Case study:Creation of flood channels and restoration of exchanges between the flood plain and the low-flow channel on the Vezouze

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Location: 48° 35' 12.42" N, 6° 29' 12.43" E

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Project overview

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Status	Complete
Project web site	http://www.onema.fr/IMG/EV/publication/rex_VezouzeGB.pdf
Themes	Flood risk management, Habitat and biodiversity, Hydromorphology, Monitoring, Social benefits, Urban
Country	France
Main contact forename	Josee
Main contact surname	Peress
Main contact user ID	User:Josee Peress
Contact organisation	AFB
Contact organisation web site	http://www.onema.fr/Hydromorphologie,510
Partner organisations
Parent multi-site project
This is a parent project encompassing the following projects	No

File:Http://www.onema.fr/IMG/EV/publication/rex VezouzeGB.pdf

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Project summary

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The work consisted of widening the river’s middle water channel in some places. For this, a protective levee has been levelled on the left bank. Two flood channels, measuring one metre on average over 6 hectares, have been dug, involving the removal of 60,000 m3 of material. Within these flood channels, wetland environments such as ponds and side channels have been created. Trees have been planted on the banks as well as helophytes in flood channels. In addition to these actions on the environment, work on the rainwater system has also been undertaken: check valves and pumping stations have been set up.

The Vezouze maintenance syndicate manages the removal of blockage and debris as required.

Monitoring surveys and results

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A pre-restoration monitoring was carried out by a consultancy in 2000 and again in 2003, 2004 and 2005 on the hydraulic component. Investigations were required to study the hydrography, hydrology, topography and geology of the land. A bibliographic study was used to describe the biological component of the aquatic environment. Post-restoration ecological monitoring (habitats, species) began in 2010 and will continue until 2014. This monitoring consists of describing the natural environment and assessing the impacts (positive and / or negative) of operations on animal and plant life, specifically targeting the restored flood plain and side channels created. The hydromorphology and biological communities living in the lowflow channel (fish, aquatic invertebrates, etc.) are however not investigated in this work.

The first results of 2010 and 2011 highlight several outstanding species for Lorraine, including insect and plant species. It will therefore be very interesting to monitor the evolution of these species on the site. Particular attention will be paid to plants receiving protected status, as these species were most likely to have been introduced during the restoration work.

The ecological evolution of the site is very satisfactory. The results of monitoring attest to the positive effects of the work on biodiversity with the presence of wildlife characteristic of wetlands and the presence of outstanding species in terms of flora and insect life. The evolution and diversification of the side channels, which have a dense vegetation of helophyte-type plants, are also very conducive to pike reproduction (even though there is no monitoring of this aspect, side channels here show strong potential).

Hydraulically, the results are equally satisfactory. Upstream to the restored area, height and surfaces of areas flooded in Lunéville have significantly diminished.

As the primary objective of this restoration is flood defence, the explanation to elected representatives of the benefits of preserving the flood storage area and diversifying habitats in the flood plain has led to the setting up of a project that reconciles hydraulic and ecological objectives. Cross-cutting objectives particularly motivated elected representatives who were thus able to meet the expectations of the local population in terms of safety and landscaping issues. These developments make it possible to combine flood management and improvement of the ecological status of the river.

In addition, a pedestrian path has been created in the area and its regular use reflects the renewed interest of local people for the site. Previously, they tended to avoid this unattractive, unsightly sector. The work thus helped to enhance “nature” in a peri-urban area.

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Image gallery

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The Vezouze at Lunéville before restoration work. The levee on the left bank prevents flood storage in the flood plain (Rhin-Meuse Water Agency)

Flood plain of the Vezouze. Creation of a flood channel on the left bank - work phase – July 2007 (Philippe Russo - Rhin-Meuse Water Agency)

Flood plain of the Vezouze. Flood channel on the left bank - 6 months after the work - December 2007 (Philippe Russo - Rhin-Meuse Water Agency)

Flood plain of the Vezouze. Flood channel on the left bank - 2 years after the work - May 2009 (Pierre Mangeot - Rhin-Meuse Water Agency)

Catchment and subcatchment Select a catchment/subcatchment Site Edit site Name La Vezouze WFD water body codes FRCR286 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 10 - 50 m Average bankfull channel width (m) 2020 m <br />0.02 km <br />2,000 cm <br /> Average bankfull channel depth category Average bankfull channel depth (m) Mean discharge category 1 - 10 m³/s Mean annual discharge (m3/s) 6.86.8 m³/s <br />6,800 l/s <br /> Average channel gradient category 0.001 - 0.01 Average channel gradient 0.0015 Average unit stream power (W/m2) 5.001575.002 W/m² <br /> Project background Edit project background Reach length directly affected (m) 10001,000 m <br />1 km <br />100,000 cm <br /> Project started 2007/05/01 Works started Works completed Project completed 2007/08/31 Total cost category 1000 - 5000 k€ Total cost (k€) 19301,930 k€ <br />1,930,000 € <br /> Benefit to cost ratio Funding sources Regional Directorate for the Environment (DIREN): 20.5%, Water agency: 34% 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 Quantity & dynamics of flow, Continuity for organisms Biology Physico-chemical Other reasons for the project Measures Edit Measures Structural measures Bank/bed modifications Construction of flood channels, Removal of material, Pond creation, Side channel creation, setting up of check valves & pumping stations Floodplain / River corridor Tree planting, Planting of helophytes at the foot of banks Planform / Channel pattern Channel widening 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/pdf/Vezouze GB BD2.pdf All information on this page is copied from the AFB, The French Agency for biodiversity. Supplementary Information Edit Supplementary Information