A nearshore model to investigate the effects of seagrass bed geometry on wave attenuation and suspended sediment transport |
| |
Authors: | Shih-Nan Chen Lawrence P Sanford Evamaria W Koch Fengyan Shi Elizabeth W North |
| |
Institution: | (1) Centre for Estuarine and Marine Ecology, Netherlands Institute of Ecology (NIOO-KNAW), Yerseke, The Netherlands |
| |
Abstract: | The effects of seagrass bed geometry on wave attenuation and suspended sediment transport were investigated using a modified
Nearshore Community Model (NearCoM). The model was enhanced to account for cohesive sediment erosion and deposition, sediment
transport, combined wave and current shear stresses, and seagrass effects on drag. Expressions for seagrass drag as a function
of seagrass shoot density and canopy height were derived from published flume studies of model vegetation. The predicted reduction
of volume flux for steady flow through a bed agreed reasonably well with a separate flume study. Predicted wave attenuation
qualitatively captured seasonal patterns observed in the field: wave attenuation peaked during the flowering season and decreased
as shoot density and canopy height decreased. Model scenarios with idealized bathymetries demonstrated that, when wave orbital
velocities and the seagrass canopy interact, increasing seagrass bed width in the direction of wave propagation results in
higher wave attenuation, and increasing incoming wave height results in higher relative wave attenuation. The model also predicted
lower skin friction, reduced erosion rates, and higher bottom sediment accumulation within and behind the bed. Reduced erosion
rates within seagrass beds have been reported, but reductions in stress behind the bed require further studies for verification.
Model results suggest that the mechanism of sediment trapping by seagrass beds is more complex than reduced erosion rates
alone; it also requires suspended sediment sources outside of the bed and horizontal transport into the bed. |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|