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Environment Bulletin: SUDS – The soap goes on…

From 6 April 2015, planning authorities will now require sustainable drainage systems (SUDS) for the management of run-off from “major developments” in England, unless these are “demonstrated to be inappropriate”.

There is no guidance on what is meant by “inappropriate”, though previously the government has considered whether SUDS would not be required where their cost exceeds that of using conventional drainage.

“Major developments” include one or more of the following:

  • developments of 10 dwellings or more;
  • residential developments on a site of 0.5ha or more where the number of dwellings is not known;
  • developments with floor space of 1000m2 or more;
  • development on a site of 1ha or more;
  • minerals development; or
  • waste development.

This requirement for SUDS in “major developments” is in addition to the existing requirement in the National Planning Policy Framework that all new developments in areas at risk of flooding should give priority to the use of sustainable drainage systems.

Sustainable drainage systems (sometimes, misleadingly, known as sustainable urban drainage systems) or SUDS are systems which collect surface water run-off and release it slowly. Examples include permeable paving, soakaways, swales and ditches and green roofs. This approach is in contrast to conventional drainage which seeks to discharge surface water straight into the public sewer or watercourses as quickly as possible. SUDS are designed to mimic how the water would have drained had the site been undeveloped and they reduce the risk of surface water flooding. In addition, SUDS can improve water quality and provide areas for wildlife and public greenspaces.

However, SUDS can have drawbacks for developers. Perhaps most significantly, they can sterilise parts of the land for buildings and thus affect the viability of the development. Moreover, the costs of designing and implementing SUDS, including negotiations for adoption by the local water company, may exceed a conventional system, especially while experience of SUDS is in its infancy. Care will also have to be taken in their design to ensure maintenance is not too onerous. In terms of SUDS design, DEFRA published “Non-statutory technical standards for sustainable drainage systems” in March 2015 to support the policy change. These are effectively outcome-based standards and do not prescribe a particular type of system in a given situation, leaving flexibility for developers when designing their particular scheme.

The government has been looking at how to implement the use of SUDS in development for over 5 years now since the Flood and Water Management Act 2010. Its initial proposals, published in 2011, were for a separate SUDS approval body running parallel to the planning system. However, significant concerns from developers about the practicalities of this scheme led to a re-think and a change of approach. The implementation via the planning system and the limits of application to only “major developments” were announced in December 2014 and were intended to address concerns about excessively onerous burdens on development and unnecessary delay in gaining the development consents.

Under the changes to planning policy which took effect on 6 April 2015, local planning authorities, when considering planning applications should:

  • consult the relevant lead local flood authority(the unitary authority or county council) on surface water management of the scheme;
  • satisfy themselves that the proposed minimum standards of operation are appropriate; and
  • use planning conditions or planning obligations to ensure clear arrangements are in place for maintenance of SUDS over the lifetime of the development.

There are a number of points developers may want to consider in light of these changes:

  • Early consideration of integration of SUDS into master planning of development schemes for “major developments”;
  • Early discussions with water authorities about adoption or consideration of long-term maintenance arrangements;
  • Maximising the amenity and biodiversity benefits of SUDS to enhance the planning application; and
  • Where a scheme is close to the “major development” threshold, careful consideration of whether SUDS would work in the scheme or whether the scheme viability would be improved by falling outside of the “major development” criteria.

The government has said that it will keep SUDS policy under review, in particular whether it should be expanded to include developments below the “major development” threshold. It is also expected that lead local flood authorities will shortly be developing standing advice to planning authorities on surface water management for smaller developments, so, when this arrives, it will need to be considered when planning any development.

It seems that SUDS are here to stay, so learning how to use them to the greatest benefit in your scheme is vital to gain a commercial advantage.


The content of this page is a summary of the law in force at the present time and is not exhaustive, nor does it contain definitive advice. Specialist legal advice should be sought in relation to any queries that may arise.

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