Case study:Recreation of a sinuous low-flow channel in the Merloz

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Location: 46° 8' 58.94" N, 5° 36' 12.46" E

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Project overview

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Status	Complete
Project web site
Themes	Habitat and biodiversity, Hydromorphology, Monitoring, Water quality
Country	France
Main contact forename	Cyril
Main contact surname	Frequelin
Main contact user ID
Contact organisation	Syndicat intercommunal à vocation unique Lange-Oignin
Contact organisation web site
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 Merloz stream flows in urban and peri-urban areas over a length of three kilometers, seven kilometers from the source. Historically, the Merloz underwent several dredging and straightening operations, determining a significant loss of habitats diversity. Due to land use constraints, remeandering of the watercourse could not be targeted, therefore the rehabilitation actions included the reconstruction of a sinuous low flow channel with a morphologically varied cross section. This was carried out installing artificial berms placed alternately in the right and left sides. The banks were revegetated and protected with bioengineering techniques when necessary.

Monitoring surveys and results

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The installation of artificial berms allow to reconnect the low flow and a flood channel, to reduce the low flow channel and to increase the flow section. The increase of channel sinuosity has improved the flows and habitats diversification. The limited monitoring data currently available do not allow a proper assessment of the operation. However, many spawnings sites(lake trout and whitefish) were observed during the winter after works.

Lessons learnt

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Image gallery

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The channelized Merloz presents a very poor habitat diversity (September 2004).

The channelized Merloz (September 2004).

The Merloz in December 2008: a sinous low flow channel was recreated.

The Merloz after works in April 2009.

The Merloz in April 2009: the reduction of the riverbed width make a low flow channel and a flood channel appear.

The merloz after restoration, in September 2009: the banks were well revegatated.

Catchment and subcatchment Select a catchment/subcatchment Edit the catchment and subcatchment details (affects all case studies in this subcatchment) Catchment River basin district River basin Subcatchment River name Merloz Area category 10 - 100 km² Area (km2) Maximum altitude category 200 - 500 m Maximum altitude (m) Dominant geology Siliceous Ecoregion Western Highlands Dominant land cover Waterbody ID Site Edit site Name Merloz WFD water body codes FRSRDR11041 WFD (national) typology WFD water body name Pre-project morphology Single channel, Straight Reference morphology Single channel, Sinuous, Pool-riffle 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 Gravel, Cobble River corridor land use Urban Average bankfull channel width category 2 - 5 m Average bankfull channel width (m) 44 m <br />0.004 km <br />400 cm <br /> Average bankfull channel depth category 0.5 - 2 m Average bankfull channel depth (m) Mean discharge category Mean annual discharge (m3/s) 1.11.1 m³/s <br />1,100 l/s <br /> Average channel gradient category Average channel gradient Average unit stream power (W/m2) Project background Edit project background Reach length directly affected (m) 235 m0.235 km <br />23,500 cm <br /> Project started 2008/09/01 Works started 2008/09/01 Works completed 2009/12/01 Project completed Total cost category 100 - 500 k€ Total cost (k€) 152 k€152,000 € <br /> Benefit to cost ratio Funding sources Water Agency, General council, Regional Council, Department of fisheries Cost for project phases Phase cost category cost exact (k€) Lead organisation Contact forename Contact surname Investigation and design Water Agency Stakeholder engagement and communication Water Agency Works and works supervision Water Agency Post-project management and maintenance Water Agency Monitoring Water Agency Reasons for river restoration Edit reasons for restoration Mitigation of a pressure Flood defence Hydromorphology Channel pattern/planform, Quantity & dynamics of flow, Flow velocities Biology Fish: Abundance, Fish: Species composition Physico-chemical Other reasons for the project Bank erosion Measures Edit Measures Structural measures Bank/bed modifications Deflectors, Bank reprofiling Floodplain / River corridor Planform / Channel pattern 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 Quantity & dynamics of flow Yes Yes Yes Improvement Channel pattern/planform Yes Yes Yes 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: Species composition Yes Yes Yes Awaiting results Fish: Abundance Yes Yes Yes Awaiting results 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 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