The cooccurrence of coastal and riverine flooding leads to compound events with substantial impacts on people and property in low-lying coastal areas. Climate change could increase the level of compound flood hazard through higher extreme sea levels and river flows. Here, a bivariate flood hazard assessment method is proposed to estimate compound coastal-riverine frequency under current and future climate conditions. A copula-based approach is used to estimate the joint return period (JRP) of compound floods by incorporating sea-level rise (SLR) and changes in peak river flows into the marginal distributions of flood drivers. Specifically, the changes in JRP of compound major coastal-riverine flooding defined based on simultaneous exceedances above major coastal and riverine thresholds, are explored by midcentury. Subsequently, the increase in the probability of occurrence of at least one compound major coastal-riverine flooding for a given period of time is quantified. The proposed compound flood hazard assessment is conducted at 26 paired tidal-riverine stations along the Contiguous United States coast with long-term data and defined flood thresholds. We show that the northeast Atlantic and the western part of the Gulf coasts are experiencing the highest compound major coastal-riverine flood probability under current conditions. However, future SLR scenarios show the highest frequency amplification along the southeast Atlantic coast. The impact of changes in peak river flows is found to be considerably less than that of SLR. Climate change impacts, especially SLR, may lead to more frequent compound events, which cannot be ignored for future adaptation responses in estuary regions.

中文翻译：

---

气候变化和美国沿海沿岸河水复合洪灾的变化

沿海和河流洪水的共同发生导致复合事件，对低洼沿海地区的人员和财产产生重大影响。气候变化可能会通过更高的极端海平面和河流流量来增加复合洪灾危害的程度。在此，提出了一种双变量洪水灾害评估方法，以估计当前和未来气候条件下沿海-河滨河的复合频率。通过将基于海平面上升（SLR）和峰值河流流量的变化纳入洪水驱动力的边际分布，采用基于关联函数的方法来估算复合洪水的联合恢复期（JRP）。具体而言，到本世纪中叶，人们开始探索基于同时超过主要沿海和河流阈值的同时超出量而定义的主要沿海-河流复合洪灾的JRP变化。随后，在给定的时间段内，至少发生了一次复合性主要沿海-江河洪水泛滥的可能性的增加。拟议的综合洪水灾害评估是在美国连续海岸沿线的26个成对的潮汐-河沼站进行的，并提供了长期数据和确定的洪水阈值。我们表明，在当前条件下，东北大西洋和墨西哥湾沿岸的西部地区经历的最大的主要沿海-河滨复合洪水概率最高。但是，未来的SLR场景显示了东南大西洋沿岸的最高频率放大。峰值河流量变化的影响被发现比SLR的影响要小得多。气候变化的影响，尤其是SLR，可能导致更频繁的复合事件，