Sustainable drainage set to be mandated at new developments, UK Government confirms

Pictured: Flooding in Hereford

The Department for Food, the Environment and Rural Affairs (Defra) has this week confirmed that this mandate is in the pipeline and will be implemented through changes to the 2010 Flood and Water Management Act.

The hope is to alleviate pressures on drainage and sewerage systems by ensuring that natural drainage patterns can be better replicated in developed areas. SuDS can include features like grassy areas, permeable surfaces, wetlands, water tanks and water butts.

“Housebuilding is a priority for this Government though new development risks reducing the capacity of the land to provide natural drainage and has the potential to increase surface water runoff,” Defra’s review documents state.

“Buildings and impermeable surfaces concentrate rainwater, which runs off into our sewerage rather than being naturally absorbed into the ground and rivers. Separating surface water so that it is diverted to water gardens or wetlands and does not mix with sewage improves water quality, creates new habitats for species and acts as a carbon sink.”

Defra is proposing that the requirement for SuDS to be fitted in new developments is broadened. At present, it only applies to developments of more than ten homes. A broadening would cover smaller developments and developments in urban areas for non-domestic use.

The Department has also heard evidence that there are not, at present, specific regimes to check whether developers had constructed SuDS as agreed. It is, therefore, seeking to move past its current “planning-led” approach with non-statutory technical standards and increased checking rules and maintenance rules for developers.

Defra is now preparing to launch a consultation on the changes to fine-tune its approach. Mandates are then set to come into effect in 2024. In the meantime, Defra will assess potential burdens on developers and how they should be managed, including improving SuDS-related skills across the built environment sector.

In her Ministerial foreword to the review document, Environment Secretary Therese Coffey stated that she believes the Government “needs to go further” to ensure that the increasing demand for housing water and sewerage is met in a sustainable way, and to improve the climate resilience of water systems.

Weather patterns across much of England during the latter period of 2022 resulted in droughts followed by flooring. The year through to October was the driest on record since 1976 according to the Met Office. Most regions declared drought, prompting interventions from water companies.

Because soils remained drier than usual following rain in autumn, heavy rains did contribute to flooding in several regions in the last quarter of 2022. Flooding was recorded in Dorset in October, before the county faced a second wave of flooding in November and a third in December. November also saw flooding in Tenby, Wales; Angus, Scotland; and Nottingham, Loughborough, Coventry, Wolverhampton and Wiltshire in England. The year ended with severe flooding in Dumfries, Scotland.

Coffey advocates in her foreword for an “integrated way of managing” water, ensuring resilience of supply in the face of megatrends like urbanization and climate change. This approach includes managing rainwater close to where it falls.

Environment Minister Rebecca Pow added: “The benefits of SuDS are many – from mitigating flood risk by catching and storing surplus water and reducing storm overflow discharges, to enhancing local nature in the heart of our developments and helping with harvesting valuable rainwater.

“Taking a more consistent and effective approach to sustainable drainage systems will improve the resilience of our drainage and sewer infrastructure while reaping these broader benefits.”

Defra has not yet assessed the topic of retrofitting SuDS in existing developments. The Department claims this lies beyond the remit of the legislation and regulation set to be changed.

A welcome change

Responding to Defra’s announcement, the UK Green Building Council’s public affairs and policy adviser Philip Box said:  “As one of more than 40 experts who wrote to the Prime Minister to recommend this move, we welcome the Government’s commitment to normalising drainage principles that protect both natural and built environments.

“Well-designed sustainable drainage is widely recognised as the best way to manage flooding risks and pollution overflows – both serious challenges to communities that will worsen as our climate changes.

“With a wide range of potential benefits ranging from biodiversity gain to improved air quality, we look forward to further details arising from the Government’s consultation.”

The Council wrote to Prime Minister Rishi Sunak in December 2022, noting that at least 3.2 million properties are at risk of surface water flooding in the UK and that floods already cost an average of £1.3bn per year in damages alone. It implored Sunak to heed the Government’s own Climate Change Risk Assessment, which recognises flood risk as the highest level climate threat to the UK.

Environmental Audit Committee chair Philip Dunne MP added that it is “absolutely right” for the Government to “address the major and complex challenge of easing pressure on the [water] system”.

“Its intent for new developments to include sustainable drainage systems is absolutely the right direction, and was a key recommendation in our report that considered water quality,” Dunne said. “Developers must not simply have the right to connect to an overloaded sewerage system and not contribute to improvements.”

The report mentioned by Dunne was published this time last year.