The Sequential Test in Practice: How Inspectors Actually Decide Flood Risk Cases

The Sequential Test is the NPPF's primary mechanism for steering development away from areas at risk of flooding. In theory, it is straightforward: if there are reasonably available sites at lower flood risk, development should go there instead. In practice, it is one of the most contested and misunderstood requirements in planning.

Our analysis of appeal decisions involving the Sequential Test reveals a more nuanced picture than the policy text suggests. Inspectors apply the test with considerable pragmatism, and understanding how they approach it can make the difference between a successful application and an unnecessary refusal.

NPPF paragraphs 173 to 180 (December 2024) set out the flood risk framework. Paragraph 173 establishes the principle: inappropriate development in areas at risk of flooding should be avoided by directing development away from areas at highest risk. Where development is necessary in such areas, it should be made safe for its lifetime without increasing flood risk elsewhere.

Paragraph 174 requires the Sequential Test to be applied to all development in flood risk areas. The test must now consider flood risk from **all sources** — not just rivers and the sea, but also surface water, groundwater, and sewers. This was a significant change in the December 2024 revision, broadening the scope of the test considerably.

Paragraph 175 introduced a practical exception: where a site-specific Flood Risk Assessment demonstrates that no built development, access routes, or vulnerable elements would be located on any part of the site at risk of flooding from any source — now or in the future — the Sequential Test need not be applied. This carve-out is particularly relevant for larger sites where flood risk affects only a portion of the land.

The appeal record shows that inspectors take a structured but pragmatic approach to the Sequential Test. Several key principles emerge from the case law and decision letters:

Inspectors consistently hold that the area of search for alternative sites must be defined reasonably. For a local housing need, the search area is typically the local authority area. For a specialist use — such as a water treatment works or a site-specific employment use — the search area may be much narrower. The applicant must justify the area of search, and inspectors will scrutinise whether it is genuinely appropriate or artificially constrained.

A site is not "reasonably available" simply because it exists. It must be available for the type of development proposed, at the time needed, and capable of accommodating the development. Sites that are allocated for other purposes, subject to ransom, or not genuinely on the market are not reasonably available. Inspectors have consistently rejected arguments that theoretical brownfield sites in Flood Zone 1 represent reasonably available alternatives when those sites are not actually deliverable. The High Court confirmed this broad, common-sense approach in Mead Realisations Ltd v Secretary of State for Levelling Up, Housing and Communities [2024] EWHC 279 (Admin): an alternative site need not be able to accommodate the precise development proposed, in its exact form, quantum and timescale, to count as reasonably available.

This is perhaps the most important practical point. In practice, a clear failure of the Sequential Test is normally determinative. National flood-risk policy is directive: development should not be permitted where there are reasonably available sites at a lower risk of flooding. The test functions as a strong policy hurdle rather than a routine balancing exercise, and inspectors give a clear failure substantial weight.

This does not make the Sequential Test an absolute statutory bar. It is a material consideration that, in principle, falls to be weighed in the overall planning balance alongside the benefits of a scheme. But in practice a clear failure is very difficult to overcome, and applicants should not assume that public benefits such as housing delivery will outweigh it.

Where the Sequential Test is passed (or where failure is not considered determinative), the Exception Test under paragraph 178 applies to more vulnerable and highly vulnerable uses in higher flood zones. The Exception Test requires both wider sustainability benefits and a demonstration that the development will be safe for its lifetime. Both limbs must be satisfied.

Our analysis of refused applications and dismissed appeals identifies recurring errors in how the Sequential Test is approached:

**Inadequate alternative site assessment.** Simply listing sites and stating they are unavailable is insufficient. Inspectors expect a systematic assessment showing the availability, suitability, and deliverability of each alternative site considered. A table with brief notes is not enough — the reasoning must be transparent.

**Artificially narrow search areas.** Defining the search area as the immediate locality to exclude lower-risk alternatives elsewhere in the district is a red flag for inspectors. Unless there is a genuine locational requirement for the development, the search area should be district-wide as a minimum.

**Ignoring surface water flood risk.** Since the December 2024 NPPF changes, the Sequential Test must consider all sources of flooding. Applications that only address fluvial flood zones and ignore surface water risk are vulnerable to objection from the Environment Agency and refusal by the local authority.

**Failing to update the assessment.** A Sequential Test prepared two years ago for a pre-application may be out of date by the time the application is determined. Site availability changes, new allocations come forward, and flood risk data is updated. Inspectors expect the evidence to be current.

Paragraph 180 states that the Sequential Test does not need to be applied where a site has been allocated in a development plan that applied the test at the plan-making stage — unless there has been a material change in flood risk information since allocation. This is important for allocated sites, but does not help windfall proposals.

For windfall development, the local authority is responsible for applying the Sequential Test. In practice, many authorities struggle with this — they may not have a current Strategic Flood Risk Assessment, or their assessment of alternative sites may be cursory. Where the authority's Sequential Test evidence is weak, applicants can strengthen their position by providing their own robust assessment.

For applicants dealing with the Sequential Test, the evidence suggests several practical steps:

**Define the search area transparently and justify it.** If you are proposing a use with a genuine locational requirement, explain why. If the search area is district-wide, say so and assess all reasonable alternatives.

**Assess alternatives systematically.** For each alternative site, address availability (is it on the market or allocated?), suitability (can it accommodate your development?), and achievability (can it be delivered in the relevant timeframe?). Use a consistent methodology.

**Address all sources of flood risk.** Check the Environment Agency's surface water flood maps and groundwater maps as well as the Flood Map for Planning. The December 2024 NPPF requires consideration of all sources.

**Articulate the public benefits clearly.** If the Sequential Test is borderline, the strength of the public benefits becomes critical. Housing delivery, affordable housing provision, economic regeneration, and community infrastructure are all relevant to the planning balance.

**Keep the evidence current.** Update your Sequential Test assessment if there has been any material change since it was first prepared. Inspectors will check.

The Sequential Test is a policy requirement, not a bureaucratic hurdle. But it is also not the binary pass/fail that many applicants and authorities treat it as. Understanding how inspectors actually apply it — with pragmatism, proportionality, and an eye on the planning balance — is essential for navigating flood risk in the planning system.