Structural approach to the erosion beach of Wenduine and the silting u harbour channel Blankenberge

In 2017, the Coastal Division started a study to tackle structurally the erosion problems of the beach of Wenduine and the silting up of the harbour channel of Blankenberge.  A new higher West dam in Blankenberge and one or more groynes in Wenduine stand out as the best solutions. Both the beach of Wenduine and the harbour channel of Blankenberge are locations where intensive maintenance is needed. To offer the desired safety against storm surges from the sea, beach nourishments are carried out along the entire coast. At the level of Wenduine, the coastline shows a slight nick which makes this zone subject to enhanced erosion. The beach profile seems here insufficiently stable. Therefore, it was necessary to carry out frequent maintenance nourishments to compensate for the erosion after several storms. The erosion problem in Wenduine also leads to an increased sand transport direction Blankenberge. The marina of Blankenberge has a short, narrow though shallow harbour entrance near the sea that silts up in a very short term. Annual storms cause a rapid silting up of the harbour channel, resulting in a dangerous situation for the pleasure boating. Along with the dredging, it makes for a difficult accessibility of the marina. In order to obtain a structural solution for both locations, a study was started in 2017 into possible measures. Several design scenarios were explored using numerical modelling of currents, wave action and morphology. Subsequently the alternatives were compared to each other in terms of effectiveness, or to the extent in which the silting up in Blankenberge and the erosion in Wenduine would be reduced, in terms of nautical accessibility, swimming safety, coastal safety, scenic and living aspects, cost-efficiency, and environmental impact. The feasibility phase of this study has meanwhile been completed and shows that there are good technical solutions, which give cost recovery in the short to medium term.

In Wenduine, the solution is in the construction of a groyne east of the built-up area or a groynes’ field. These groynes provide a more stable beach, whereby less erosion occurs, less maintenance nourishments will be necessary to ensure safety and allowing the sand transport direction Blankenberge to decrease. For Blankenberge, the construction of a higher and longer West dam was chosen. This dam is able to better prevent the longshore sand transport, which will greatly decrease the silting up of the harbour channel. The new dam will be at least 150 metres longer than the current low dam. The existing East dam with the protected wooden pier will be maintained. The establishment of both preferred alternatives means the start of the process towards implementation. Through further consultation with the stakeholders, the design will further be refined so as to take optimally into account the use of the beach, the accessibility of the marina, the interaction with the existing concrete pier on the West dam, etc. The technical design of the dam and the groynes, the preparatory soil investigations and the licensing phase (MER procedure) will start in parallel.