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Where do SuDS fit within the new planning system?

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Little Easton: An award-winning scheme that combines rain gardens, permeable hard surfaces and beautiful amenity into a new build development in Essex. © Refolo Landscape Architects

Embedding sustainable water management must be at the core of development planning, starting with mandatory SuDS implementation across England, argues Cristina Refolo.

As the UK moves forward with wide-ranging planning reforms, the essential role of sustainable drainage systems (SuDS) is becoming increasingly important. The UK’s disjointed and ageing sewerage infrastructure continues to battle with higher-intensity rainfall, probably as a result of climate change. Due to this, the risk of flooding in urban areas has increased dramatically.

One way to combat this risk is through SuDS, including nature-based solutions such as rain gardens, greenblue roofs and detention basins. In densely populated urban areas, where many surfaces are impermeable and natural infiltration and drainage are restricted, SuDS work by providing alternatives to channelling surface water run-off into nearby watercourses through pipes and sewers that were not designed for that volume of flow. Although the principal function of SuDS must be related to capturing rainwater close to where it falls, it can often provide multiple simultaneous blue-green infrastructure benefits that include amenity, biodiversity, filtration and improvement in water quality and attenuation.

We know that the government aims to deliver 1.5 million new homes over the next five years and intends to speed up planning approval. With this in mind, it is important not to lose sight of the critical role SuDS play as key blue-green infrastructure. Therefore they must be woven into the emerging planning reforms.

A brief history of Schedule 3

In 2007, the UK suffered severe summer floods. As a result of this, Westminster passed the Flood and Water Management Act 2010, introducing measures to reduce flood risk, which was likely being exacerbated by climate change. Lead Local Flood Authorities (LLFAs), responsible for managing local flood risk, were created. Schedule 3 of the Act established a new legal framework for the design, approval, adoption, and maintenance of SuDS in new developments across England and Wales. Its key provisions included incorporating SuDS for all new developments (above a certain size) and the creation of SuDS Approval Bodies (SAB). These SABs were to approve proposed developments and potentially adopt and maintain them if they serve multiple properties. The right to connect to a public sewer would be conditional on SAB approval.

While Schedule 3 has been implemented in Wales, it has not yet in England. Defra had set the implementation of Schedule 3 in England for 2024. However, at the time of writing this article, Schedule 3 has not been adopted, despite the scale of housebuilding the government is proposing. This leaves developers, local authorities and water companies with no clear guidance or timescale for mandatory SuDS requirements.

Policy review: Where do SuDS fit?

National Planning Policy Framework (NPPF)

The updated National Planning Policy Framework (NPPF), which sets out the government’s planning policies for England, was revised in December 2024. The revised document followed a consultation exercise that demonstrated strong evidence for changes being needed in relation to the ‘sequential test’, ‘SuDS’ and ‘natural flood management’.

Changes in the NPPF relating to SuDS and sustainable development include:

1. A clarification of SuDS terminology

The NPPF updated the SuDS definition in its glossary, to clarify that a wide range of interventions, suitable for both small and large developments, qualify as SuDS. The 2024 NPPF glossary reads as follows:

“… Sustainable Drainage System: A sustainable drainage system controls surface water run off close to where it falls, combining a mixture of built and nature-based techniques to mimic natural drainage as closely as possible, and accounting for the predicted impacts of climate change. The type of system that would be appropriate will vary from small scale interventions such as permeable paving and soakaways that can be used in very small developments to larger integrated schemes in major developments…”

2. Removal of limitations for SuDS on major developments only

The new NPPF paragraph 182 removes the limitation for SuDS to be considered only on ‘Major Developments’ and promotes the consideration of SuDS for all developments, proportionate to the scale and nature of the scheme. The new wording also stresses that SuDS should provide multiple benefits wherever possible:

“... Applications which could affect drainage on or around the site should incorporate sustainable drainage systems to control flow rates and reduce volumes of runoff, and which are proportionate to the nature and scale of the proposal. These should provide multifunctional benefits wherever possible, through facilitating improvements in water quality and biodiversity, as well as benefits for amenity. Sustainable drainage systems provided as part of proposals for major development should:

a) take account of advice from the Lead Local Flood Authority;

b) have appropriate proposed minimum operational standards; and

c) have maintenance arrangements in place to ensure an acceptable standard of operation for the lifetime of the development.”

