Defra publishes research recommendations to update Non-Statutory Technical Standards for SuDS

Defra recently published its research project to review and recommend updates to the Non-Statutory Technical Standards for Sustainable Drainage Systems (SuDS) in England.

The proposals would, if adopted, bring the standards in line with current best practice according to the construction industry research and information association (CIRIA) SuDS Manual. This means that the ideas and principles detailed in the report should not be new to any good SuDS practitioner.

There is an upfront recognition of key principles which, if followed, are more likely to result in a good design:

  • Following a ‘SuDS approach’ (i.e. keeping water on the surface, management train, managing water close to the source, delivering multiple benefits)
  • Early and integrated design (i.e. considering water management in the layout at an early stage)
  • Embedding SuDS within the development planning process

The proposed standards themselves would replace S1 to S6 in the current Non-Statutory Technical Standards for England with six new standards:

  • Standard 1: Runoff destinations – covers the SuDS discharge hierarchy, with the inclusion of rainwater re-use and harvesting as the first destination where possible
  • Standard 2: Everyday rainfall – covers interception of the first 5mm of rainfall
  • Standard 3: Extreme rainfall – updates, clarifies and standardises the existing approach to greenfield runoff and volumes. Introduces the concept of a ‘relaxation factor’ for pre-developed sites
  • Standard 4: Water quality – covers the management and protection the quality of surface and groundwater
  • Standard 5: Amenity – covers multi-functionality and place-making
  • Standard 6: Biodiversity – emphasises the link with local biodiversity strategies and biodiversity net gain.

Each of these standards are also accompanied by additional information and guidance. For example, there are further recommendations on hydrological estimation methods and water quality assessment methods, which will help ensure more consistency in approaches. There is also guidance on what evidence should be presented to show that the standard has been met.

Defra publishes research recommendations to update Non-Statutory Technical Standards for SuDSThe proposed standards are complementary and reinforce each other. For instance, the requirement to manage everyday rainfall will strongly encourage source control features such as green roofs and small raingardens (under the current standards such features are often over-looked due to the focus on managing extreme rainfall). This in turn will also directly contribute to meeting the amenity and biodiversity standards. Clearly early involvement and effective communication within a multi-disciplinary design team (drainage, landscape, ecology) will be essential to ensure all the opportunities are taken and potential benefits realised and encourage innovation.

Although there seems to be no movement towards making them statutory, the proposed standards are a very welcome shift towards reinforcing the requirement for multi-benefit SuDS in England.  This will be helpful to those Local Authorities with which we have worked closely to support their aspiration to maximise benefits from SuDS, which has been difficult to realise through the legislation and standards currently in place. The clarifications will also help to provide guidance to responsible developers who want to meet other policy requirements through SuDS (e.g. green infrastructure provision, potable water, biodiversity net gain, health and well-being).

As the report notes however, there is much work to be done to develop the tools and metrics needed whilst also aligning other national policies. Both developers and local authorities will need support, wider expertise, and resourcing to be able to design and assess SuDS proposals against the new standards.

Want to know more?

Email Anna Beasley for more information on how we can support Local Authorities with SuDS guidance, tools and training. Or for details on how we can support developers in delivering multiple benefits through SuDS design email Marta Lubiejewska.

You can also find out more information about these services by visiting our Local Flood Risk Management web pages.

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