Case study:Recreation of a low-flow sinuous channel in an urban stretch of the Montvaux stream

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Location: 49° 7' 22", 6° 4' 50"
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Project overview

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Status Complete
Project web site
Themes Habitat and biodiversity, Hydromorphology, Monitoring, Social benefits, Water quality, Urban
Country France
Main contact forename municipality
Main contact surname Municipality of Chatel-Saint-Germain
Main contact user ID
Contact organisation Municipality of Châtel-Saint-Germain
Contact organisation web site http://www.chatel-saint-germain.fr/
Partner organisations
Parent multi-site project
This is a parent project
encompassing the following
projects
No
The Montvaux stream before and after restoration works.

Project summary

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The Montvaux stream, is a 10 Km long tributary of the Moselle. Upstream of the municipality of Châtel-Saint-Germain, this river still has good hydromorphological characteristics. Conversely, crossing the urban area of Châtel-Saint-Germain, the river was straightened, the banks were stabilized by the creation of a concrete channel, with a rectangular oversized (5 to 6 meters wide)cross-section . Originally, these works allowed to create storage pools in order to feed mills and forges. Afterwards, as a result of the uptake of the main sources in the valley for drinking water supply, the water depth at low water had become very low, reduced to 1-3 centimeters. This induced reduction of the aquatic habitats, eutrophication of the environment and bas smells. The substrate of the bottom of the bed, the flow speed and the bed depth were homogenized, degrading habitats and preventing the development of aquatic life. Faced with the deterioration of the watercourse, both in terms of landscape and of morphological and biological features, the municipality of Châtel-Saint-Germain decided to undertake a restoration project. The works included the redesigning of a meandering low flow channel and the introduction of benches. The low-flow channel was made using topsoil wrapped in coir geotextile. The banks were seeded with a mixture of grass species and about 700 helophytes were planted the following year.

Monitoring surveys and results

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After project management was reduced to a biennial cutting of the banks vegetation and, when needed, removal of waste (plastic, etc…) and of major obstacles to the flow. A preliminary study was carried out in 1996. After works, no scientific monitoring was planned, but the river banks were vegetated and the diversification of flows and bed depth was ensured. There were no longer stagnant water or siltation.

Lessons learnt

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Image gallery


The Montvaux stream in Châtel-Saint-Germain, before the restoration works.
The Montvaux stream during the restoration works (October 1999).
The Montvaux stream eight months after the restoration, in June 2000..
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Catchment and subcatchment

Catchment

River basin district Rhin-Meuse
River basin Lorraine

Subcatchment

River name Montvaux
Area category 10 - 100 km²
Area (km2)
Maximum altitude category 100 - 200 m
Maximum altitude (m)
Dominant geology Siliceous
Ecoregion Western Plains
Dominant land cover Urban
Waterbody ID



Site

Name Montvaux
WFD water body codes FRCR354
WFD (national) typology
WFD water body name
Pre-project morphology Single channel, Straight, Entrenched
Reference morphology Single channel, Sinuous
Desired post project morphology
Heavily modified water body true
National/international site designation
Local/regional site designations
Protected species present
Invasive species present
Species of interest
Dominant hydrology Quick run-off
Dominant substrate Bedrock
River corridor land use Urban
Average bankfull channel width category Less than 2 m
Average bankfull channel width (m)
Average bankfull channel depth category 0.5 - 2 m
Average bankfull channel depth (m)
Mean discharge category
Mean annual discharge (m3/s) 0.2
0.2 m³/s
200 l/s
Average channel gradient category
Average channel gradient 2.4
Average unit stream power (W/m2)


Project background

Reach length directly affected (m) 400 m
0.4 km
40,000 cm
Project started 1999/10/01
Works started 1999/10/01
Works completed 1999/12/01
Project completed
Total cost category
Total cost (k€) 147 k€
147,000 €
Benefit to cost ratio
Funding sources Water Agency, Direction régionale de l’environnement (DIREN)

Cost for project phases

Phase cost category cost exact (k€) Lead organisation Contact forename Contact surname
Investigation and design 10.67
10.67 k€
10,670 €
Stakeholder engagement and communication Water Agency
Works and works supervision 137.2
137.2 k€
137,200 €
Water Agency
Post-project management and maintenance Water Agency
Monitoring 1 - 10 k€ Water Agency



Reasons for river restoration

Mitigation of a pressure
Hydromorphology Quantity & dynamics of flow, Channel pattern/planform, Width & depth variation
Biology Fish: Abundance, Invertebrates, Macrophytes
Physico-chemical Oxygen balance, Nutrient concentrations
Other reasons for the project Landscape enhancement, Recreation


Measures

Structural measures
Bank/bed modifications Extensive planting, Introduction of gravel
Floodplain / River corridor
Planform / Channel pattern Adding sinuosity
Other
Non-structural measures
Management interventions
Social measures (incl. engagement) Improved public access
Other Information provision, Participation in design


Monitoring

Hydromorphological quality elements

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative
Quantity & dynamics of flow Yes No No No No Improvement
Channel pattern/planform Yes No No No No Improvement
Width & depth variation Yes No No No No Improvement

Biological quality elements

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


Fish: Abundance Yes Yes Yes Yes Improvement
Macrophytes Yes Yes Improvement

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 awareness of river Yes Yes Yes Improvement


Monitoring documents



Additional documents and videos


Additional links and references

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Supplementary Information

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