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The story behind Adelaide's unique dodge tides

Brett Williamson, Friday February 17, 2017 - 14:00 EDT
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Dodge tides are only experienced in a few locations around the world, including Adelaide. - ABC

Dodge tides are a well-known phenomenon among Adelaide's ocean lovers but reportedly happen in only a few other places around the world.

The term dodge tide dates back to when Matthew Flinders first mapped the coast of South Australia, according to James Chittleborough of the National Tidal Unit at the Bureau of Meteorology.

It refers to tides with little or no height variance.

"[Flinders] noticed the tides missed the usual timing several times a year and coined that the tide was dodging," Mr Chittleborough told Afternoons.

He said the phenomena was only reported as happening in one other place in the world, the Gulf of Mexico, and possibly at a gulf near Nova Scotia and in the Gulf of Carpentaria.

Mr Chittleborough said dodge tides were different to neap tides, when water movements were at their smallest change.

"Tides are essentially driven by the Moon and the Sun, with the Moon having twice of the effect of the Sun.

"In a few places in the world, due to the symmetry of the oceans and how the tidal waves respond, the effects of the Sun and Moon are about equal.

"The effects actually cancel each other out so that we get no tidal movement whatsoever for a day or two.

"It's quite a unique phenomenon.



"Other places have what we call a spring neap cycle, but in Adelaide the neap tides are quite weak and several times a year the tide [movement] almost disappears."

Mr Chittleborough said other locations around the world had similar water height changes as a dodge tide but their natural variations were not as high as in the Gulf St Vincent.

"In Adelaide, we have quite substantial tides of several metres [normally]," he said.

"Normally we are used to [around] two metres of tide going up and down each day.

"It's quite noticeable here and has effects on shipping and so forth."


- ABC

© ABC 2017

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