What next for flood risk and sustainable drainage standards?

Director, Neil Jaques, leads the water teams at Motion, advising clients on flood risk and drainage strategies for a range of residential, mixed-use and employment schemes.  In the following article, he examines the impact of recent updates to flood-risk guidance and sustainable drainage standards.

Compulsory rainwater harvesting

Climate change and population growth continue to place increasing strain on the UK’s water networks.  As parts of the country experience acute water shortages during periods of drought, more innovative and resilient strategies are required to address this growing challenge.  In response, new national standards for sustainable drainage systems (SuDS) now position rainwater harvesting as a key requirement for most developments in England.

At Motion, we welcome the new overarching guidance, which seeks to establish a more structured and consistent approach to sustainable drainage.  We have already adapted drainage strategies for development proposals in water-stressed areas to reflect this shift.   The former requirement to demonstrate water neutrality in planning applications (now withdrawn by Natural England) has provided our teams with valuable experience in developing practical and effective engineering solutions.

One such project involved support for redevelopment of the Rapkyns Estate near Broadbridge Heath, enabling expanded residential accommodation for pupils at New Barn School, which supports children with autism and associated needs.  The lessons learned from this project, alongside numerous other applications requiring water neutrality strategies, can now be directly applied to the interpretation and implementation of the updated national SuDS standards.

Regardless of differing views on the widespread adoption of rainwater harvesting for new developments, it is clear that this measure has sat at the top of the sustainable drainage hierarchy for some time.  The key challenge for engineers will be to engage proactively with local authority officers and other key stakeholders to ensure these requirements are applied pragmatically and efficiently.

The end of sequential testing?

The government’s Planning Practice Guidance for flood risk and coastal change has recently been updated.  Notably, the sequential test may no longer be required where a site-specific Flood Risk Assessment (FRA) can demonstrate that layout, design and mitigation measures will protect occupants and users from current and future surface-water flood risk for the lifetime of the development, without increasing flood risk elsewhere.

However, this update addresses only one aspect of flood risk and will place even greater emphasis on the need for robust justification and detailed FRAs to support applications.  The sequential test will remain a central consideration for most development proposals, particularly where other sources of flood risk are present.

If you need timely, climate-mitigation advice with your next project, email me at njaques@motion.co.uk 

An abridged version of this article first appeared in issue 28 of Insight