The shallowness of the foreshore can change the degree of breaking and the spectra of the wave such that the overtopping volume is affected by the same dike geometry or material. The water depth at the toe of the structure and the slope of the foreshore transform the wave properties, and the impact is significant when wave breaking occurs in front of the structure i.e., shallow foreshore. The dike geometry and the material are also important parameters affecting the overtopping volumes. The incident wave characteristics and water level at the toe of the structure are the key hydrodynamic inputs to estimate the wave overtopping. The accurate assessment of wave overtopping parameters is an essential step in the design of coastal structures, as the flood protection performance of the structure depends on the volume of water passing over during extreme events. Finally, some of the remaining uncertainties that need further exploration are discussed. The variation in performance of the formulas for different foreshore slopes is demonstrated. Additional research is needed to understand the (residual) influence on the wave overtopping of the foreshore slope and relative magnitude of the infragravity wave height to the sea-swell wave height at the dike toe, especially for extremely shallow foreshore conditions. We find that predicting wave overtopping for extremely shallow foreshore conditions still requires improvement. The recent developments in wave overtopping research on very shallow and extremely shallow foreshore conditions have been reviewed using this dataset to reflect the existing uncertainties and challenges in the wave-overtopping literature. This work presents a new experimental dataset focused on very shallow and extremely shallow foreshore conditions for a range of foreshore slopes (i.e., 1/20, 1/35, 1/50, and 1/80) and relative water depths. In engineering applications, it is important to know the performance and limitations of the different formulas. Although the accuracy of the predictions has improved due to each approach’s contributions, the formulations’ performance depends on their range of applicability. Nowadays, several empirical formulations based on small-scale experiments are available in the literature to predict the mean overtopping discharge at dikes on shallow foreshores. Wave overtopping is a critical parameter in the design of coastal defense structures.
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