For the first time, large-scale tests have shown that salt marshes act as a buffer zones and attenuate waves, even in extreme conditions such as storm surges.
In combination with vegetation, they reduce waves by approximately 20% over a distance of 40 meters. This means that dikes behind salt marshes can be a lot lower and cheaper.
Bregje van Wesenbeeck, a specialist in nature-based engineering at Deltares, said: “Our computer models were already telling us that marshes can attenuate waves in extreme conditions as well, but scale testing and field measurements were confined to small waves. In Hannover, we looked at what happens to marshes during storms.”
It emerged that, even in these conditions, marshes remain functional and intact. “There is no vertical erosion, even though some of the vegetation is lost,” she added.
Bregje believes that the experiments were a major step forward in terms of quantifying the role of ecosystems in flood prevention.