Salt marshes protect coastlines during storms
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Researchers in the Netherlands transported sections of salt marsh to a wave tank and tested how well they withstood extreme conditions.
Scientists from University of Twente, Deltares, and other institutions built a 300-square-meter salt marsh in the Delta Flume and exposed it to waves reaching 2 meters (6.6 feet) high for nearly 29 hours. They found the marsh seabed lost only 7 millimeters (0.28 inches) of elevation, remaining largely stable even under intense wave action.
The plants within the marsh also helped reduce wave energy, providing between 6% and 22% additional attenuation with smaller waves and up to 6% with larger waves. The experiment showed that, on average, only 30% of plant material was lost, meaning marshes can continue protecting coastlines even after multiple storms.
Researchers then combined these findings with global data, discovering salt marshes are most effective on coasts with waves under 1 meter (3.3 feet), where they can reduce wave energy by up to 50%. This research helps coastal managers better predict how marshes will perform during storms and integrate them into coastal defense strategies. Wetterskip Fryslân, a water authority in the Netherlands, already used the findings to reduce costs in a dike reinforcement project.
Scientists emphasize that protecting existing salt marshes and restoring lost ones is important for coastal safety, biodiversity, and carbon storage, though marshes can disappear if they lack enough sediment or experience significant erosion.
