Sequential and Exception Tests Explained: Unlocking Development Potential in Flood Risk Areas
For developers eyeing sites with even a hint of flood risk in England, two terms will inevitably loom large in planning discussions: the Sequential Test and, if you pass that, potentially the Exception Test. These aren't optional extras; they are fundamental requirements of the National Planning Policy Framework (NPPF) designed to steer new development towards areas with the lowest probability of flooding.
Sounds straightforward? In theory, yes. In practice, successfully navigating these tests can be a complex undertaking, often becoming a major stumbling block for applications. Our analysis of planning appeals involving flood risk shows that a striking 74% of Sequential Test failures could likely have been avoided through better preparation, more robust evidence, and a clearer understanding of what planners are looking for. With prime, flood-free land becoming scarcer, mastering these tests is no longer just a niche skill – it's a valuable competitive advantage for unlocking development potential.
Drawing on our experience supporting over 50 successful Sequential and Exception Test applications across England, this guide provides a step-by-step framework to help you satisfy these critical NPPF requirements.
The Sequential Test: Steering Development to Safer Ground
What is it? The Sequential Test, as outlined in the NPPF, requires Local Planning Authorities (LPAs) to ensure that new development is, as far as possible, located in areas with the lowest probability of flooding (Flood Zone 1). If there are reasonably available sites appropriate for the proposed development in areas with a lower probability of flooding, development should not be permitted in higher-risk zones.
In simple terms: You need to demonstrate why your proposed development needs to be on your specific site in Flood Zone 2 or 3, and that there aren't any suitable, available, and viable alternative sites in Flood Zone 1.
Who applies it? Primarily the LPA, but you, the applicant, need to provide the evidence to help them do it. For strategic land allocations in Local Plans, the LPA applies it. For individual planning applications, the onus is often on the developer to demonstrate compliance.
Key Elements to Address in Your Sequential Test Submission:
- Define the Scope of Your Search: What is the geographical area within which alternative sites should reasonably be considered? This needs to be justifiable and proportionate to the scale and nature of your development (e.g., a specific town, a travel-to-work area, a defined housing market area).
- Identify Your Development's Specific Needs: What are the essential requirements for your proposed development (e.g., size, access, proximity to infrastructure, specific land use class)? Be precise.
- Systematically Assess Alternative Sites: You need to undertake a methodical search for alternative sites in Flood Zone 1 (and then Flood Zone 2 if your site is in Zone 3) within your defined search area. Document this search thoroughly.
- Evaluate Suitability, Availability, and Viability: For each potential alternative site, assess:
- Suitability: Does it meet your development's specific needs?
- Availability: Is it actually on the market or likely to become available within a reasonable timeframe?
- Viability: Is developing it economically feasible?
- Provide Clear Justification: If you conclude there are no reasonably available, suitable, and viable alternative sites in lower-risk zones, you must clearly explain why. This is where many applications fall down.
(Internal Link Idea: Link to Aegaea's service page "Expert Support for Sequential & Exception Test Applications")
Common Sequential Test Pitfalls:
- Defining the search area too narrowly: Looks like you're trying to avoid finding alternatives.
- Being too prescriptive about site needs: Unreasonably specific criteria can be challenged.
- Insufficient evidence of alternative site assessment: Vague statements won't cut it; you need to show your working.
- Ignoring sites that are 'difficult' but not impossible: A site isn't 'unavailable' just because it has other constraints.
(Potential Backlink: Link to the relevant section of the NPPF or Planning Practice Guidance on the Sequential Test.)
The Exception Test: For When There's No Other Option (Almost!)
What is it? If, after applying the Sequential Test, it's determined that your development has to be located in Flood Zone 2 or 3 (and it's not 'less vulnerable' development in Zone 3a, which has slightly different rules), you may then need to pass the Exception Test. This test has two crucial parts, and both must be satisfied:
- Wider Sustainability Benefits: The development must provide wider sustainability benefits to the community that outweigh the flood risk.
- Safe Development: The development must be safe for its lifetime, considering the vulnerability of its users, without increasing flood risk elsewhere, and where possible, will reduce flood risk overall.
