Application of offshore breakwaters to the UK: A case study at Elmer Beach

The use of offshore breakwaters in the UK is relatively uncommon with only 6 schemes constructed to date (early 1998). The use of this technology in t he UK is examined via a case study of the 8-unit Elmer Beach offshore break water scheme which fronts a shingle beach. Profile line surveying and aeria l survey data are used to show the development of the planform during the f irst 38 months and the development is compared to empirical design guidelin es. Also an intensive fieldwork program investigated shingle transport insh ore of the breakwaters using sediment tracing techniques. The results show that the scheme exhibited rapid changes to planform during the first 6 mont hs, with shingle salients and sand tombolos developing in the fee of the br eakwaters. Changes to planform after this time were less marked, although a reas of continued erosion/accretion were identified. The sediment transport experiments identified sediment pathways and rates of transport in the lee of the breakwaters. It is suggested that the breakwaters have reduced shin gle transport by a factor of at least 2 compared to similar open beaches.