Wave height and setup in the sheltered area of a segmented, detached, rubble-mound, zero-freeboard breakwater on a steep beach

An experimental study of the wave behavior in the sheltered area of a segmented, detached, rubble-mound, zero freeboard breakwater (ZFB) on a steep beach is presented. Six regular and one irregular incident wave cases were considered. It was deduced that the wave height distribution in the sheltered area of the ZFB was influenced: (a) in the region near the symmetry axis normal to the ZFB mainly by wave transmission over the ZFB crest, and (b) in the region shoreward of the gaps between the segments of the ZFB mainly by wave diffraction from the gaps. The average wave heights in the sheltered area of the ZFB, normalized to the incident wave height, increase with increasing incident wave period and decreasing incident wave height. The wave setup distribution in the sheltered area of the ZFB was influenced both by wave breaking on the structure and the development of currents. Wave setup increases with increasing incident wave height. The transmission of waves over the ZFB induces transfer of energy to higher frequencies of the power spectrum. This transfer is sustained in the sheltered area of the ZFB, and it increases with increasing incident wave period or height.