Many estuaries contain sandy beaches that provide habitats and offer protective buffers for wetlands and infrastructure, alongside cultural and recreational resources. Research underpinning coastal management tends to focus on tide‐ and swell‐dominated sandy beaches, but little attention is given to beaches in estuaries and bays (BEBs) that exist along a continuum of wind/swell wave, tide and riverine influence. BEBs are subject to less wave energy than open coast locations because of the generally narrow window of directions for which ocean waves can propagate through the entrance. However, when storm wave direction coincides with the orientation of the estuary or bay entrance, waves can penetrate several kilometres inside. Here we focus on eight BEBs in two major bays/estuaries in Sydney, Australia and present observations from before and after a major extratropical storm with waves from an atypical direction in June 2016. We quantify magnitudes of beach erosion and recovery rates for 3 years post‐storm. We show that when high‐energy storm waves penetrate bays and estuaries, BEBs can undergo up to 100% of subaerial beach erosion. Three years after the storm, only 5 of the 29 (17%) eroded subaerial beach profiles had recovered to their pre‐storm volume. This is likely due to the lack of low‐frequency, beach‐building waves at BEBs under modal weather conditions in between storms, in contrast to open coast beaches. We also show that the recovery of BEBs may be limited by the absence of adjacent sediment reservoirs due to the dominance of tidal processes mid‐channel. Our study highlights the unique behaviour of BEBs relative to beaches on the open coast, and that shifting wave direction needs to be considered in long‐term beach resilience under climate change. © 2020 John Wiley & Sons, Ltd.

中文翻译：

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波浪方向的变化引发了河口和海湾海滩的严重侵蚀，风暴后恢复有限

许多河口包含沙滩，这些沙滩提供栖息地并为湿地和基础设施提供保护性缓冲带，以及文化和娱乐资源。支撑海岸管理的研究往往集中在潮汐和潮汐主导的沙滩上，但是对于沿风浪，潮汐和河流影响的连续性而存在的河口和海湾（BEBs）的海滩却鲜有关注。由于海浪可以通过入口传播的方向通常很窄，因此BEB的波浪能要比沿海地区少。但是，当风暴波的方向与河口或海湾入口的方向一致时，波会穿透内部几公里。在这里，我们重点介绍悉尼两个主要海湾/河口的八个BEB，澳大利亚和本国在2016年6月发生的大温带风暴之前和之后的观测结果中，都出现了来自非典型方向的波浪。我们对风暴后3年的海滩侵蚀和恢复率进行了量化。我们表明，当高能风暴波穿透海湾和河口时，BEB可能遭受高达100％的空中海滩侵蚀。暴风雨三年后，在29个侵蚀的空中海滩下，只有5个（17％）恢复到了暴风雨前的水平。与露天海岸的海滩相比，这可能是由于在风暴之间的模态天气条件下，BEB缺乏低频的海滩建造波。我们还表明，由于潮汐中游通道占主导地位，BEBs的回收可能受到邻近泥沙储集层的缺乏的限制。我们的研究凸显了BEB相对于开阔海岸海滩的独特行为，并且在气候变化下的长期海滩复原力中需要考虑波浪的移动方向。分级为4 +©2020 John Wiley＆Sons，Ltd.