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People and Process-Based River
Management: Restoring River Processes;
Natural Flood Management; Healthy
Catchments
16TH ANNUAL NETWORK CONFERENCE
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Restoring Wandle Park
Restoring a forgotten river in urban
South London
Colin Toovey, Marc Pieris and Ian Dennis
May 2015
October 2014
Personal Introduction
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Colin Toovey MEng (Hons) MICE CEng 2004 – 2006: C.J. Thorne & Co. Ltd • Site Engineer 2006 – present: Royal Haskoning / Royal HaskoningDHV • Senior Fluvial & Coastal Engineer
October 2014
River Restoration…?
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October 2014
Presentation Structure
History of Wandle Park
The Problem
The Solution
The Vision
The Scheme
The Challenges
The Solutions and Lessons
Completed Scheme
Summary and Future
Questions
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October 2014
River Wandle Early History
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Wandle Park
17th/18th Century: Working river (tobacco & textile Industries). 19th Century: 90 mills 1890: Park opened (oldest public open space in south London) ‘proceedings were enlivened by personages swimming in the lake that should have known better!’
October 2014
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River Wandle ‘Recent’ History
Wandle Park
Impacts of urbanisation: • Erratic water supply and
lowering of the water table • Poor water quality • River declared Open Sewer in
1960s • River culverted and old
channel infilled in 1967 • Significant pollution incident in
2007
October 2014 7
Original river channel alignment
Culverted river
River ‘lost’ to local community
Loss of historic landscape
Park users unaware of river
flowing beneath park!
Manhole covers
Willow trees
Decline in park usage
Anti-social behaviour
Flood risk
Poor biodiversity
Loss of natural river processes
Wandle Park – The Problem
October 2014
Overview 2010 – Scheme proposed to restore the river and park
Wandle Trust, London Borough of Croydon & Environment Agency
Wider catchment-based restoration
Drivers for restoration Improving the park for people
Improving the park for nature
WFD delivery (mitigation measures for HMWB)
Partnership approach Integrated design team
Royal HaskoningDHV (river works and other engineering design)
LDA Design (landscaping)
Funding Mayor of London ‘Help a London Park’ (public vote)
Heritage Lottery Fund
Barratt Homes
Total funding £3.5m (€4.5m)
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Wandle Park – The Solution
October 2014
Wandle Park – The Vision
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October 2014
Wandle Park – The Scheme
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October 2014 11
Soil Movement and Land Quality • Contaminated land • Materials movement • Human health & environment
Flood Risk & Engineering Design • Flood risk & modelling • Inlet/outlet design • Vandalism
Wandle Park – The Challenges
Existing Infrastructure • Culverts upstream & downstream • Utilities (electricity & surface water) • Inaccurate service plans • Approvals & lead-in times
Environment • Room for natural processes • Established trees • Land & water quality • Flora & fauna
River restoration in an urban environment:
October 2014
Soil Movement & Land Quality:
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Wandle Park – Approach & Lessons
Early Ground Investigation
Aligning new river channel avoid known
areas of contamination
Early dialogue with contaminated land
officer regarding remediation strategy
(capping layer)
Use of excavated material in landscaping
Recycling of concrete from culvert for
gabions
No off-site soil disposal, small import
volumes
Competent contractor
• Contaminated land • Materials movement • Human health & environment
October 2014 13
Wandle Park – Approach & Lessons
Early dialogue and site meetings with
service companies.
Detailed surveys (GPR, Culvert
Survey)
Avoidance where possible
(steepening slopes and alignment
changes to avoid services)
Service diversions
Existing Infrastructure
• Culverts upstream & downstream • Utilities (electricity & surface water) • Inaccurate service plans • Approvals & lead-in times
October 2014 14
Wandle Park – Approach & Lessons
Natural processes Gravels reinstated and allowed to
create natural features Limited bank readjustment within
main channel Land & water quality
Protected with capping layer Not remobilised by
geomorphological adjustment Large number of established trees
Root Protection Areas Steepen banks and realign
channel Create new habitats and contribute
towards GEP for MWB
Environment
• Room for natural processes • Established trees • Land & water quality • Flora & fauna
October 2014 15
Flood Risk & Engineering Design
Wandle Park – Approach & Lessons
Trash screen required (67% blockage for 1:100 year event)
Hydraulic modelling undertaken using ISIS
Reduced flood risk due to larger flood channel
Climate change Construction - bypass channel as
opposed to damning off and over-pumping
Scour Vandalism
• Flood risk & modelling • Inlet/outlet design • Vandalism
October 2014 16
Wandle Park – Completed Scheme
Visitor numbers up
All ages
Disabled access
School visits
Health benefits and
well-being
Challenges overcome
Park opened in 2012, attracted over 7,000 people
October 2014 17
Wandle Park – Completed Scheme
October 2014 18
Wandle Park – Completed Scheme
October 2014
Summary
Embracing history of park River as a focal point for urban regeneration Societal benefits (despite some vandalism!)
Increased visitor numbers Improved “sense of place” and connection with local community Reduced anti-social behaviour
Environmental benefits Improved biodiversity Contribution towards WFD delivery Connectivity with downstream restoration sites
Highly Commended at Landscape Institute Awards (2015)
Future Queen Elizabeth II ‘Field in Trust‘ - additional protection from
any future redevelopment.
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