The flood sequential test at application stage
The sequential test is a gateway, not a balance. Most failures trace back to an area of search the council never agreed, or a schedule with no dates.
The sequential test at application stage asks one question: are there reasonably available sites, appropriate for the proposed development, in areas at lower risk of flooding. If the answer is yes, the application should be refused, whatever the merits of the site. It is a gateway rather than a balancing exercise, and it fails more applications than the technical flood work ever does, usually because the applicant defined the area of search to suit the site rather than agreeing it with the authority first.
The test now considers flooding from all sources, not just rivers and the sea, which has widened it considerably.
When the test applies
The national flood risk policy applies the sequential test to development in areas at risk of flooding. Guidance sets out the situations where it need not be applied, and the ones that matter in practice are minor development, householder extensions, and changes of use, with the exception of changes of use to caravan, camping, chalet, mobile home or park home sites.
Two points catch consultants out.
First, a site in Flood Zone 1 is not automatically exempt. Where the site is at risk from surface water, groundwater, sewers or reservoirs, the authority can and increasingly does require the test, because the policy is now framed around risk from any source.
Second, a change of use exemption does not carry with it an exemption from the flood risk assessment or from the vulnerability classification, which can move even when nothing is built. That interaction is covered in our note on flood risk and change of use applications.
Where the test does apply and the development is more vulnerable in a higher risk zone, the Exception Test follows it. The two are separate exercises and passing one says nothing about the other.
Agreeing the area of search
This is the step that decides the outcome, and it should happen before any site is assessed.
Guidance expects the area of search to be agreed with the local planning authority. The logical basis depends on the development. For open market housing it is usually the local authority area or the housing market area. For a school or a health facility it is the catchment the facility serves. For employment it may be a functional economic area. For a proposal tied to a specific operational need, such as an extension to an existing business, the area can be narrower, but the justification has to be about the development rather than about the applicant's landholding.
Put the proposed area of search in writing at pre-application, with the reasoning, and ask the case officer to confirm it. A short email confirming the area is worth more at determination than twenty pages of site assessment carried out against an area the council never accepted.
Where the authority will not engage, state clearly in the submission what area you adopted and why, and show that you tested a wider area as a sensitivity check.
Identifying reasonably available sites
Reasonably available means available now or within a reasonable timeframe, and appropriate for the proposed development. The sources a council expects you to have searched are consistent.
- Site allocations in the adopted local plan and in any emerging plan that has reached a material stage.
- The strategic housing or economic land availability assessment.
- The brownfield land register, both parts.
- Sites with extant planning permission that have not been implemented.
- Sites publicly marketed for sale or to let at the time of the search.
- Any call for sites responses the council has published.
Record the date you ran each search. Flood searches and site availability both move, and an undated schedule invites a request to redo it.
Appropriate does not mean identical. A site does not become inappropriate because it is 10 per cent smaller or because the applicant does not own it. It does become inappropriate where it could not accommodate the development in a form that delivers the same function, and that judgement has to be explained rather than asserted.
Comparing sites on risk from all sources
For each candidate site, set out the flood zone, the surface water risk, and any other source that applies, with the source and date of each check. Then compare.
| Comparison | What it means for the test |
|---|---|
| Candidate wholly in Zone 1 with low surface water risk | Lower risk than a Zone 3 application site, so it must be properly discounted or the test fails |
| Candidate in Zone 1 with high surface water risk | May not be at lower overall risk, and the assessment should say so with evidence |
| Candidate partly in Zone 2 | Compare the developable area, not the whole site, and show the constraint on a plan |
| Candidate in the same zone as the application site | Not at lower risk, so it does not defeat the test, but say so rather than omitting it |
Do not reduce this to a single colour-coded column. A consultee reading the schedule needs to see which dataset produced each conclusion.
Recording why a site was discounted
Every discounted site needs a stated reason and evidence for it. The reasons that hold up are that the site is not available, that it is not of a size or configuration that could accommodate the development, that it is subject to a constraint that rules it out, or that it is not deliverable within a reasonable timeframe.
The reasons that do not hold up: the applicant does not own it, the applicant could not afford it, the landowner has not offered it without any enquiry having been made, or the scheme would be less profitable there. Viability on its own is not a basis for discounting a site in this test, and saying so plainly is better than dressing it up.
Where a site has been discounted because the owner will not sell, evidence the enquiry. An undated assertion that a landowner is unwilling carries no weight.
Where an allocation does the work
If the site is allocated in the development plan and the sequential test was applied at plan-making stage to that allocation, the application-stage test does not need to be repeated for the principle of development.
Check what the allocation actually covers. An allocation for 50 homes does not carry a sequential test for a 150-home scheme on the same land, and an allocation for employment does not carry one for residential. Where the proposal differs materially from what was tested, the test comes back.
Cite the plan, the policy number and the evidence base document that records the test. Officers appreciate being told where to look.
Why tests get rejected
An area of search drawn around the applicant's landholding. A schedule with no dates. Discounting on viability. Ignoring surface water. Comparing the application site against sites the authority does not accept as reasonable alternatives, while omitting the ones it does. Treating the test as a commentary rather than as a schedule of sites with reasons.
There is one more, subtler failure: passing the sequential test and then presenting the flood risk assessment as though it also answers the test. They answer different questions. A site can be made safe and still fail the sequential test, and a betterment argument does not substitute for it, as our note on flood risk betterment explains.
Presenting it in the submission
Produce it as a standalone document rather than a section buried in the planning statement. Include the agreed area of search with a plan, the date and source of every search, the schedule of sites with the risk information and the reason for discounting each, the conclusion, and any correspondence confirming the area of search.
Keep it to the point. A Sequential Test that runs to fifteen pages of policy recital and two pages of site assessment is the wrong way round.
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Frequently asked questions
Does the sequential test apply to a site in Flood Zone 1?
It can. National guidance frames the test around risk from any source, so a Zone 1 site with high surface water, groundwater or sewer flood risk may still need one. Check the authority's strategic flood risk assessment and its validation list, and ask the case officer rather than assuming Zone 1 means exempt.
Who decides the area of search?
It should be agreed with the local planning authority before sites are assessed. The basis depends on the development: the housing market area for open market housing, the catchment for a school or health facility, a functional economic area for employment. Get confirmation in writing at pre-application stage.
Can I discount a site because I do not own it?
No. Ownership is not a reason a site stops being reasonably available. Nor is affordability or lower profitability. Acceptable reasons are that the site is unavailable in fact, cannot accommodate the development, is ruled out by another constraint, or is not deliverable within a reasonable timeframe, each with evidence.
Is a site allocation enough to avoid the test?
Where the sequential test was applied to that allocation at plan-making stage, the application-stage test does not need repeating for the principle of development. Check what was actually tested. A different scale or a different land use from the allocation brings the test back, so cite the policy and the evidence base document.
Is the sequential test the same as the exception test?
No. The sequential test asks whether lower risk sites are reasonably available. The exception test, which applies afterwards in defined circumstances, asks whether wider sustainability benefits outweigh flood risk and whether the development will be safe for its lifetime. Passing one says nothing about the other.
Sources and further reading
This article is general guidance about the planning system in England and, where stated, the rest of the UK. It is not legal or professional advice. Check your local planning authority’s validation requirements and take professional advice for your specific site.