Changes to Planning Practice Guidance on Flood Risk & Coastal Change | September 2025 Update
In September 2025 (17.09.2025), the Government updated key parts of the Planning Practice Guidance (PPG) on flood risk and coastal change. These updates affect how the sequential approach and sequential test must be applied in planning applications and local plans.
For developers and landowners, the changes provide some helpful clarifications. But they also create new challenges and raise questions about how consistently the policy will be applied. Below we set out the changes, what they mean in practice, and how our consultants see the positives and limitations.
Key takeaways
- Changes have been made to paragraphs 23, 27 and 28 with the addition of 27a (now its own separate paragraph)
- A robust site-specific flood risk assessment can sometimes remove the need to apply the sequential test (paragraph 27).
- New guidance on defining the area of search ensures proportionality and context-specific application (paragraph 27a).
- A “reasonably available” site can include land outside the applicant’s control or even multiple smaller sites (paragraph 28).
Paragraph 23: The aim of the sequential approach
Paragraph: 023 Reference ID: 7-023-20220825
Overview
This paragraph explains the purpose of the sequential approach: to prioritise development in areas at little or no risk of flooding. It emphasises steering development away from current and future flood risk areas, covering all sources of flooding (river, coastal, and surface water). It also underlines that the sequential approach is the most effective way of managing flood risk.
What has changed?
The changes to Paragraph 23 are the removal of the sentence “Even where a flood risk assessment shows the development can be made safe throughout its lifetime without increasing risk elsewhere, the sequential test still needs to be satisfied.”
What this means
Developers and decision-makers need to demonstrate that they have factored in both present and projected flood risks across all sources. This aligns with the growing emphasis on climate change impacts and the need for consistent risk assessment. It also means proposals in areas at risk of surface water flooding will be subject to the same level of scrutiny as those in tidal or fluvial zones.
Paragraph 27: How should the sequential test be applied to planning applications?
Paragraph: 027 Reference ID: 7-027-20220825
Overview
Paragraph 27 sets out when and how the sequential test should be applied to planning applications. It confirms that both “major” and “non-major” developments in flood risk areas are subject to the test, with exemptions listed in the NPPF. It also provides guidance on proportionality and the role of site-specific Flood Risk Assessments (FRAs).
What has changed?
Where a site-specific FRA can clearly demonstrate that design, layout, and mitigation would keep future occupiers safe from surface water flood risk without increasing risk elsewhere, the sequential test does not need to be applied.
“In applying paragraph 175 [of the NPPF] a proportionate approach should be taken. Where a site-specific flood risk assessment demonstrates clearly that the proposed layout, design, and mitigation measures would ensure that occupiers and users would remain safe from current and future surface water flood risk for the lifetime of the development (therefore addressing the risks identified e.g. by Environment Agency flood risk mapping), without increasing flood risk elsewhere, then the sequential test need not be applied”
It also confirms that the absence of a 5-year housing land supply is not a relevant consideration in applying the sequential test for individual applications. However, housing considerations, including housing land supply, may be relevant in the planning balance, alongside the outcome of the sequential test.
What this means
For sites at risk of surface water flooding, there is now an opportunity to unlock development. What is unclear is that this only appears to apply to surface water flooding. Sites at risk of fluvial or tidal flooding do not benefit from the same opportunity, even though paragraph 23 requires all sources to be treated consistently. This inconsistency is likely to be contested or likely to be updated in due course. It is recognised that fluvial flooding can be mitigated through exercises such as flood compensation but this does not appear to have carried through like surface water has. We further recognise that the sequential approach could negate the need for the test on sites of fluvial and tidal risk alongside surface water.
Paragraph 27a: How should the area of search for the sequential test be identified?
Paragraph: 027a Reference ID: 7-027a-20220825
Overview
This brand-new paragraph provides detailed guidance on how to define the area of search when applying the sequential test to individual planning applications. It recognises that this varies depending on the type, scale, and location of development.
“For a non-major housing development, it would not usually be appropriate for the area of search to extend beyond the specific area of a town or city in which the proposal is located, or beyond an individual village and its immediate neighbouring settlements.”
“Major development” is defined by the Town and Country Planning (Development Management Procedure) (England) Order 2015 (Article 2).
‘Non major development’ is any development falling below the above thresholds but excluding minor development. For example, a planning application for 8 dwellings an office building creating 750 square metres of floor space, or a development with a site area of 0.4 hectares. Paragraph: 051 Reference ID: 7-051-20220825
What’s changed?
This is an entirely new section, which clarifies that:
- The area of search should relate to the catchment and needs of the development.
- For small-scale housing, the area of search is usually limited to the town, city, or village where the proposal is located.
- A pragmatic approach should be taken for small extensions to existing buildings or where flood risk is widespread (e.g. coastal towns, river valleys).
- For infrastructure of regional/national importance, the area of search may extend beyond local authority boundaries.
