Flood Risk Zones.
Land mapped by its probability of flooding from rivers and the sea, ignoring existing defences. Zone 2 is medium probability, Zone 3 high — and the higher the zone, the harder a residential scheme is to justify.
- Development in Zone 1 with a drainage strategy
- Less vulnerable uses in Zone 2 with an FRA
- Raising finished floor levels where the zone allows
- Water-compatible uses in higher zones
- Residential in Zone 2 — sequential test
- Any "more vulnerable" use in Zone 3a
- Basement dwellings in Zone 2 or 3
- Sites over 1ha anywhere
- Housing in Zone 3b, the functional floodplain
- Development that increases risk elsewhere
- Schemes with no safe access and egress in a flood
Flood zones show probability before defences, so a site behind a wall still sits in the zone. Development is steered to the lowest-risk land available through the sequential test: if reasonably available sites exist in a lower zone, the application should be there instead.
Where the sequential test is passed but risk remains, the exception test applies — the scheme must deliver wider sustainability benefits and be safe for its lifetime without increasing flood risk elsewhere. Residential is a "more vulnerable" use, which is why housing in Zone 3 is the hardest case.
A site-specific flood risk assessment is required for any development in Zone 2 or 3, and for sites over one hectare anywhere. The Environment Agency is a statutory consultee and its objection is, in practice, decisive.
The sequential test is where these applications are won or lost, and it is an evidence exercise, not an argument: define the search area, show what was reasonably available, and show why it did not work. A weak sequential test invites refusal regardless of the design.
Check the zone before the layout. Moving vulnerable uses to upper floors and putting parking or plant at ground level is the standard response, and it is far cheaper to design in than to retrofit after an Environment Agency objection.
How schemes actually fare inside this designation — approval rates, appeal survival, which authorities apply it hardest — needs the designation joined to the decision record. That join isn’t built, so those figures aren’t published here. We won’t estimate them.
Check which flood zone a site sits in before committing to a residential layout — the zone decides whether the sequential test applies at all.