Case study:Voorste Nete at Dessel

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Location: 51° 13' 55.80" N, 5° 9' 0.77" E

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Project overview

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Status	Complete
Project web site
Themes	Fisheries, Habitat and biodiversity, Hydromorphology, Monitoring
Country	Belgium
Main contact forename	Nick
Main contact surname	Elbourne
Main contact user ID	User:NickRRC
Contact organisation	River Restoration Centre
Contact organisation web site	http://www.therrc.co.uk
Partner organisations	University Hasselt, Centre for Environmental Sciences, Diepenbeek
Parent multi-site project
This is a parent project encompassing the following projects	No

Source of photographs - ECRR 2008. Upper row (left and right): original reach of the Voorste Nete. Middle row (left and right): Excavation of a 5 m wide stretch for placing the bentonite mat and refilling with the original sand. Bottom row (left and right): Diverted reach of the Voorste Nete, dug out in sand filled bentonite lining with transferred substrate from the original reach, and the same stretch 6 months later during first monitoring showing the changes in dimensions caused by a summer storm in 2004.

Project summary

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In 2004 a reach of 1.3km of the small, channelized lowland brook, Voorste Nete, was diverted because of sand mining activities. The sinuosity of the newly created reach of the Voorste Nete, 1.9km in length, was based on old maps, aerial photography and field measurements. The new brook was hydrologically isolated with a bentonite mat preventing water loss due to a decline of the groundwater level. The sides of the bentonite were placed upright for 0.5m and the lining was filled with the original sand from digging out the new reach.

Originally the newly created streambed has a weak meandering channel pattern (sinuoscity 1.1), and was 1m wide at the bottom and 2m wide at the top. In August 2004, a summer storm caused severe erosion and had a noticeable impact on the profile. In the first three years, mechanical weed clearance was only conducted once in the upstream reach of the diversion in autumn 2005. In 2007, mechanical weed mowing was executed for the total stream.

Monitoring surveys and results

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Lessons learnt

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Catchment and subcatchment

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(affects all case studies in this subcatchment)

Catchment

River basin district	Meuse
River basin	Meuse

Subcatchment

River name	Meuse
Area category	more than 10000 km²
Area (km2)	465465 km² <br />46,500 ha <br />
Maximum altitude category	100 - 200 m
Maximum altitude (m)	200200 m <br />0.2 km <br />20,000 cm <br />
Dominant geology	chalk and loess
Ecoregion	Western Plains
Dominant land cover	Intensive agriculture, Urban
Waterbody ID

Other case studies in this subcatchment: Aaijen- Removal of bank fixation, Meers - Floodplain lowering, Reméandration du Geer à Grand-Axhe, Rijkelse Bemden - River bed widening

Site

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Name	Voorste Nete
WFD water body codes
WFD (national) typology
WFD water body name
Pre-project morphology
Reference morphology
Desired post project morphology
Heavily modified water body	No
National/international site designation
Local/regional site designations
Protected species present	Yes
Invasive species present	No
Species of interest	Spined loach, Three-spined stickelback, Nine-spined stickelback, Gudgeon, European eel (Anguilla anguilla)
Dominant hydrology
Dominant substrate
River corridor land use	Intensive agriculture (arable)
Average bankfull channel width category	2 - 5 m
Average bankfull channel width (m)	22 m <br />0.002 km <br />200 cm <br />
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

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Reach length directly affected (m)	19001,900 m <br />1.9 km <br />190,000 cm <br />
Project started	2004/04/01
Works started	2004/04/01
Works completed	2004/06/01
Project completed	2004/06/01
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			University Hasselt	Alain	De Vocht

Reasons for river restoration

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Mitigation of a pressure	Aggregate/mineral extraction
Hydromorphology	Channel pattern/planform, Width & depth variation, Substrate conditions, Quantity & dynamics of flow
Biology	Fish: Species composition, Fish: Age structure, Fish: Abundance, Invertebrates: Taxonomic composition
Physico-chemical	Oxygen balance
Other reasons for the project

Measures

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Structural measures
Bank/bed modifications	Translocation of original substrate into new channel; Alteration in channel dimensions
Floodplain / River corridor
Planform / Channel pattern	Channel naturalisation; Creation of new meandering channel
Other
Non-structural measures
Management interventions	Weed clearance
Social measures (incl. engagement)
Other

Monitoring

Hydromorphological quality elements

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quality elements

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

Biological quality elements

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quality elements

Element	When monitored		Type of monitoring		Control site used	Result
	Before measures	After measures	Qualitative	Quantitative
Invertebrates	Yes	Yes	No	Yes	Yes	Improvement
Macrophytes	Yes	Yes	No	Yes	Yes	Improvement
Angiosperms	Yes	Yes	No	Yes	Yes	Improvement
Fish: Species composition	Yes	Yes	No	Yes	Yes	No change
Fish: Abundance	Yes	Yes	No	Yes	Yes	Improvement

Physico-chemical quality elements

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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

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

Monitoring documents

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Image gallery

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Additional links and references

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Link	Description

Supplementary Information

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