Sequential Test (Flood)
The Sequential Test is a policy mechanism that steers new development away from areas at highest risk of flooding. If your site falls within Flood Zone 2 or 3, the local planning authority must be satisfied that the Sequential Test has been passed before granting planning permission. It is deceptively simple in concept but frequently misunderstood in practice.
Typical Cost
£300 – £5,000+
Turnaround
1 – 6 weeks
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What is a Sequential Test (Flood)?
The Sequential Test requires the decision-maker to consider whether there are reasonably available sites at lower flood risk that could accommodate the proposed development. The principle is straightforward: development should be directed to areas with the lowest probability of flooding. Only where there are no reasonably available alternative sites should development in areas at higher flood risk be considered. The Sequential Test is set out in paragraphs 161-165 of the NPPF and the accompanying Planning Practice Guidance on Flood Risk and Coastal Change.
When is a Sequential Test (Flood) required?
The Sequential Test applies to all planning applications for development in Flood Zone 2 (medium probability of flooding) and Flood Zone 3 (high probability). There are limited exceptions: it is not required for minor development (householder applications), changes of use, or development that is allocated in the local plan through a Sequential Test that has already been applied at the plan-making stage. For all other applications in Flood Zones 2 and 3, the applicant must demonstrate that the Sequential Test is passed, either by agreement with the local authority or through submission of a Sequential Test report.
What does a Sequential Test (Flood) include?
A Sequential Test report identifies the type of development proposed and the flood risk context of the application site, defines an appropriate search area for alternative sites (agreed with the local authority), identifies and assesses reasonably available sites within that search area that are at lower flood risk, evaluates whether those alternative sites are suitable and available for the proposed development, and concludes whether the Sequential Test is passed. The report must present a transparent and evidence-based analysis — simply asserting that no alternatives exist will not suffice.
How much does a Sequential Test (Flood) cost?
A Sequential Test report is relatively inexpensive to prepare, typically costing between £500 and £1,500. The main cost is the professional time spent identifying and assessing alternative sites. For straightforward cases where the search area is limited and few alternatives exist, the cost will be at the lower end. More complex cases — particularly where the search area is large, the development type could theoretically locate anywhere, or the authority challenges the applicant's approach — can cost more. The report is usually prepared by a planning consultant rather than a flood risk specialist.
Who can prepare a Sequential Test (Flood)?
Sequential Test reports are typically prepared by planning consultants who understand the NPPF policy framework and the flood risk sequential approach. The report does not require specialist hydrological expertise — that is the role of the Flood Risk Assessment. However, the planning consultant must be able to define an appropriate search area, identify alternative sites using planning databases and land availability assessments, and construct a robust argument for why the test is passed. RTPI members with planning policy experience are best placed to prepare these reports.
How long does a Sequential Test (Flood) take?
A Sequential Test report can usually be prepared within 1 to 2 weeks. However, agreeing the search area and methodology with the local planning authority should ideally be done at the pre-application stage, which may take several weeks of correspondence. The key constraint is often the local authority's capacity to engage on the Sequential Test methodology before submission, rather than the time needed to prepare the report itself.
Frequently Asked Questions
What is the Sequential Test for flood risk?
The Sequential Test is a policy requirement in the NPPF that directs new development to areas with the lowest probability of flooding. Before granting planning permission for development in Flood Zones 2 or 3, the planning authority must be satisfied that there are no reasonably available sites at lower flood risk where the development could be located. It is applied sequentially — Flood Zone 1 is preferred over Flood Zone 2, which is preferred over Flood Zone 3.
How do I define the search area for alternative sites?
The search area should reflect the catchment area within which the development could reasonably be expected to locate. For a local housing need, this might be the parish or the local planning authority area. For a regional facility or commercial development serving a specific catchment, it might be broader. The search area should be agreed with the local planning authority, ideally at the pre-application stage. An inappropriately narrow search area will be challenged, but equally the area should not be so wide as to be impractical.
Does the Sequential Test apply to householder applications?
No. The Sequential Test does not apply to minor development, including householder applications such as extensions, loft conversions, and outbuildings. It also does not apply to changes of use (except to a more vulnerable use). A Flood Risk Assessment will still be needed for householder applications in Flood Zone 2 or 3, but the Sequential Test itself is not required. This exemption recognises that homeowners cannot reasonably be expected to relocate to an alternative site.
What makes a site 'reasonably available'?
A site is reasonably available if it is suitable for the proposed development, is available for development, and could accommodate the development within a reasonable timescale. Sites that are allocated in the local plan for other uses, have unresolvable planning constraints, are not on the market, or are otherwise not deliverable would not normally be considered reasonably available. The assessment should be proportionate and evidence-based, drawing on the council's Strategic Housing Land Availability Assessment or equivalent.
Can the Sequential Test be applied at the plan-making stage?
Yes, and this is the most efficient approach. When sites are allocated for development in the local plan, the council should apply the Sequential Test as part of the site selection process. Where a site has been allocated through a plan-level Sequential Test, the applicant does not need to repeat the exercise at the application stage. However, this only applies if the Sequential Test was applied at plan-making and the development proposed is consistent with the allocation.
What happens if the Sequential Test is not passed?
If the Sequential Test is not passed — meaning there are reasonably available alternative sites at lower flood risk — the planning authority should refuse permission, unless there are other material considerations that outweigh the flood risk concern. In practice, failing the Sequential Test is a very difficult obstacle to overcome, as the NPPF places strong emphasis on directing development away from flood risk areas. This is distinct from the Exception Test, which is a further hurdle applied to certain types of development that pass the Sequential Test.
Do I need both a Sequential Test and an Exception Test?
Not necessarily. The Sequential Test must be passed first. If it is passed, certain types of development in Flood Zone 3 (and some in Flood Zone 2) must also pass the Exception Test, depending on the vulnerability classification of the proposed use. For example, 'more vulnerable' uses such as housing in Flood Zone 3a must pass both tests. 'Less vulnerable' uses such as offices in Flood Zone 3a need the Sequential Test but not the Exception Test. The flood risk vulnerability classification tables in Planning Practice Guidance set out which combinations require the Exception Test.
Can I include brownfield status as a factor in the Sequential Test?
The brownfield or greenfield status of the application site is not a factor in the Sequential Test itself — the test is purely about flood risk. However, if alternative sites are all greenfield while the application site is brownfield, this can be a relevant material consideration in the overall planning balance. Some authorities also give weight to the regeneration benefits of developing brownfield sites in the wider decision, even where flood risk is a consideration.
What evidence do I need for the Sequential Test?
You need to demonstrate a systematic search for alternative sites. Evidence typically includes a clearly defined search area agreed with the council, identification of available land using the council's housing land supply data, Strategic Housing and Economic Land Availability Assessment, and commercial property databases, an assessment of each alternative site's flood zone status, suitability, and availability, and a clear conclusion explaining why the application site is the only reasonably available option.
How does the Sequential Test work for self-build or custom build?
The Sequential Test applies to self-build and custom build plots in the same way as any other residential development. However, the personal circumstances of the applicant — such as existing land ownership or family connections to the area — may narrow the scope of the reasonable search area. Some councils accept that a self-builder who already owns a plot has a more limited range of alternatives than a volume housebuilder, though this is not universally accepted and should be discussed at pre-application stage.