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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Image gallery

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Catchment and subcatchment Select a catchment/subcatchment Edit the catchment and subcatchment details (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 Edit site 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 Edit project background 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 Edit reasons for restoration 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 Edit Measures Structural measures Bank/bed modifications Translocation of original substrate into new channel, Alteration in channel dimensions Floodplain / River corridor Planform / Channel pattern Channel naturalisation, Meandering channel Other Non-structural measures Management interventions Weed clearance Social measures (incl. engagement) Other Monitoring Hydromorphological quality elements Edit Hydromorphological quality elements Element When monitored Type of monitoring Control site used Result Before measures After measures Qualitative Quantitative Biological quality elements Edit biological 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 Edit 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 Edit Other responses Element When monitored Type of monitoring Control site used Result Before measures After measures Qualitative Quantitative Monitoring documents Upload monitoring documents Additional documents and videos Upload additional documents Additional links and references Edit links and references Link Description http://www.ecrr.org/archive/conf08/pdf/proceed10.pdf De Vocht et al. (2008) Ecological Evaluation of a Technically Restored Lowland Watercourse in Flanders, Belgium, p.583-592. Supplementary Information Edit Supplementary Information