On the Design of Quasi-static Berm Breakwaters

When a coastal engineer is upon the task of designing a rubble-mound breakwater structure, the available design options include the conventional breakwater and the berm breakwater. For a conventional breakwater design, based on individual stone mass stability, design rules and formulae are available in the technical literature (CIRIA, 2007; USACE, 2002). For berm breakwaters (Figure 1), rubble mound structures that are constructed using smaller (lighter) stones than those required for conventional two-layer armoured breakwaters, limited guidance is available. The original berm concept idea was the use of a wide, porous mass of quarry stone constructed as a horizontal berm that intended to allow for stone motion under wave action, causing consolidation and nesting of stones leading to reshaping of the berm material under design storm conditions, as well as the formation of a milder but stable seaward profile. Presently, PIANC (2003) guidelines list the following types of berm breakwaters: 1. Non-reshaping statically stable berm breakwaters or Icelandic-type berm breakwaters