Salt Marshes Help Shield Coasts From Extreme Storm Waves

WHO:

Nature - Researchers studied salt-marsh vegetation, sediment, and wave attenuation; the marsh vegetation was predominantly *Elymus athericus*, with *Atriplex* species and *Aster tripolium* also present.

Nature - The marsh blocks came from Peazemerlannen nature reserve on the mainland Wadden Sea coast in the Netherlands.

Phys.org - Researchers transported salt-marsh sections to an experimental facility to test their response to extreme storm surges.

WHAT:

Nature - A large-scale physical-model experiment tested wave attenuation and vegetation damage in a wave flume. The study’s global statistical model found that vegetation wave attenuation decreased with higher incoming wave height (β = −1.3258, P < 0.001) and longer exposure (β = −0.0494, P < 0.001); the model had pseudo-R² = 0.97.

Nature - The experiment used two salt-marsh profiles, each 71 m long and 2.0–2.2 m wide, built from 66 marsh blocks. The Delta Flume is 300 m long, 5 m wide, and 9.5 m deep.

Nature - The tested marsh water depths were 1.5 m, 2.5 m, and 4.0 m; significant wave heights were 0.75 m, 1.25 m, and 2.00 m. Runs included approximately 100 waves for short tests and 1,000 waves for longer tests, with sequences testing light damage, substantial damage, and mowed vegetation.

Nature - After 21 hours of extreme-wave forcing, average marsh-surface lowering was 7 mm, less than the 43–48 mm standard deviation among 32 measurement locations.

Nature - Root biomass was concentrated near the surface: 78% was in the top 5 cm. Mean substrate organic matter was 4.7% ± 1.7%, ranging from 2.3% to 7.6%.

Phys.org - The experiment found that salt-marsh sediment and vegetation can remain largely intact during extreme storm surges. The results were published in *Nature* and *Communications Sustainability*.

WHERE:

Nature - The experiment was conducted in the Delta Flume at Deltares; the transplanted marsh was collected at Peazemerlannen, Netherlands.

Phys.org - The research addresses coastal protection in the Netherlands and other regions; the experimental facility was described as capable of producing the world’s largest artificial waves.

WHEN:

Nature - Marsh blocks were harvested in September and October 2023; installation at the flume began in December 2023; experimental wave runs began in February 2024.

WHY:

Nature - Researchers used severe wave conditions to conservatively assess vegetation damage and wave attenuation, including the effects of progressive damage and removal of above-ground vegetation.

HOW:

Nature - Researchers transplanted marsh blocks onto a sand bed, measured waves with gauges, and compared attenuation in runs with vegetation against runs without above-ground vegetation.

Nature - The global assessment used coastal-profile and vegetation datasets and estimated exposure during storms with recurrence periods of 100 to 1,000 years.

(UPDATED October 22, 2026 11:11 UTC)

Salt-marsh vegetation and sediment remained largely intact in a large-scale experiment simulating extreme storm surges, suggesting these natural landscapes can help protect coastlines. Researchers moved sections of marsh from the Peazemerlannen reserve on the Netherlands’ Wadden Sea coast to Deltares’s Delta Flume, where they built two profiles and tested waves of different heights and water depths. The marsh was dominated by sea couch grass, alongside other salt-tolerant plants. Researchers measured how waves changed as they crossed the vegetation, including after damage and removal of above-ground plants. Wave protection declined as incoming waves grew higher and exposure lasted longer. Yet after 21 hours of extreme-wave forcing, the marsh surface had lowered by an average of just 7 millimeters. The findings, published in Nature and Communications Sustainability, could inform coastal protection planning in the Netherlands and elsewhere.