Sustainable Urban Drainage Systems (SUDS)

What are SUDS?

SUDS, or Sustainable Urban* Drainage Systems are a sequence of water management practices(1) and facilities(2) designed to drain surface water in a manner that will provide a more sustainable approach than what has been the conventional practice of routing run-off through a pipe to a watercourse.

*The use of the word 'urban' is frequently omitted, but the meaning is still the same.

1. Practices involved are what is termed 'good housekeeping' or 'best management practices'. Such practices include:

  • Mitigation of accidents that may result in pollution incidents;
  • Reduction of polluting activities;
  • Reduction of polluting materials;
  • Bunding of oil tanks;
  • Water harvesting.

2. Facilities are generally constructed arrangements. Such facilities include:

  • Permeable surfaces;
  • Filter strips;
  • Filter and infiltration trenches;
  • Swales;
  • Detention basins;
  • Underground storage;
  • Wetlands;
  • Ponds.

Other facilities exist that often come as proprietary products offering hydraulic controls or silt trap arrangements. These may also incorporate materials with properties able to encourage adsorption of certain polluting substances such as oils and toxic metals.

SEPA is the statutory agency responsible for protecting the water environment in Scotland, under the Water Environment Water Services (WEWS) Act. On that basis SEPA requires the use of effective, appropriate Sustainable Urban Drainage Systems (SUDS) features in new developments.

Developers, SEPA and Scottish Water are encouraged to discuss proposed developments at an early stage, even before approaching the planning authority. Government planning advice is available in Planning Advice Notes (PANs) and Scottish Planning Policy (SPP) releases from the Scottish Government external link.  

A national stakeholder group was established in 1997 - the Sustainable Urban Drainage Scottish Working Party (SUDSWP). The SUDSWP website provides more information on SUDS. 

How are SUDS regulated?

Under the Water Environment (Controlled Activities) (Scotland) Regulations 2011 it is a general* requirement for new developments with surface water drainage systems discharging to the water environment that such discharges will pass through SUDS. All reasonable steps must be taken to ensure protection of the water environment.

* Two exceptions exist to this requirement:

1. Where the development is only a single dwelling;

2. Where the discharge is directly to coastal waters (this does not including transitional waters).

The Controlled Activities Reguations (CAR) provide regulation under General Binding Rules (GBRs) 10 and 11 for SUDS. Please refer to the Related Items box for more information.

SUDS in Scotland - the Scottish SUDS database

The findings of a major survey into the use of sustainable urban drainage are summarised in the SNIFFER report external link (SR (02) 09), 'SUDS in Scotland - the Scottish SUDS database'. The survey highlighted that the use of SUDS has become standard practice in Scotland, with over 700 sites being listed and nearly 4000 systems having been implemented.