Flood risk can affect the layout, access and acceptability of development. Start the checks before the design is fixed, including on sites outside the higher river and sea flood zones.
Start with the FRA requirement
The Environment Agency’s planning guidance identifies when an FRA is needed. Check the whole application site, its proposed use and future risk, rather than relying on a postcode or one map layer.
| Site or proposal | Initial position | What to check next |
|---|---|---|
| Flood Zone 2 or 3 | An FRA is required. Zone 3 includes the functional floodplain, Zone 3b. | Identify the relevant zone and development vulnerability. |
| Flood Zone 1, at least one hectare | An FRA is required, including a site of exactly one hectare. | Check all flood sources and the proposed drainage approach. |
| Flood Zone 1, below one hectare | An FRA can still be required. | Check present and future surface water risk, critical drainage problems and local flood evidence. |
| Changes of use or minor works | Do not assume an automatic exemption. | Check the use, vulnerability, flood risk and applicable standing advice. |
What do the flood zones tell you?
NPPF Annex F defines river and sea flood zones. These classifications do not take account of flood defences. They must be read alongside evidence about other sources and future risk.
| Zone | Meaning | Practical implication |
|---|---|---|
| 1 · Low probability | Less than 0.1% annual probability of river or sea flooding. | Other sources and the one-hectare trigger still matter. |
| 2 · Medium probability | River: 0.1–1% annually. Sea: 0.1–0.5% annually. | An FRA and a vulnerability check are needed. |
| 3a · High probability | River: at least 1% annually. Sea: at least 0.5% annually. | Check compatibility and the relevant planning tests. |
| 3b · Functional floodplain | Land where water must flow or be stored during flooding. | Use the local Strategic Flood Risk Assessment to identify it. |
The Flood Map for Planning is the starting point for planning evidence. Also read the council’s Strategic Flood Risk Assessment (SFRA), including relevant maps and updates. Save the map dates and site boundary used in the review.
An FRA, the sequential test and drainage are different
An FRA examines the site’s flood risks and proposed response. The sequential test considers whether suitable lower-risk sites are reasonably available. An exception test applies in certain circumstances, depending on vulnerability and flood zone. A drainage strategy addresses how the development manages water.
Current NPPF policies F5 and F6 contain specific exemptions. For example, F5 includes a surface-water-only route where an FRA demonstrates lifetime safety without increasing risk elsewhere. This is not a blanket exemption from preparing an FRA. Confirm which tests apply with the planning authority.
How does the type of development affect the assessment?
The proposed use affects how vulnerable the development is to flooding. A dwelling, warehouse and emergency facility do not have identical risk profiles. Use the classifications and compatibility table in Annex F, rather than assuming every use is acceptable in the same location.
Extensions and changes of use also need a proportionate review. For some minor development, the Environment Agency’s standing advice for preparing an FRA provides a suitable route. Check its scope carefully; it is not a universal substitute for specialist assessment.
What should you prepare for the assessment?
A clear information pack helps the assessor identify gaps early. Ask them to confirm the required evidence before commissioning surveys or modelling.
- A red-line site boundary, measured area and current topographical information.
- Existing and proposed uses, layouts, floor levels and access arrangements.
- Relevant mapping, the SFRA, known flood history and earlier reports.
- The proposed development lifetime and any vulnerable users or operations.
- Available drainage records, proposed discharge arrangements and design constraints.
- A record of authority advice, assumptions and unresolved information requests.
The assessment should explain the relevant flood mechanisms, consequences and proposed response. Where specialist modelling is necessary, agree its scope. The Environment Agency provides guidance on modelling for FRAs.
Climate allowances depend on the flood source, location and assessment circumstances. Use the applicable Environment Agency climate change allowances; do not apply one percentage to every type of flood calculation.
Coordinate the evidence before the layout is fixed
- 01 · Screen
Identify the zone, other flood sources, site area and development type.
- 02 · Scope
Confirm the FRA, planning tests and drainage evidence with the appropriate advisers.
- 03 · Resolve
Use the findings to coordinate levels, access, layout and mitigation before submission.
Make a single drawing register. Record which layout and levels the flood, drainage, landscape and ecology teams have used. ACP’s guidance on coordinating habitat and drainage drawings provides a practical way to manage that interface.
Where a project may require environmental impact assessment, EIA screening and scoping should be considered separately. An FRA does not decide whether EIA is required.
Common planning questions
Can I prepare the FRA myself?
Some straightforward proposals fall within published standing advice. Many sites need specialist judgement, surveys or modelling. Check the advice’s scope and discuss the evidence with the planning authority before deciding who should prepare it.
Does an existing flood defence remove the need for an FRA?
No. Flood zones are defined without defence benefits. An assessment may need to consider residual risk, including what happens if a defence fails or is exceeded.
Can I leave flood risk until after planning permission?
Do not assume that a condition can resolve whether the development is acceptable. Establish the evidence required for the application early, including where outline permission is sought.
Does an FRA guarantee permission?
No. It informs the planning decision. Flood risk, the relevant planning tests, the development plan and other material considerations still need to be assessed.
References and scope
- Environment Agency: Flood risk assessments — applying for planning permission
- NPPF Annex F: flood zones, vulnerability and compatibility
- NPPF: Managing flood risk and coastal change — policies F4–F8
- Environment Agency: Climate change allowances
- Environment Agency: Preparing an FRA — standing advice
Sources checked 16 October 2026. This guide covers England. Check the current local plan, validation requirements and site-specific advice before submitting an application.