Ebb-Jet Dynamics and Transient Eddy Formation at Tauranga Harbour: Implications for Entrance Channel Shoaling

In 1992 the entrance channel through the tidal inlet to Tauranga Harbour, which is located along the Bay of Plenty littoral drift system, was deepened from 10 m to 14 m. The deepened channel has become a sediment trap for littoral drift bypassing and tidal current driven sediment transport through t...

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Bibliographic Details
Published in:Journal of coastal research 2009-01, Vol.25 (1), p.234-247
Main Authors: Spiers, Kyle C., Healy, Terry R., Winter, Christian
Format: Article
Language:English
Subjects:
Channels
Coastal hydrodynamic modelling
Coastal zone management
Data collection
Deltas
Dredging
Eddies
eddy formation
Entrances
Flow velocity
Fluid dynamics
Harbors
Harbours
Headlands
Inlets
Littoral drift
Marine
Modeling
navigation channel shoaling
RESEARCH PAPERS
Sand
Sediment transport
Sediments
Simulations
Studies
Throat
Tidal currents
Tidal inlets
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Summary:In 1992 the entrance channel through the tidal inlet to Tauranga Harbour, which is located along the Bay of Plenty littoral drift system, was deepened from 10 m to 14 m. The deepened channel has become a sediment trap for littoral drift bypassing and tidal current driven sediment transport through the inlet. Since 1992, there has been an increase in maintenance dredging requirements at the inlet, because of sand accumulation along the southeastern border of the entrance channel. Previous studies have identified an ebb tide–induced eddy operating on the eastern side of the ebb-jet as it exits the tidal gorge. In this article, the eddy system has been simulated with a validated two-dimensional hydrodynamic model, detailing time-varying current patterns over the ebb-tidal delta. Particular emphasis is placed on defining the trajectory of the eddy and evaluating its influence on the observed sedimentation patterns. The model results indicate the formation of opposing eddies on either side of the entrance channel, both of which are transient in nature. The centre of the eastern eddy propagates seaward along the downdrift margin of the entrance channel as the ebb-jet lengthens. Bathymetric survey residuals between 2004 and 2006 confirm significant accumulations of sediment along this downdrift margin. The evidence is consistent that the eddy system exerts a directional control over transport of sediments entrained by waves over the ebb-tidal delta.
ISSN:0749-0208
1551-5036
DOI:10.2112/07-0947.1