Case study:Knock Burn low flow channel

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Location: The following coordinate was not recognized: 339612 374557.The following coordinate was not recognized: 339612 374557.

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Project overview

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Status	Complete
Project web site
Themes	Environmental flows and water resources, Habitat and biodiversity, Social benefits, Urban
Country	Northern Ireland
Main contact forename	Judith
Main contact surname	Bankhead
Main contact user ID	User:judithbankhead
Contact organisation	Rivers Agency, Northern Ireland (DARDNI)
Contact organisation web site	http://www.dardni.gov.uk/rivers
Partner organisations
Parent multi-site project
This is a parent project encompassing the following projects	No

Knock Burn low flow channel post works

Project summary

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As part of a larger biodiversity project for Stormont Estate, enhancement works were required for the Knock Burn. The burn had been overwidened in past years, resulting in a shallow, slow flowing channel, which required regular maintenance due to silt accumulation. It was decided to cretae a sinuous low flow channel, using the silt and bed material to creat a narrower, faster flowing channel. No additional materials were added to the channel, and land drainage was picked up during the new channel creation. All 200m of the project was completed in one day, using a mini digger. The planform of the channel was designed on site, by working downstream and trying to follow the flow patterns as they appeared.

Monitoring surveys and results

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Pre and post photographs were taken. A standard maintenance post audit form was completed 9 months after the project was completed. Annual photography is used to monitor the project. Assessment carried out during photography shows that the channel is maintaining itself overall, with fish present (which had not been the case before). Wetland vegetation has developed on the secondary channel, helping to stabilise the silty substrate

Lessons learnt

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Be opportunistic. The upper stretch of the work has been more successful than the lower reach, probably due to a backwater effect from a pond at the downstream end, and partially due to the reduction of energy through the full reach. Since completion in 2011, no further maintenance work has been required (up to 2014), which is a cost savings for the Agency.

The technique will be used again in future projects.

Image gallery

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Catchment and subcatchment Select a catchment/subcatchment Site Edit site Name Knock Burn WFD water body codes GBNI1NE050503087 WFD (national) typology WFD water body name Lagan Pre-project morphology Artificial channel Reference morphology Desired post project morphology Low gradient passively meandering Heavily modified water body Yes National/international site designation Local/regional site designations None Protected species present No Invasive species present No Species of interest Dominant hydrology Artificially regulated Dominant substrate Silt River corridor land use Parklands garden Average bankfull channel width category 2 - 5 m Average bankfull channel width (m) Average bankfull channel depth category Less than 0.5 m Average bankfull channel depth (m) Mean discharge category 0.1 - 1.0 m³/s Mean annual discharge (m3/s) Average channel gradient category 0.001 - 0.01 Average channel gradient Average unit stream power (W/m2) Project background Edit project background Reach length directly affected (m) Project started Works started Works completed Project completed 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 Edit reasons for restoration Mitigation of a pressure Hydromorphology Biology Physico-chemical Other reasons for the project Measures Edit Measures Structural measures Bank/bed modifications Floodplain / River corridor Planform / Channel pattern Other Non-structural measures Management interventions 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 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 Supplementary Information Edit Supplementary Information