3. Redefinition of ‘sequential test’

A sequential test in flood risk assessments directs new development to areas with the lowest flood risk. This is achieved by comparing the proposed development site with other ‘reasonably available sites’ to identify the one with the lowest risk. The goal is to avoid development in areas of high flood risk, and encourage it ideally in Flood Zone 1. The test requires developers and decision-makers to demonstrate that there are no other reasonably available sites in areas at lower risk of flooding that could accommodate the development. However, the phrase has long been criticised for being too vague and open to interpretation, leading to inconsistent application by local authorities and developers. The new NPPF adds paragraph 175, which states that a sequential test is not needed when a development is located outside areas of flood risk (Flood Zones 2 or 3). This change, however, does not remove the need for SuDS features within developments. There is a risk that the lack of a sequential test will mean some developments may proceed without sufficient assessment of how they impact natural drainage patterns or connected habitats beyond the site boundary. This could lead to fragmented or poorly integrated SuDS schemes that fail to deliver their full environmental benefits, such as flood mitigation, biodiversity support and water quality improvement.

NPPF paragraph 175 reads as follows:

“…The sequential test should be used in areas known to be at risk now or in the future from any form of flooding, except in situations where a site-specific flood risk assessment demonstrates that no built development within the site boundary, including access or escape routes, land raising or other potentially vulnerable elements, would be located on an area that would be at risk of flooding from any source, now and in the future (having regard to potential changes in flood risk)….”

A commitment to changing Flood Risk and Coastal Change Planning Practice Guidance (PPG)

In line with evolving climate data, national planning policy, and lessons from flood events, the government has pledged a commitment to update the PPG. The guidance is expected to address climate change, providing guidance on flood zones and SuDS, and include a better definition of ‘reasonably available sites’ for the sequential test.

The impact of the NPPF and PPG on the planning system

The NPPF and the PPG shape planning decisions and enforcement practices but are not enforceable in the strict legal sense. Enforcement of planning control is governed primarily by legislation, and the NPPF advises that enforcement action is discretionary, and local planning authorities should act proportionately. The NPPF supports authorities in deciding enforcement actions and informs local plans.

While the NPPF is not legally binding in the sense of being a law or regulation, it is a material consideration in planning decisions and carries significant weight. Ignoring the NPPF or PPGs can lead to a finding that a planning decision was unlawful, which has consequences. The inclusion of SuDS elements in these policies and guidance is an important step forward. In summary, the new NPPF strengthens the expectation that all developments integrate natural flood management approaches, especially through SuDS, and clarifies their multifunctional role in delivering flood resilience, biodiversity and amenity benefits.

The Water Gardens: new green roofs increase storm-water infiltration within the site and reduce the heat island effect in addition to providing food and habitat to a wide range of species.
© Refolo Landscape Architects
Little Easton: The green-blue infrastructure incorporated into a 44 residential development in Essex won several awards.
© Refolo Landscape Architects
Where else are SuDS mentioned in the current planning reforms?

As the Land Use Framework advances, and amendments to the Planning and Infrastructure Bill are debated, it remains crucial to emphasise the vital role that green and blue infrastructure play in shaping healthy, vibrant communities, benefiting people, wildlife and water alike.

The Landscape Institute’s Policy & Public Affairs Committee is actively involved in advocating for amendments that emphasise the critical role of blue and green infrastructure within planning policy. The Wildlife and Countryside Link, a coalition of environmental organisations, including the Landscape Institute, is backing one key amendment that is currently being considered as part of the Planning and Infrastructure Bill. It called on the Secretary of State to exercise powers under Schedule 3 of the Flood and Water Management Act 2010, within six months of the Act’s passage, to make SuDS mandatory for all new developments. This proposal underscores the growing consensus that there is an urgent need to embed sustainable water management at the core of development planning. The amendment wasn't accepted by the Bill Committee at the time of writing, though there may be other opportunities as it progresses to the House of Lords.

In conclusion

While SuDS are referenced throughout the NPPF, and in potential future amendments to the PPG, these policies and guidelines are not legally binding, although they exert considerable influence through shaping local plans. The enactment of Schedule 3, however, would mean that all developers and local authorities must follow the same standards, as SuDS would become mandatory. This would create a level playing field so responsible developers incorporating SuDS cannot be undercut by others who are less concerned about the negative consequences of SuDS avoidance for households and neighbourhoods. Embracing naturebased solutions wherever feasible would unlock the multiple benefits that SuDS offer; not only enhancing communities but also providing developers with more cost-effective and sustainable alternatives to traditional drainage systems.

Equally crucial is the accurate interpretation and ongoing maintenance of SuDS. The original design approved at the planning stage must be properly implemented at the construction stage. The SuDS must then be effectively maintained and clearly understood by subsequent landowners or design teams if ownership changes. Unfortunately, the original intent is frequently compromised when sections of the system are selectively modified, disrupting continuity and undermining, or even nullifying, the intended benefits. Such alterations often stem from fundamental misunderstandings of SuDS.

Finally, a phobia of SuDS due to ignorance of its multiple benefits needs to be addressed. SuDS must be demystified by education and research and positively endorsed by all sectors of the industry.

Cristina Refolo CMLI is an accredited Building with Nature Assessor and specialises in nature-based water management. She has a background in socio economic-environmental studies from the London School of Economics.
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