Case study:Remeandering of the Drugeon and integrated management of its catchment

From RESTORE
Jump to: navigation, search
4.00
(one vote)


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


Location: 46° 51' 59", 6° 12' 29"
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 In progress
Project web site
Themes Environmental flows and water resources, Habitat and biodiversity, Water quality
Country France
Main contact forename Jean-Noël
Main contact surname Resch
Main contact user ID
Contact organisation Communauté de communes du plateau de Frasne et du val du Drugeon
Contact organisation web site http://http://www.val-drugeon.org/
Partner organisations
Parent multi-site project
This is a parent project
encompassing the following
projects
No
The Drugeon at Bonnevaux: many meanders are reconnected and recreated and the straightened channel is filled.

Project summary

Edit project overview to modify the project summary.


The Drugeon is a 35 km long mid-mountain river, tributary of the Doubs. Moraine deposits allow the presence of many wetlands . The Drugeon valley is biologically very rich: 48 species of protected plants including 3 in Europe, 54 species of dragonflies including 4 protected, 80 species of butterflies including 7 protected species, 280 bird species observed (123 nesting ), 3 included in the Habitats directive. Between the late 50s and early 70s, heavy hydraulic works were carried out. Marshes and bogs were drained due the straightening and dredging of the Drugeon and its tributaries. These works, allowing to transform into agricultural land only 200 hectares, reduced by more than 8 km the length of the river and led to riverbed incision, degradation of habitats, warming of water, inducing in its turn algal development. As a result large Plecoptera and freshwater crayfish (Austropotamobius pallipes) totally disappeared and the fish abundance collapsed. From the 1990s on, awareness of environmental damage by local actors, naturalists, anglers, academics and public officers of the Ministry of Environment allowed the establishment of the " Drugeon valley protection" LIFE project, that was carried out between 1993 and 1997. After this, other restoration works have been implemented in the framework of a multiannual programme. The main goals of the restoration activity were to restore the morphology and functionality of the Drugeon and its tributaries and to improve their water quality. Depending on the constraints (land availability, social issues) and main biological goals, different strategies were applied: • at the sources of Drugeon , measures to diversify the flow by adding roughness; • in the upstream stretch , where the former meanders had been bypassed but not filled, the straightened bed was filled and the meanders reconnected; no bioengineering protection was used, except at intersections between the old meanders and the straightened channel, where willow fascines were installed; • in the middle stretch , many meanders are reconnected and recreated ; in some cases the straightened channel is filled, in others it remains active, and a hydraulic work splits the water flow between the meander and the straightened channel; • in the lower Drugeon valley, until the confluence with the Doubs , present land uses did not allow to restore the old river course; however, the section was diversified, with the creation of a high flow and a low flow bed, the latter lined with berms , blocks and groynes; in parallel, river bed recharge with gravel and pebble taken from the former banks was carried out.

Monitoring surveys and results

Edit project overview to modify the Monitoring survey and results.


Since 1997, the restoration works have allowed the recovery of 7 km of meanders and about 300 ha of wetlands and dry grasslands. The monitoring showed an improvement in habitats quality, although variable depending on the restoration techniques used and on the specific stretches. Anomalies in relation to species distribution suggested impacts due to diffuse chemical pollution (wood processing, rail network ballast, etc.) for which specific measures have been defined. Soon after the works the groundwater table raised by several tens of cm, and later as much as 70 to 80 cm in the upstream and middle Drugeon . The diversity of the techniques used and the extended monitoring allowed to draw some conclusions about the experience, e.g.: the deepening of meanders must be very limited, it is better to undersize the bed and choose an almost rectangular section, allowing self-adjustments of the bed by the river dynamics ; filling of the straight channel should take into account the compaction of the filling material, in order to avoid that the old channel is reactivated during floods. The local population is globally satisfied with the results of the project. The budget showed that the cost of restoration was of the same order of magnitude of the expenses for the straightening of the river system. Since 2003, the site is part of the Ramsar network. In 2004, a prefectural decree issued a protected biotope status on 3,000 hectares of wetlands. The future restoration measures will be more directed towards the improvement of water quality by treating urban wastewater , renewing networks and controlling agricultural pollution.

Lessons learnt

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


Image gallery


A distribution weir allows to get water into the meander (October 2008).
the Drugeon rectified at Bannans.
The Drugeon at Bonnevaux. The meanders are reconnected and the straightened channel is filled.
ShowHideAdditionalImage.png


Catchment and subcatchment

Catchment

River basin district Rhône - Méditerranée
River basin

Subcatchment

River name Drugeon
Area category
Area (km2) 170
170 km²
17,000 ha
Maximum altitude category
Maximum altitude (m)
Dominant geology
Ecoregion Western Highlands
Dominant land cover
Waterbody ID



Site

Name Drugeon valley
WFD water body codes FRDR2024
WFD (national) typology
WFD water body name
Pre-project morphology Artificial channel
Reference morphology Sinuous
Desired post project morphology
Heavily modified water body No
National/international site designation International - RAMSAR site
Local/regional site designations
Protected species present Yes
Invasive species present No
Species of interest
Dominant hydrology
Dominant substrate
River corridor land use
Average bankfull channel width category 5 - 10 m
Average bankfull channel width (m)
Average bankfull channel depth category
Average bankfull channel depth (m)
Mean discharge category 0.1 - 1.0 m³/s
Mean annual discharge (m3/s)
Average channel gradient category
Average channel gradient
Average unit stream power (W/m2)


Project background

Reach length directly affected (m) 37000
37,000 m
37 km
3,700,000 cm
Project started
Works started 1997/01/01
Works completed
Project completed
Total cost category
Total cost (k€) 2873
2,873 k€
2,873,000 €
Benefit to cost ratio
Funding sources Agence de l’eau, État, Union européenne, conseil général, conseil régional, Conseil supérieur de la pêche, communauté de communes du plateau de Frasne et du val du Drugeon

Cost for project phases

Phase cost category cost exact (k€) Lead organisation Contact forename Contact surname
Investigation and design
Stakeholder engagement and communication 143.910
143.91 k€
143,910 €
Works and works supervision 2368.360
2,368.36 k€
2,368,360 €
Post-project management and maintenance
Monitoring



Reasons for river restoration

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


Measures

Structural measures
Bank/bed modifications adding roughness
Floodplain / River corridor
Planform / Channel pattern Re-meandering, Reconnection of cutoff meander
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
Quantity & dynamics of flow Yes Yes No Yes No Improvement
Flow velocities No Yes No No No Improvement

Biological quality elements

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

Physico-chemical quality elements

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative
Temperature No Yes No No No
Oxygen balance No Yes No No No

Any other monitoring, e.g. social, economic

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


Monitoring documents



Additional documents and videos


Additional links and references

Link Description

Supplementary Information

Edit Supplementary Information