boite à outils

Thrilling high tides and ’the tide of the century’

’Mum, Dad - the sea has gone!’
Children are often baffled the first time they go to the beach at low tide.

In Brittany, we have some seriously fascinating tides! Come and witness this fantastic spectacle in the most beautiful bay in Brittany, Morlaix Bay.

What is a tide, anyway?

On the coast, twice a day, the sea draws away then returns a few hours later, in a constant coming-and-going. These cyclical movements of around 12 hours that cause the water level to rise and fall are known as tides.

It’s the result of great masses of water from the seas and oceans being displaced, connected to the pull of the moon and the sun. The variation between high tide and low tide is affected by the position of the sun and moon in relation to earth.

Grande marée en baie de Morlaix Bretagne Finistère

What’s a really high tide?

The French Marine Hydrographic and Oceanographic Service (known as SHOM) is based in Brest but they define the strength of the tides for the whole of France. To do this, they use a number between 20 and 120 that represents the variation between between the water-level at high tide and that of low tide: this variation is called the tidal coefficient

  • 20 = Exceptionally low neap tide
  • 45 = Average neap tide
  • 70 = Average tide
  • 95 = Average high spring tide
  • 120 = Exceptionally high spring tide

This figure is not the same in every place or at every tide, as it varies depending on the time of year, the topography of the site and the tide cycle. When we talk about very high tides, we’re referring to a tidal coefficient of 95 to 110.

What about this ’tide of the century’?

On Saturday 21st March 2015, we will experience what’s known as ’a tide of the century’, with a tidal coefficient of 119. The last time this happened was in March 1997 and the next will be in March 2033, so they are unmissable events. They only happen every 18 years and they coincide with the spring equinox.

A ’tide of the century’ is unusual in that it has an extremely high tidal coefficient of between 110 and 120.

The tide of the century in Morlaix Bay

With such high tidal coefficients, Morlaix Bay transforms into a sandy playground at low tide (as the sea disappears), giving a difference of more than 8 metres between the water-level at high tide and at low tide.

It’s spectacular to watch, as the beautiful bay gradually empties of water, revealing rocks, sandy stretches, swathes of kelp and oyster beds. It’s a whole new world to discover!

Ile Louet à marée basse, Baie de Morlaix Bretagne Finistère Carantec

This is the time for the walkers, artists, photographers, naturalists and shellfish-gatherers to make the most of the landscapes that are brought to light. Don’t forget that the high tide, especially during a huge swell, can bring magnificent jets and sprays of water as the sea crashes against the rocks.

The topography of Morlaix Bay makes it a great spot for shellfish-gathering almost all year round, as the low tide reveals great stretches of sand. Because of the sea that comes and goes, this area (known as the ’estran’ in French) has a flora and fauna that are incredibly divers, and a great variety of habitats: sandy zones, rocky or even silty areas.

Please do be careful when exploring - remember that these are fragile natural environments!

Beautiful... but dangerous

To make the most of this magnificent maritime spectacle in safety, here are some tips from the Coastguards at Primel-Plougasnou:

  • Make sure you know when the next high tide is coming back, by using tide timetables. With strong coefficients, the rising tide comes in very quickly in this Bay.
  • Make sure you’re back on dry land well before your feet get wet.
  • Keep a careful eye on the time.
  • Calculate how long it will take you to get back to shore.
  • Keep an eye on your surroundings and any hazards between you and the shore.
  • Keep a mobile phone with you.
  • Avoid going out alone, and if you have to, make sure you tell others where you are heading.

For any emergencies at sea, remember the rescue number: 196.

Port de Locquirec en hiver, lumières de Bretagne