GEOMETRICAL DESIGN OF BERM BREAKWATERS

Abstract

Cooperation between the authors has led to a number of papers on main design parameters for berm breakwaters. These were the recession at the berm of a berm breakwater for assumed design conditions and main armour rock class, as well as the functional behaviour (wave overtopping and reflection), where often allowable overtopping rates determine the crest height of the structure. They also gave guidance on how some geometrical aspects may influence the recession. For example a flatter down slope, a higher berm level and a higher toe level all decrease the expected recession. Expected recession and expected wave overtopping (or requested crest height) are only two parameters that influence the design of the cross-section of a berm breakwater. In order to design a complete cross-section many more design decisions have to be taken into account. In the past clear design rules on determining a full cross-section of a berm breakwater were lacking and design was based on the experience with earlier designs (in Iceland and Norway)or simply on good reasoning and then testing the structure in a hydraulic laboratory. This paper gives guidance on all relevant geometrical design parameters.