Case study:Eau Blanche River (Walphy - LIFE project)

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Location: 50° 5' 21", 4° 32' 14"
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Project overview

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Status Complete
Project web site http://walphy.be
Themes Habitat and biodiversity, Hydromorphology, Monitoring
Country Belgium
Main contact forename Alexandre
Main contact surname Peeters
Main contact user ID User:AlexBE
Contact organisation Service Public de Wallonie (SPW)
Contact organisation web site http://walphy.be
Partner organisations University of Liege, University of Namur
This is a parent project
encompassing the following
projects
Bocq river (Walphy - LIFE project)
Eau Blanche at Nismes: meandering channel (one year post completion)

Project summary

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In the context of fulfilling the Water Framework Directive requirements, the LIFE+ project Walphy allowed experimental restoration projects to be undertaken on two medium-size catchments of the Meuse basin in Wallonia (Belgium) between 2009 and 2014: the Bocq catchment and the Eau Blanche Catchment. This five-year long project was funded by the European Union and the Service Public de Wallonie (SPW). It involved three institutions: the SPW was in charge of the experimental restoration projects while the Universities of Liège and Namur were responsible for evaluating the success of the restoration projects.

The Eau Blanche is a medium-size gravel-bed river. Its downstream reach (13 km) is characterized by a low gradient (1-2 ‰), a low energy (specific stream power at the bankfull stage: 20 W/m²) and a wide floodplain (around 600 m). Its channel have been straightened and embanked over the last few centuries (sinuosity index decreased from 1.6 to 1.1), which has led to significant loss of habitat.

A multi-scale assessment of hydromorphological conditions of the Eau Blanche catchment has led to several restoration projects on a total length 6 km. They consist of measures of different ambitions such as reconnecting remnant meander, meandering river channel and habitat diversification. In addition, we undertook locally to improve fish shelters and spawning areas.

Monitoring surveys and results

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The success of the restoration projects was evaluated on the basis of a multi-disciplinary monitoring.

Hydromorphology was evaluated on three restored sites using microhabitat survey and three indices of physical quality. For all sites, hydromorphology was significantly improved 10-20 months post-rehabilitation, through the diversification of flows (depth, substrate, water velocity) and the creation of habitats (e.g. fish shelters, spawning areas and woody debris). The most positive effects were observed for the most ambitious projects (meandering river channel and reconnecting remnant meander compared to habitat diversification).

Biological quality, based on macroinvertebrates and fish communities, has generally showed a status quo or a slight increase 10-20 months post-completion. As for hydromorphology, we might conclude that the most ambitious rehabilitation measures have resulted in the most positive effects. However, it would be prudent to await the results of the next monitoring surveys (4 years post-completion).

The geomorphological monitoring has focused on the effect of rehabilitation measures on river dynamic (bedload transport, bank erosion) and the effectiveness of spawning gravel rehabilitation.

Lessons learnt

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- Despite the short period of time (5 years) of this project, we realized afterwards the importance of achieving a multi-scale assessment and an initial state (pre-restoration) prior to restoration work.

- We implemented a wide range of demonstration techniques and we compared them in terms of cost-effectiveness (see the Manual of River Restoration Techniques on http://www.walphy.be/index.php?page=guide-technique).

- Most of the restoration projects could be implemented without acquiring the land but rather through negociations with the local community. This underlines the importance of engaging the local community.

- The time span of the project allowed us only 1-2 years of monitoring (post-restoration). Fortunately, the SPW funded a long-term monitoring (>3 years), which is crucial for accurate evaluation of success, especially for biological indicators.

- Finally, we hope the project to give a boost to future restoration projets in Wallonia.


Image gallery


Straightening of the Eau blanche river
Remeandering river channel at Nismes
Remeandering river channel at Nismes
Habitat diversification at Mariembourg
Habitat diversification at Mariembourg
Habitat diversification at Mariembourg
Reconnecting a remnant meander at Boussu-en-Fagne
Reconnecting a remnant meander at Boussu-en-Fagne
Reconnecting a remnant meander at Boussu-en-Fagne (1 year post-completion)
Electrofishing at Boussu-en-Fagne
Educational pathway at Nismes
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Catchment and subcatchment

Catchment

River basin district Meuse
River basin Meuse

Subcatchment

River name Eau Blanche
Area category 100 - 1000 km²
Area (km2) 259
259 km²
25,900 ha
Maximum altitude category 200 - 500 m
Maximum altitude (m) 305
305 m
0.305 km
30,500 cm
Dominant geology Shale, limestone
Ecoregion Western Plains
Dominant land cover Grassland, pasture
Waterbody ID MM05R, MM06R, MM07R



Site

Name
WFD water body codes
WFD (national) typology
WFD water body name
Pre-project morphology
Reference morphology
Desired post project morphology
Heavily modified water body
National/international site designation
Local/regional site designations
Protected species present
Invasive species present
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
Average unit stream power (W/m2)


Project background

Reach length directly affected (m) 6000
6,000 m
6 km
600,000 cm
Project started 2009/01/01
Works started
Works completed
Project completed 2014/12/31
Total cost category
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
Stakeholder engagement and communication
Works and works supervision
Post-project management and maintenance
Monitoring



Reasons for river restoration

Mitigation of a pressure
Hydromorphology Channel pattern/planform
Biology
Physico-chemical
Other reasons for the project


Measures

Structural measures
Bank/bed modifications Creation of fish spawn nursing places
Floodplain / River corridor Habitat diversification
Planform / Channel pattern Creation of meanders, 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

Biological quality elements

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

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


Monitoring documents



Additional documents and videos


Additional links and references

Link Description

Supplementary Information

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