Dutch salt marsh flume test finds little erosion, but weaker wave protection in major storms
Researchers moved 306 square metres of Wadden Sea salt marsh into the Delta Flume and exposed it to waves up to 2 metres high. The seabed dropped by an average of just 7 millimetres after 21 hours, but vegetation damage reduced its extra wave attenuation: the Nature study found the strongest effect on coasts with waves up to 1 metre, where it can reach 50 per cent.
Bottom line — The researchers say salt marshes can complement dikes, with vegetation adding up to 50 per cent wave attenuation on lower-energy coasts.
Go deeper 7
-
The experiment ran for about 29 hours in total, according to the University of Twente; the seabed measurement was taken after 21 hours.
-
The University of Twente reports vegetation provided 6–22 per cent additional attenuation with 75-centimetre waves, and up to 6 per cent with 2-metre waves.
-
Nature reports above-ground biomass fell to 20–25 per cent of its starting level after 21 hours; stem length fell by 47 per cent.
-
Global analysis found vegetation’s added attenuation typically exceeds 10 per cent where waves over marshes stay below about 1 metre, according to the University of Twente.
-
Wetterskip Fryslân said the findings have already helped save millions of euros on the Koehool–Lauwersmeer dike reinforcement project.
-
The University of Twente notes salt marshes can retreat or disappear if sediment supplies are insufficient or their edges erode.
-
An SMC España commentary questioned how well the experiment’s wave periods, exposure cycles and constrained flume setting represent natural conditions.