Sustainable drainage systems (SUDS)

Figures: Examples of SUDS (rainwater retention and collection gutter)


A key component of FPRM are so-called ‘sustainable drainage systems (SUDS)’.  SUDS are an approach to surface water management that combines a sequence of management practices and control structures designed to drain surface water in a more sustainable fashion than some conventional techniques.

In addition restoration of retention either through natural elements or artificial structures (e.g. retention reservoirs) in urban watercourses may be effective. Although most SUDS are not designed to cope with large flooding events as their primary purpose is often for water quality management [*1].

SUDS are a sequence of management practices and control structures which can drain surface water in a more natural way than most conventional techniques [*2]. For many SUDS (the source control options) the idea is to retain the storm water as close as possible at the source (source-control) and to make use of small scale structures.



Conventional systems and SUDS approach the issue of stormwater control from different perspectives:

  • The conventional approach to stormwater control is to directly drain stormwater flows as quickly as possible to the nearest receiving watercourse or sewer system to avoid the risk of flooding and to protect human health.
  • SUDS aim to:
    •  treat stormwater as close as possible to its source,
    • reducing runoff volumes,
    • pollutant loads and flow rates by collecting,
    • temporarily storing and subsequently discharging at a controlled rate to the soil or the downstream receiving watercourse or sewer.

As well as ensuring individual safety and flood protection, SUDS also aim to improve the urban environment through their potential for multifunctional use. For example, as well as providing stormwater control, retention basins can also act as recreational areas and provide habitat for wildlife.

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Flood probability reduction measures



*1 Evans et al. (2004a)

*2 CIRIA (2007)



Further Information