Influence of oblique wave attack on wave overtopping and forces on rubble mound breakwater crest walls

At the crest of rubble mound structures a crest wall is often present to reduce the consumption of material compared to breakwaters without a crest wall. To design the crest wall several methods based on estimates of the hydraulic wave loads are available. These methods are focussed on waves that approach breakwaters perpendicular. In practice, the dominant wave conditions are often not perpendicular but approach the breakwater under an angle. Oblique waves can significantly reduce the amount of wave overtopping and reduce the wave loads on coastal structures compared to perpendicular waves. Therefore, physical model tests have been performed in a wave basin where the wave loads on crest walls and the wave overtopping discharges have been measured under oblique wave attack. Design guidelines have been developed to take the reduction due to oblique waves into account. Together with available methods to predict the wave forces and wave overtopping for perpendicular wave attack, the obtained results enable a more advanced design of crest walls.