HISTORY

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The Marais Poitevin once was a vast limestone plateau eroded during the last great glaciation. The significant decrease of sea level that occured 80 000 and 10 000 years ago results in an increase in the power of the rivers. The most tender formations eroded faster, gradually forming a large basin. In the middle of it remained 'mounds', corresponding to more resistant calcareous soils : The ISLES of MARAIS POITEVIN. 

About 10,000 years ago, the sea level began to slowly rise, which led to the gradual filling of the Gulf, known as the Gulf of Pictons. 
Until the Middle Ages, the Gulf of the pictons fumes. About the year 1000, Guillaume V le Grand founded the present abbey of Maillezais and in 1068, the abbey Saint Vincent of Nieul-on Autise quickly receives the support of the powerful counts of Poitou. 
The abbeys are rich and powerful. They will finance major drainage works. The project is so big that they will join forces and combine their efforts. As the land of those marshes does not belong to them, they will ask permission from the local lords. Pierre de Velluire will even give his land in concession.

These works will last from the end of the 10th to the 11th century. The 'savages' of the marsh have to participate willingly or not. They will start by constructing a belt of dikes inside which they will dig a network of FOSSES - CONCHES - RIGOLES. These ducts drain the rainwater and return it to the outside of the belt, which is the birth of the first dried swamps. Unfortunately, the war of 100 years and then the wars of religions will stop this work. Nature quickly regained its rights and the destruction of the dikes quickly destroyed the efforts made. 
Then HENRI IV had the will to dry out the Marsh. 
Peace returned, this King of France wants to eradicate epidemics and discover arable land to fight famine. First problem the kingdom's finances are at the lowest. 
Protestant funds will allow the job to be done with the arrival of Flemish and Dutch engineers. They were masters in the marshy problems, the polders in the Netherlands can proove that. At their head, the engineer BRADLEY to whom the King will award the title of 'Master of the dykes and canals' of the kingdom.

Bradley will start by raising a dike facing the sea, 2 to 3 meters high, in order to preserve the tidal lands, then another dike against the runoff water from the upstream, in order to prevent the flooding of the land. Thus the upstream will protect the downstream and become the flood swamp or Marsh "wet". The downstream protected by these two dikes thus becomes cultivable it is the marsh not flood or Marsh "desiccated". The wet marsh is sacrificed, it collects rainwater. Often inundated, it is not exploitable. The desiccated swamp is fertile, cereals and livestock thrive. 
In those times, there is no energy. A unique system will then emerge under the impulse of Bradley, then of Siette, engineer of King Louis XIII, THE DOOR A FLOTS. It is a sluice that closes itself by the rise of the tide and when sea goes down, preventing the rise of salt water in the first case and allowing rivers and canals to flow to the sea in the second case. Some of these doors are still working today. The Marais Poitevin was then in its current form, unique in the world.