LANDSCAPING SERVICES
And it addresses both flooding and
Permeable paving and swales
provide a gradual supply of clean
water for other SuDS features.
pollution issues by storing and
cleaning water runoff at source,
avoiding drains surcharging and
downstream flooding. CBPP removes
water-borne pollution and provides
a gradual flow of clean water at the
head of the ‘SuDS management train’
enabling safe, open SuDS features on
the surface and enhancing landscape
design and biodiversity. This
technology also eliminates the cost of
pipework, gulleys and manholes.
Reduced Costs
These savings are demonstrated by
the Lamb Drove SuDS Monitoring
project, which assesses various SuDS
techniques, including CBPP, in a
management train, compared with a
conventional piped drainage system
nearby. Completed in 2006, Lamb
Drove in Cambourne, Cambridgeshire
was selected as a SuDS Showcase
Guidance and Case Studies
project within the FLOWS (Living with The Monitoring Report noted capital Flood Risk in a Changing Climate) cost savings of £314 per home using programme funded by the European SuDS, with further potential savings Regional Development Fund (ERDF). available through more holistic design. project will be launched at Flood Expo
The SuDS scheme was designed by Further Savings Birmingham NEC, and free tickets
Royal HaskoningDHV with Robert
Bray Associates and applied to a
conventional housing layout, based
around two cul-de-sacs. Two SuDS
management trains serve distinct
sub-catchments before linking at the
bottom of the site. The permeable
paving avoids additional land-take
for storage and supplies a controlled
flow of clean water to other, ‘soft
landscape’ SuDS features such as
swales, filter strips, under-drained
swales, detention basins and, finally,
a detention pond at the bottom of the
Having said that, further cost savings
are unaccounted for in these cost
comparisons. The SUDS at Lamb
Drove achieve 100% of the required
flow rate reduction by providing
attenuation storage within the site and
the immediately adjoining greenway
land. This represents a saving as there
is no reliance on strategic balancing
lakes, which have associated capital
costs, maintenance and land take
requirements.
site. Also, Lamb Drove SUDS do not
Despite layout constraints, natural and therefore avoid any connection
flow routes have been optimized
through the site for low and high
flows, as well as for exceedance. SuDS
have been integrated with landscape
design adding amenity, interest
and biodiversity to an otherwise
unremarkable scheme, and a holistic
connect to the adopted public sewer
and annual charges for storm water
disposal. Additional efficiencies
could have been achieved if the SuDS
had been integrated into the original
residential design – rather than
retrofitted to an existing design – as
a part of a wider Integrated Drainage
approach taken. Strategy for the complete Cambourne
Overall, whole-life-costs were The project also includes some SuDS
much lower than those for the features for demonstration purposes,
conventional piped drainage system. rather than necessity.
A new Interpave case study on this
on September 11th and 12th at the
are available at www.thefloodexpo.
co.uk. Here, Interpave’s presentation
by Dr Nick Gorst, in Theatre 25 on
Thursday 12th September at 14.00,
will demonstrate permeable paving’s
successful long-term performance,
minimal maintenance and cost-
benefits over conventional paving
and drainage. It will also explore new
regulatory requirements, technical
innovations and permeable paving
applications for SuDS.
In particular, the recently published
Edition 7 of Interpave’s definitive
guidance – ‘Design and Construction of
Concrete Block Permeable Pavements’
– includes the latest permeable
paving techniques. These include an
updated design methodology – in some
cases resulting in thinner, lower-cost
constructions, enhanced water storage
using flow controls and thin CBPP
overlays to improve existing road bases.
development using SuDS principles.
Interpave’s guide documents
and case studies are freely
available to download at
www.paving.org.uk