APPLICATION OF CROSS-SHORE MORPHOLOGICAL MODELS FOR PERCHED BEACHES

Abstract

Perched beaches are beaches that are supported at the offshore side by a submerged structure. The advantages of such design schemes are that less dredged material is required, and more protected waters are created in front of the beach. Apart from the hydraulic stability of the submerged structure itself, the stability of the beach needs to be studied in order to make sure it fulfils the requirements during its design lifetime. Aspects that play a role here are the expected sand losses over the submerged structure, the (dynamic) equilibrium profile of the beach and the performance during storm conditions. In order to study the morphological responses of such beaches, morphological models should be applied that can take into account the influence of the submerged structure. This paper discusses two cross-shore models that have been used to study a large perched beach project that is under construction in unusually deep waters, severe wave climate (mostly unidirectional) and small tidal range. The models applied are SBEACH (Larson et al., 1989) and CROSMOR (Van Rijn et al., 2003). First the models are validated and calibrated hydrodynamically by comparing the wave transmission and wave setup with measurements from 2D flume tests. Next, the models have been used to predict the future cross-shore development of the beach.