Model Study of the Influence of Submerged Tidal Barriers on Estuarine Mixing and Exchange Processes
Publication: Journal of Hydraulic Engineering
Volume 132, Issue 10
Abstract
Model studies have been undertaken to study the spatial and temporal development of a brackish pool within an impoundment supplied by a freshwater inflow and bounded by an impermeable barrier that is overtopped periodically by a tidally generated saline water inflow. The results demonstrate the relative influence of the freshwater inflow and downstream tidal conditions in controlling the temporal development of this pool. In particular, the experimental data illustrate that the dimensions of the brackish pool reach equilibrium after a specific number of tidal cycles, with the normalized thickness of the pool being dependent primarily on the strength of the freshwater inflow. The density structure of the water within the impoundment is interpreted in terms of two contributory processes, namely, (1) turbulent entrainment of fresh receiving water into the saline intrusion; and (2) shear-induced interfacial erosion of the brackish water by the overriding fresh water during receding tidal conditions. A scaling analysis shows that the temporal growth of the brackish pool thickness can be parameterized successfully in terms of a volume ratio representing the dilution capacity of the freshwater stored in the impoundment during the saline intrusion phase.
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Acknowledgments
The study was supported by a Grant No. EPSRC-6BGR/M42459/01 from the UK Engineering and Physical Research Council (EPSRC). The writers acknowledge this support and express their appreciation of stimulating discussions on barrage hydrodynamics with Professors Richard Burrows, Ron Smith, and Roger Falconer and Dr. Giordano Lipari and Dr. Andrew Riddle (Brixham Environmental Laboratory, Astra Zeneca Ltd.) (who also provided field data from the Tees Barrage), Finally, they are grateful to Dr. Adam Mellor and the Northern Ireland Department of Agriculture and Rural Development for supplying Lagan Weir field data for comparison against model predictions.
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Information & Authors
Information
Published In
Journal of Hydraulic Engineering
Volume 132 • Issue 10 • October 2006
Pages: 1033 - 1043
Copyright
© 2006 ASCE.
History
Received: Jan 21, 2005
Accepted: Oct 26, 2005
Published online: Oct 1, 2006
Published in print: Oct 2006
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