Sustainable Urban Drainage Systems (SUDS)

SUDS are a range of techniques that aim to mimic the way rainfall drains in natural systems within urban areas. Many existing urban drainage systems can cause problems of flooding, pollution or damage to the environment and are not proving to be sustainable in the long term. As development intensifies, less water filters through the soil, leading to increased flows. As the UK climate has become more prone to heavy rainfall in recent years, this has put pressure on drainage systems.

Technical information

Water management is now a crucial part of sustainable building practice. Current legislation, from The Flood and Water Management Bill 2011 to Planning Policy Statements.

SUDS are a range of techniques that aim to mimic the way rainfall drains in natural systems within urban areas. Many existing urban drainage systems can cause problems of flooding, pollution or damage to the environment and are not proving to be sustainable in the long term.

National, regional and local planning policies encourage the adoption of sustainable drainage systems and high standards of water efficiency. The construction of new developments should enable the incorporation of greater water efficiency.

To avoid the need for planning permission, new driveways should be constructed using permeable paving or gravel.

Despite SUDS being generally more complex than conventional drainage, case studies have shown that properly designed SUDS solutions, can deliver a saving of 10% on capital costs, when compared with conventional drainage methods.

SUDS solutions are more complex than conventional drainage as they include a variety of components; each having different approaches to managing flows, storage volumes, water quality and providing amenity and biodiversity benefits. Often SUDS schemes use a combination of these processes and components may use a number of mechanisms.

There are a number of SUDS techniques and the particular combination of techniques employed on any one development depends on the local conditions at any site. A summary of the techniques that could be employed include:

• Green roofing or rain/grey water harvesting techniques

• Swales grassed depressions which lead surface water overland from the drained surface to a storage or discharge system, typically using the green space of a roadside margin

• Basins designed to hold back storm runoff for a few hours and to allow the settlement of solids

• Infiltration trenches which are excavated trenches, filled with stone to create an underground reservoir

• Permeable pavements using permeable concrete blocks, crushed stone or porous asphalt

• A filter drain is a trench covered with gravel or rock that redirects surface and groundwater away from an area. They have perforated hollow pipes along the bottom to quickly vent water that seeps down through the upper gravel or rock

• Ponds or wetlands which can be designed to cope with variations in water levels during storms, or prolonged periods of wet weather thereby enhancing flood-storage capacity.

Sustainable Drainage schemes are beneficial because:

• They do not contribute to flooding

• They encourage wildlife

• Create new wetland habitat, which is threatened in the UK

• Provide visually attractive, and educational amenities

• They mitigate issues around surface water run-off that can contain contaminants such as oil, toxic metals, etc

• Help to maintain ground water levels and in turn the flow in watercourses during dry weather.

• Potential to earn additional credits under the Code for Sustainable Homes.



Hints & Tips

We provide a Sustainable Drainage Design service through our partner company Geo Environmental Sciences Limited (GESL) comprising of a range of options for planners, architects, installers or homeowners. Dependent upon requirements we offer Desk Study, Site Visit, Ground Investigations or Designs for Soakaways, Swales and Basins.

Installing porous paving should only be undertaken by a trained installer who can calculate the soils permeability and appropriate requirements of specially graded sub-base aggregates.

To avoid requirement of planning permission, driveway and parking areas should be built using permeable surfaces.

Managing the site can improve quality. Prevention includes design, maintenance and the education of users.

Permeable surfaces and filter drains have a volume of permeable material below ground to store surface water.

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.