Physics

Geology

Pathology

Flume

Mathematics

Mechanics

Marsh

Biology

Atmospheric sciences

Optics

Statistics

Oceanography

Mathematics education

Microscale chemistry

Soil science

Turbulence

Breaking wave

Wave flume

Attenuation

Geotechnical engineering

Ecology

Particle image velocimetry

Vegetation (pathology)

Particle (ecology)

Flow (mathematics)

Flexibility (engineering)

Wetland

Hydrology (agriculture)

Particle velocity

Environmental science

Wave propagation

Medicine

Salt marsh

Coastal Engineering

Vegetation can contribute to coastal defence by damping incoming waves. However, prior studies have shown that attenuation varies greatly among plant species. Plant flexibility is a mechanical property that is commonly omitted, but varies considerably between shrubs and grasses on salt marshes. Therefore, we present an experimental study in a laboratory wave flume with artificial vegetation that differs in flexibility only. We measured wave attenuation and water particle velocities around rigid and flexible salt marsh vegetation. Waves were measured using a series of gauges and Particle Image Velocimetry (PIV) was used to measure spatio-temporal variations of water particle velocities in the x-z plane around the vegetation. Our results show that flexible vegetation attenuates waves up to 70% less than rigid vegetation due to swaying of flexible plants. Furthermore, we find that rigid vegetation modifies the velocity structure, whereas flexible vegetation does not. Specifically, a mean current in the direction of wave propagation develops around the canopy and the horizontal particle velocities are amplified directly above the canopy. These results indicate that plant flexibility is a key parameter in the wave-vegetation interaction that controls wave damping and velocity structure.

Experimental study on vegetation flexibility as control parameter for wave damping and velocity structure