A LARGE PERCHED BEACH SCHEME IN DEEP WATERS

Nowadays the need for creating land to establish new cities at more favourable locations, namely close to water, has increased. These new reclaimed cities are expanding more offshore, therefore facing severe and challenging wave conditions. Combining conventional coastal protection design (e.g. rock/concrete revetments) with these challenging conditions is expensive and non- attractive for visual, environmental and social aspects. Alternatives can be considered where hard and soft coastal protection measures are combined. Perched beaches are typically artificial beaches that are supported or partly protected at the offshore side by a (submerged) barrier. The advantages of such design schemes are that less dredged material is required than in a full “open” beach solution and less rock than in a full hard solution. At the same time, protected waters are created in front of the beach reducing the risk of significant loss of dredged material. There is a strong interaction between the barrier and the beach. The design of the barrier (quite exposed to wave action) not only depends on its standalone stability but also on the effect it has on the artificial beach, as related to the transmission performance, which is mostly influenced by the crest elevation. Moreover, water level setup and flushing are relevant aspects for safe bathing on a microtidal coast.