changes in the frequency and intensity of extremes are analyzed over the Atlantic, Pacific, and the Great Lakes regions. Univariate and multivariate trend tests including Mann Kendall, Covariance Inversion Test, Covariance Sum Test, and Covariance Eigenvalue Test are applied. In addition, a new multivariate index based on the contributing flood drivers transformed into a probability space is proposed, and its application to study compound flooding is investigated. Overall, results show increased risks of individual and compound flooding over the Atlantic coast and varying trends in the Pacific and Great Lakes regions. The multivariate trend indices show consistent results in most scenarios. The proposed index provides a simple and flexible measure to analyze the spatial and temporal variation of compound flooding risks at different thresholds. The results highlight the importance of considering nonstationary compound flood events to develop resilience strategies in coastal environments.

中文翻译：

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加拿大沿海地区个体和多元复合洪水驱动因素的最新趋势

全球一半以上的人口和沿海地区的大多数城市面临沿海洪灾的风险。个别极端事件的发生变化以及水文和沿海变量之间的相互作用会加剧洪灾风险。尽管已经进行了广泛的研究来孤立地理解和预测不同类型的洪水灾害，但复合洪水的时空趋势和变化性（即由多个驱动因素引起的洪水）仍然是一个悬而未决的问题。这项研究调查了可能导致加拿大沿海复合洪水的多种驱动因素的个体和联合时间变化，包括总水位，风暴潮，降水和水流。分析了大西洋，太平洋和五大湖地区的极端频率和强度的长期变化。应用了单变量和多变量趋势检验，包括Mann Kendall，协方差反转检验，协方差和检验以及协方差特征值检验。此外，提出了一种基于将洪水驱动因素转化为概率空间的新的多元指标，并研究了其在复合洪水研究中的应用。总体而言，结果表明，大西洋沿岸的个人和复合洪水的风险增加，太平洋和大湖地区的趋势也有所变化。在大多数情况下，多元趋势指数显示出一致的结果。拟议的指标提供了一种简单灵活的措施来分析不同阈值处的复合洪水风险的时空变化。