Retrofitting Sustainable Drainage Systems
Pilot Study - Portslade
BHCC Green Infrastructure Briefing 16.04.2015
Ben Kimpton Dip(Hort) BSc MSc MCIEEM - TEC
Gary Grant BSc CEnv FCIEEM - GIC
Content
 How do SuDS fit into GI?
 SuDS in a Nutshell
 The Findings
 The Fantastic
What is Green Infrastructure?
“GI is a strategically planned and
delivered network of high quality
green spaces and other environmental
features.
It should be designed and managed
as a multifunctional resource capable
of delivering a wide range of
environmental and quality of life
benefits for local communities”.
Natural England
Green Infrastructure – Key Principles
Benefits of Green Infrastructure and SuDS
The multiple functions that GI assets provide are underpinned
by the concept of ‘ecosystem services’.
In the recent UK National Ecosystem Assessment these
services were divided into four categories:
 Supporting Services – ecosystem processes (soils/plants)
 Regulating Services – control mechanisms (flood control)
 Provisioning Services – products (water supply)
 Cultural Services - non-material benefits (visual amenity)
Regulating Services
Provisioning
 Climate change – e.g. reducing surface water flooding
Services
 Detoxification/purification in soil, water and air
 Hazard regulation – water attenuation
 Pollution control
 Pollination
What
are SuDS?
Portland
Reduces
Provisioning ic
Surface Flooding
 Reduce the amount and rate of surface water leaving sites
 One of the most effective ways of managing flood risk
 Alternative approach to conventional drainage systems
 Contribute to climate change mitigation and adaptation
 Can also improve water quality through bioremediation, increase
landscape amenity value, boost biodiversity (Ecosystem Services)
 Made up of a series of interventions – ‘SuDS train’
 The aim is to mimic natural drainage processes
Water Sensitive Urban Design
SuDS incorporate a range of different techniques:
 Rain gardens
Provisioning
Services
 Filter strips / filter drains
 Green roofs
 Permeable paving
 Stockholm ‘ tree-pits’
 Rainwater harvesting – tanks, diverted down-pipes
 Swales
 Retention / detention basins
 Ponds / wetlands
NB: A combination of techniques is often the most effective
Project Background
Provisioning Services
 Carried out by The Green Infrastructure Consultancy (GIC) and
The Ecology Consultancy (TEC)
 Commissioned by BHCC through the Brighton & Lewes Downs
Biosphere programme
 Funded by Natural England under the Green Infrastructure Challenge
Fund (2014/15)
 Supports Brighton & Hove’s work as a Lead Local Flood Authority
 Feasibility Study of the potential to retrofit Urban SuDS in Portslade
 Focussed principally on the creation of ‘rain gardens’ on public land
Scale
Services selected on the basis they are prone to
Provisioning
7 areas (sub-catchments)
surface water flooding and historic flooding events have occurred.
Method
Provisioning Services
7 Survey Areas (sub-catchments) selected on the basis they’re prone to
surface water flooding and historic flooding events have occurred.
 natural gradient - direction of surface water flow?
 evidence of standing water - where would water collect?
 building and greenspace features - down pipes, existing GI assets etc.
 drainage - how and where does water enter and exit the site?
 access and use - who uses the site and what is the level of use?
 visibility - is the site in the public domain and highly visible?
 services - what services are present and where are they located?
SURVEY AREA 4
Street Name/s:
Buckler Street
Description:
Densely developed area of housing located in gently
sloping valley running north-south through south
Portslade. Buckler is a short section of road joining
Bamfield Street (to the north) with Elm Road (to the
south). The central section is pedestrianised.
Problem/flood history:
Surface water flows both east and west down Bampfield
Street and Elm Road, collecting in the lowest point where
Buckler Street is located. As Bampfield Street is on higher
ground water also flows into Buckler Street from the
north. Buckler Street is indicated by the Environment
Agency on their uFMfSW as being susceptible to a 1:30
year flood event with c.6 properties in the location
experiencing flooding in 2014.
