Case study:Partial removal of weir on the Sanguèze at Mouzillon

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Location: 47° 8' 23", -1° 17' 5"
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Project overview

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Status Complete
Project web site
Themes Habitat and biodiversity, Hydromorphology, Monitoring
Country France
Main contact forename Antoine
Main contact surname Charrier
Main contact user ID
Contact organisation Institution Interdepartmentale du bassin de la Sèvre Nantaise
Contact organisation web site
Partner organisations
Parent multi-site project

Case_study:Adaptive management of hydraulic structures in the Sèvre nantaise and Thouet basins

This is a parent project
encompassing the following
projects
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Project summary

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More than 300 sites in the Sèvre Nantaise and Thouet basins with hydraulic structures underwent participative multicriteria analysis in order to develop programmes to help meet targets defined in the French SAGE process as well as delivering improvements to meet Water Framework Directive objectives. On the Sanguèze at Mouzillon one of three pilot schemes was implemented (the other two were on the Thouet at Le Tallud and on the Moine at Cholet). The average water level at the La Motte reservoir near Mouzillon was lowered, through partial removal of the weir downstream. As a result the orginal sinuous water body was partially restored.

Works included allowing self restoration of sinuous channel in the previously impounded stretch.

Monitoring surveys and results

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Lessons learnt

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Image gallery


The La Motte reservoir, on the Sanguèze river, in 2003, before works.
The La Motte reservoir, in 2004, after works. The original sinous water body was partially restored.
The water body in 2006, two years after works: the river banks were revegeteted.
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Catchment and subcatchment

Catchment

River basin district Loire-Bretagne
River basin Sevre nantaise

Subcatchment

River name Sanguèze
Area category 1000 - 10000 km²
Area (km2) 2356 km²
235,600 ha
Maximum altitude category 100 - 200 m
Maximum altitude (m)
Dominant geology Siliceous
Ecoregion Western Plains
Dominant land cover
Waterbody ID



Site

Name La Motte reservoir in Mouzillon
WFD water body codes
WFD (national) typology
WFD water body name
Pre-project morphology Impounded
Reference morphology Sinuous
Desired post project morphology
Heavily modified water body Yes
National/international site designation
Local/regional site designations
Protected species present No
Invasive species present No
Species of interest
Dominant hydrology
Dominant substrate Gravel
River corridor land use Extensive agriculture
Average bankfull channel width category 10 - 50 m
Average bankfull channel width (m)
Average bankfull channel depth category
Average bankfull channel depth (m)
Mean discharge category
Mean annual discharge (m3/s)
Average channel gradient category
Average channel gradient 1.54
Average unit stream power (W/m2)


Project background

Reach length directly affected (m)
Project started 2004/01/01
Works started
Works completed
Project completed
Total cost category
Total cost (k€)
Benefit to cost ratio
Funding sources Water Agency, Department level councils of the vendee, Loire Atlantique

Cost for project phases

Phase cost category cost exact (k€) Lead organisation Contact forename Contact surname
Investigation and design 50
50 k€
50,000 €
Geolittomer, Université de Nantes (Régis Barraud)
Stakeholder engagement and communication
Works and works supervision
Post-project management and maintenance
Monitoring



Reasons for river restoration

Mitigation of a pressure Agriculture
Hydromorphology Channel pattern/planform, Continuity for organisms, Flow velocities, Width & depth variation
Biology Fish: Species composition, Invertebrates, Macrophytes
Physico-chemical
Other reasons for the project Habitat enhancement


Measures

Structural measures
Bank/bed modifications Weir lowering
Floodplain / River corridor
Planform / Channel pattern Topographic and landscape restoration
Other
Non-structural measures
Management interventions
Social measures (incl. engagement)
Other


Monitoring

Hydromorphological quality elements

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative
[[]]

Biological quality elements

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative
Fish: Abundance Yes Yes Yes Awaiting results
Invertebrates Yes Yes Yes Awaiting results
Macrophytes Yes Yes Yes Awaiting results

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

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative
Public perceptions Yes


Monitoring documents



Additional documents and videos


Additional links and references

Link Description
http://www.sevre-nantaise.com
http://www.valleeduthouet.fr

Supplementary Information

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