Case study:Remeandering of the Drésine and of the Remoray stream

From RESTORE
Jump to: navigation, search
0.00
(0 votes)


To discuss or comment on this case study, please use the discussion page.


Location: 46° 45' 47", 6° 15' 35"
Edit location
Loading map...
Left click to look around in the map, and use the wheel of your mouse to zoom in and out.


Project overview

Edit project overview
Status Complete
Project web site
Themes Environmental flows and water resources, Habitat and biodiversity, Hydromorphology
Country France
Main contact forename Bruno
Main contact surname Tissot
Main contact user ID
Contact organisation Association des amis du site naturel du lac de Remoray
Contact organisation web site http://http://www.maisondelareserve.fr/association.php
Partner organisations
Parent multi-site project
This is a parent project
encompassing the following
projects
No
This case study hasn’t got a picture, you can add one by editing the project overview.

Project summary

Edit project overview to modify the project summary.


The Remoray stream is a 1.7 km long tributary of the Drésine . The Drésine flows 7.6 kilometers before getting into Lake Remoray, located in the nature reserve, which includes a glacial lake and wide peat bogs . It is home to numerous protected , rare and/or endangered species in France. Between the early XIX century and the late 1980s, several streams were straightened and widened in order to drain the swamp and create new agricultural plots. In the end, no agricultural land was obtained, despite the negative effects on the environment: the groundwater table was lowered and the swamp gradually dried, reducing habitats and species, both in the peat bogs and in the streams, especially birds and amphibians, but also fish: the lake trout was no longer spawning in the area. The main goals of the project were to restore the hydraulic conditions in the marsh, raising the groundwater level, and to recreate aquatic habitats especially for lake trout and invertebrates. The restoration measures took place from downstream to upstream between 1999 and 2000. A new mouth of the Drésine was constructed, using 650 acacia stakes in order to obtain a stable section at the confluence with the lake, which is subject to strong level fluctuations, thus avoiding any possibility of regressive erosion. Starting from this stabilized section the meanders were reopened following the old course. The extracted material was deposited in the straight bed, at each end of which a waterproof sill was constructed, consisting of a wooden frame covered with a PVC tarpaulin and 300 m3 of silt, so as to stop any erosion of the marsh from this low point . A complete filling of the straight bed would have been preferable, but it would have required a too large volume of material. Upstream of the straightened stretch, three sills are built to stop the regressive erosion , and raise the river bed. Works on the Remoray stream were carried out at the end of winter 2001. A sinuous channel 5 to 40 meters east was realized using a mini-excavator. Little sills to compensate the steep slope were built. The old bed is filled with materials of the path used for the remeandering works of Drésine.

Monitoring surveys and results

Edit project overview to modify the Monitoring survey and results.


The remeandering works allowed to multiply by three the length of the Drésine . The piezometric monitoring shows that the groundwater table has raised by 50 cm. The restoration of the marsh water regime has allowed the recolonization by several species formerly present (especially Odonata, Lepidoptera, red frogs and birds). The self re-vegetation of the restored meanders provided a cooling effects on waters and contributed to the diversification of flows, favorable for aquatic fauna. A better structured population of trout and a high number of smolts were also observed.

Lessons learnt

This case study hasn’t got any lessons learnt, you can add some by editing the project overview.


Image gallery


View on the marsh of the Remoray Lake, in October 2008.
The Drésine after the remeandering works.
The Remoray stream several years after the remeandering works.
ShowHideAdditionalImage.png


Catchment and subcatchment

Catchment

River basin district Rhône - Méditerranée
River basin

Subcatchment

River name Drèsine
Area category
Area (km2)
Maximum altitude category
Maximum altitude (m)
Dominant geology
Ecoregion Western Highlands
Dominant land cover
Waterbody ID



Site

Name Remoray
WFD water body codes FRDR12055
WFD (national) typology
WFD water body name
Pre-project morphology Artificial channel
Reference morphology Actively meandering
Desired post project morphology
Heavily modified water body No
National/international site designation France - Réserve Naturelle
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 Less than 2 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 0.001 - 0.01
Average channel gradient
Average unit stream power (W/m2)


Project background

Reach length directly affected (m)
Project started
Works started 1999/12/01
Works completed 2000/02/29
Project completed
Total cost category
Total cost (k€) 56.4
56.4 k€
56,400 €
Benefit to cost ratio
Funding sources Agence de l’eau (35 %), État (27 %), Union européenne (18 %), Conseil supérieur de la pêche et association locale pour la pêche (11 %), Fondation Nature et Découverte (9 %) .

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 56.4
56.4 k€
56,400 €
Post-project management and maintenance
Monitoring



Reasons for river restoration

Mitigation of a pressure Land drainage
Hydromorphology Channel pattern/planform, Connection to groundwaters, Quantity & dynamics of flow
Biology Fish, Invertebrates
Physico-chemical
Other reasons for the project


Measures

Structural measures
Bank/bed modifications
Floodplain / River corridor
Planform / Channel pattern Re-meandering, Adding sinuosity
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
Connection to groundwaters No Yes No Yes No Improvement
Quantity & dynamics of flow No Yes No Yes No Improvement

Biological quality elements

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative
Fish No Yes No Yes No Improvement
Invertebrates No Yes No No No 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
Riparian vegetation No Yes No No No Improvement


Monitoring documents



Additional documents and videos


Additional links and references

Link Description

Supplementary Information

Edit Supplementary Information