What are Sustainable Drainage Systems?

Sustainable Drainage Systems (SuDS) are not new. They are, quite simply, nature’s way of dealing with rainfall.

At its simplest, rain falling on the land may evaporate or be absorbed into the soil, nourishing the natural habitat. Otherwise, it flows overland into ponds, ditches, watercourses and rivers, helping to sustain life by replenishing water resources.

It is only recently that the balance of this natural water cycle has been disrupted. Modern urban development with its houses, roads and other impermeable surfaces has increasingly altered the way that rainwater finds its way into our soils, rivers and streams. Surface water has for many years been collected and piped directly into our ditches and rivers. Conveying water away as quickly as possible from a development may adequately protect the immediate development from flooding but increases the risk of flooding occurring downstream. This unsustainable approach to surface water drainage, together with the potential effects of a changing climate, has contributed to some very serious consequences on life, property and the environment – as evidenced by the disastrous flooding experienced throughout the UK during the summer of 2007. 

A return to more natural, sustainable methods of dealing with surface water from development has benefits for:

  • Water quality – SuDS can help prevent and treat pollution in surface water runoff, protecting and enhancing the environment and contributing towards Water Framework Directive objectives.
  • Amenity – SuDS can have visual, recreational and sociological benefits for the community.
  • Biodiversity – SuDS can provide the opportunity to create and improve habitats for wildlife, enhancing biodiversity.

The Essex SuDS Design Guide (currently under review) forms the local standards for Essex and, together with the National Standards, strongly promotes the use of SuDS, which help to reduce surface water runoff and mitigate flood risk.

The National Planning Policy Framework (NPPF) provides support for decision-making in relation to SuDS through two key paragraphs:

Paragraph 155: Inappropriate development in areas at risk of flooding should be avoided by directing development away from areas at highest risk (whether existing or future).

Where development is necessary in such areas, the development should be made safe for its lifetime without increasing flood risk elsewhere.  

Paragraph 165: Major developments should incorporate sustainable drainage systems unless there is clear evidence that this would be inappropriate. The systems used should:

  1. take account of advice from the lead local flood authority;
  2. have appropriate proposed minimum operational standards;
  3. have maintenance arrangements in place to ensure an acceptable standard of operation for the lifetime of the development; and
  4. where possible, provide multifunctional benefits.

Page updated: 10/03/2020


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