Sustainable (Urban) Drainage Systems (SUDS): an introduction

Traditionally surface water has been removed from built up sites using underground pipe systems, which prevent flooding locally by conveying the water away as quickly as possible. This has led to alterations of natural water flow patterns which, in turn, often lead to problems elsewhere in the catchment area.

How do SUDS work?

Sustainable drainage systems (SUDS), also called sustainable urban drainage systems, are made up of one or more structures built to manage surface water runoff, used in conjunction with good management of the site. There are four accepted methods of control:

Prevention – managing the site well can improve quality. Prevention includes design, maintenance and the education of users;
Filter strips and swales - vegetated surfaces that allow water to drain evenly off impermeable areas; swales are long shallow channels, filter strips are gently sloping areas of ground. Both of these features mimic natural drainage patterns by directing runoff through vegetation, slowing and filtering the flow;
Permeable surfaces and filter drains - have a volume of permeable material below ground to store surface water. Runoff flows into this storage area via a permeable surface, such as; Grass, Gravelled areas and Paving blocks;
Infiltration devices - soakaways, infiltration trenches and infiltration basins which drain water directly into the ground. Infiltration devices can easily be integrated into landscaped areas;

These controls should be located as close as possible to where the rainwater falls, providing varying degrees of treatment for surface water through natural processes of sedimentation, filtration and biological degradation.

Environmental benefits

Sustainable drainage utilises methods that take account of quantity, quality and amenity issues in built up areas. SUDS are beneficial to the local environment and more sustainable because they:

Manage runoff flowrates;
Protect or enhance water quality;
Are sympathetic to the local environment and community needs;
Provide a habitat for wildlife in urban watercourses.

SUDS achieve these aims by:

Dealing with runoff at source (close to where the rain falls)
Managing potential pollution at its source.

SUDS is no longer simply designed for flood control, it now concentrates on balancing the impact of urban drainage on flood control and water quality management.

SUDS selection

Ultimately, the selection and design of SUDS will be multi-disciplinary processes, and not limited to one area of expertise. Unlike conventional drainage systems, factors that influence the final choice will include the planning, water quality, water resource, architectural and landscape requirements of the site.

Information Sources

More information on green roofs is available on The Construction Information Service. Subscribers to The Construction Information Service can link directly to the documents from the links below.

The Construction Information Service - Drainage

BRE

Digest 365 Soakaway design. 2003 revision
Soakaways have been the traditional way to dispose of stormwater from buildings and paved areas remote from a public sewer or watercourse. In recent years, soakaways have been used within urban, fully-sewered areas to limit the impact on discharge of new upstream building works and to avoid costs of sewer up-grading outside a development. Soakaways are seen increasingly as a more widely applicable option alongside other means of stormwater control and disposal. Describes design and construction procedures, explains how to calculate rainfall design values and soil infiltration rates, and gives some design examples.

CIRIA

Publication C506 Low-cost options for prevention of flooding from sewers
Summarises the results of a CIRIA project in which low-cost options for preventing flooding from sewers were identified and information collected on their suitability and effectiveness. The document is aimed at the needs of drainage engineers and planners working for sewerage undertakers, local authorities, contractors and developers.

Scottish Environment Protection Agency

SUDS advice note - brownfield sites
Advises on, and promotes, use of Sustainable Urban Drainage Systems (SUDS) on brownfield sites.

The Construction Information Service - Sewerage/drainage

CIRIA

Project Report PR 72 Selecting package wastewater treatment works
Reviews UK and international practice for the design, assessment and operation of small wastewater treatment systems that serve population equivalents of less then 2000.

Publication C625 Model agreements for sustainable water management systems. Model agreements for SUDS
To advise on developing and using a set of model operation and maintenance agreements and guidance documents for SUDS. Intended to cover the long-term maintenance of water management systems. Model agreements are legal documents and will form the basis of agreements between two parties, such as the customer and the maintenance provider.

Publication C626 Model agreements for sustainable water management systems. Model agreement for rainwater and greywater use systems
To advise on developing and using a set of model operation and maintenance agreements and guidance documents for rainwater/greywater use systems. Intended to cover the long-term maintenance of water management systems. Model agreements are legal documents and will form the basis of agreements between two parties, such as the customer and the maintenance provider.

Publication C630 Sustainable water management in land-use planning
Looks at the issues of sustainable water management and puts them in context of land-use planning. Considers the planning system in England and Wales, the planning of water resources and waste water planning. Offers guidance and recommendations.

