River Cole, LIFE demonstration project
River Cole, LIFE demonstration project
THIS IS UNDER CONSTRUCTION
The River Cole is a tributary of the Thames and flows from the spring near the town of Swindon and flows through the National Trust owned estate Coleshill until it reaches the Thames.
Drivers and Pressures
Historical management has deteriorated the ecological value of the Cole. The river was straightened for more efficient flow for water mills and later enlarged to prevent flooding of agricultural lands in the original floodplain. The connection between the floodplain and river has been lost and nearby sewage treatment plants cause organic pollution.
The Cole demonstration project was part of the River Demonstration Project together with the river Skerne and river Brede projects. This collaboration between British and Danish water managers tried to apply state-of-the-art restoration techniques and to demonstrate these projects to a wider audience of European water managers.
The global objective of the demonstration project consists of three goals:
- Restoration of river and floodplain in terms of physical features, flood storage, habitat diversity and visual appearance.
- Application of innovative restoration techniques and best management practice, within a sustainable agricultural system.
- Furthering of knowledge and understanding of river restoration by monitoring to a very high degree, and by practical demonstration of the results.
No specific objectives were found in the available documents
No success criteria were found in the available documents
To restore the river, a historical buried course was excavated. This small meandering channel had more natural bed and bank structures. This new restored course was attached to the existing old course. The mill leat was preserved with intentions to restore the mill. Downstream of the mill, the bed was raised and the channel was made smaller. A few backwater pools were kept and the mature riverside trees were spared. By making the stream less deep and smaller, the hydrological connection with the floodplains improved and the flood frequency increased.
Before restoration started, several indicators were monitored to see what the reference situation is for post-restoration monitoring.
- River channel vegetation was monitored qualitatively by assessing the number of species found per 500 meter channel length.
- Aquatic macro-invertebrates were monitored by assessing the species richness
- Fish were monitored by assessing the grams biomass per m2, fish density and species richness.
- Birds were monitored by assessing the assemblage of breeding birds and abundance
- Geomorphological monitoring was carried out by mapping channel cross sections and physical habitat mapping.
- The water quality monitoring was focused on suspended sediment concentration and concentration of nitrogen (total oxidized nitrogen) and phosphorus (soluble reactive phosphorous) compounds
- Flood protection
- The hydrological regime was monitored by modeling the flood frequency.
- Social-economic factors
- Economic benefits for six categories (water quality, amenity, fisheries, agriculture, flood defense and recreation) were calculated.
The post-restoration monitoring consists of two methods. First, the same indicators and monitoring techniques used in the pre-restoration monitoring are repeated for post-restoration monitoring. One exception is the assessment of public perception via a questionnaire, which was only done after restoration.
The other method is comparing the data to another location, in this case downstream of the river. This was done to assess the impact of the restoration on the downstream areas, but it can also be used to compare the results of the restoration between the restored site and a control site.
Expectations and Response
It was expected that the new meandering channel would provide better habitat opportunities for river species. The hydro-morphology and flood frequency in the floodplain would improve because of the more natural channel dimension. The full results can be found in the final report: The effects of river restoration on the R. Cole and R. Skerne demonstration sites: Final Report, River Restoration Centre March 1999
Macrophyte species richness increased immediately after restoration. Marginal emergent plant species richness increased significantly, but submerged aquatic plants showed a less immediate effect. The control site downstream was not affected by the restoration works.
The new channel was quickly recolonized by macro-invertebrates, but the more uncommon taxa related to more mature habitats were not present yet after 1 year. 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, however the highest measured biomasses and densities were found just downstream of the restored reach. The species richness remained unchanged.
For Birds, the number of breeding wetland species did not increase 1 year after restoration. The abundance of Yellow Wagtails (Motacilla flava) increased significant. Casual inspection suggested that there was little change 2 years after restoration.
The river length was increased by 30%. The cross-sectional area was considerably smaller and less deep. The number of natural in-channel features like riffles had increased after restoration.
The suspended sediment concentration increased after the restoration works compared to upstream control sites. The nutrient concentrations showed no changes.
The restoration measures recreated a more natural flooding regime. Prior to restoration, flooding in the Cole was infrequent, but after restoration 10% of the floodplain is influenced by the more regular flooding regime of 17 days per year.
Public perception was measured via a questionnaire and 53% of the replyers in Coleshill mostly approved the measures while 17% strongly approved.
The economic benefits of the restoration over a 25 year period was estimated to range from £38,000 to £347,000, mostly from recreation and conservation benefits.
The demonstration project in total was a collaboration between water managers in the UK and Denmark. However, the restoration itself was carried out by national, regional and local partners of both governmental and private sectors. The partners both worked on the river Cole and Skerne (Holmes et al., 1998). The project partners of the river Cole were:
- National Rivers Authority
- English Nature
- Darlington Borough Council
- Countryside Commission
- Northumbrian Water
- Department of Agriculture N. Ireland
- River Restoration Centre
- National Trust
- Scottish Natural Heritage
The total budget of the project submitted to the EU-LIFE project was € 1,758,621.29, because Denmark was the leading partner. The UK budget was initially set at £850,000, but increased interest and support let the total project budget grow to almost £1 million.
The project budget for both the Skerne and Cole was divided in 4 elements, each with a set amount of budget.
- £350,000 for construction contracts
- £200,000 for pre- and post-restoration monitoring studies
- £190,000 for management, promotion, compensations and administration
- +/- £190,000 for survey, design, contract documentation and site supervision
The EU contribution to the total project was € 749,172.67.
Contact person within the organization
River Restoration Centre
Dr. Ulrika Åberg
Tel.: 0044 1234 752979
Extra background information
Holmes, N.T.H., Nielsen, M.B., Vivash, R., Ottosen, O., Janes, M., Sørensen, H., Kronvang, B., Svendsen, L.M., Brookes, A., Fisher, K., Møller, B., Newson, M., Sear, D., Hoffmann, C.C., Pedersen, M.L., Øvig, L. (1998) Restoration of the Rivers Brede, Cole and Skerne: A joint Danish and British EU-LIFE demonstration project I – V,Aquatic Conservation: Marine and Freshwater Ecosystems 8:185 - 255
The effects of river restoration on the R. Cole and R. Skerne demonstration sites: Final Report, River Restoration Centre March 1999
Brochure River Cole, restored 1995/6, River Restoration Centre
- Establish environmental flows / naturalise flow regimes
- Increase flood frequency and duration in riparian zones or floodplains
- Shallow water courses
- Initiate natural channel dynamics to promote natural regeneration
- Remeander water courses
- Improve backwaters
- Construct semi-natural/articificial wetlands or aquatic habitats