Manuals and guidelines for different types of breakwaters and coastal structures have been issued before this time, e.g. the Shore Protection Manual (1984), CIRIA/CUR (1991), CUR (1995), and PIANC (1992). The types of breakwaters treated in these manuals and reports have mainly been conventional rubble mound breakwaters and caisson type breakwaters.
The berm breakwater concept is fairly old, but was not used very much until the 1980's when it was
einvented"" to provide wave protection for an airport runway extension into the sea in Dutch Harbor, Alaska in the Aleutian Islands (Rauw, 1987). The concept was also used later for the design of the berm breakwater at Keflavik, Iceland in 1983 (Baird and Woodrow, 1987). Since that time, many berm breakwaters have been built in Iceland and throughout the world. The primary advantage of the berm breakwater is that the armour stones are smaller than in a conventional rubble mound breakwater. Hence, the berm breakwater can be constructed with commonly available heavy construction equipment and from local quarry sites at a cheaper cost.
Along with the experience gained in the construction of the berm breakwaters now built, a substantial amount of research on different aspects of the concept has been carried out. However, the results of this research and practical experience is scattered throughout the literature. PIANC decided, therefore, to form a Working Group under MarCom to formulate guidelines for the design of berm breakwaters.
The following terms of reference were given to the Working Group by PIANC MarCom in 1998 :
Berm breakwaters have become in many cases an attractive, both technically and economically, rubble mound breakwater in exposed locations. This type of breakwater has up to now been mainly used in Canada, Iceland, Norway and Denmark (Faero Islands). The main advantage of the berm breakwater is that smaller stones can be used on this dynamic stable berm breakwater than on a static stable conventional rubble mound breakwater. Hence, conventional contractors equipment can be used to move and place the cover stones rather than heavy specialty equipment, which has to be used for lifting heavy cover blocks for the static stable rubble mound breakwater.
To be investigated
Considerable research has been carried out on berm breakwaters through the recent years (e.g. EU-MAST I and MAST II projects, etc.) covering theoretical and experimental work as weIl as compilation of practical experience. There are however no general guidelines on the design of this type of breakwater taking recent research results and practical experience into account.
The task of the Working Group will be to study the different research results and compile all relevant information into practical guidelines for the design of berm breakwaters.""
Although some 60 berm breakwaters have been built throughout the world and considerable research and practical experience have been compiled for berm breakwaters, there is still a need for additional research. The berm breakwater off ers great flexibility for the designer. The design should be ""supply based"" and not necessarily ""demand based"". Hence, the specifications should be ""functional specifications"" and not ""demand specifications"".
The designer will not necessarily find ""easy"" guidelines in this report or answers to his or her practical questions, e.g. the width of the berm or the crest height of a berm breakwater vs. significant wave height, because there is no ""universaI"" answer to these questions. On the other hand the experienced designer will find helpful information (with some detailed background) on the issues he or she has to address during the design process. For these reasons, then, the title of this report is ""State of the Art on the Design and Construction of Berm Breakwaters"" and not ""Guidelines for the Design and Construction of Berm Breakwaters"".
Because of the restrictions on report lengths set by PIANC, emphasis in this report is put on the items specific to the design and construction of berm breakwaters. Details of those issues common to all breakwaters is left out, i.e. environmental conditions, soil stability, etc."