Ecological restoration of the Rhone at Vion and Chambon

A global and ambitious programme

The ecological restoration of the sectors of Vion and Chambon is part of a huge programme initiated in 1998 by local actors including CNR. It involves the sections of the river located over its entire length. Carried over to the Rhone Plan of 2006, it is also part of the European Framework Directive on Water aimed at reaching the good ecological state of aquatic habitats.

Success already proven in other territories

Since 2009, Girardon spur dikes have been dismantled in 7 sections of the old Rhone. Ecological observations showed that the restoration of the Rhone favours the typical species of large rivers and increases the biological diversity of the alluvial plain.

The goals targeted

Return the Rhone to more natural functioning with more space to evolve and with sediment transport partially restored.
Favour biodiversity, by re-establishing habitats favourable for a large number of species, including certain rare or protected ones.
Increase the positive effects of floods, especially in the oxbows, thereby favouring “self-maintenance” to limit clogging by sediments, and allow erosion processes that diversify ecosystems.
Prepare the river’s resilience to climate change, by favouring exchanges between all the aquatic habitats composing it: main channel, secondary branches, wetlands, underground aquifers, etc.

The actions carried out

Remove the Girardon spur dikes.
Excavate the beds of former oxbows and new secondary branches.
Return to the river fines and coarse materials taken from earthworks leading to the return of sediment continuity and restoring the river bed.
Plant varied and adapted species (black and white poplars, white willows, etc.) to combat colonisation by invasive species.

The works accomplished

Spur dikes of Vion and the oxbow of Lemps:

Dismantling of the Girardon structures (2.4 km of dikes; 63,000 m³ of rockfill removed and recycled).
Excavation of secondary branches (2 km).
Creation of islets (7).
Reinforcement of the riparian forests and combat against invasive species.

Wetland of Saint-Estève:

Excavation and development of a wetland (6 ha).
Plantation of an aquatic reedbed.

In all, more than 180,000 m³ of sediments will be reintroduced into the Rhone, including 40,000 m³ of gravel from the spur dikes of Vion. On the sites of Lemps and Saint-Estève, the historic gravel embankments (580,000 m³), resulting from the construction of the hydroelectric development of Gervans in 1971, are not planned to be restored to the Rhone. They will be removed by river and recycled via the circular economy.

The calendar

The earthworks will take place from September to February over several years, to limit impacts on the biological cycles of plant and animal species as well on as the use of the site for leisure purposes.

Vion: from September 2025 to February 2029
Lemps: from September 2025 to February 2030
Saint-Estève: from September 2029 to February 2033

A project designed in concert

For 20 years, the global project of the ecological restoration of the Rhone has been carried out in parallel by a scientific research programme, RhônEco, that above all performs ecological monitoring. Regular dialogue with CNR makes it possible to adapt actions according to feedback from the field and check the efficiency of the measures taken.

Extensive consultation was carried out with the territories, river users, (walkers, anglers, cyclists, hunters, canoeists, etc), the neighbouring population, nature associations, scientists, and institutional and financial actors such as the State, the Rhone-Mediterranean-Corsica Water Agency and the European Union. Different visits to sites and workshops led to the shared conception of this project of proven utility.

With the support of partners:

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