Case study:Tall River

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Location: 54° 26' 21.93" N, 6° 35' 14.76" W
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Project overview

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Status Complete
Project web site
Themes Fisheries, Flood risk management, Habitat and biodiversity
Country Northern Ireland
Main contact forename Judith
Main contact surname Bankhead
Main contact user ID
Contact organisation Rivers Agency Northern Ireland (DARDNI)
Contact organisation web site http://www.dardni.gov.uk/index/rivers.htm
Partner organisations
Parent multi-site project
This is a parent project
encompassing the following
projects
No
Bay 2 and stone cascade - 2006

Project summary

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The Tall River is a main tributary of the River Blackwater, flowing through Co. Armagh. It is a slow flowing, low energy river within an agricultural catchment. The river had been subject to an arterial drainage scheme in the 1960s, which deepened and widened the river as well as disconnecting it from its floodplain. The 1.2km Tall River scheme was the first project within Northern Ireland to address the specific need to enhance the riverine environment, rather than being attached to a larger flood prevention scheme. Works could only be carried out in-channel and on the National Trust owned right bank due to landowner restrictions. The aim of the protect was to create shallow slack-water habitat through the creation of bays. These would provide shelter for fish fry and invertebrates during high flows and aimed to increase macrophyte diversity within the reach. Stone cascades were also installed to direct flow away from potentially erodable banks. A repeat RCS carried out two years post works indicated an increase in emergent vegetation and macrophyte diversity. The bays are inundated at high flows, acting as a fish refuge, however due to siltation these may be becoming too shallow. Following the creation of stone cascades greater flow variation has been ovserved. The success of the bays appears to depend on the presence, or otherwise, of a structure deflecting water into them. If the project was to be carried out again more consideration should be given to the location of the bays within the overall flow regime or alternatively structures that would maintain flows into the bay should be included in the design.

Plus, part of a wider scheme developing footpath access along the river.

Monitoring surveys and results

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Lessons learnt

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Image gallery


Downstream bays after two years - 1998
Bay 2, heavily vegetated - 2012
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Catchment and subcatchment



Site

Name Tall River
WFD water body codes 10611
WFD (national) typology
WFD water body name
Pre-project morphology Over deepened, Over-widened channel as a result of arterial drainage
Reference morphology Narrower, Sinuous channel with shallow margins
Desired post project morphology
Heavily modified water body No
National/international site designation
Local/regional site designations
Protected species present No
Invasive species present No
Species of interest
Dominant hydrology
Dominant substrate Clay
River corridor land use Agriculture (arable)
Average bankfull channel width category
Average bankfull channel width (m)
Average bankfull channel depth category
Average bankfull channel depth (m)
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Mean annual discharge (m3/s)
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Average channel gradient
Average unit stream power (W/m2)


Project background

Reach length directly affected (m) 12001,200 m <br />1.2 km <br />120,000 cm <br />
Project started 1995/07/01
Works started
Works completed
Project completed 1996/12/01
Total cost category
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Benefit to cost ratio
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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

Supplementary funding information

Information about cost of scheme not available



Reasons for river restoration

Mitigation of a pressure Habitat creation, fisheries, floodplain reconnection
Hydromorphology Flow dynamics
Biology Fish, Invertebrates, Macrophytes
Physico-chemical
Other reasons for the project


Measures

Structural measures
Bank/bed modifications Creation of four bays on right hand bank
Floodplain / River corridor Connection to wider floodplain
Planform / Channel pattern Creation of backwater
Other
Non-structural measures
Management interventions
Social measures (incl. engagement) Improved public access
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
Macrophytes Yes Yes Yes Yes No Improvement
Fish No Yes No Yes 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

Link Description
http://www.therrc.co.uk/mot/Tall 3.8 25Apr2013 Av.pdf RRC Manual of River Restoration Techniques entry

Supplementary Information

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