Case study:Restoration of side channels of the Loire and its tributaries

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Location: 46° 19' 22.55" N, 1° 4' 2.73" E

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Project overview

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Status	Complete
Project web site
Themes	Flood risk management, Habitat and biodiversity, Hydromorphology
Country	France
Main contact forename	Laëtitia
Main contact surname	Boutet-Berry
Main contact user ID
Contact organisation	DREAL + FDPPMA, local AAPPMAs, river associations
Contact organisation web site	http://http://www.hauts-de-france.developpement-durable.gouv.fr/
Partner organisations	AELB, FDPPMA, Onema (National Agency for Water and Aquatic Environments), regional councils, general councils, associations, regional conservatories of natural areas (CREN), regional conservatory of the banks of the Loire and its tributaries (Corela), departmental territorial directorates (DDTs), regional directorates of the environment, agriculture and housing (DREALs)
Parent multi-site project
This is a parent project encompassing the following projects	No

Projects in the River Loire. BD carthage et agences de l’eau Source: Conseil supérieur de la pêche (CSP), PLGN unit (2005).

Project summary

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The plan initiated by the State, Etablissement public Loire, the Regions and Loire-Bretagne water agency covers the implementation “of an overall development plan for the Loire in order to ensure the safety of the population, protection of the environment and economic development”.These operations were covered by two different programmes:

- For sites within the Public River Domain of the Loire and the Allier, operations were primarily carried out as part of the river bed restoration programme, under the guidance and project management of the State;

- For the other tributaries or private land on the banks of the Loire and the Allier, operations were carried out under another chapter of the Plan Loire: the natural environment restoration programme. In this case, the project owners were the departmental ederations for fishing and the protection of the aquatic environment (FDPPMA) or local authorities.

The operations consist in readjusting downstream connecting weirs between the main channel and side channel at the water level exceeded in the spring for 45 days, every fifth year. For pike spawning grounds of the middle Loire, re-connection projects are often positioned near to the water level of the average interannual rate. Given the lowering of the groundwater and lack of maintenance, it is usually necessary to thin the plant cover over old channels to restore sunlight conditions favourable to the development of the herbaceous layer and biological production. The works consist of carefully treating riverside vegetation, while respecting its overall balance, but also its role in the composition of water habitats.

Monitoring surveys and results

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Twenty-three side channels underwent a plant and/ or fish diagnostic in 1998 to identify intervention to be conducted. In accordance with the current situation and constraints, this preliminary study resulted in the identification and localisation of objectives as well as hydraulic requirements of each intervention.

More comprehensively, multidisciplinary monitoring was carried out on five restored river side channels on the middle Loire.

The physical and chemical features of water were analysed five times a year; the hydraulic operation of each site (floodability / connectivity), and biological factors (invertebrates, zooplankton, fish and vegetation) were monitored and analysed for each area during the 2002 campaign. The monitoring of side channels by the CSP (now Onema), was completed in 2007. Since then, the monitoring measures are taken care by different project owners involved in restoration projects.

Water quality monitoring in the side channels showed the reconnection of some of these areas. Overall, benthic macrofauna is high (138 taxa) and vegetation is fairly homogeneous, dominated by red canarygrass (Phalaris arundinacea).

As far as fish populations are concerned, reproduction has been observed in each of the monitored side channels, but the water deficit in 2002 caused large functional differences between the restored areas, due to their morphological heterogeneity.

In most of the restored sites, egg spawning and the presence of young pike have been highlighted by netting and electrofishing during the breeding season, before the period of migration of juveniles to the main channel.

Lessons learnt

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Image gallery

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Le Gros Ormeau side channel before reconnection work. August 1999. (DPPMA d’Indre-et-Loire).

Reconnection of Le Gros Ormeau side channel with the Loire. September 1999.(DPPMA d’Indre-et-Loire).

Le Gros Ormeau side channel after reconnection with the Loire. October 1999. (DPPMA d’Indre-et-Loire).

Reconnection of Le Gros Ormeau side channel with the Loire. August 2000. (DPPMA d’Indre-et-Loire).

Catchment and subcatchment Select a catchment/subcatchment Site Edit site Name WFD water body codes Middle Loire: RGR007a to RGR007d Downstream Loire: RGR007e to RGR007f WFD (national) typology WFD water body name Pre-project morphology Reference morphology Desired post project morphology Heavily modified water body No National/international site designation Local/regional site designations Protected species present No Invasive species present No Species of interest Dominant hydrology Dominant substrate River corridor land use Average bankfull channel width category more than 50 m Average bankfull channel width (m) Average bankfull channel depth category Average bankfull channel depth (m) Mean discharge category 100 - 1000 m³/s Mean annual discharge (m3/s) 500500 m³/s <br />500,000 l/s <br /> Average channel gradient category Average channel gradient Average unit stream power (W/m2) Project background Edit project background Reach length directly affected (m) Project started 1995/01/01 Works started Works completed Project completed 2005/01/01 Total cost category 1000 - 5000 k€ Total cost (k€) 16001,600 k€ <br />1,600,000 € <br /> Benefit to cost ratio Funding sources Water agency Loire - Bretagne (AELB), regional councils, general councils, unions of rivers, departmental Federations for fishing and the protection of the aquatic environment (FDPPMA). Cost for project phases Phase cost category cost exact (k€) Lead organisation Contact forename Contact surname Investigation and design Stakeholder engagement and communication Works and works supervision Post-project management and maintenance Monitoring Reasons for river restoration Edit reasons for restoration Mitigation of a pressure Flood risk management Hydromorphology Freshwater flow regime, Quantity & dynamics of flow, Width & depth variation Biology Fish: Abundance Physico-chemical Other reasons for the project Redeploy the energy of the river into the secondary channels to stop the incision process, Restore ecological diversity of the river environment. Measures Edit Measures Structural measures Bank/bed modifications treating riverside vegetation, Weir modification Floodplain / River corridor Planform / Channel pattern Other Non-structural measures Management interventions Social measures (incl. engagement) Other Monitoring Hydromorphological quality elements Edit Hydromorphological quality elements Element When monitored Type of monitoring Control site used Result Before measures After measures Qualitative Quantitative Biological quality elements Edit biological quality elements Element When monitored Type of monitoring Control site used Result Before measures After measures Qualitative Quantitative Physico-chemical quality elements Edit Physico-chemical quality elements Element When monitored Type of monitoring Control site used Result Before measures After measures Qualitative Quantitative Any other monitoring, e.g. social, economic Edit Other responses Element When monitored Type of monitoring Control site used Result Before measures After measures Qualitative Quantitative Monitoring documents Upload monitoring documents Additional documents and videos Upload additional documents Additional links and references Edit links and references Link Description http://www.onema.fr/sites/default/files/EN/EV/publication/rex LoireGB.pdf All information on this page is copied from the AFB, The French Agency for biodiversity. Supplementary Information Edit Supplementary Information