26.10.2026
DHA’s in-house Flood Risk Assessment engineers, Chris Smoker and James Marsh, explain what the August 2026 NPPF changes mean in practice for developers, landowners and planning applications.
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Flood risk has long been an important consideration when assessing the suitability of land for development. However, changes introduced through the August 2026 National Planning Policy Framework (NPPF) provide greater clarity around when the Sequential Test is required and, importantly, introduce a more proportionate approach for certain sites affected solely by surface-water flooding.
The changes form part of a wider restructuring of national flood-risk policy. Flood risk and coastal change are now addressed through a dedicated suite of policies, F1-F9, within Chapter 18 of the NPPF. The overarching objective remains clear: development should be steered away from areas at risk where possible and, where development does take place, it should be safe for its lifetime without increasing flood risk elsewhere.
The Sequential Test is intended to steer new development towards areas with the lowest risk of flooding. Where the test applies, the principle is that development should not be located in an area at risk of flooding if an appropriate and reasonably available alternative site exists in an area at lower risk.
Crucially, the Sequential Test is concerned with flood risk from all sources, rather than simply flooding from rivers and the sea.
For some development proposals, this has historically created difficulties where only a relatively small part of an otherwise suitable site is shown as being at risk of surface-water flooding.
“One of the most significant changes relates to sites affected by surface-water flooding,” explains Chris Smoker, who leads DHA’s Infrastructure team. “Previously, even a relatively small area of mapped surface-water risk could trigger the need for a Sequential Test. This could require an applicant to demonstrate that there were no reasonably available alternative sites in areas at lower risk.”
The revised NPPF provides an important new route for sites where surface water is the only source of flood risk.
Under Policy F5, the Sequential Test does not need to be applied in specified circumstances where a site is at risk solely from surface-water flooding and the proposed layout, design and mitigation can demonstrate that occupiers and users will remain safe from current and future surface-water flood risk throughout the lifetime of the development, without increasing flood risk elsewhere.
Chris’s view is that this introduces a more proportionate approach.
“Where surface water is the only source of flood risk, a Sequential Test may not be required if a site-specific Flood Risk Assessment clearly demonstrates that the development’s layout, design and mitigation will keep people safe throughout its lifetime without increasing flood risk elsewhere. Although this approach had already emerged through updated Planning Practice Guidance, its inclusion within the NPPF provides welcome clarity and gives it greater policy weight.”
The practical significance is that a modest area of surface-water risk need not necessarily lead to a search for alternative development sites. Instead, greater emphasis can be placed on whether the flood risk can be understood, managed and appropriately addressed through the design of the development itself. This could be particularly important for otherwise sustainable and suitable development sites where surface-water constraints are relatively localised.
The revised approach also provides greater clarity about the geographical extent of the Sequential Test where it is required.
Policy F5 now states that the area over which alternative sites are considered should not be greater than the anticipated catchment of the development in terms of its likely occupiers or users. This is an important clarification because the previous framework did not expressly define how geographically extensive the search for alternative sites should be.
James Marsh, an Associate in DHA’s Infrastructure team, believes this should help avoid unnecessarily wide or unrealistic searches for alternative sites.
For developers, this means that the scope of a Sequential Test should have a logical relationship with the development being proposed and the market or community it is intended to serve, rather than defaulting automatically to an extensive administrative search area.
However, James stresses that the Sequential Test has not been removed.
“It still applies to flooding from all sources, while the new exemption is limited to sites affected solely by surface water. Where river, tidal, groundwater or another source of flooding is involved, a Sequential Test is still likely to be required.”
The change should therefore not be interpreted as a general relaxation of flood-risk policy. Rather, it provides a more targeted route for dealing with sites where surface-water flooding is the sole source of risk.
Indeed, the new policy framework arguably makes early assessment even more important. A site being located within Flood Zone 1 does not, by itself, mean that detailed flood-risk work can be discounted. Other sources of present or future flood risk may still need to be considered, and Policy F4 establishes the circumstances in which a site-specific Flood Risk Assessment is required.
