25 June 2025
On 19th June 2025, the government published updates to the National Standards for Sustainable Drainage Systems (SuDS), bringing greater clarity and structure to how SuDS are designed, implemented, and integrated within development projects.
Our Flood Risk Engineer, Thomas Sturtridge, welcomed the update as a significant and positive step for the industry.
“We now have seven concise standards, with clear definitions, that are integrated with existing legal frameworks,” Tom explains. “The standards place greater weight on the four pillars of SuDS design; Quantity, Quality, Amenity, and Biodiversity and will drive better long-term planning around water management in new developments.”
Key Changes in the New SuDS Standards
An increased emphasis on water re-use, we expect to see more rainwater harvesting and non-potable re-use of water, ensuring the first flush is kept and re-used within the site
There’s now a requirement to consider water quality, amenity, and biodiversity at the outset, designing the development around features like attenuation basins and landscaped drainage systems, ensuring they are part of the initial site layout, not added retrospectively.
QBAR (mean annual flood flow) should now be calculated using the full contributing area; including both permeable and impermeable surfaces, rather than just the impermeable area, as it was previously.
“This may lead to increased QBAR rates,” Tom notes, “and in some cases, reduced attenuation requirements. However, this will vary depending on the specific characteristics of each site and will be subject to local authority guidance.”
Our team are currently in discussions with several local authorities to better understand their evolving approach to these changes and will assess each project on a case-by-case basis to ensure the most appropriate, compliant solution.
What This Means for Future Developments
The updated guidance signals a clear direction of travel from central government. As Tom highlights:
“It’s our instinct that these Standards will act as a precursor to Schedule 3 of the Flood and Water Management Act 2010 being enacted. This will not only mean the mandatory inclusion of SuDS into new developments (including single houses) but also calls for the formation of SuDS Approval Bodies (SABs). “With this guidance now in place, and with stronger backing legally, we recommend early engagement to ensure SuDS design is integrated into a development as soon as possible,” adds Tom.
Need Advice?
With these changes now published, engaging a flood risk and drainage specialist early in the planning process is more important than ever.
Tom Sturtridge
tom.sturtridge@m-ec.co.uk
01530 264753
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