Sequential test search areas and how to define one

The flood sequential test search area is agreed, not assumed, and it is the part of the test most often got wrong. National planning practice guidance expects the area of search to reflect the nature of the development, which for most proposals means the local planning authority's administrative area, narrowed to a settlement or a defined locality where the development serves that locality. What it never means is the land the applicant happens to own.

Agree the area with the case officer in writing before you start searching. A search over the wrong area is wasted work, and an inspector will say so.

What the sequential test asks

The test directs development towards areas at the lowest risk of flooding. Where there are no reasonably available sites in Flood Zone 1, the search moves to Flood Zone 2, and only then to Flood Zone 3.

Since the December 2024 revision of the National Planning Policy Framework the test has considered flood risk from all sources rather than rivers and the sea alone, so surface water, groundwater, sewers and reservoirs all count. The current edition, published on 17 August 2026, uses policy codes in place of paragraph numbers, so take the code from the published Framework rather than from an older document.

Two things the test is not. It is not a viability test, so the applicant's commercial preference for a particular site carries no weight. And it is not satisfied by showing that the proposed site is suitable, because the question is whether a site at lower risk is reasonably available.

Where the test is passed, a sequential approach still applies within the site itself. Put the built development, and particularly the sleeping accommodation, on the higher ground and the parking and open space on the lower, then show it on a plan with levels.

Defining the area of search

The guidance ties the area to the development, which gives a defensible structure rather than a free choice.

Write down the justification for the area in a short method statement, with the date, the officer's agreement and the reasoning. Where the development has a genuine locational requirement, say what it is and evidence it rather than asserting it.

A rural example that works: a village hall replacement serving one parish can reasonably be searched across that parish and its immediate approaches, because a hall three villages away does not meet the need. A rural example that does not: a 40-dwelling market housing scheme searched across one village, when the housing need is district-wide.

Identifying reasonably available sites

The guidance describes a reasonably available site as one in a suitable location for the type of development, with a reasonable prospect of being available to be developed at the point in time envisaged.

The sources to search, and to list in the document:

• allocations in the adopted local plan and in any emerging plan at an advanced stage
• the authority's strategic housing or employment land availability assessment
• the brownfield land register
• sites with extant planning permission not yet implemented
• sites publicly marketed for sale or to let at the time of the search
• any site the council itself identifies during pre-application discussion

Record the date you searched and keep the evidence. A search run eight months before submission invites the officer to ask what has changed, and on a long-running application you may have to refresh it.

Ask the council directly whether it is aware of alternative sites. If the answer is no, that answer is worth more in your document than any amount of negative searching.

Discounting sites and recording why

Every site identified has to be dealt with, and the reasons for discounting have to be the right kind of reasons.

Legitimate grounds include that the site is too small for the quantum proposed, that it is in a different flood zone at equal or higher risk, that it is not available because it is occupied or committed to another use, that it carries an overriding constraint such as a designation incompatible with the development, or that it is not suitable for the type of development proposed.

Grounds that fail: the applicant does not own it, the applicant cannot afford it, the owner will not sell at the price offered, the site is less profitable, or the applicant's business is already established on the application site. Inspectors have consistently treated ownership-based reasoning as fatal to a sequential test, and those decisions are indicative of the approach rather than binding precedent.

Set the results out as a table, one row per site, with the site name, its reference, its area, its flood zone, the source it came from and the reason for discounting. Keep the reasoning to one or two sentences each. A reader should be able to audit the whole search in two minutes.

Where the test is passed by the plan

An allocation in an adopted development plan will normally have been through the sequential test at plan-making stage, and the guidance indicates the test does not need to be reapplied at application stage in that situation.

Three qualifications matter in practice. The allocation has to cover the development now proposed, so a scheme materially different from the allocated use may fall outside it. The flood risk evidence may have moved on, particularly where updated climate change allowances or new surface water mapping have changed the zone or the extent. And the authority can still ask for the test where circumstances have changed since adoption.

Where you rely on the plan, say which allocation, which policy, which examination document dealt with the test, and why nothing material has changed. That is three sentences, and it saves a round of correspondence.

Urban sites with no alternatives

A genuine answer of no reasonably available alternatives is perfectly acceptable, and on a constrained town centre regeneration site it is often the right answer. The document still has to prove it rather than assert it.

The strongest urban sequential tests do four things. They show the search was over the whole authority area, not the applicant's shortlist. They include a map with the sites identified and their flood zones marked. They explain why each site cannot deliver the proposal. And they confirm the council was asked and had nothing to add.

Where surface water is the driver rather than fluvial risk, resist the temptation to overstate the mapped extent, because the published surface water information has known limitations at property scale. The sensible reading of that data is covered in reading the surface water flood risk map without overstating it.

If the test passes and the Exception Test is then engaged, that is a separate two-limb assessment rather than a continuation of the same argument, and the Exception Test has its own evidence requirements around wider sustainability benefits and safety for the lifetime of the development.

Writing the test so it survives scrutiny

A document that holds up has a predictable shape: the proposal and its flood zone, the vulnerability classification, the agreed area of search with its justification, the sources searched with dates, the site-by-site table, the conclusion, and a short note on the sequential approach within the site.

Keep it separate from the flood risk assessment. A Sequential Test that is buried as section 7 of a Flood Risk Assessment gets missed by consultees and by committee members, and it reads as an afterthought. Two documents, cross-referenced.

Three habits that make the difference. Date-stamp the search. Name the person at the council who agreed the area. Include the negative result, because a search that finds nothing is only credible if the reader can see where you looked.

Residual risk management belongs in the flood risk assessment rather than here, and the measures available are set out in residual flood risk and property flood resilience measures.

To see which flood and drainage documents your site is likely to need, enter your postcode on PlanScope and work through the guided questions. For specialist technical reports, qualified professional input may be required.

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.