Case study:Knock Burn low flow channel

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Location: 54° 35' 58", -5° 50' 21"
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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.


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Catchment and subcatchment



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

Reach length directly affected (m) 200m
0.2 km
20,000 cm
Project started 2010/12/02
Works started 2011/01/24
Works completed 2011/01/24
Project completed 2011/01/25
Total cost category Less than 1 k€
Total cost (k€)
Benefit to cost ratio
Funding sources Department for Agriculture and Rural Development - Rivers Agency

Cost for project phases

Phase cost category cost exact (k€) Lead organisation Contact forename Contact surname
Investigation and design Less than 1 k€ Department of Agriculture & Rural Development Rivers Agency Judith Bankhead
Stakeholder engagement and communication Less than 1 k€ Department of Agriculture & Rural Development Rivers Agency Judith Bankhead
Works and works supervision Less than 1 k€ Department of Agriculture & Rural Development Rivers Agency Judith Bankhead
Post-project management and maintenance Less than 1 k€ Department of Agriculture & Rural Development Rivers Agency Judith Bankhead
Monitoring Less than 1 k€ Department of Agriculture & Rural Development Rivers Agency Judith Bankhead

Supplementary funding information

Work carried out under the auspices of maintenance of the designated watercourse - adaptive mainteneace



Reasons for river restoration

Mitigation of a pressure aim to creat more sustainable and environmentally improved channel
Hydromorphology over widened watercourse with laminar slow flow
Biology lack of fish life
Physico-chemical
Other reasons for the project part of estate biodiversity plan. Maintenance benefits for Rivers Agency


Measures

Structural measures
Bank/bed modifications Creation of low flow channel
Floodplain / River corridor
Planform / Channel pattern Re-meandering
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
Channel pattern/planform Yes Yes Yes No No Improvement

Biological quality elements

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative
Fish Yes Yes Yes No No Improvement
Macrophytes Yes Yes Yes No No Improvement

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

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Supplementary Information

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