Saturday, March 21, 2015

'Tides of the century' in France

Storms and high tides in Saint-Malo (Brittany, France) from Easy Ride.
During Ulla, Dirk, Christine storms in Saint-Malo, February 2014

The bay of St Malo knows among the highest tides in the world.
The so-called "tide of the century" in fact happens every 18 years.
The moon alignment with the sun adds to the gravitational pull on the seas,
creating a high point in the 18-year lunar cycle.

Thousands of people gathered at Mont Saint-Michel in northern France on Saturday to watch what is being called "the high tide of the century".

The exceptionally high spring tide, swollen by a "supermoon" effect linked to the solar eclipse on Friday, was predicted to cut off the picturesque island from the mainland with a wall of water as high as a four-storey building.
Friday’s tidal surge was not as high as the 46 feet predicted, and a tiny sliver of causeway no more than a few metres wide resisted the surge of water pushed by the moon's huge gravitational pull on the sea.
However, Saturday's tide on the long, sloping estuary of the River Couesnon could yet go higher, although scientists said low air pressure may have lessened the phenomenon.
As the surge began to make its way along the coast and tidal estuaries surfers took to the water in Pontaubault and waves crashed onto seawalls.

MareeInfo : Tide in Saint Malo today
Exceptional High Spring Tide at Saint Malo (height:13.35m 43.8ft),
the highest spring tides in Europe
The moon acts as a magnet on the oceans.

Its force of attractions is twice as strong as that of the sun.
The sea advances and retreats twice a day with a time shift of 50 minutes each day.

When the moon is above the sea, it attracts the water towards it and so the sea level rises and the tide comes in.
Six hours later, the moon is no longer above the sea and the force of attraction disappears.

The tide then goes out.
The power of the force varies depending on the positions of the sun and moon respectively in relation to the earth.
When the three are aligned the attraction is at its peak.
This is the time of the high tide : during this period the sea advances and retreats the farthest.

Police had difficulty holding back the 10,000-strong crowd eager to get pictures of the scene in the final minutes before the surge on Friday evening, with the tourist hotspot lit up as night fell with 60 spotlights for the occasion.
Mont Saint-Michel, which was named a UNESCO World Heritage site in 1979, is situated one kilometre off the coast of Normandy.
The rocky outcrop is home to the famous Norman Benedictine Abbey of St-Michel.
Michael Dodds, the director of the regional tourism committee, said: "This natural phenomenon is an incredible opportunity for tourism in Brittany at this time of year."

Highest tides at Mont Saint-Michel seen by drone from FLY HD.
On February 21 the tidal coefficient reached 117.
The Mont Saint-Michel 11th century abbey is expected to be entirely surrounded by the English Channel with waters rising by a staggering 14 metres. 
"The eclipse and the tide are linked" said Kevin Horsburgh, head of the Marine Physics and Ocean Climate research group at Britain's National Oceanography Centre (NOC).
"For an eclipse to take place, the sun, the Earth and the moon need to be in a straight line, which is also an essential condition for high tides," he added.

The bay on the coast of Normandy has some of the strongest tides in the world.
Eleven departements along the coast of northern France are on alert for fear of flooding and residents have been told to stay away from beaches and coastal areas.
Similar surges are predicted along the coast of Britain and the Netherlands over the weekend.
The last ‘tide of the century’ was on March 10, 1997 and the next will be on March 3, 2033, making the description something of a misnomer.
The predictions are based on the tide coefficients used by scientists to forecast wave size.
With 120 being the highest, they project a 119 on Saturday.

Until 1879 Mont Saint-Michel was cut off from the mainland during each high tide.
That year a permanent causeway was built to prevent the tide from scouring the silt around the island.
The coastal flats were reclaimed for pastureland, reducing the distance between the shore and the island.
The effect was to encourage the silting-up of the bay.
In 2009 work began on building a hydraulic dam using the waters of the river Couesnon and the tides to help remove the accumulated silt, and make Mont Saint-Michel an island again.
Last year a new 2,500ft bridge was opened to the public.
The bridge allows the waters to flow freely below and around the island at high tide.

 Saint Malo & Le Mont Saint Michel Bay with the Marine GeoGarage

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