SUDS (Sustainable Urban Drainage Systems)
Progressive urban development has resulted in rapid increases in
run-off to watercourses following storm
events. Because rainfall can travel quickly to the watercourse via
impermeable surfaces there is very little natural infiltration or
retention to reduce levels of pollutants such as silt, organic matter and
recent years there has been a rising rate of flooding incidents, some on a
very large scale. The reasons for these are complex and inter-related,
but they include:
increase in occurrences of very heavy rainfall over short periods;
this may be a side effect of global warming;
water tables arising from higher rainfall;
in the speed at which rainfall finds its way into rivers and streams.
This can be caused by
large new developments (including roads) which have surfaces which
do not absorb water, or
changes to agricultural practice which reduce water retention at
times of heavy rainfall;
development in areas which should be reserved for flood management;
to drainage patterns and systems (whether designed or accidental)
which reduce capacity to handle peak flows;
poor maintenance of surface water drains.
drainage systems (known as SUDS) offer an alternative approach to
traditional drainage. SUDS employ a whole
suite of techniques to effectively manage drainage at
source including dry ditches (swales), detention/attenuation
ponds, and integrated constructed wetlands, all of which aim to detain run-off and release it
slowly into watercourses or to ground. Source control techniques are
also increasingly popular - such as the use of porous (as opposed to
impermeable) paving and 'green roofs' which allow rainwater re-use.
techniques reduce the likelihood of flash flooding and
result in greatly improved water
quality. SUDS schemes are often cheaper and easier to maintain than
traditional engineered drainage solutions involving gully pots and petrol
larger SUDS systems such as wetlands added value is provided by improved
wildlife habitat and recreational potential.
The use of
SUDS to reduce levels of diffuse pollution and
flooding is common in Europe and North America, and is rapidly
becoming more widespread
in the UK as local authorities see the benefits to water quality and flood
management. Scotland has been particularly active in this area for
some years, and the EA works with SEPA (the Scottish Environment
Protection Agency) and the Environment and Heritage Service in Northern
Ireland to develop guidance and encourage their use. The EA drive
the use of SUDS in the UK.
Working closely with the EA, the
Partnership is implementing SUDS at various sites in the catchment area,
and will promote the concept to local developers, monitoring the results
over a period of time.
SUDS in the
bathing beach has failed to comply with the Bathing
Water Directive Guideline standards in 10 out of the last 12 years,
despite significant investment in reducing point source inputs. The main
reason for this non-compliance is the Bourne stream, which discharges
close to the bathing beach.
Bourne Stream was identified as offering an ideal opportunity to focus
research on SUDS and a range of related issues; the Environment Agency has
played a key role through it Research & Development (R&D)
programme with the aim of improving water quality in the stream and at the
bathing beach at Bournemouth Pier.
and wetlands project at Alderney were established to install in-stream SUDS in
by Borough of Poole, with a financial contribution from English Nature,
they have been successful at improving water quality and demonstrating the environmental benefits of
SUDS techniques to the local community.
Since then further
projects at Coy Pond
Gardens and Bourne Valley
Park have utilised external funding to improve water
quality & amenity value in other areas.
We have also been busy talking about
March 2002 the Partnership, led by the Environment Agency, initiated a SUDS workshop
for Poole and Bournemouth local authority planners
delegates. Both LAs have since issued a supplementary planning
guidance (SPG) to advise developers and builders on the use of SUDS.
Stream SUDS were described in an article in the CIRIA Sustainable
Drainage newsletter (Issue
4, July 2003) written by Neil Smith of the
April 2005 the Partnership hosted a SUDSnet
group visit to the Bourne Valley when delegates had a chance to
see and hear at first hand about our SUDS design and performance.
See also SUDSnet News (Issue
2, June 2005, pdf) and CIRIA Sustainable Drainage News (Issue
8, August 2005)
from Bournemouth University utilise the Bourne Valley SUDS for research purposes; we
publish their papers here.
Drainage Systems (SUDS) June 2002
Borough of Poole Supplementary Planning Guidance
and the Law
papers from Coventry University consider SUDS from the point of view of
habitat quality and public safety:
A.P., Whitehouse D. and Smith S.J. (c. 2001) Wildlife Protection Law as
a Barrier to Sustainable Drainage Wetlands and Pools in the UK and
Elsewhere: A Proposal for Legislative Change (pdf,
N. (2003) Personal Injury Litigation as a Barrier to the Adoption of
Sustainable Drainage Ponds - A Proposal for Legislative Reform
Urban Drainage Systems - an Introduction", SEPA/EA
Policy Guidance Note 25 (Development and Flood Risk), July 2001
'H', The Building Regulations 2002 Edition, April 2002, DTLR
- "Scope for the Control of Urban Runoff"
- "Infiltration Drainage - Manual of good practice"
- "Sustainable Urban Drainage Systems - design manual for
England and Wales"
- "Sustainable Urban Drainage Systems - best practice
is the Construction Industry Research & Information