Mont-Saint-Michel Bay


The Mont-Saint-Michel Bay is located between Brittany and the Normandy peninsula of Cotentin. The bay is part of the club of the world's most beautiful bays and is listed as a UNESCO world heritage site. Due to the significant tidal movements in this region a large part of the bay is uncovered at low tide. There are two granitic islands in the bay: Tombelaine and the Mont-Saint-Michel. Many birds and harbor seal live in this area.

General considerations

Mont-Saint-Michel Bay is about in size.

Adjacent towns and villages

The following towns and villages surround the bay, from north to south:

Rivers

Three small rivers end in the bay : the Couesnon, now blocked to the west of Mont Saint-Michel by a causeway, the Sée and the Sélune. The very low slope of the bay and the very large tides formed a mascaret in those rivers that can travel upstream for many kilometers.
Three larger rivers end in the bay: the Sélune, the Sée and mainly the Couesnon that, accordingly to some local folk stories, was originally the boundary between Normandy and Brittany but then moved to the West of the Mont placing it in Normandy. In reality the boundary is not at the river location but further to the west, at the foot of Mont Saint-Broladre.

Biggest tides in Europe

Some of the biggest tides in Europe occur in Mont-Saint-Michel Bay: with an average amplitude, they reach in average and up to during the highest tides. This is due in part to the low depth of the bay and the barrier effect from the Cotentin Peninsula.
The ocean moves very fast, both at low and at high tide, up to away. The tides have been described by Victor Hugo as "à la vitesse d'un cheval au galop ". In reality the full extent of the tides is only visible at the entry of the bay and its actual speed is closer to a walking human, the fastest observed being around 6.1 km/h.
The tides mix the water, creating a rich local ecosystem. The intertidal zone, the coastal area affected by the tides is about 200 km2 wide.
During the highest tide, a tidal bore can be observedless so since the bay has been under restoration work.

Levee and polders

The levee

s have been developed in Mont-Saint-Michel Bay from the 8th century or earlier than that. Between "Pointe de Château-Richeux" and Mont Saint-Broladre seashell deposits have been used to create levees around Dol marsh. To the East of Sainte-Anne chapel is the "Duchesse-Anne" levee. It is long. It was built during the 11th century using granite rocks. It marks the southern border of the polders.
In 1856, M. Mosselman, founder of the "Cie des Polders de l'Ouest", was given a concession to cultivate 3,800 hectares of shoreline between Sainte-Anne chapel, Moidrey bay, Roche-Torin and the Mont Saint Michel.