Case study:River Cole- Life Project

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Location: 51° 37' 53.16" N, 1° 39' 45.56" W

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Project overview

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Status	Complete
Project web site
Themes	Flood risk management, Habitat and biodiversity, Hydromorphology, Monitoring, Social benefits
Country	England
Main contact forename	Martin
Main contact surname	Janes
Main contact user ID	User:UlrikaRRC
Contact organisation	River Restoration Centre
Contact organisation web site	http://www.therrc.co.uk
Partner organisations	European Commission (LIFE funding), River Restoration Project (now River Restoration Centre), Environment Agency, National Trust, Countryside Commission, English Nature (now Natural England)
Parent multi-site project	Case_study:River restoration: Benefits for integrated catchment management
This is a parent project encompassing the following projects	No

The restored Cole river

Project summary

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The River Cole at Coleshill is a tributary of the Thames and flows through National Trust owned farmland, North East of Swindon on the Oxfordshire and Wiltshire border.

Background: The river has a long history of modifications and already the Domesday Book of 1086 has a record of a mill in Coleshill. On the earliest map from the area, dated 1666, the river appears to have been straightened for milling. The section downstream of the mill has more recently been enlarged to safeguard agricultural production from flooding. Until the late 1700s, the mill was fed by a small artificial channel carrying water from the Cole, but by 1818 the mill leat had been largely extended to take the entire flow of the Cole, and most of the old river course filled in. This type of historical management is typical of many other rural rivers in the United Kingdom.

Restoration: The River Cole was included in a joint initiative between England and Denmark to demonstrate best practice in urban and rural river rehabilitation and encourage river restoration in Europe. The wider aim was to promote further river restoration and demonstrate how river restoration could provide multiple benefits such as enhancement in wildlife, landscape, recreation, water quality, fisheries, amenities and other local interests.

The restoration of the River Cole was initiated in July 1995. The site consists of a 2.5 km long reach divided into two parts, upstream and downstream of the mill. Upstream of the mill the river was restored to its original course (retaining a small flow in the mill leat) to join the old surviving mill by-pass channel. This new smaller channel encourages beneficial flood storage on the fields and allows fish to pass the mill weir. Downstream the river was reduced in size and remeandered across the old course to a more natural profile, retaining existing mature riverside trees. The restoration of bed level, water level and flood regime was achieved by cutting the new meandering river at a much higher level, similar to that prior to the last major deepening scheme of the 1970s.

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Monitoring surveys and results

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Pre-monitoring:

Ecology

• Macrophytes - number of species found per 500 meter channel length. • Macro-invertebrates - species richness and abundance, and as an indicator for water quality/organic pollution (BMWP). • Fish - biomass, density and species richness. • Birds - the assemblage of breeding birds and abundance

Hydromorphology

• Geomorphology - channel cross sections and physical habitat mapping. • The water quality - suspended sediment concentration, nitrogen and phosphorus. • Modeling flood frequency.

Post- monitoring:

Repetition of pre-monitoring was carried out 1 and 2 years after restoration, as well as a public perception survey. Due to its importance as a demonstration project, further monitoring been carried out by Master and PhD students.

Expectations and results:

It was expected that the new meandering channel would provide better habitat opportunities for aquatic species and the hydromorphology and flood frequency in the floodplain would improve because of the more natural channel dimension.

Ecology

Plant species richness increased immediately after restoration. Marginal emergent plant species richness increased significantly, but submerged aquatic plants showed a less immediate effect. The new upstream channel was quickly recolonized by macro-invertebrates. The downstream reach did not change significantly, but some more niche specific taxa were found 12 years after implementation. Two new species were found in the restored Cole, one stonefly (Leuctra geniculata) and a caddis fly (Athripsodes albifrons) Fish biomass and density returned to pre-restoration levels, and species richness remained unchanged. However, long-term surveys have shown an overall decline in fish density at both restored and control sites, indicating impact from an external factor. The number of breeding wetland species did not increase in the first year. The abundance of Yellow Wagtails (Motacilla flava) increased significantly. Casual inspection suggests little change after two years.

Hydromorphology

The river length was increased by 30%. The cross-sectional area was considerably smaller and less deep. The number of natural in-channel features, such as pools and riffles, increased after restoration. In the downstream section maturing trees also provide woody debris, creating habitats and flow diversity. The restoration measures recreated a more natural flooding regime.

