Abstract The work highlights the importance of directional spreading effects on wave overtopping estimation in shallow and mild sloping foreshores. Wave short-crestedness leads, in general, to a reduction of mean overtopping discharges on coastal structures. In the present work, the case of a sea dike with gentle foreshore in very and extremely shallow water conditions is analysed. Physical model tests have been carried out in order to investigate the effect of directional spreading on overtopping and incident wave characteristics. In the present experimental campaign, the effect of wave spreading has only been investigated for perpendicular wave attack. Results show that directional spreading is proved to cause a reduction of average discharge of sea dikes with gentle and shallow foreshore. Expressions for the reduction factor for directional spreading are derived, fitted on the tested database. The use of this reduction factor leads to more accurate prediction and avoids overtopping overestimation, however reduction-factor formulations are overtopping-formula depending.

中文翻译：

---

定向传播对平缓浅滩海堤波浪漫顶的影响

摘要 这项工作强调了定向传播效应对浅层和轻度倾斜前滨的波浪越顶估计的重要性。一般来说，波浪短顶会导致沿海结构上的平均漫溢流量减少。在目前的工作中，分析了在极浅和极浅水条件下具有平缓前滨的海堤的情况。已经进行了物理模型测试，以研究定向传播对漫溢和入射波特性的影响。在目前的实验活动中，仅针对垂直波攻击研究了波传播的影响。结果表明，定向扩散被证明会导致平缓浅滩海堤的平均流量减少。导出定向传播的折减系数表达式，并拟合在测试数据库上。使用此缩减因子可实现更准确的预测并避免过度高估，但是缩减因子公式取决于过度公式。