Mise à jour le 13 January 2022

Adapting 15 facilities to restore ecological continuity

Actions on watersheds

Background

The river Longèves merges with the river Vendée and flows into the sea, after crossing marshland in the Poitou region. The Longèves river is recognised as a biological reservoir and belongs to the eel priority action area ). Many structures situated on watercourses represent  obstacles to the migration of fish. Ecological continuity restoration work is therefore required on both  rivers. Subjects still to be dealt with are complex due to structures with multiple and often conflicting uses. Compromises must be found through negotiation or a search for new techniques.

Schedule & Location

1st quarter 2021 / 4th quarter 2024
on the Longèves river and its tributaries and on the Vendée river.

Objective

The objectives of this action are:

  • To restore ecological continuity from the source of the Longèves river to the Atlantic Ocean, passing through Vendée river and the Ilôts stream.
  • Test specific adaptation work, on the river Longèves and in the marshlands downstream.
  • Disseminate this knowledge on the specific environments to other water stakeholders.

Description of the action

This action is broken down into several sections:

1- Adaptation or removal of 10 works on the Longèves river and the Ilots stream

This involves adapting or removing 4 works listed on the list of obstacles to water flow on the Ilôts stream.

Two  works at Moulin Garreau are also concerned. As a result, hydraulic modelling will be conducted to divide flows in order to conciliate economic use of water and ecological continuity.

Finally, the Longèves river crosses the Hermenault ‘s Castle and has to cross 4 facilities which constitute obstacles to ecological continuity: 2 weirs, an equine pool and a bridge.

2- Adaptation of marshland crossing developments on 5 works on the Vendée river

 The Vendée river has indeed 5 forebays  along it up to the Atlantic Ocean. Therefore, in the summer, it does not flow or barely flows through these structures. This makes restoration of ecological continuity impossible with the usual crossing developments. Maintaining works is also essential to preserving marshlands which is why innovative solutions need to be looked for.

Main results expected

15 adapted works.

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