Case study:Diversion of the River Nith

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Location: 55° 22' 42", -4° 18' 11"
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Project overview

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Status Complete
Project web site
Themes Economic aspects, Habitat and biodiversity
Country Scotland
Main contact forename Charles
Main contact surname Perfect
Main contact user ID
Contact organisation Centre for River EcoSystem Science
Contact organisation web site
Partner organisations East Ayrshire Council, SEPA, Scottish Natural Heritage, RSPB, Nith Salmon Fisheries Board, New Cumnock Angling Association, Halcrow, River Restoration Centre
Parent multi-site project
This is a parent project
encompassing the following
projects
No
Plan of 2000 Nith channel diversion. From RRC Manual of Techniques (2002) - courtesy of the River Restoration Centre.

Project summary

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PHASE 1: 2000 - Temporary diversion of the Nith to the north west of its current floodplain to allow for coal extraction by Scottish Coal.

The Nith is an important salmon and trout fishery, however overgrazing, agriculture and past open-cast mining along the reach have affected invertebrate populations and fish spawning grounds.

The primary restoration criteria for the 2000 restoration were:

- design which would convey a 1 in 50 year flood.

- channel which would not dry up during low flow.

- design mimicing pre-diversion channel - ie. similar meander loops, pool-riffle-run sequences and channel profiles.

- design which would create opportunities for enhancement of biodiversity (over and above pre-diversion conditions).

Work commenced in April 2000 and was completed during September of the same year.


PHASE 2: During 2004, the former course was enhanced and reconnected to the rest of the river and the temporary channel cut off to allow mining to progress across the floodplain. The site was subject to significant post-restoration biological monitoring as part of a PhD programme through CRESS (Centre for River Ecosystem Science - University of Stirling) - to ensure the new channel was performing well, ecologically.


2000: channel bed/ground layer consisted of existing substrate with clay lining. 2004: Geotextile reinforcement of banks, to reduce bank erosion. Clay mattress lining to prevent water percolating through unconsolidated substrate and flowing as groundwater through potentially contaminated mine tailings. Gravel added to bed to create habitat diversity for invertebrates and fish. 2000: Containment bund constructed to prevent flooding of mine workings.

Monitoring surveys and results

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Lessons learnt

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Image gallery


Channel diversion in construction (2000). Courtesy of the River Restoration Centre.
Diverted channel once connected (2000). Courtesy of the River Restoration Centre.
Diversion channel prior to connection - rip-rap and riffle visible (2000). Courtesy of the River Restoration Centre.
Diversion channel (2004) showing geotextile bank reinforcement and profiled gravel bed for habitat enhancement. Courtesy of the River Restoration Centre.
Diversion channel (2004) showing geotextile bank reinforcement, profiled gravel bed and in-channel boulder placement for habitat enhancement. Courtesy of the River Restoration Centre.
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Catchment and subcatchment

Catchment

River basin district Scotland RBD
River basin Solway

Subcatchment

River name Nith
Area category 1000 - 10000 km²
Area (km2) 1230
1,230 km²
123,000 ha
Maximum altitude category 200 - 500 m
Maximum altitude (m) 500
500 m
0.5 km
50,000 cm
Dominant geology
Ecoregion Great Britain
Dominant land cover
Waterbody ID



Site

Name Nith, west of New Cumnock
WFD water body codes 10612
WFD (national) typology Mid, Small, Calcareous
WFD water body name River Nith (u/s New Cumnock)
Pre-project morphology
Reference morphology Reproduce hydromorphology and planform of former channel.
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 Primarily salmon and brown trout.
Dominant hydrology
Dominant substrate Mixed gravel, pebble and boulder
River corridor land use Pasture and open-cast mining.
Average bankfull channel width category 2 - 5 m
Average bankfull channel width (m) 4.5
4.5 m
0.0045 km
450 cm
Average bankfull channel depth category
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) 3000
3,000 m
3 km
300,000 cm
Project started
Works started 2000/04/01
Works completed 2000/09/01
Project completed
Total cost category more than 10000 k€
Total cost (k€) 3900000
3,900,000 k€
3,900,000,000 €
Benefit to cost ratio
Funding sources Scottish Coal

Cost for project phases

Phase cost category cost exact (k€) Lead organisation Contact forename Contact surname
Investigation and design Halcrow
Stakeholder engagement and communication
Works and works supervision Morrison
Post-project management and maintenance
Monitoring University of Stirling

Supplementary funding information

Phase 1: 3900000 (thousands of euros)



Reasons for river restoration

Mitigation of a pressure
Hydromorphology
Biology
Physico-chemical
Other reasons for the project Original course running over coal deposits. Channel diverted to exploit resource, while maintaining WFD status.


Measures

Structural measures
Bank/bed modifications Introduction of gravel, Habitat diversification, Bank stabilisation, Bank protection
Floodplain / River corridor Containment bund to prevent flooding
Planform / Channel pattern
Other Addition of boulders to bed, Fish habitat restoration
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

Biological quality elements

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative
Macrophytes Yes Yes No Yes Yes Awaiting results
Invertebrates Yes Yes No Yes Yes Awaiting results

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
Channel bed morphology. Yes Yes No Yes No
Substrate particle size/composition. No Yes No Yes No


Monitoring documents



Additional documents and videos


Additional links and references

Link Description
http://www.cress.stir.ac.uk/news/documents/CharlesPerfect.pdf Macroinvert. Monitoring
http://www.bbc.co.uk/radioscotland/gallery/landscapes water/ 2004 Diversion Image Gallery - BBC Scotland
http://www.therrc.co.uk/MOT/Final Versions (Secure)/11.2 Nith.pdf RRC - Manual of Techniques (2013 update)

Supplementary Information

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