Thesis
Field analysis of flow, suspended sediment, and mixing dynamics at the confluence of the Snake and Clearwater Rivers with an acoustic Doppler current profiler
Washington State University
Master of Science (MS), Washington State University
2018
Handle:
https://hdl.handle.net/2376/103446
Abstract
The flow, suspended sediment transport, and mixing dynamics at river confluences play a crucial role in influencing the societal and environmental function of these fluvial regions. However, the ability to collect detailed field data on these phenomena has only recently become feasible for studies of large river confluences due to the widespread availability of Acoustic Doppler Current Profilers (ADCPs). This study analyzes data collected with an ADCP at the confluence of the Snake and Clearwater Rivers with the objectives of further developing current methods of data analysis with an ADCP and contributing toward a more complete understanding of how different confluence characteristics influence flow, suspended sediment transport, and mixing processes at large river confluences. Evaluation of two common methods for defining secondary velocity components from ADCP data reveals the importance of defining secondary velocities relative to a channel-scale primary flow direction when cross-stream flows in the confluence region characterize the secondary flow structure. Attempted bin-by-bin calibration of relative backscatter intensity with point-integrated measurements of suspended sediment concentration reveals the limitations of such an approach when sediment concentrations and particle sizes are not large enough relative to frequency-based backscatter sensitivity to produce a strong correlation. Depth-averaged values of uncalibrated relative backscatter intensity are compared with corresponding values of estimated suspended sediment concentration to expose how distributions of relative backscatter intensity may incorrectly represent the distribution of suspended sediment concentrations when there are significant differences in suspended sediment characteristics between confluent flows. Observed mixing characteristics at the Snake-Clearwater Confluence during the study campaign illustrate how differences in temperature between confluent flows can lead to rapid lateral transfer of flows and suspended sediment concentrations, the transition from vertical to horizontal structuring of the mixing interface within the confluence hydrodynamic zone, and flow stratification that creates a stabilized vertical temperature gradient. However, the collected data was unable to provide a clear representation of vertical mixing or lack thereof for suspended sediment concentrations within the study region.
Metrics
11 File views/ downloads
19 Record Views
Details
- Title
- Field analysis of flow, suspended sediment, and mixing dynamics at the confluence of the Snake and Clearwater Rivers with an acoustic Doppler current profiler
- Creators
- Donald C. Jones
- Contributors
- John Petrie (Degree Supervisor)Timothy R. Ginn (Degree Supervisor)
- Awarding Institution
- Washington State University
- Academic Unit
- Civil and Environmental Engineering, Department of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University; [Pullman, Washington] :
- Identifiers
- 99900525274401842
- Language
- English
- Resource Type
- Thesis