Sequential Test

The Sequential Test, set out in paragraphs 173 to 176 of the NPPF, requires development to be steered to areas with the lowest risk of flooding from any source, taking climate change into account. Where it is not possible to locate development in low-risk areas, reasonably available sites in medium-risk areas must be considered before high-risk areas. The test applies to both major and non-major development.

The September 2025 update to Planning Practice Guidance, Paragraph 027, introduced an important refinement, which we covered in our Sequential Test update 2025 article. Where a site is at risk only from surface water flooding, and a site-specific Flood Risk Assessment demonstrates that the proposed layout, design and mitigation measures will keep occupiers and users safe from current and future surface water flood risk for the lifetime of the development, without increasing flood risk elsewhere, the Sequential Test need not be applied.

This is a meaningful change. For sites caught by the Environment Agency’s December 2024 surface water mapping update, which materially expanded the areas shown to be at surface water risk, it provides a proportionate route through. It does not, however, remove the need for rigorous evidence. The exemption is conditional on the FRA demonstrating lifetime safety, and the burden of that demonstration sits with the applicant.

The exemption applies to surface water only. Sites at risk from rivers, the sea, groundwater, reservoirs, sewers or other sources still require the Sequential Test where the development is in Flood Zone 2, 3, or otherwise caught by the policy.

A Sequential Test is required for major and non-major development where any proposed building, access or escape route, land-raising or vulnerable element will be:

• in Flood Zone 2 or 3, or in Flood Zone 3b where the development is not incompatible
• in Flood Zone 1 where the Strategic Flood Risk Assessment shows increased flood risk during the lifetime of the development
• subject to sources of flooding other than rivers or sea
• within ‘Flood Zones plus climate change’ areas at increased future risk

A Sequential Test is not required for householder development, small non-domestic extensions under 250m², or for changes of use (other than to caravan, camping, chalet, mobile home or park home sites). It also does not apply where development is on a site already allocated through the sequential test at plan-making stage and there have been no significant changes to flood risk.

Following the 2025 update, the test may also not be needed where a site is solely at risk from surface water flooding and a site-specific FRA demonstrates lifetime safety without increasing flood risk elsewhere. For new build development caught by the surface water mapping changes, this is often the most direct route to a defensible position.

The exemption is not automatic. It rests on the technical strength of the FRA, including the design of mitigation, the demonstration of safe access and egress, and the management of residual risk for the full lifetime of the development.

The Sequential Test is planning-led. The flood risk input supports it; it does not drive it.

In practice, this means the planning consultant defines the area of search, identifies reasonably available alternative sites, and constructs the policy argument. We provide the flood risk evidence that underpins it: comparative flood risk analysis across alternative sites, lifetime-safety demonstrations under the surface water exemption, and clear, proportionate FRAs that the planning consultant can rely on within their submission.

Our role is to give planning consultants confidence that the flood risk position will hold up to scrutiny from the local planning authority and the Environment Agency. That includes being honest about where a Sequential Test argument is weak and where a different approach, such as relying on the surface water exemption, or revisiting the development boundary, is more likely to succeed.

We work regularly with planning consultants on contentious sites where the flood risk evidence base needs to be technically robust and defensible from the outset. Early engagement matters: scoping the flood risk position before the planning argument is fixed avoids the rework that follows when the two are developed in isolation.