The construction of a new sea dike is initiated by the municipality of Middelkerke. The design of the new sea dike should try to find a balance between coastal safety, efficient beach maintenance (aim at beach nourishments every 5 years by providing a sufficiently large sand) The redevelopment of the sea dike is initiated by the municipality of Middelkerke and is based on a compromise between coastal safety, minimum beach maintenance (striving for 5-yearly beach nourishment by sufficient large sand buffer), and an attractive beach and sea dike for tourists and commercial activities. The sea dike is divided into different zones depending on the destination. In residential zones, for the first time on our coast, the concept of 'reinforced grass dike' is used. Grass-covered sand berms will be constructed in front of the existing sea dike to create a sufficient sand buffer to keep wave overtopping within the safety criterion (1 l/s/m) during the 1000-year storm. In the other zones, where the sea dike has a higher touristic/commercial function, the sea dike will be redesigned according to the concept of 'stilling wave basin' (SWB). This consists of a double row of storm walls where the most seaward has the function of projecting the rising water upwards, limiting the wave overtopping volume over the most landward wall. There are also zones with a terraced dike and an underground car park.
Wave flume test FHR
The different cross-sections were each tested for wave overtopping and wave impact by means of physical scale model research in our wave flume. The normative storm has a return period of 1000 years, taking into account sea level rise until 2070. A beach profile was constructed in the flume that is a schematization of the modelled eroded beach profile after the 1000-year storm. The model sections of the sea dike with wave damping extension were custom milled at an external supplier, resulting in a high accuracy of the complex geometry with roundings and openings in the walls. The measuring setup to measure forces and transients in the various design sections were designed and realized in-house. Based on the results of the test campaign, the safety requirements of the design were verified for acceptable wave overtopping. The measured wave impacts were used by the designers to dimension the structural elements (e.g. the reinforcement of the SWB walls).