Abstract As sea level rises and development of the coastal zone continues, coastal flooding poses an increasing risk to coastal communities. Wave runup can contribute many meters to the vertical reach of the sea, especially on steep gravel beaches, and wave overtopping is a key contributor to coastal flooding along coastlines exposed to energetic wave conditions. However, operational forecasting of wave overtopping has rarely been attempted due to the need for high-resolution inshore water levels and wave conditions, up-to-date coastal profile and sea defence information, and availability of models or formulae that can robustly predict overtopping for a range of coastal profile types. Here, we have developed and tested an efficient forecasting system for providing operational warnings up to three days in advance for the entire 1000 km coastline of southwest England, called SWEEP-OWWL, which is capable of predicting wave runup elevation and overtopping volumes along the energetic and macrotidal coastline, featuring embayed, sandy, gravel, and engineered regions. Existing flood warning systems have used the process-based hydrodynamic model XBeach, but due to the computational cost, have resorted to populating look-up tables using off-line simulations and only a single realisation of the coastal bathymetry. Instead, SWEEP-OWWL runs in ‘real-time’ using a computationally efficient suite of empirical shoaling, breaking, runup, and overtopping equations at 184 coastal profiles, forced with hydrodynamic information from a regional 1-km spectral wave and hydrodynamic model. Importantly, the forecast system can be updated with the latest coastal profile data with no extra computational cost, which is shown to improve the accuracy of predicted overtopping rate by an order of magnitude in some cases. Compared to visual observations of flooding events from live streaming webcams around the southwest, the system correctly predicted the presence or absence of wave overtopping with 97% accuracy and showed skill in differentiating between low and high hazard events. Reliable forecasts of wave overtopping could considerably enhance a coastal community’s ability to prepare and mitigate against the risk to life, property, and infrastructure during coastal flooding events, and the developed system shows that this can be achieved using a single desktop PC for entire regions featuring both natural and man-made sea defences.

中文翻译：

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预测人工设计和自然防御的海岸线的沿海溢流

摘要 随着海平面上升和沿海地区的持续发展，沿海洪水给沿海社区带来了越来越大的风险。波浪爬高可以为海洋的垂直范围贡献数米，特别是在陡峭的砾石海滩上，而波浪漫顶是沿着暴露于高能波浪条件的海岸线发生沿海洪水的关键因素。然而，由于需要高分辨率的近岸水位和波浪条件、最新的海岸剖面和海防信息，以及可以可靠地预测海浪溢流的模型或公式的可用性，因此很少尝试对海浪溢流进行业务预测。一系列沿海剖面类型。这里，我们开发并测试了一种高效的预报系统，可以为英格兰西南部 1000 公里的整个海岸线提供最多三天的操作警告，称为 SWEEP-OWWL，它能够预测沿高能和大潮汐的波浪爬高高度和溢流量海岸线，以海湾、沙地、砾石和工程区域为特色。现有的洪水预警系统已经使用了基于过程的流体动力学模型 XBeach，但由于计算成本，已经使用离线模拟填充查找表，并且仅对沿海测深进行了单一实现。相反，SWEEP-OWWL 在 184 个海岸剖面上使用一套计算效率高的经验浅滩、破碎、爬升和越过方程“实时”运行，使用来自区域 1 公里光谱波和水动力模型的水动力信息。重要的是，预测系统可以使用最新的海岸剖面数据进行更新，而无需额外的计算成本，这表明在某些情况下可以将预测的漫顶率的准确性提高一个数量级。与西南地区的实时流媒体网络摄像头对洪水事件的视觉观察相比，该系统以 97% 的准确率正确预测了海浪漫顶的存在与否，并显示了区分低危险事件和高危险事件的技巧。可靠的海浪淹没预报可以大大提高沿海社区在沿海洪水事件期间准备和减轻生命、财产和基础设施风险的能力，