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

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Location: 46° 45' 47.36" N, 6° 15' 34.63" E

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Project overview

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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

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Project summary

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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

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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

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Image gallery

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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.

Catchment and subcatchment Select a catchment/subcatchment Edit the catchment and subcatchment details (affects all case studies in this 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 Edit 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 Edit 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€) 56.456.4 k€ <br />56,400 € <br /> 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 56.456.4 k€ <br />56,400 € <br /> Post-project management and maintenance Monitoring Reasons for river restoration Edit reasons for 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 Edit 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 Edit 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 Edit 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 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 Riparian vegetation No Yes No No No Improvement Monitoring documents Upload monitoring documents Additional documents and videos Upload additional documents Case study description by ONEMA (French National Agency for Water and Aquatic Environments) (in French) Additional links and references Edit links and references Link Description Supplementary Information Edit Supplementary Information