Sediment transport due to river plumes in stratified, rotationally-influenced lakes
Abstract/Contents
- Abstract
- River inflows are often the dominant source of sediment, contaminants, and nutrients into an aquatic system and the dynamics of these flows dictate the fate of introduced constituents and their impact on the lake. The form of the river plume depends on the density of the river flow relative to the ambient surface waters. For instance, a dense river plume will plunge beneath the surface and, in a deep stratified system, will intrude into the water column at a depth of neutral buoyancy. While near-field (momentum-dominated) mixing between the plume and ambient water masses dictates the depth of an inflow intrusion, once the intrusion forms, the plume is influenced by buoyancy and rotational forces. The far-field plume is characterized by a balance between rotation and buoyancy forcing and the mid-field is defined as the adjustment region between the near-field momentum dominated region and the far-field geostrophic plume region. We have employed both field observations and numerical modeling to investigate sediment transport dynamics from intrusive plumes in the mid- and far-field regions. Field observations of multiple river inflows were collected in Pallanza Bay of Lake Maggiore, Italy, a stratified, rotational lacustrine system. We verified that the measured inflow intrusion speeds in Pallanza Bay were well characterized by a simple buoyancy-driven plume scaling. The effective sediment settling speed was shown to be one order of magnitude larger than the expected settling speed based on particle size, which can be due to effects such as particle flocculation and convective sedimentation. We also investigate the role of ambient stratification on the plume dynamics in the mid and far-field regions with a three-dimensional numerical model that was extensively validated with observations. An analytical expression was developed to predict the extent of sediment (in the along-plume direction) using the flow rate and ambient stratification. Finally, an idealized numerical model was employed to extend the range of conditions and to investigate the role of the lateral boundary in a lake on the plume transport dynamics. The lateral boundary modifies the amount of material that is trapped in a recirculating region near the mouth relative to the amount transported along the boundary. The plume propagation speed and thickness, which differ for buoyant and intrusive plumes, are shown to dictate the extent of sediment transport across a wide range of conditions. The timescale of sediment settling relative to the timescale of plume development will dictate sediment transport in a lake. In particular, the sediment settling timescale relative to the timescale of far-field plume development will dictate whether the sedimentation extent increases or decreases with the basin Rossby number.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2016 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Scheu, Kara R |
|---|---|
| Associated with | Stanford University, Department of Civil and Environmental Engineering. |
| Primary advisor | Fringer, Oliver B. (Oliver Bartlett) |
| Thesis advisor | Fringer, Oliver B. (Oliver Bartlett) |
| Thesis advisor | Fong, Derek |
| Thesis advisor | Koseff, Jeffrey Russell |
| Thesis advisor | Monismith, Stephen Gene |
| Advisor | Fong, Derek |
| Advisor | Koseff, Jeffrey Russell |
| Advisor | Monismith, Stephen Gene |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Kara R. Scheu. |
|---|---|
| Note | Submitted to the Department of Civil and Environmental Engineering. |
| Thesis | Thesis (Ph.D.)--Stanford University, 2016. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2016 by Kara Rose Scheu
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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