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Inlet Morpho-Dynamics During a Storm Event Inferred from Tidal Records: A Case Study Of The Brunswick River, NSW, Australia

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Author(s): Thuy T. T. Vu, Peter Nielsen, David P. Callaghan

Journal: International Journal of Engineering Research
ISSN 2319-6890

Volume: 2;
Issue: 2;
Start page: 38;
Date: 2013;
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Keywords: Brunswick Heads | morphodynamic timescale | 24.5 hour moving window | morphodynamics | tidal response.

ABSTRACT
A 24.5h moving window is used to analyse storm effects on thetidal dynamics. Compared to earlier studies using windowlengths varying between 2h (for tsunami analysis) to 14 daysfor tidal inlet analysis, the present method provides goodresolution of variations of hydraulic efficiency during storms orfloods. The importance of de-trending before carrying out theharmonics analysis has been studied and it was found to behighly important. De-trending involved removing the 24.5hmean before harmonic analysis. The main results are themorphodynamic timescale Tmorph and the varying responsefunctions F1 and F2 of the diurnal and semi-diurnal tidalconstituents through a storm event at the Brunswick River,Australia.Tmorph is inferred from time series of primary semi-diurnalgain G2(t)= |F2| with an exp(-t/Tmorph) curve fit. The resultsshow only insignificant morphological change. Thus, thechanges in tidal response for this medium sized catchment aremainly due to hydraulic effects. These include the influence ofriver flow Qf via the non-linear friction term and increasedestuary surface area during the flood. The traces of both F1(t)and F2(t) in the complex plane show an equilibrium before thestorm, dynamic change during the storm and relaxationmimicked by exp(-t/Tmorph) after the storm.
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