Undular tidal bore dynamics in the Daly Estuary, Northern Australia |
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| Authors: | Eric Wolanski David Williams Simon Spagnol Hubert Chanson |
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| Affiliation: | a Australian Institute of Marine Science, PMB No. 3, Townsville MC, Queensland 4810, Australia;b Department of Infrastructure, Planning and Environmental, Natural Resources Division, PO Box 30, Palmerston 0831, Northern Territory, Australia;c Department of Civil Engineering, University of Queensland, Brisbane, Queensland 4072, Australia |
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| Abstract: | Measurements in the macro-tidal Daly Estuary show that the presence of an undular tidal bore contributed negligibly to the dissipation of tidal energy. No recirculation bubble was observed between a trough and the following wave crest in the lee waves following the undular bore. This differs to stationary undular bores in laboratory experiments at larger Froude numbers where a recirculation bubble exists. Secondary motions and the turbulence generated by the undular bore had no measurable influence on the sediment transport. This situation contrasts with the intense sediment resuspension observed in breaking tidal bores. The tidally averaged sediment budget in the Daly Estuary was controlled by the asymmetry of tidal currents. The undular bore may widen the river by breaking along the banks that it undercuts, leading to bank slippage. A patch of river-wide macro-turbulence of 3-min duration occurred about 20 min after the passage of the bore during accelerating tidal currents. |
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| Keywords: | tidal bore recirculating flow sediment transport tide-velocity asymmetry turbulence |
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