Case study:Wandle River Restoration Project: Hackbridge

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Location: 51° 22' 37.67" N, 0° 9' 37.40" W
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Project overview

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Status Complete
Project web site
Themes Habitat and biodiversity, Hydromorphology, Social benefits
Country England
Main contact forename Tim
Main contact surname Longstaff
Main contact user ID User:Pollygwenbryant
Contact organisation Wandle Trust
Contact organisation web site http://www.wandletrust.org
Partner organisations London Borough of Sutton
Parent multi-site project

Case_study:River Wandle Restoration Project

This is a parent project
encompassing the following
projects
No
Hackbridge Restoration © Wandle Trust

Project summary

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This project is one of four sites delivered through the Defra Catchment Restoration Fund.

Designs were developed based on detailed 2D flood modelling undertaken in conjunction with cbec eco-engineering. Practical works were delivered during Summer 2014 with appointed contractors, Cain Bioengineering.

  The work started with the removal of old toe-boarding from around the edge of Culvers Island. The island was re-profiled with a new bank line created using hazel faggot bundles secured with chestnut stakes and backed with coir netting. Sediment from the channel was then placed behind the new bank line.  

  The weir structures either side of the island were removed and the river channel narrowed using a combination of chestnut posts and hazel faggot bundles or gabion stone.

  A causeway was built to create a backwater pond area using coir geotextile layered over a bed of stone and weighed down with gravel and sediment and planted with aquatic plants. The new island banks were re-graded to create a gradually sloped bank to which a variety of aquatic vegetation was planted with a team of 60 volunteers over three days.

  Variations in depth, width and the introduction of gravel, small boulders and Large Woody Debris have all provided a diversity of habitats and increased the flow diversity of the channel throughout the site.

Monitoring surveys and results

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Lessons learnt

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Challenges:

- Very urban nature of the site. Complex flood modelling and design was required.

- Multiple underground utilities which had to be identified and avoided during the works.

- Many and varied stakeholder needs and opinions.


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Catchment and subcatchment

Catchment

River basin district Thames
River basin London

Subcatchment

River name Wandle (Carshalton Branch at Carshalton)
Area category 10 - 100 km²
Area (km2)
Maximum altitude category 100 - 200 m
Maximum altitude (m) 160160 m <br />0.16 km <br />16,000 cm <br />
Dominant geology Calcareous
Ecoregion Great Britain
Dominant land cover Suburban
Waterbody ID GB106039017640



Other case studies in this subcatchment: Butter Hill Phase 2, River Wandle Restoration Project, River Wandle: Butter Hill Phase 1, River Wandle: Silt & SuDs


Site

Name
WFD water body codes GB106039017640
WFD (national) typology
WFD water body name Wandle (Carshalton Branch at Carshalton)
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)
Project started 2012/09/01
Works started 2015/03/01
Works completed
Project completed
Total cost category
Total cost (k€)
Benefit to cost ratio
Funding sources

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 Quantity & dynamics of flow,  Width & depth variation
Biology fish passage, fish habitat, invertebrates, plants
Physico-chemical improved oxygenation
Other reasons for the project enhanced aesthetics


Measures

Structural measures
Bank/bed modifications Weir removal, Habitat diversification
Floodplain / River corridor Marginal wetland berms created
Planform / Channel pattern Increase in-channel hydromorphological diversity
Other
Non-structural measures
Management interventions
Social measures (incl. engagement) Community involvement, Aesthetics
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
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Any other monitoring, e.g. social, economic

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative


Monitoring documents



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Supplementary Information

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