the essential
Since July 2024, work has been underway in the town of Auzits. At issue: the reopening of the Riou Viou, blocked since the First World War, and extended in the 1970s. This fragile structure presented a risk of obstruction and flooding.
With the industrialization linked to the mining activity of the Decazeville Basin, many watercourses have been moved, rectified or even diverted. In Auzits, the Riou Viou crosses the village via an underground structure built during the First World War and extended in the 1970s. Undersized, the channeled passage increases the risk of flooding in the village, even more so when ice jams occur. find themselves trapped at the entrance to the structure, obstructing the flows and encouraging overflow.
This structure also presents a degraded structural state which constitutes a threat to civil security in the event of collapse. Between the risks of flooding and environmental, structural or landscape issues, work to reopen the Riou Viou has been underway since July. In the upstream sector, the Riou Viou first reveals itself in a restricted area between buildings and the departmental road. Downstream, it is free to find a space for mobility and a natural flood expansion zone.
Towards a renaturation and the reopening of the departmental road
This work is made complex by the fact that it involves multiple stakeholders: department, community of municipalities, etc. Last year, the bridge was rebuilt by the department, with the removal of the central pier in order to avoid ice jams. The Community of Communes of Pays Rignacois holds responsibility for management of aquatic environments and flood prevention (GEMAPI). She delegated her control to the union of the middle Célé-Lot basin.
The completion of the structural work is scheduled for around November 10. For Benoit Olivié, mayor of Auzits, “this was the most complicated part to carry out. We should now be calm in relation to the ten-year flood.” The structural work is being carried out by the Sévigné d’Aguessac company, with the release of the water from the Riou Viou planned for October 30 (water law). The Auzits town hall “very much appreciated the attentiveness, the quality and the seriousness of the company.”
Then, the renaturation work on the site will take place. The departmental road crossing Auzits will reopen during the month of November to all traffic. The end of the work will be followed by the “village heart” operation which will begin in February 2025.
A budget of 825,000 euros hors taxes
The cost of the work is €825,000 excluding tax (including the additional cost of €200,000 for the management of polluted soil present on the site). Funding is provided by the State (30%), the Adour-Garonne Water Agency (23%), the Occitanie Region (12%), ADEME (10%), and the community of communes of Rignac region (25%). A request for additional aid was sent to the Heritage Foundation to reduce the burden on the community of municipalities.
As part of the “CéLot’omne” event, led by the union of the Célé-Lot median basin, and dedicated to flood prevention, the organization set up, for the second consecutive year, the “Crue Tour “. An initiative which offers a series of visits to the sites which have benefited from the work, in connection with prevention. On October 15, 2024, elected officials, partners, water stakeholders and citizens were transported by bus to discover the projects. If they stopped at Auzits, they also discovered the flood protection hedge planting project in Boisse-Penchot, and the objectives underway in Figeac. This year, the event brought together around forty people.
Fording crossings closely scrutinized
DDM – BHSP
Since 2023, the joint association of the Célé-Lot median basin has been carrying out a multi-year plan for the management of watercourses and aquatic environments. The Hydrétudes firm is currently mandated by the joint union to study the crossing points on foot or with machines, on the Riou Viou route in Auzits, Aubin and Cransac. Thus, since last September and until next March, Charlotte Cuisenier (engineer) and Denis Ducrocq (surveyor technician) have been going into the field to collect data.
“Four ford crossings and structures have been identified as leading to morphological disorders on the river. In the case of the Riou Viou, they are reinforced with a concrete slab taking place in the bed of the river. These artificial developments form a waterfall and a pit downstream, an excess width of the bed and leading to an accumulation of sediment upstream. The poor condition (slumping of the slabs, cracks, flow) of these structures threatens their use After a diagnostic phase. developments, solutions will be proposed, to combine hydromorphological restoration and uses, in order to improve the functioning of the stream and maintain a crossing”, explains Sylviane Faure, of the joint union.
This stretch of water was selected for this operation because it is identified as a refuge area for aquatic fauna in the event of severe low water (notably observed in 2019, 2022 and 2023), thanks to the maintenance of pockets of water during drought.
