VUB scientists discover that tides, not just waves, define the sandy Belgian coast

VUB scientists discover that tides, not just waves, define the sandy Belgian coast

Findings are an important step in protecting the coast against climate change

Waves are often the driving force behind erosion and sanding of beaches, but in Belgium the tide is at least as important. This is evident from doctoral research carried out at the Vrije Universiteit Brussel within the CREST project, which seeks scientific insight into all kinds of coastal processes with the safety of the Belgian coast as a goal. It represents a major step forward in the protection of the Belgian coastal zone against the impact of climate change. The fact that the tides have such a major impact on our beach formation is due to our location near the Strait of Calais, which means our coast is characterised by a 4m tidal difference, while the wave impact is relatively small,” explains researcher Evelien Brand. “As a result, the effect of variations in tidal range is as great as the effect of variations in wave height. This is unique off the Belgian coast, because sandy coasts are often wave-dominated.”  

For her PhD research in engineering, Evelien Brand carried out measurements on the beach near Mariakerke and Groenendijk for 12 weeks between 2017 and 2019, under the guidance of Professor Margaret Chen and Dr Anne-Lise Montreuil of VUB’s Hydrology and Hydraulic Engineering Department (HYDR). This research shows that the strong tidal currents carry sand away during spring tides and the beach recovers during neap tides, when the difference between high and low tides is minimal.

Separate approach required

Currently, to arm coastal zones against the rising sea level caused by global warming, ‘soft’ measures such as sand nourishments are usually put in place. However, due to the unusual nature of the Belgian coast, these efforts, which are typical for the protection of wave-dominated coasts, cannot simply be copied.

Brand: “The Belgian coast, with the port of Zeebrugge among other things, has a high economic value and also houses almost half a million people. Due to climate change, this zone is coming under increasing pressure. Action is certainly needed to minimise the impact of rising sea levels, but in order to work effectively, it is important that we first map out the dynamics behind our coastline. One way to protect our tidal-dominated coastal zone is to raise the tidal banks.”

The research is part of the CREST project, in which several Flemish universities and institutions are participating and which is financed by the Scientific Research Fund (FWO). 

For more information:

Evelien Brand
Hydrology and Hydraulic Engineering
+31 650 455 559  

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