Case study:Diversion of the River Nith

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Location: 55° 22' 42.47" N, 4° 18' 11.36" W

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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

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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.

Catchment and subcatchment Select a catchment/subcatchment Edit the catchment and subcatchment details (affects all case studies in this subcatchment) Catchment River basin district Scotland RBD River basin Solway Subcatchment River name Nith Area category 1000 - 10000 km² Area (km2) 12301,230 km² <br />123,000 ha <br /> Maximum altitude category 200 - 500 m Maximum altitude (m) 500500 m <br />0.5 km <br />50,000 cm <br /> Dominant geology Ecoregion Great Britain Dominant land cover Waterbody ID Site Edit 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) 4.54.5 m <br />0.0045 km <br />450 cm <br /> 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 Edit project background Reach length directly affected (m) 30003,000 m <br />3 km <br />300,000 cm <br /> Project started Works started 2000/04/01 Works completed 2000/09/01 Project completed Total cost category more than 10000 k€ Total cost (k€) 39000003,900,000 k€ <br />3,900,000,000 € <br /> 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 Edit reasons for 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 Edit 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 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 Macrophytes Yes Yes No Yes Yes Awaiting results Invertebrates Yes Yes No Yes Yes Awaiting results 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 Channel bed morphology. Yes Yes No Yes No Substrate particle size/composition. No Yes No Yes No Monitoring documents Upload monitoring documents Additional documents and videos Upload additional documents Additional links and references Edit 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 Edit Supplementary Information