Hydrodynamic modelling of wave interactions with sea dikes on shallow foreshores : a systematic approach by physical and numerical modelling

Low-lying coastal urban areas are increasingly vulnerable to flood risks due to climate change induced sea level rise. The Belgian coast is no exception to this, which is characterised by a hybrid beach-dike coastal defence system that protects high-rise buildings on the crest and the hinterland against flooding. This coastal defence system consists of a steep-sloped sea dike fronted by a high beach or – in short – a sea dike on a shallow foreshore. Because of the complex nature of waves interacting with sea dikes on shallow foreshores, design and safety assessment methodologies depend on a range of engineering tools, including: (1) physical modelling (scale model tests) and derived empirical prediction models, and (2) numerical modelling. More than 400 tests were conducted in a wave laboratory using state-of-the-art methods, and were subsequently used to derive, improve or verify various prediction formulas. The numerical modelling consisted of a detailed validation of computational fluid dynamics simulations with large scale wave laboratory tests and an in-depth comparison with other computer models widely applied in coastal engineering. This dissertation delivers an important contribution to the improvement of design and safety assessment methods for the specific case of a sea dike on a shallow foreshore, so that unnecessary conservatism or catastrophic underestimation is further reduced