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Particle Responses to Near-Bed Shear Stress in a Shallow, Wave- and Current-Driven Environment
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  • Grace Chang,
  • Galen Egan,
  • Joseph D McNeil,
  • Samuel McWilliams,
  • Craig Jones,
  • Frank Spada,
  • Stephen G. Monismith,
  • Oliver B. Fringer
Grace Chang
Integral Consulting Inc.

Corresponding Author:[email protected]

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Galen Egan
Stanford University
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Joseph D McNeil
Environmental Engineering and Limnological Services
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Samuel McWilliams
Integral Consulting Inc.
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Craig Jones
Integral Consulting Inc.
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Frank Spada
Integral Consulting Inc.
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Stephen G. Monismith
Stanford University
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Oliver B. Fringer
Stanford University
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Abstract

Novel analysis of in-situ acoustic and optical data collected in a shallow, wave- and current-driven environment enabled determination of: (1) particle characteristics that were most affected by near-bed physical forcing, and (2) characteristic shear stress, τchar, at which the rate of changes to particle characteristics were most pronounced. Results indicated that moderate τchar values of 0.125 Pa drove changes in particle composition during summer. In winter, particle concentration effects were most affected at τchar of 0.05 Pa, suggesting dominance of fluff layer resuspension. Changes to particle size were most relevant during a biologically productive springtime period, with initiation of particle disaggregation occurring most commonly at τchar of 0.25 Pa. The values of τchar determined from acoustic and optical data are consistent with laboratory-based measurements of critical shear stress for resuspension of site sediments, and with typical critical shear stress values for resuspension of cohesive sediments as reported in the literature.