The greater flexibility for certain surface-water sites comes with a corresponding need for robust technical evidence.
Where an applicant seeks to rely on the new approach, it will be important for the Flood Risk Assessment to do more than simply identify the mapped extent of flooding. The assessment needs to demonstrate how risk has influenced the design and how people and property will remain safe over the development’s lifetime.
Depending on the site, this could include consideration of:
This reflects the broader objective of the revised NPPF Chapter 18, which is not simply to classify flood risk but to ensure that development is safe for its lifetime, does not increase risk elsewhere and incorporates sustainable drainage where appropriate.
The revised NPPF does not just change the approach to the Sequential Test. It also places greater emphasis on how surface water should be managed through the design of new development.
Policy F8 states that development proposals which could affect drainage on or around a site should incorporate Sustainable Drainage Systems (SuDS) to control the rate and reduce the volume of surface-water runoff. Importantly, the policy looks beyond their purely drainage function, encouraging SuDS to provide wider benefits for water quality, biodiversity and amenity wherever possible.
The revised NPPF also explicitly requires SuDS to be designed in accordance with the National Standards for Sustainable Drainage Systems, published by Defra in June 2025. The standards cover seven key areas, including runoff destinations, management of everyday and extreme rainfall, water quality, amenity, biodiversity and the design of drainage for long-term operation and maintenance.
This means that drainage strategies increasingly need to demonstrate more than simply where surface water will go. The aim should be to manage rainfall as part of an integrated site-wide strategy which considers flood risk alongside landscape, ecology, biodiversity and placemaking.
The NPPF also makes clear that suitable maintenance arrangements should be established to ensure that SuDS continue to operate to an acceptable standard throughout the anticipated lifetime of the development. For major development, proposals should also take account of advice from the relevant Lead Local Flood Authority.
For development teams, this reinforces the importance of considering drainage at the outset of the design process. Features such as attenuation basins, swales, rain gardens, permeable paving and other measures can potentially be integrated into the landscape and public realm, rather than being treated simply as engineering infrastructure accommodated once a layout has already been established.
This stronger emphasis on multifunctional SuDS also complements the wider message running through the revised flood-risk policies: flood risk and drainage should inform the design of development from the beginning, rather than being addressed retrospectively.
Potentially, yes.
Sites should still undergo appropriate flood-risk screening at an early stage, but the changes may provide a clearer pathway for sites where relatively localised surface-water flooding had previously triggered a disproportionately extensive Sequential Test exercise.
For landowners and developers considering the potential of a site, the important first step is therefore to understand the source and nature of the flood risk, rather than looking only at its Flood Zone designation.
Chris believes that the revised approach could help unlock sites previously constrained by relatively limited surface-water flooding.
“The key is to consider flood risk early and use the technical evidence to inform the layout—not simply address it once the design has already been fixed.”
That point is particularly important. Early flood-risk advice can influence where buildings are positioned, where access is provided, how finished levels are established and how drainage and landscape infrastructure are incorporated into a scheme. Addressing these issues during initial feasibility and concept design can help avoid costly redesign later in the planning process.
The revised NPPF should therefore be seen as an opportunity for a more proportionate, evidence-led approach, rather than a weakening of the importance given to flood risk.
For sites affected solely by surface-water flooding, the changes may provide greater flexibility where technical evidence can demonstrate a safe and sustainable solution. For sites affected by other sources of flooding, the Sequential Test remains an important component of the planning process.
Either way, the message for development teams is the same: understand flood risk early and allow the evidence to inform the scheme from the outset.
DHA’s in-house Flood Risk Assessment engineers can support projects from initial site appraisal and flood-risk screening through to detailed Flood Risk Assessments, Sequential Test advice and drainage strategies. Working alongside DHA’s planning and design teams, early technical input can help identify constraints, establish the appropriate planning strategy and shape a development that responds positively to flood risk from the outset.
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