Case study:Bocq river (Walphy - LIFE project)

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Location: 50° 19' 21", 5° 0' 31"
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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
Eau Blanche River (Walphy - LIFE project)
Overview of the restoration projects undertaken on the Bocq catchment

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 Bocq is a medium-size gravel-bed river which has been strongly impacted by numerous barriers, impeding the free movement of fish and bedload (an average of one weir every 1.8 km). In addition, some river reaches have been straightened over the last few centuries, which has led to significant loss of habitat.

A multi-scale assessment of hydromorphological conditions of the Bocq catchment has led to a large-scale restoration project implemented mainly in the lower and middle course of the Bocq River itself. 22 barriers (mainly old weirs of an average height of 1.35 m) have been removed or modified in order to reconnect the Bocq with the Meuse and to improve access to areas of spawning grounds. To date, only two barriers remain in the middle Bocq. In addition, 3.6 km of modified reaches were improved through a wide range of rehabilitation techniques such as designing sinuous channels, re-instating spawning grounds, improving fish shelters, improving culvert bed, etc.

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 five 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).

Biological quality, based on macroinvertebrates and fish communities, has generally showed a status quo or a slight increase 10-20 months post-completion. Nevertheless, ambitious rehabilitation measures such as weir removal and meanders restoration have resulted in the most positive effects, while less ambitious measures such as habitat diversification have led to more contrasted results. In addition, restoration of the longitudinal connectivity was beneficial for Grayling, designated as Natura 2000 species, and for eels, concerned with the Benelux convention.

The geomorphological monitoring has focused on the effect of barriers on sediment transport 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


Bocq: Rehabilitation projects
Barriers location on the Bocq catchment pre and post Walphy project
Bocq at Yvoir: Fish passage
Bocq at Yvoir: Pre-barrages
Bocq at Yvoir: Weir removal
Bocq at Yvoir: Weir removal
Bocq at Spontin: Weir removal
Bocq at Spontin: Rock ramp
Bocq at Braibant: Bypass channel
Leignon at Ciney: Habitat diversification
Bocq at Emptinale: Designing sinuous channel
Bocq at Gemenne: Wood addition
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Catchment and subcatchment

Catchment

River basin district Meuse
River basin Meuse

Subcatchment

River name Bocq
Area category 100 - 1000 km²
Area (km2) 237
237 km²
23,700 ha
Maximum altitude category 200 - 500 m
Maximum altitude (m) 305
305 m
0.305 km
30,500 cm
Dominant geology Limestone, sandstone
Ecoregion Western Plains
Dominant land cover Grassland, cropland, forest
Waterbody ID MM28R and MM30R



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)
Project started 2009/01/01
Works started
Works completed
Project completed 2013/12/31
Total cost category 1000 - 5000 k€
Total cost (k€) 2861
2,861 k€
2,861,000 €
Benefit to cost ratio
Funding sources LIFE 07

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 Impoundments (not hydropower)
Hydromorphology Continuity for organisms, Continuity of sediment transport
Biology
Physico-chemical
Other reasons for the project


Measures

Structural measures
Bank/bed modifications Barrier removal
Floodplain / River corridor Creation of fish spawn nursing places, Improvement culvert bed
Planform / Channel pattern Adding sinuosity
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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