Publication C635 Designing for exceedance in urban drainage - good practice
Provides good practice for the design and management of urban sewerage and drainage systems to reduce the impacts from drainage exceedance. It includes information on the effective design of both underground systems and overland flood conveyance. It also provides advice on risk assessment procedures and planning to reduce the impacts that extreme events may have on people and property within the surrounding area.

Publication C697 SUDS manual
Provides guidance on the planning, design, construction and maintenance of Sustainable Drainage Systems (SUDS) to assist with their effective implementation within developments. Addresses landscaping, biodiversity issues, public perception and community involvement as well as water quality treatment and flood risk management.

Publication C698 Site handbook for the construction of SUDS
Describes how Sustainable Drainage Systems differ from conventional drainage. Provides guidance on general construction issues, construction planning, erosion, sediment and pollution control, inspections, method statements, emergency contacts and components. For use on site.

Report R 134 Sediment management in urban drainage catchments
Looks at the effects of managing sediment in the urban drainage system. Cleaning routines, problems, sources, characteristics and quantities are examined. Improvements to cleaning operations are suggested.

Report R 183 Management of gully pots for improved runoff quality
Gully pots act as runoff inlet points to surface water sewers, combined sewers and highway drains. Their primary purpose is to intercept solid material that otherwise would cause blockages in the sewerage system. They also act as water seals to prevent the escape of odour from combined sewers. Gully pots can however provide a reservoir of contaminated sediment and a source of polluted liquor, which can be flushed into sewers and watercourses during maintenance or storms.

Croft Consultants

Design and maintenance of culverts - guide for designers and managers (revised 2004)
Introduces the design and maintenance of culverts and their use in drainage and erosion control.

Drainage of paved areas and buildings - basic features and fixtures (revised 2004)
Discusses the basic features and fixtures of drainage of paved areas and buildings.

Environment Agency

Sustainable drainage systems (SUDS) - an introduction
Highlights environmental problems caused by conventional urban drainage systems and presents some of the alternative design methods which have been found to be effective in reducing them. The techniques described are effective for reducing the impact of surface water discharges. Covers source control and prevention techniques, permeable conveyance systems, and passive treatment systems.

Highways Agency

DMRB Volume 4 Section 2 Part 1 (HA 106/04) Geotechnics and drainage. Drainage. Drainage of runoff from natural catchments
Offers guidance on how to deal with surface water runoff from natural catchments draining towards trunk roads (including motorways.) The aim is to limit the frequency and severity of flooding incidents caused by runoff from beyond the highway boundary.

DMRB Volume 4 Section 2 Part 8 (HA 118/06) Geotechnics and drainage. Drainage. Design of soakaways
Gives design guidance on how soakaways may be incorporated into systems used to treat and store road runoff prior to discharging to ground. It describes the steps needed to protect receiving groundwater and the constraints these may place on soakaway design and construction.

The Construction Information Service - Sewage treatment/sterilisation

BRE

Good Building Guide 42 Part 1 Reed beds: application and specification

Good Building Guide 42 Part 2 Reed beds: design, construction and maintenance
This guide describes typical applications and design specifications for reed beds treating settled domestic wastewater.

Report 420 Reed beds for the treatment of domestic wastewater
Draws upon work from around the world to produce an up to date guide to reed beds. The design guidance contained in this report covers the most common types of reed beds that are likely to be employed in the UK in the near future. The common systems covered are: Vertical flow, Horizontal flow, for secondary treatment, and. Horizontal flow, for tertiary treatment.

Other sources of information

UK SUDS database

The objective of the database is to gather together information, knowledge and experience on Sustainable Drainage System sites in the UK (in terms of location, design, operation and maintenance, cost performance, etc.), and to disseminate this information across the Industry to raise awareness and promote knowledge-sharing. For further information see http://www.suds-sites.net/.

SUDS - Sustainable drainage systems: promoting good practice

A CIRIA initiative to promote SUDS to industry, by offering methods of remediation and good practice, supported by case studies.

SEPA - SUDS research and monitoring

Provides information about the Scottish Environmental Protection Agency’s SUDS related work, likely future activities and the roles of different stakeholders.

UK Environment Agency – SUDS: an introduction

Explains briefly the problems with traditional drainage practices, outlines why SUDS offer a more sustainable option for drainage and provide links to sources of further information.

SUDSnet

SUDSnet provides a UK-wide network for researchers, practitioners, agencies, developers and those who are interested in Sustainable Urban Drainage Systems.

SUDSnet is funded by an EPSRC Network Grant and is held jointly by Coventry University and the Urban Water Technology Centre (UWTC) at the University of Abertay Dundee.

Written March 2007