Constraints:
Narrow pavement and road on both Bampfield Street and
Elm Road. Parking bays in frequent use.
Opportunities:
Pedestrianised central section provides a relatively large
area for attenuation. Rainwater down-pipes from three
adjacent properties could be diverted.
SuDS Solutions:
The use of a Stockholm tree pit across the whole
pedestrianised area to increase water storage capacity.
Mature trees/shrubs could be retained and incorporated.
Area to be covered with both permeable paving and rain
gardens, subject to detailed design. Water flow from
Bampfield Street end to be diverted into the SuDS via a
drop kerb at northern end.
Indicative cost:
Potential (max.) area:
£20-40K
220m2
Potential attenuation:
Other GI benefits:
Will vary according to final size/depth of SuDS feature.
Could provide biodiversity and visual amenity benefits.
The greatest social benefits would be derived from
community involvement in managing (gardening) the
planting scheme.
Priority
Medium
General Findings
Provisioning Services
 0.5 hectares of SuDS could potentially be delivered. Significant improvements can be
made through the first phase of micro-projects, which will reduce the risk of flooding.
 SuDS features identified are located in the middle / lower catchment of the
valley that runs north-south through west Portslade.
 Always consider the SuDS management (treatment) train. Appropriate land-use
planning and management in the upper catchment must prevent and control the source
of water and SuDS features will become overloaded.
 In Portland, rain gardens very similar to those proposed in Portslade can reduce the
volume of surface water run-off by 80% (1:25 event).
 Actual volumes that can be attenuated will depend on the type and size of the
interventions, installed at each site. More detailed estimates or models can only be
provided following detailed design.
 ‘Urban-creep’ is prevalent. Long-term programme to promote and incentivise ‘de-paving’
and/or the use of domestic rainwater harvesting should be launched.
Site Specific Findings
Provisioning Services
 Survey Area 2 (Portslade Village) offers the greatest opportunity in terms of the
number of SuDS options and their combined surface area.
 Three Survey Areas have public open spaces that could be utilised for SuDS
features i.e. Survey Area 2 (Victoria Recreation Ground), Survey Area 3
(Lock’s Hill Recreation Ground) and Survey Area 7 (Vale Park).
Survey Area 2a(1) - Lock’s Hill Potential Rain Garden
Survey Area 2a(1) - Lock’s Hill Potential Rain Garden
Portland Rain Gardens
Portland Rain Gardens
Portland Rain Gardens
Portland Rain Gardens
Portland Rain Gardens
Lyon Rain Gardens
Lyon Urban Wetlands
London Park Rain Garden
Hackney Urban Swale
Hackney Urban Swale
Case Study
Greening The BIDS (London Bridge)
Tyers Estate Rain Garden Planter
Rain gardens that are cost-effective and without any major barriers to
development have been targeted as flagship projects
• Location: Tyers Estate – Leathermarket JMB, off Bermondsey Street
• Partners: Leathermarket JMB, Peter De Hann Charitable Trust, Groundwork
London, residents, volunteers, Southwark Council
• Delivery: Spring 2013
Cost: £5K
• Provides an exemplar for local residents
• Forms part of a 3 year community garden project on Tyers and Whites
Ground Estates
• Potential to be rolled out across the BID and other social housing estates
Estates Greening Rain Garden
Estates Greening Rain Garden
Fair Street Rain Vertical Rain Garden
• Location: Junction of Tooley Street and Fair Street
• Partners: Fair Street Housing, GLA, CRP
• Delivery: Spring 2013
Cost: £10K
• Multiple options including hanging green walls/screens, vertical rain garden
and ground level rain gardens
• Under-utilised space under housing block. Space could also be used for
public seating
• Downpipes and below pavement drainage strips are both present for
diversion/use
• Provides a green link between Potters Field Park and St. John’s Churchyard
Fair Street – Option 1
Tooley Street, London
Tooley Street, London
Thank You
Any Questions?
[email protected]
[email protected]