What Is a Flood Risk Sequential Test? (And When Do You Need One?)

What the Sequential Test is for

The Sequential Test is the national planning policy mechanism for steering new development away from flood risk. It is set out in Chapter 18 of the National Planning Policy Framework (Policy F5) and explained in the Planning Practice Guidance on flood risk and coastal change.

The question it asks is simple: are there reasonably available sites, appropriate for the proposed development, in areas at a lower risk of flooding than the application site? If there are, the development should not be permitted on the higher-risk site. The test comes before any consideration of flood defences or mitigation. Good design cannot make up for choosing a higher-risk site when a lower-risk one was available.

When do you need a Sequential Test?

In practice, councils ask for a Sequential Test when development is proposed in Flood Zone 2 (medium probability) or Flood Zone 3 (high probability) on the Environment Agency's Flood Map for Planning. The policy applies to flood risk from all sources, so it can also be relevant where a site in Flood Zone 1 is at risk from surface water or other sources now or in the future.

There are important exceptions:

• Minor development and most changes of useNational policy exempts some minor development and most changes of use from the Sequential and Exception Tests, although a site-specific flood risk assessment is still needed. Changes of use to caravan, camping or chalet sites and to mobile or park homes are not exempt.
• Sites allocated in the local planWhere a site has been allocated in the development plan and the Sequential Test was applied at plan-making stage, it usually does not need to be repeated for a proposal consistent with that allocation, unless circumstances have changed.
• Development that is not sensitive to floodingWater-compatible development and some essential infrastructure are treated differently. The vulnerability classification in NPPF Annex F determines what applies.

Defining the area of search

The area of search is the area within which alternative sites are looked for. National policy is clear that it should reflect the catchment for the type of development and the need it is meeting. It should not be drawn so widely that it becomes meaningless, or so narrowly that no alternatives could ever exist.

For general housing, the whole local planning authority area is often the starting point. For development meeting a specific local need, such as a neighbourhood shop, a school extension or housing for a particular settlement, a narrower area can be justified. Whatever you choose, explain why. An unjustified area of search is one of the most common reasons councils reject a Sequential Test.

What counts as a “reasonably available” site?

A site is reasonably available if it is in a suitable location for the type of development and there is a reasonable prospect of it being available when needed. Current guidance makes several points that catch applicants out:

• Ownership is not the testA site does not have to be owned or controlled by the applicant to be reasonably available. Dismissing alternatives simply because you do not own them will not satisfy the council.
• Evidence mattersSources such as local plan allocations, the council's land availability assessment (SHLAA or HELAA) and brownfield land registers are the usual starting point. Where a site is discounted, give the reason and the evidence.
• Combinations and smaller sitesGuidance recognises that a combination of smaller sites could sometimes accommodate the development. These possibilities should be considered rather than ignored.
• Lower-risk parts of the same siteIf part of your site is at lower risk, the sequential approach also applies within the site: the most vulnerable uses should be placed in the lowest-risk areas.

The Exception Test

Passing the Sequential Test is not always the end of the matter. Depending on the flood zone and the vulnerability of the development (NPPF Annex F, Table 3), the Exception Test (Policy F6) may also be required. For example, it applies to more vulnerable development such as housing in Flood Zone 3a.

To pass the Exception Test, you must show both that the development will provide wider sustainability benefits to the community that outweigh the flood risk, and that it will be safe for its lifetime, taking account of the vulnerability of its users, without increasing flood risk elsewhere and, where possible, reducing flood risk overall. The second part relies on a site-specific flood risk assessment.

Why Sequential Tests fail

• No justified area of searchAn area drawn tightly around the site with no explanation.
• Alternatives dismissed without evidenceSites ruled out because the applicant doesn't own them, or with no evidence about availability.
• Missing obvious sourcesIgnoring the council's own allocations, land availability assessment or brownfield register.
• Wrong flood zone or vulnerabilityUsing out-of-date flood mapping, or the wrong vulnerability class for the use.
• Confusing the testsRelying on flood defences or mitigation to pass the Sequential Test, when those belong to the flood risk assessment and Exception Test.

Getting it done quickly

A Sequential Test is often the item holding up validation. If your site is in Bristol, our fixed-fee Bristol Sequential Test service produces a submission-ready report from Environment Agency and Bristol City Council data within 24 hours of payment. See also our guide to the Sequential Test for Bristol planning applications.

The same fixed-fee service covers Manchester, Birmingham, Chelmsford, Gateshead, Tameside, Runnymede, East Riding of Yorkshire, Wigan, York, Spelthorne, Oxford, Plymouth, Lichfield, Dover, Hull, Medway, Lewes District and Northumberland, each with a local guide to what the council expects. See all the council areas we cover.

For sites elsewhere, or where flood risk is one of several issues, our pre-application advice service can set out the flood risk strategy before you commit to an application. If you are not sure what else your application needs, try our free planning validation checklist.

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