Coastal floods are driven by many hydro-meteorological forcing factors, among which are mean sea levels, tides, atmospheric storm surges, and waves. Depending on these conditions, wave overtopping may occur and, in some cases, lead to a significant flood. In the present study, we investigate the effect of the stochastic character of waves on the flood itself using a phase-resolving wave model (SWASH). We focus on the macro-tidal site of Gâvres (France), consider two past flood events (both resulting from wave overtopping), and investigate how the effect of randomness of waves on the flood is changing with the forcing conditions and the time span (minutes to hours). We clearly show that the effect of waves’ stochasticity on the flood itself is far from being negligible and, especially on a short time scale (~15 min), generates an uncertainty comparable to that induced by the sea-level rise scenarios, as long as the still water level remains smaller than the critical level above which overflow occurs. This implies that lower confidence should be assigned to flood projection on sites where wave overtopping is the main process leading to flood.

中文翻译：

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海浪随机性对沿海洪水的影响及其海平面上升的变化

沿海洪水是由许多水文气象强迫因素驱动的，其中包括平均海平面，潮汐，大气风暴潮和海浪。根据这些条件，可能会发生波浪超顶，并在某些情况下导致大面积洪水泛滥。在本研究中，我们使用相位分辨波模型（SWASH）研究波浪的随机特征对洪水本身的影响。我们关注法国Gâvres的大潮地点，考虑过去发生的两次洪水事件（都是由于波浪超顶造成的），并研究波浪随机性对洪水的影响如何随强迫条件和时间跨度而变化（分钟到几小时）。我们清楚地表明，波浪的随机性对洪水本身的影响远非微不足道，尤其是在短时间内（约15分钟），只要静止水位仍然小于发生溢流的临界水位，就会产生与海平面上升情景所引起的不确定性相当的不确定性。这意味着在波浪过顶是导致洪水的主要过程的地点，应将较低的置信度分配给洪水预测。