]> 2026-04-12T07:38:36+00:00 Case study:Restoring the natural dynamics of the upper Adour 500 en All information on this page is copied from the AFB, The French Agency for biodiversity. Approved 0.0135 0.01 - 0.1 30 10 - 50 m 42.2338455 Restoration of side channels Removal of bunds by regrading the banks Creation of secondary channels Bank protection Planting Restoration works: Water agency (50%) Departmental council (10%) Regional council (20%) Maintenance works: Water agency (50%) Regional council (20%) Yes No Yes false Fluvial.png Upper adour.png An alluvial bar on the upper Adour before (above) and after (opposite) the works. (Source: Véronique de Billy – Onema). The upper Adour with a treated left bank. (Source: Véronique de Billy – Onema). Yes 43.065093,0.1491049 Jean-Luc Cazaux Countering the development of Japanese knotweed Change in debris and dead wood management to minimum intervention 9.57 10 - 100 m³/s Restoration of side channels, Removal of bunds by regrading the banks, Creation of secondary channels, Bank protection, Planting,,, ,Countering the development of Japanese knotweed, Change in debris and dead wood management to minimum intervention,, A pre-works survey showing the hydro-geomorphological functioning of the Adour was carried out. It was based on expert opinion and observations of the river’s morphological characteristics (flow pattern, erosion zones, disconnected secondary channels) and any changes over time. Since the end of the works, no specific monitoring has been carried out, with the exception of regular observations in the field. The restoration works diversified the flow pattern and habitats, making possible salmonid reproduction. An immediate effect of reconnecting the side channels was an increase in the mobility space of the river and a decrease in flooding risks (greater dissipation of energy, a reduction in vertical and lateral erosion processes, stabilisation of banks, etc.). The awareness on the part of the elected officials of the need to protect biodiversity and the creation of a comprehensive, integrated and pragmatic approach to river management, in close contact with the local population, guarantee the success of the project. The guiding principles behind the restoration and maintenance works have now been adopted by the towns downstream. The intermunicipal association has also made significant financial savings thanks to the halt of the previous large-scale and expensive work programmes. 23404 2004-01-01Z 2453005.5 1997-01-01Z 2450449.5 Complete in order to protect nearby land and homes from flooding, work was regularly done on the river with the main objective being to narrow the river bed and to create a single channel. In the process, alluvial bars along the entire upstream section were systematically removed and the resulting sediment was spread along the banks to form bunds. This contributed to incision of the river bed and disconnection of side channels from the main channel. It also resulted in significantly destabilising the river banks. The works consisted of removing the bunds by regrading the banks and modifying the management techniques for accumulated debris and dead wood. The side channels that had been cut off were restored and a network of secondary channels was created to manage flooding. Bank-protection systems were installed only as needed and exclusively using bio-engineering or mixed techniques. Sectors with sparse vegetation were planted. Finally, efforts were made to counter the development of Japanese knotweed, an invasive species. ■ Post-restoration management A track parallel to the banks, at least ten metres from the river in the riparian vegetation and open only to maintenance personnel and local land owners, was created to facilitate maintenance and provide access to the river in the event urgent action is required during a flood. Vegetation is cut on a very selective basis in order to preserve the habitats of the animals that depend on the aquatic environments. Management of accumulated debris and jams is kept to a minimum. An assessment now determines whether debris and jams constitute an effective obstacle to the flow of water and only the “risky” situations are managed by removing any vegetation and raking the sediment to a depth of 80 cm. Restoring the natural dynamics of the upper Adour restoring the natural dynamics of the upper adour No 12100 Japanese knotweed (Fallopia japonica) Flood risk management Habitat and biodiversity Hydromorphology 794 500 - 1000 k€ FRFR236 and FRFR237B 2018-06-26T11:51:00Z 2458295.99375 2019-01-03T08:53:37Z 2458486.8705671 Restoring the natural dynamics of the upper Adour