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

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Location: 51° 30' 1", -0° 29' 19"
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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
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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

Lessons learnt

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Catchment and 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) 181
181 m
0.181 km
18,100 cm
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

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

Reach length directly affected (m) 800 m
0.8 km
80,000 cm
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

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

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

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

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

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Before measures After measures Qualitative Quantitative


Monitoring documents



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Additional links and references

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Supplementary Information

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