RESTORATION OF THE POYAT STREAM (42)

Restoring the watercourse to its original bed and culvert recreation to allow the removal of two structures (Loise catchment area), Loire, France, 2024

CONTEXT AND OPPORTUNITY

The Poyat is a left-bank tributary of the Ruisseau de Fonbonne, itself part of the catchment area of the Loise, a right-bank tributary of the Loire. The Poyat catchment area is very small: around 5 km² for approximately 3 kilometres of watercourse.
This area (the Fontbonne stream catchment) is home to the white-clawed crayfish (Austropotamobius pallipes, classified as endangered by the IUCN). These populations are exceptional in the département.

Restoration work has already been carried out downstream of the Ruisseau de Poyat and on the Fontbonne to restore habitats favourable to the species and enable the watercourses to recolonise (removal of a pond and hydro-morphological restoration of the watercourse, project to restore a culvert to ensure ecological continuity, restoration of banks using plant techniques and fencing).

PURPOSE OF THE PROJECT

Until now, the Poyat stream has been perched on the western slope with a straight course, partitioned by two impassable structures. These two structures are the last obstacles upstream of the main course of the Poyat. Restoring the watercourse to its original bed and removing the two structures will reopen the watercourse as far as its sources, potentially allowing white-clawed crayfish to re-colonise. The Poyat has relatively sustained low-water flows, making it an important refuge area in summer.

The project also involves restoring the watercourse to its original talweg, thereby improving the dynamics of the alternating flow facies and increasing and improving fish habitats.

This will also reconnect the watercourse to the low-lying wetland on the site, which will enhance the local hydrology, particularly during periods of severe low water. The installation of fencing will limit the impact of livestock trampling.

AT A GLANCE

  • Localisation : Loire (42), France
  • Stream : Ruisseau de Poyat
  • Open kilometers : 2km up to the sources
  • Key species: Salmo trutta, Austropotamobius pallipes, Cottus gobio, Lampetra planeri
  • Project by :  SISMAE
    Partners : Open Rivers Programme, Loire Bretagne Water Agency, Patagonia, Fondation Nature et Découverte, European Rivers Network

See

Les 2 ouvrages avant travaux (seuil et passage busé) © SISMAE

Passage busé avant et après travaux © SISMAE

Le projet vu du ciel © SISMAE

Après travaux, janvier 2025 © SISMAE

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