Waves, turbulence, mud, and worms : sediment transport and boundary layer dynamics in an estuary
Abstract/Contents
- Abstract
- Cohesive sediment transport is a ubiquitous geophysical process that affects coastal erosion management and the prediction of nutrient and contaminant fluxes in the environment. These phenomena are often simulated in numerical sediment transport models, but fundamental questions remain regarding how to best parameterize the small-scale physical processes that cause, and result from, erosion of cohesive sediment from the bed. This research leverages advances in acoustic Doppler velocimetry to elucidate (a) the combined role of waves and currents in exerting stresses on a sediment bed, (b) the erosive response to those stresses, and (c) the feedback effects on the flow in the form of sediment-induced stratification. These analyses are based on data collected during three one-month-long field deployments on the shallow shoals of South San Francisco Bay. From those observations, we found that biological roughness elements protruding from the sediment bed resulted in a mean velocity profile qualitatively similar to that found in canopy shear mixing layers. The near-bed momentum flux was often dominated by a wave component, which was generated by interactions between the wavy flow and the rough bed. This enhanced roughness was capable of increasing the bottom drag coefficient by up to a factor of three relative to measurements over smoother sediment beds. In terms of erosion, we found that waves were much more effective than tidal turbulence at eroding sediment, though this varied depending on the relative water depth and extent of bed armoring. Finally, we found that sediment-induced stratification could reduce bottom drag by suppressing near-bed turbulent momentum fluxes, though turbulent sediment fluxes remained unaffected. In summary, this work presents a novel view of the governing physical processes at the sediment-water interface, and the results can be applied towards parameterizing boundary layer dynamics and erosion in numerical sediment transport models
Description
| Type of resource | text |
|---|---|
| Form | electronic resource; remote; computer; online resource |
| Extent | 1 online resource |
| Place | California |
| Place | [Stanford, California] |
| Publisher | [Stanford University] |
| Copyright date | 2020; ©2020 |
| Publication date | 2020; 2020 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Author | Egan, Galen Charles |
|---|---|
| Degree supervisor | Monismith, Stephen Gene |
| Thesis advisor | Monismith, Stephen Gene |
| Thesis advisor | Fringer, Oliver B. (Oliver Bartlett) |
| Thesis advisor | Koseff, Jeffrey Russell |
| Degree committee member | Fringer, Oliver B. (Oliver Bartlett) |
| Degree committee member | Koseff, Jeffrey Russell |
| Associated with | Stanford University, Civil & Environmental Engineering Department. |
Subjects
| Genre | Theses |
|---|---|
| Genre | Text |
Bibliographic information
| Statement of responsibility | Galen Egan |
|---|---|
| Note | Submitted to the Civil & Environmental Engineering Department |
| Thesis | Thesis Ph.D. Stanford University 2020 |
| Location | electronic resource |
Access conditions
- Copyright
- © 2020 by Galen Charles Egan
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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