Spatial distribution of overtopping on rubble mound breakwaters under oblique waves

This study investigates the effect of wave obliquity on overtopping for rubble mound breakwaters with a CoreLoc armour layer. In particular, the study is based on experimental investigations on fishing harbours in the Sultanate of Oman, comprising 2D and 3D tests. In both cases, overtopping under perpendicular and oblique cyclonic waves was measured. The physical model tests were carried out in the wave flume and in the wave basin of Padova University. The scales of the experiments have been defined according to the dimension of the available artificial model units (CoreLoc). The overtopping discharge was evaluated in 2D and 3D tests collecting water passing over the structure crest, neglecting the percolation through the upper layer. For the wave basin tests, the overtopping discharge was evaluated in up to 4 different positions. As expected, overtopping discharge is smaller under oblique waves. However, the measurements are very dis-homogenous along the crest. Visually, it looks like the incident oblique wave is scattered by the initial portion of the breakwater and propagates along the structure, merging with the same wave. Crests and troughs are combined in specific points, determined by wave obliquity and wavelength. Possible scattering points are the roundhead, breakwater bents and other discontinuities. The aim of this paper is to verify if the experimental reduction of overtopping due to wave obliquity can be interpreted by a diffraction pattern.