Difference between revisions of "Case study:Langonnet river"

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|Name=Langonnet River
|WFD water body code=FRJ471400A
|WFD (national) typology=HER1-12 / HER2-60  
      Langonnet River
|Pre-project morphology=Single channel,Straight
|WFD water body code=
|Reference morphology=Single channel,Sinuous
|Heavily modified water body=No
|WFD (national) typology=
|Protected species present=No
      HER1-12 / HER2-60 (FRJ471400A
|Invasive species present=No
|WFD water body name=
|Avrg channel gradient=0.005117
|Pre-project morphology=
      Single channel,Straight
|Reference morphology=
      Single channel,Sinuous
|Heavily modified water body=
|Local site designation=
|Site designation=
|Protected species present=
|Invasive species present=
|Dominant hydrology=
|Dominant substrate=
|River corridor land use=
|Average bankfull channel width category=
|Avrg bankfull channel width=
|Average bankfull channel depth category=
|Avrg1 bankfull channel depth=
|Mean discharge category=
|Mn discharge=
|Average channel gradient category=
|Avrg channel gradient=

Revision as of 10:10, 10 February 2014

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Location: 48° 5' 34", -3° 30' 18"
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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 Yohann
Main contact surname FUENTES
Main contact user ID
Contact organisation (FORECASTER)
Contact organisation web site
Partner organisations
Parent multi-site project
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encompassing the following
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Project summary

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Over the years, heavy hydraulic works were carried out on the Lagonnet River, such as straightening and widening of the river course, causing habitat depletion and lowering of the water table. The main goals of the restoration activity were to restore the morphology and functionality of the river and to improve the habitat diversification. A preliminary assessment, carried out in 2001, has defined the technical goals: to improve the longitudinal and cross section profile diversification, to define a narrower flow section (especially in low water) and a sequence of riffles and pools. The reactivation of the river dynamics allow to keep the restoration results on the long term. The works included the installation of 24 sills and 239 groynes (in blocks or wooden). Berms are also created along 250 m and blocks are put in place on the riverbed. The maintenance of 2687 m of riparian forest and new plantation along 1400 m of river banks were carried on.

Monitoring surveys and results

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Lessons learnt

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Image gallery

Examples of intervention on the Lagonnet river.
Blocks put in place on the Lagonnet river bed.

Catchment and subcatchment


River basin district Loire-Bretagne
River basin Loire


River name Langonnet
Area category 10 - 100 km²
Area (km2) 34 km²
3,400 ha
Maximum altitude category 100 - 200 m
Maximum altitude (m)
Dominant geology Siliceous
Ecoregion Central Plains
Dominant land cover
Waterbody ID


Name Langonnet River
WFD water body codes FRJ471400A
WFD (national) typology HER1-12 / HER2-60
WFD water body name
Pre-project morphology Single channel, Straight
Reference morphology Single channel, Sinuous
Desired post project morphology
Heavily modified water body No
National/international site designation
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
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 0.005117
Average unit stream power (W/m2)

Project background

Reach length directly affected (m) 5300 m
5.3 km
530,000 cm
Project started 2000/01/01
Works started
Works completed 2006/01/01
Project completed
Total cost category more than 10000 k€
Total cost (k€)
Benefit to cost ratio
Funding sources

Cost for project phases

Phase cost category cost exact (k€) Lead organisation Contact forename Contact surname
Investigation and design more than 10000 k€ 150315 k€
150,315,000 €
Fishermen (20%) Yohann Fuentes
Stakeholder engagement and communication
Works and works supervision
Post-project management and maintenance 5000 - 10000 k€
Monitoring FDPPMA 56.

Reasons for river restoration

Mitigation of a pressure
Hydromorphology Channel pattern/planform, Quantity & dynamics of flow, Width & depth variation
Biology Fish: Species composition
Physico-chemical Temperature
Other reasons for the project Landscape enhancement


Structural measures
Bank/bed modifications
Floodplain / River corridor
Planform / Channel pattern re-meandering
Non-structural measures
Management interventions
Social measures (incl. engagement)


Hydromorphological quality elements

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative
Channel pattern/planform Yes Yes

Biological quality elements

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative
Fish: Species composition Yes Yes

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
Temperature Yes Yes

Monitoring documents

Additional documents and videos

Additional links and references

Link Description

Supplementary Information

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