Sustainable Urban Drainage (SUDS)

Why is it important?

SUDS are a range of techniques that aim to mimic the way rainfall drains in natural systems within urban areas. As the UK climate has become more prone to heavy rainfall in recent years, this has put pressure on traditional drainage systems.

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

  • 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.

Hints & Tips

  • 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.