Trial Application of the Revised British Standard on Breakwaters at Three Distinct Sites

The British Standard 6349 series covers maritime works with Part 7 addressing breakwater design and construction. The current version of Part 7 was published in 1991 and is undergoing a major revision with publication due in 2023. The revised Part 7 will introduce updated design approaches, in part based on new approaches proposed in the forthcoming Eurocode on coastal structures (EN 1991-1-8), expected to be published in 2026. The updated approaches represent a significant change in design practise and therefore require clear communication, training, support and (importantly) validation through trial applications. This paper documents trial applications of the new standard at three sites with distinctly different environmental characteristics:

• A site on the United Kingdom (UK) Dorset coast benefitting from medium-term nearshore wave measurements in a micro-tidal environment.

• A site on the UK Somerset coast benefitting from medium-term offshore wave measurements in a macro-tidal environment.

• A site on the British Virgin Islands (BVI) Atlantic coast without any measured wave data in a micro-tidal cyclone prone environment.

The design approaches taken for each site are described with comparisons drawn between deterministic and probabilistic analyses, the prerequisites to allow application of each and the contrasting levels of risk management and optimisation possible.

The paper draws conclusions regarding the ease of use of the revised BS 6349-7 (draft) standard, lessons learned that may lead to changes to the standard before publication, and compares and contrasts the differing design routes available based on the perceived level of project risk and supporting data/methodologies available.