Case study:Habitat Improvements on the River Colne at West Drayton

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Location: 51° 30' 0.52" N, 0° 29' 19.29" W

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Project overview

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Status	In progress
Project web site
Themes	Fisheries, Habitat and biodiversity
Country	England
Main contact forename	Phil
Main contact surname	Belfield
Main contact user ID
Contact organisation	Environment Agency
Contact organisation web site	http://www.gov.uk/government/organisations/environment-agency
Partner organisations	Environment Agency, West Drayton Angling Club
Parent multi-site project
This is a parent project encompassing the following projects	No

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Project summary

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Overall aims included:
- Increase survival rate of juvenile coarse fish by increasing amount of suitable habitat.
- Increase variety of in-channel habitat throughout the previously dredged section to provide habitat for juvenile and adult coarse fish.
Specific aims were:
- Create backwaters in low ground along the true right bank.
- Create new marginal habitat amongst areas of heavy siltation on the true right bank.
- Open up old ditch that used to flow in the smaller u/s weir pool.
- Add localised gravel shoals to the river bed.

Description of works:
- Creation of projections using coir rolls along line of silt deposition boundary, open at downstream end and lightly planted to create shallow marginal habitat for juvenile fish.
- Raise bed in localised areas using gravel shoals to add variety to instream habitat. Shoals should strengthen natural features where deposition is occurring naturally. Mitigate loss of water holding areas by creating backwaters.
- Use present low lying land and re-open old features that have become filled in and overgrown. New wetted ditch to provide alternative migratory route for coarse fish and extend type of habitat found in Bigely Ditch.
- If possible lower height of sluices at mill or footbridge. - Dredging in 1998 resulted in loss of habitat suitable for juvenile fish including loss of marginal habitat by siltation.
- Enhancements have potential to extend wet-woodland and increase potential water vole habitat.

Monitoring surveys and results

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Fisheries survey
River Habitat Survey
River Corridor Survey

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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 Colne Subcatchment River name Colne and GUC (from confluence with Chess to Ash) Area category 100 - 1000 km² Area (km2) Maximum altitude category 100 - 200 m Maximum altitude (m) 181181 m <br />0.181 km <br />18,100 cm <br /> Dominant geology Calcareous Ecoregion Great Britain Dominant land cover Improved grassland Waterbody ID GB106039023090 Other case studies in this subcatchment: Colne Brook, Fishery/habitat enhancement on the Grand Union Canal, Uxbridge Moor Backwater Site Edit site Name WFD water body codes GB106039023090 WFD (national) typology WFD water body name Colne and GUC (from confluence with Chess to Ash) Pre-project morphology Reference morphology 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 Dominant hydrology Dominant substrate River corridor land use Average bankfull channel width category Average bankfull channel width (m) 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) 800 m0.8 km <br />80,000 cm <br /> Project started 2008/01/01 Works started Works completed Project completed Total cost category 10 - 50 k€ Total cost (k€) Benefit to cost ratio Funding sources Natural England 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 Reasons for river restoration Edit reasons for restoration Mitigation of a pressure Hydromorphology Continuity for organisms, Substrate condtitions, Width & depth variation Biology Fish, Vertebrates Physico-chemical Other reasons for the project Landscape enhancement Measures Edit Measures Structural measures Bank/bed modifications Installation of coir rolls, Introduction of gravel Floodplain / River corridor Planform / Channel pattern Creation of backwater Other 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 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 Monitoring documents Upload monitoring documents Additional documents and videos Upload additional documents Additional links and references Edit links and references Link Description Supplementary Information Edit Supplementary Information