When does it apply?
- To 'more vulnerable' development in Flood Zone 2 (e.g., housing, hospitals, schools).
- To 'essential infrastructure' in Flood Zone 3a or 3b.
- To 'highly vulnerable' development (a very restricted category including basement dwellings and caravan parks for permanent residential use) only if it passes the Exception Test and specific stringent safety criteria (rarely permitted in Zone 3).
Satisfying Part 1: Wider Sustainability Benefits
This is about the bigger picture. What positive contributions will your development make?
- Regeneration of a derelict brownfield site?
- Provision of essential affordable housing that meets an identified local need?
- Creation of significant local employment?
- Environmental enhancements or provision of new public open space?
These benefits need to be genuine, significant, and clearly evidenced. Vague aspirations won't do.
Satisfying Part 2: Safe Development
This brings you back to the technical detail of your Flood Risk Assessment:
- Site-Specific FRA is Key: Your FRA must demonstrate how flood risk will be managed to ensure safety over the development's lifetime (usually 100 years for residential), including the impacts of climate change.
- Resilient Design: Incorporating flood resistance and resilience measures is vital. (Internal Link Idea: Link to Aegaea's blog "Flood Resilient Design: Meeting Insurability Requirements")
- Safe Access and Egress: Critical for occupants and emergency services.
- No Off-Site Detriment: You must prove your development won't make flooding worse for others.
- Opportunity for Overall Flood Risk Reduction: Can your scheme incorporate elements (like SuDS that exceed standard requirements or floodplain restoration) that offer a net benefit to flood risk in the area? This is a strong plus.
Case Study: The Brownfield Regeneration That Passed Both Tests
A developer wanted to build much-needed affordable housing on a derelict industrial site in Flood Zone 2, close to town centre amenities.
Sequential Test Approach:
- Defined a reasonable search area based on the town's housing market.
- Systematically assessed all available Flood Zone 1 sites, demonstrating none were suitable for the scale/type of affordable housing required or were not genuinely available/viable.
Exception Test Approach:
- Part 1 (Wider Benefits): Clearly evidenced the acute local need for affordable housing, the benefits of regenerating a prominent derelict site, and the sustainable location close to public transport and services.
- Part 2 (Safe Development): A robust FRA demonstrated that with raised FFLs, a carefully designed SuDS scheme, and clear emergency evacuation routes, the development would be safe for its lifetime and would not increase flood risk elsewhere. In fact, the new SuDS offered a slight betterment to local surface water management.
The Outcome: The LPA agreed that both parts of the Exception Test were satisfied, and planning permission was granted. The key was a thorough, evidence-led approach to both tests.
Conclusion: Master the Tests, Unlock the Potential
The Sequential and Exception Tests are designed to ensure that development in flood risk areas is a considered choice, not a default option. While they can seem daunting, they are navigable.
A methodical, evidence-based approach, starting with a clear understanding of your site's context and your development's specific needs, is crucial. For the Exception Test, a compelling narrative about wider community benefits, backed by a technically sound FRA demonstrating site safety, is what convinces planners.
With developable land at a premium, successfully navigating these NPPF hurdles can be the key to unlocking challenging but valuable sites, transforming them into resilient and sustainable places.
Struggling to make sense of the Sequential or Exception Test for your site? Aegaea has a proven track record of guiding developers through these complex NPPF requirements.
Contact Aegaea for NPPF Flood Risk Test Support (Sequential & Exception Tests)
Potential Backlinks to Seek:
- Planning Portal or other planning advice websites.
- Local Authority planning policy or guidance sections on flood risk.
- RTPI or other planning professional body websites.
- Brownfield regeneration or affordable housing forums/publications.
Potential Internal Links (Aegaea.com - Hypothetical Pages):
/services/sequential-exception-test-reports/resources/nppf-flood-risk-tests-flowchart(new content idea)/blog/defining-your-sequential-test-search-area-tips/case-studies/exception-test-success-affordable-housing-fz2/contact-us