]> 2026-04-16T14:40:32+00:00 Case study:Reopening of the culverted Redon river 500 en All information on this page is copied from the AFB, The French Agency for biodiversity Approved 3 2 - 5 m Reopening of culverted river Bank stabilisation Planting Meandering channel Symasol departmental environmental and agriculture division the French National Agency for Water and Aquatic Environments (Office National de L’Eau et des Milieux Aquatiques) Fédération départementale de la pêche (departmental fishing federation) local fishing association the commune. Agence de l’eau (Water Agency) (31%) General Council (28%) Regional Council (10%) Symasol (31%). Yes No Yes false Quarry without restoration.png Buried river.png After 2 years.png Redon after restoration.png Overview of the quarry before restoration work - 2007 (Symasol) The Redon buried in the downstream section. Before restoration work -2007 (Symasol) The Redon in the downstream section, 2 years after restoration work - 2009 (Symasol) The Redon after the reopening and development of the low water channel - 2009 (Symasol) No 46.337915,6.432466 Maxime Symasol Chateauvieux 0.5 0.1 - 1.0 m³/s Reopening of culverted river, Bank stabilisation, Planting,,,Meandering channel, ,,, Pre-restoration works monitoring have been carried out. It includes a topographic survey for a hydraulic analysis of the site. Furthermore, fish rescue by electric fishing was performed at the opening of the culvert. Fish stocks were monitored following the culvert removal on the Redon, six months after the restoration work. As part of the appraisal of the “Crossborder river contractforthe southwest part of Lake Geneva” (2006-2012), fish stocks were monitored in all the watercourses in the area covered by the SYMASOL. For this, the fish population was counted in the Redon at the location of the work site in the summer of 2011, four years after the restoration work. An IBGN survey was conducted in 2009 (two years after the work) by a consultancy. Lake trout can now swim up the whole length of the Redon. Six months after the works, about 230 river trout were recorded throughout the reopened stretch, i.e. 3,800 individuals per hectare against only fifteen or so individuals identified during the fish rescue operation. The results of the 2011 electric fishing confirm the trend noted six months after work was completed. Thus, 48 trout were counted on the upstream station, i.e. 3,678 individuals per hectare. These results are very positive and seem to indicate that the fish population is stabilising in the part of the watercourse where the culvert has been removed. The IBGN analysis suggests that the quality of water is restrictive in this portion of the Redon. The taxon indicator (Hydropsychidae) is relatively tolerant to poor water quality and taxonomic diversity is quite low (18 taxons identified). However, the absence of a sampling point before the restoration work does not allow the observation of a potential gain in terms of water quality or habitat diversity due to removal of the culvert. The outcome in terms of overall assessment is excellent from the point of view of elected officials, residents and fishing stakeholders. Pursuant to the River Contract (2006-2012), a general policy to review weirs preventing river continuity was implemented. Rocky boulders or bypasses were set up to make weirs passable. 23353 Symasol, departmental environmental and agriculture division, the French National Agency for Water and Aquatic Environments (Office National de L’Eau et des Milieux Aquatiques), Fédération départementale de la pêche (departmental fishing federation), local fishing association, the commune. Reopening of 230 metres of the Redon. Overview of the site after restoration work -2009 (River next to parking lot) (Symasol). 2007-01-01Z 2454101.5 Quarry after restoration.png 2006-09-01Z 2453979.5 Complete 1.5 km from its outlet, the Redon had been culverted for the purposes of a quarry. The passage of the river through a concrete culvert covering a 230 metre stretch prevents many of the fish from the lake from swimming upstream, to an ideal breeding ground. The quarry where the culvert is located is no longer active, therefore 230 metres of the culverted river were reopened. In order to diversify the environment, a meandering bed was created. Plantation was used to protect the banks and the longitudinal section was stabilised Reopening of the culverted Redon river reopening of the culverted redon river Yes 230 river trout lake trout Environmental flows and water resources Habitat and biodiversity 145 100 - 500 k€ FRDR11140 2018-06-19T13:18:31Z 2458289.0545255 2019-01-02T16:41:00Z 2458486.1951389 Reopening of the culverted Redon river