Wave‐Driven Sediment Resuspension Within a Model Eelgrass Meadow

Abstract

Wave velocity and suspended sediment concentration were measured over a sand bed with and without a model eelgrass meadow. The model meadow was geometrically and dynamically similar to the marine eelgrass Zostera marina. Meadows were constructed with three stem densities: 280, 600, and 820 stems/m2. Ripples formed within the meadow only when the spacing between stem rows was larger than the wave excursion. When ripples formed, the ripple geometry was the same as that observed for bare bed. When ripples were present, the near-bed turbulent kinetic energy (TKE) was dominated by the ripple-generated turbulence, and both the near-bed TKE and averaged suspended sediment concentration were similar across all meadow densities and bare bed at the same wave velocity. When ripples were absent, the near-bed TKE was dominated by the stem-generated turbulence, and the averaged suspended sediment concentration was reduced, compared to cases with ripples but at the same wave velocity. For conditions with and without a model meadow, the sediment diffusivity inferred from vertical profiles of suspended sediment concentration increased linearly with distance from the bed. ©2019. American Geophysical Union. All Rights Reserved.