- Large-scale developments may sometimes be split across alternative lower-risk sites, but only if those sites still serve the intended market effectively.
What this means
The introduction of paragraph 27a brings much-needed clarity. Developers can now better understand how wide their search for alternative sites needs to be. LPAs are given flexibility to apply proportionality, especially in locations where avoiding flood risk altogether is not realistic. For applicants, this means site justifications must be tailored to the nature of the proposal, with evidence that the chosen search area is appropriate. Even with the clarity, Aegaea would advise early engagement with the LPA and case officer where possible.
Paragraph 28: What is a ‘reasonably available’ site?
Paragraph: 028 Reference ID: 7-028-20220825
Overview
This paragraph defines what makes a site “reasonably available” in the context of the sequential test. To qualify, an alternative site must be suitable for the type of development proposed, meet the same needs, and be realistically deliverable in the same timeframe.
What has changed?
The September 2025 update reinforces and clarifies the earlier guidance rather than introducing new principles. Key points include:
- Ownership is irrelevant – alternative sites do not need to be owned by the applicant to be considered reasonably available.
- Multiple sites – in some cases, a proposal could be accommodated across several smaller sites, provided they collectively meet the development need.
- Deliverability and timing – the update places greater emphasis on whether alternative sites could realistically be promoted and developed in line with the same aspirations and timeframe as the site under consideration.
What this means
Whilst in some circumstances an alternative site may be better suited on paper, it may still not be considered reasonably available should it not accommodate the same needs (size, units, massing, benefits to the existing area – remembering the sequential test isn’t just for residential development) or meet the same timescales as the site under consideration.
The Good, the Bad and the Ugly
Good
Developments at risk of surface water flooding may now avoid the sequential test if an FRA proves they can be made safe. This creates more flexibility and recognises the role of post-development mitigation.
Bad
This flexibility does not extend to fluvial or tidal flood risk. Paragraph 23 requires all sources to be considered consistently, yet paragraph 27 only allows FRAs to bypass the test for surface water. With large areas of England in fluvial flood zones and a pressing need for housing, this feels like a missed opportunity.
Ugly
Disputes are likely to continue. Local authorities and developers will face challenges over how far this new guidance can be applied to other sources of flooding. Until the policy is clarified, sites in fluvial zones may remain stalled even when mitigation could provide safe solutions. This inconsistency is likely to be contested or likely to be updated in due course. It is recognised that fluvial flooding can be mitigated through exercises such as flood compensation, but this does not appear to have been carried through like surface water has. We further recognise that the sequential approach could negate the need for the sequential test on sites of fluvial and tidal risk alongside surface water. An approach we promote regularly, where possible.
The importance of modelling
With the new emphasis on future risk and site-specific mitigation, high quality modelling will be essential. In particular:
- Direct rainfall modelling will become more important to capture how development changes surface water flows.
- Drainage systems and their capacity will need to be fully assessed within FRAs.
- Post-development impacts will need to be demonstrated in more detail to show occupiers can remain safe and flood risk will not increase elsewhere.
At Aegaea we have a dedicated team of modellers who specialise in these types of assessments. By combining detailed hydraulic modelling with planning policy expertise, we can help you unlock sites that might otherwise stall under the sequential test.
Changes in practice
Whilst these changes are new, Aegaea have been applying this approach for several months with success in securing planning permission for developments, even following initial refusal.
Case Study: Permission Secured After Successful Appeal in Petersfield
Aegaea provided a detailed Flood Risk Assessment (FRA) and SuDS drainage strategy to support an outline planning application for a hotel and cycle centre near Petersfield. Following refusal by the South Downs National Park Authority (SDNPA), our ongoing technical input was instrumental in securing planning permission at appeal.
Case Study: Sequential Test Not Required for Zone 2 Flood Risk Assessment in Lewisham
We recently worked alongside the team at Maddox Planning and AAVA Architecture on behalf of Land Development Property Group Ltd to offer our flood risk consultation services for their Weardale Road, Lewisham project. After completing the construction of 14 flats, Land Development Property Group Ltd retained a parcel of land at the end of the plot, which included an existing garage.
When they sought a pre-application response from the local authority, they were informed that because the site is located within Flood Zone 2, a Sequential Test would be required, which would almost certainly result in planning permission being refused.
After considering the Flood Risk Assessment, which identified flooding risk to the site from all sources, the local authority agreed that the site was low risk for flooding and did not require a Sequential Test. Planning approval was subsequently granted.
How Aegaea can help
The updated guidance makes the sequential test more complex but also more open to site-specific evidence. To avoid wasted time and cost, it is essential to get the technical and planning case right from the outset.
At Aegaea, we provide:
- Sequential test strategies that stand up to scrutiny
- Flood Risk Assessments supported by advanced modelling
- Drainage and surface water solutions that unlock development potential
If you are promoting or submitting a site in an area of flood risk, speak to us today about how these changes could affect your plans.
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