Impact of Vegetation‐Generated Turbulence on the Critical, Near‐Bed, Wave‐Velocity for Sediment Resuspension
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Tangeta_2019_WaterResourcesResearch.pdf
Description
Published version
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877.99 KB
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Checksum (MD5)
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Author(s)
Tang, Caihong
Lei, Jiarui
Nepf, Heidi
Date Issued
July 2019
Journal
Water Resources Research
Publisher
American Geophysical Union (AGU)
Citation
Tang, Caihong et al. "Impact of Vegetation‐Generated Turbulence on the Critical, Near‐Bed, Wave‐Velocity for Sediment Resuspension." Water Resources Research 55, 7 (July 2019): 5904-5917 © 2019 American Geophysical Union
Version
Final published version
Abstract
Laboratory experiments examined the impact of model vegetation on wave-driven resuspension. Model canopies were constructed from cylinders with three diameters (d = 0.32, 0.64, and 1.26 cm) and 12 densities (cylinders/m2) up to a solid volume fraction (ϕ) of 10%. The sediment bed consisted of spherical grains with d50 = 85 μm. For each experiment, the wave velocity was gradually adjusted by increasing the amplitude of 2-s waves in a stepwise fashion. A Nortek Vectrino sampled the velocity at z = 1.3 cm above the bed. The critical wave orbital velocity for resuspension was inferred from records of suspended sediment concentration (measured with optical backscatter) as a function of wave velocity. The critical wave velocity decreased with increasing solid volume fraction. The reduction in critical wave velocity was linked to stem-generated turbulence, which, for the same wave velocity, increased with increasing solid volume fraction. The measured turbulence was consistent with a wave-modified version of a stem-turbulence model. The measurements suggested that a critical value of turbulent kinetic energy was needed to initiate resuspension, and this was used to define the critical wave velocity as a function of solid volume fraction. The model predicted the measured critical wave velocity for stem diameters d = 0.64 to 2 cm. Combining the critical wave velocity with an existing model for wave damping defined the meadow size for which wave damping would be sufficient to suppress wave-induced sediment suspension within the interior of the meadow.
MIT Department
Massachusetts Institute of Technology. Department of Civil and Environmental Engineering
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DOI of Published Version
https://doi.org/10.1029/2018wr024335
