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Sustainable Drainage (SuDS)

1. What is sustainable drainage?

SuDS are used as an alternative to conventional ways of managing surface water. The main purpose of sustainable drainage systems is to mimic the natural drainage of the site before development. This is achieved by capturing rainfall and allowing as much as possible to evaporate or soak into the ground close to where it fell. The rest is directed to the nearest watercourse to be released at the same rate and volumes as before development.

By mimicking natural drainage patterns, SuDS benefit the environment by removing pollutants - including metals and hydrocarbons from roads and car parks, before reaching a watercourse. As a result, water entering the watercourse is cleaner and does not harm wildlife habitats.

Sustainable drainage systems generally replace traditional underground piped systems that use grates or storm water drains at street level. This means any problems with the system are quicker and easier to identify than with a conventional system and are likely to be cheaper and more straightforward to rectify.

SuDS will become increasingly important for controlling surface water if rainfall levels increase due to climate change. They can also provide other benefits in developments such as passive cooling, which will again help mitigate any increase in temperatures due to climate change.

In summary, sustainable drainage has the potential to:

  • Manage runoff volumes and flow rates from hard surfaces, reducing the impact of urbanisation on flooding
  • Protect or enhance water quality (reducing pollution from runoff)
  • Protect natural flow regimes in watercourses
  • Provide an attractive habitat for wildlife in urban watercourses
  • Provide opportunities for evapotranspiration from vegetation and surface water
  • Encourage natural groundwater/aquifer recharge
  • Create better places to live, work and play
  • Offer cost effect and affordable drainage solutions

Source: CIRIA, Sustainable Drainage, 2013

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Last updated: 20 January 2017

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