Case study:Nar SSSI project

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Location: 52° 41' 59", 0° 36' 43"
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Project overview

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Status Complete
Project web site
Themes Hydromorphology, Monitoring, Spatial planning
Country England
Main contact forename James
Main contact surname Holloway
Main contact user ID
Contact organisation River Restoration Centre
Contact organisation web site http://www.therrc.co.uk
Partner organisations
Parent multi-site project
This is a parent project
encompassing the following
projects
No
River Nar after the work was completed

Project summary

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The existing river was an artificially wide channel with virtually no gradient. The existing wooden flow deflectors installed between 2002 and 2003 were insufficient in their attempts to enhance flow diversity. The project successfully narrowed the river through the construction of artificial berms mimicking those found naturally and the excavation of pools.

Monitoring surveys and results

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Lessons learnt

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Image gallery


Deflector transformed to shoulder, March 2011
Deflector transformed to shoulder, July 2011
Added sinuosity to the river, March 2011


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Catchment and subcatchment

Catchment

River basin district Anglian
River basin North West Norfolk

Subcatchment

River name Nar to confl with Blackborough Drain
Area category 100 - 1000 km²
Area (km2)
Maximum altitude category Less than 100 m
Maximum altitude (m) 95
95 m
0.095 km
9,500 cm
Dominant geology Calcareous
Ecoregion Great Britain
Dominant land cover Arable and Horticulture
Waterbody ID GB105033047791



Other case studies in this subcatchment: Castle Acre Rehabilitation Project, Narborough Rehabilitation Project, River Nar Restoration Project, River Nar, Mileham River Restoration Project, West Lexham Rehabilitation Project


Site

Name Narbough Trout Fishery
WFD water body codes GB105033047791
WFD (national) typology
WFD water body name Nar to confl with Blackborough Drain
Pre-project morphology Single channel, Straight, Embanked, High width:depth
Reference morphology Sinuous, Pool-riffle
Desired post project morphology
Heavily modified water body Yes
National/international site designation UK - Site of Special Scientific Interest
Local/regional site designations
Protected species present No
Invasive species present No
Species of interest Water Vole
Dominant hydrology Groundwater
Dominant substrate Silt, Sand
River corridor land use Urban, Woodland, Grassland
Average bankfull channel width category 10 - 50 m
Average bankfull channel width (m)
Average bankfull channel depth category 5 - 10 m
Average bankfull channel depth (m)
Mean discharge category
Mean annual discharge (m3/s)
Average channel gradient category
Average channel gradient
Average unit stream power (W/m2)


Project background

Reach length directly affected (m) 1000 m
1 km
100,000 cm
Project started 2011/02/01
Works started
Works completed 2011/03/01
Project completed
Total cost category
Total cost (k€) 3 k€
3,000 €
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

Supplementary funding information

The entire project, covering 1 km of channel, was delivered by a team of 3 people in less than 3 days and for under 3 thousand pounds. Accordingly, although early days, it seems that the Nar SSSI project can be viewed as a successful low-cost ‘quick win’ project in a constrained site.



Reasons for river restoration

Mitigation of a pressure Flood defence
Hydromorphology Quantity & dynamics of flow, Flow velocities, Channel pattern/planform
Biology
Physico-chemical
Other reasons for the project Enhancement of flow diversity


Measures

Structural measures
Bank/bed modifications Creation of shoulders, Embankment creation, Creation of pools
Floodplain / River corridor Ensure floodplains left unmodified
Planform / Channel pattern Channel narrowing
Other Maintain water vole habitat
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
Flow velocities Yes Yes Yes Awaiting results
Quantity & dynamics of flow Yes Yes Yes Awaiting results

Biological quality elements

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

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/case studies/rrc%20case%20study%20-%20narborough%202011.pdf River Restoration Centre Case Study
http://www.youtube.com/watch?v=aej4PTzf 0U&feature=plcp River Nar berm creation video

Supplementary Information

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