Social

Public perception was measured via a questionnaire and 53% of the respondents in Coleshill mostly approved with the measures while 17% strongly approved. The long-term monitoring showed that only about half of the local residents strongly (25%) or mostly (31%) approved to the river restoration project. The restoration measures showed overall positive results for the ecological status. The downstream channel benefited greatly from the restoration measures, but the new upstream course was not fenced off from cattle and has therefore little riparian vegetation. However, due to lack of initial engagement, some local residents were unhappy with the project.

Lessons learnt

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• Engaging the local community is critical • In these early days of river restoration the project showed what could be expected from a restoration project and how it develops (might be different from anticipated) – this needs to be built into decision making process • It is important to do a formal long-term management plan, and have a cooperating (and stable) land owner • The project showed a whole suite of demonstration techniques (included in the Manual of River Restoration Techniques http://www.therrc.co.uk/rrc_manual.php) • The project clearly showed the complexity of a linear system (compared with pond), and that it's difficult to distinguish success between different components • The project gave a big boost to river restoration in the UK and showed that it is possible to do “large scale” (for that time) projects

Image gallery

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Construction of the meanders

Aerial photograph of the restored channel

Bifurcation structure upstream of the mill, March 2005

Cows using the livestock crossing

Crayfish found in the river post-restoration, March 2008

The river during flood conditions, March 2010

Catchment and subcatchment Select a catchment/subcatchment Edit the catchment and subcatchment details (affects all case studies in this subcatchment) Catchment River basin district Thames River basin Vale of White Horse Subcatchment River name Cole (Bower Bridge to Thames) including Coleshill Area category 100 - 1000 km² Area (km2) Maximum altitude category 100 - 200 m Maximum altitude (m) 148148 m <br />0.148 km <br />14,800 cm <br /> Dominant geology Calcareous Ecoregion Great Britain Dominant land cover Arable and Horticulture Waterbody ID GB106039023730 Site Edit site Name River Cole WFD water body codes GB106039023730 WFD (national) typology WFD water body name Cole (Bower Bridge to Thames) including Coleshill Pre-project morphology Straight, Single channel Reference morphology Sinuous Desired post project morphology Heavily modified water body Yes National/international site designation Local/regional site designations Protected species present No Invasive species present Yes Species of interest Dominant hydrology Dominant substrate Clay, Silt River corridor land use Extensive agriculture Average bankfull channel width category Average bankfull channel width (m) 1111 m <br />0.011 km <br />1,100 cm <br /> Average bankfull channel depth category 0.5 - 2 m Average bankfull channel depth (m) Mean discharge category Mean annual discharge (m3/s) Average channel gradient category Average channel gradient 0.0008 Average unit stream power (W/m2) Project background Edit project background Reach length directly affected (m) 2500 m2.5 km <br />250,000 cm <br /> Project started 1993/04/01 Works started 1995/07/01 Works completed 1995/09/01 Project completed 1996/12/31 Total cost category Total cost (k€) 450450 k€ <br />450,000 € <br /> Benefit to cost ratio Funding sources EU LIFE Programme, Environment Agency, National Trust, Countryside Commission, English Nature 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 200200 k€ <br />200,000 € <br /> Post-project management and maintenance Monitoring Reasons for river restoration Edit reasons for restoration Mitigation of a pressure Hydromorphology Quantity & dynamics of flow, Channel pattern/planform, Width & depth variation Biology Invertebrates: Abundance, Fish: Species composition Physico-chemical Other reasons for the project Habitat diversity, Landscape enhancement Measures Edit Measures Structural measures Bank/bed modifications Planting, Depth variation Floodplain / River corridor Floodplain spillways Planform / Channel pattern Creation of secondary channel, Adding sinuosity, Creation of backwater Other Livestock access, New crossings 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 Channel pattern/planform Yes Yes No Yes No Improvement Width & depth variation No Yes Yes No No Improvement Flow velocities No Yes Yes No No Biological quality elements Edit biological quality elements Element When monitored Type of monitoring Control site used Result Before measures After measures Qualitative Quantitative Invertebrates Yes Yes No Yes No Improvement Fish: Species composition Yes Yes No Yes Yes 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 Public perceptions No Yes Yes No No No change Monitoring documents Upload monitoring documents Additional documents and videos Upload additional documents Additional links and references Edit links and references Link Description http://www.therrc.co.uk/case studies/cole brochure.pdf River Restoration Centre Case Study http://www.therrc.co.uk/rrc publications.php All published documents on the project Supplementary Information Edit Supplementary Information