Wave overtopping discharges at rubble mound breakwaters including effects of a crest wall and a berm

Abstract

Physical model tests have been performed to study wave overtopping at rubble mound breakwaters, including breakwaters with a crest wall, breakwaters with a berm, and breakwaters with a crest wall and a berm. For rubble mound structures with a protruding crest wall or with a stable berm, limited information is available in literature even though protruding crest walls and berms clearly affect wave overtopping discharges. Adding a crest wall to an existing structure, increasing the height of a crest wall, adding a berm, or increasing the width or height of a berm, can be effective measures to account for effects of sea level rise if the sea level rise appears to be more severe than the amount of sea level rise for which the structure was designed for. The present wave flume tests were used to develop guidelines for rubble mound breakwaters, including breakwaters with a crest wall or with a berm. The relative height of the protruding part of a crest wall dominates the effect of a crest wall. The berm width, berm level and wave steepness all affect the influence of a berm on the wave overtopping discharge. Moreover, it was confirmed that the wave steepness also affects wave overtopping discharges for rubble mound breakwaters without a berm or without a crest wall. The developed set of expressions for rubble mound structures has also been validated based on existing data for oblique wave attack on rubble mound breakwaters with a crest wall.