Low tide on the beaches of the west coast of La Réunion Low tide on the beaches of the west coast of La Réunion

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Low tide on the beaches of the west coast of La Réunion

The current affairs Internet site of the island of La Réunion (Zinfos974.com and linfo.re) tell of very low tides, rare for the months concerned, observed in March and April 2011.

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From the observations available from the tide gauge installed at Pointe des Galets at the end of 2007, it is possible to discover that in the past few years (2008 to 2011) for March and April sea levels did not fall as low as in 2011 (13 cm).

 

Périodes Lowest level with respect to hydrographic datum (*) Date / time UT Predicted low tide (tide tables) Reduction in height of low tide
March-April 2011 13 cm 19/03 15h30 25 cm 12 cm
March-April 2010 17 cm 28/02 16h00 20 cm 3 cm
March-April 2009 22 cm 09/03 14h20 25 cm 3 cm
March-April 2008 19 cm 07/03 15h20 25 cm 6 cm

 

 

(*) See maritime altimeter references

Average levels are generally of the order of 10cm higher during summer in the southern hemisphere and this is therefore not a good time to observe extreme levels of low tide.

Nevertheless, if we look at the older data from the float tide gauge operated by the DDE (French equipment government agency), we note that this threshold of 13 cmhas been reached and even exceeded several times in the past (some ten times for March-April between 1974 and 2005). This is therefore not the first time that this phenomenon has occurred at this time of the year.

With regard to the reduction in height of low tide of 12 cmwith reference to the tide tables, this variance between height of tide predicted and the level reached is due to meteorological conditions (atmospheric pressure and wind). This negative surge is combined with the large tidal ranges associated with the spring equinox.

Tide gauge observations at the start of 2011 at Pointe des Galets

Tide gauge observations at the start of 2011 at Pointe des Galets