Writing the sequential test section inside an FRA

The sequential test flood risk assessment section is the part of an FRA that decides whether the rest of the document ever gets read. It answers one question: whether the proposed development could reasonably be located on a site with a lower probability of flooding. If it cannot be answered persuasively, the flood mitigation design in the later sections is irrelevant, because national policy directs development away from higher risk areas before it asks how risk would be managed.

The test is applied by the local planning authority, not by the applicant. What the applicant supplies is the evidence on which the authority makes that judgement, and the quality of that evidence is what separates a two week determination from a six month argument.

Why the test sits inside the assessment on many applications

Strictly the sequential test and the flood risk assessment are different things. The test is a policy exercise about location. The assessment is a technical document about risk at the site.

In practice most councils want them in one place, usually as an early section of the Flood Risk Assessment before the site-specific analysis begins, because the officer reading it needs the location question answered first. Some authorities instead ask for a standalone document, and their validation lists say so. Check before deciding the structure.

The exemptions matter here. Householder extensions, minor development and most changes of use are generally not subject to the sequential test, so an FRA for a rear extension in Flood Zone 2 does not need this section at all. Current national policy also expects all sources of flooding to be considered rather than rivers and the sea alone, which brings surface water risk into scope on sites that sit comfortably in Flood Zone 1.

Defining the area of search with the council

Agree the area of search in writing before running the test. This is the single most useful thing a consultant can do on a flood-constrained site, and it is the step most often skipped.

The default area of search is the local planning authority's administrative area. It can reasonably be narrower where the development serves a defined catchment, for example a village school, a local convenience store or an employer relocating within a settlement. It can occasionally be wider where the authority is small and the development is strategic.

Put the proposed area of search to the case officer at pre-application with a short justification, and record their response. An applicant who runs the test across a whole district and is then told the officer expected a parish-wide search has wasted the work, and an applicant who searches one parish and is told to search the district has wasted rather more.

What counts as a reasonably available site

A site is reasonably available where it is in the area of search, in a zone of lower flood probability, suitable for the type of development proposed, and available or likely to become available within a reasonable period.

The sources to work through, in the order that produces the fewest gaps:

• Allocations in the adopted local plan and any emerging plan.
• The authority's housing and economic land availability assessment.
• The brownfield land register.
• Sites with an extant planning permission that has not been implemented.
• Sites currently marketed by agents, with the listings dated and retained.
• Any site the authority itself has previously suggested.

Ownership is not the end of the argument. A site the applicant does not own can still be reasonably available if it is on the market, and an assessment that discounts everything the applicant does not already control will be rejected. What does defeat availability is a site under option to someone else, a site with a live permission being built out, or a site with a physical or legal constraint that makes the proposed development undeliverable.

Recording the sites discounted and why

This is a table, not a narrative. One row per site, with columns for the site reference or address, its source, its area, its flood zone, its surface water risk, whether it is available, whether it is suitable, and the reason for discounting.

Write the reason as a planning reason, tied to evidence. "Too small to accommodate the proposed floorspace, at 0.3 hectares against a requirement of 1.1 hectares" works. "Not suitable" does not. Where a site is discounted on availability, state the source and the date of the enquiry.

Keep the discount reasons consistent. A site discounted as too small in one row and a smaller site accepted as a comparator elsewhere is the kind of inconsistency an objector will find.

Include the sites that were considered and passed the filters, if any. An honest test that identifies one or two possible alternatives and then explains why they are not reasonably available for this development reads far better than one that finds nothing at all.

Vulnerability classification and its effect

The flood risk vulnerability classification decides how hard the test has to work. National guidance sorts development into essential infrastructure, highly vulnerable, more vulnerable, less vulnerable and water-compatible categories, and sets out which categories are compatible with which flood zones.

The classification is a matter of fact, not preference. Residential development is more vulnerable. Basement dwellings and caravan sites for permanent occupation sit in the highly vulnerable category. Shops, offices and most commercial uses are less vulnerable. Get it wrong and the whole analysis is built on the wrong test.

Mixed use schemes take the classification of the most vulnerable element, which is why a residential upper floor above a shop is assessed as more vulnerable development rather than less.

State the classification explicitly, with the reasoning, in the same section. Officers check it first.

Where the exception test follows

Where the sequential test is passed but the vulnerability classification and flood zone combination requires it, the exception test follows. Both parts have to be satisfied.

The first part asks whether the development would provide wider sustainability benefits that outweigh the flood risk. The second asks whether the development will be safe for its lifetime, taking account of climate change, without increasing flood risk elsewhere and, where possible, reducing risk overall.

The second part is answered by the technical body of the FRA: finished floor levels, compensatory storage, flood resilient construction, safe access and egress, and a flood warning and evacuation plan. The first part is a planning argument and belongs in the planning statement as much as in the assessment. Both are covered in more depth on the Exception Test page.

Presenting the conclusion

End the section with a short conclusion that an officer can lift into a committee or delegated report.

State the area of search and that it was agreed with the authority, the number of sites considered, the number discounted and the reason categories, the vulnerability classification, and a single sentence concluding that there are no reasonably available sites at lower flood risk capable of accommodating the proposed development. Where the exception test is engaged, say so and cross-refer to the sections that answer it.

Date the search and say when the source data was downloaded. Flood mapping and site availability both change, and an assessment that is silent on its own currency invites a request to redo it. Where the test is run as a separate document, the Sequential Test page sets out what a standalone version contains.

This is general guidance, not legal advice. Check the position with your local planning authority or a qualified professional before relying on it. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval. To see which flood and drainage documents a site is likely to need, enter the postcode on PlanScope.