Flood Zone 1
Land assessed as having less than a 0.1% (1 in 1,000) annual probability of river or sea flooding. This is the lowest-risk flood zone.
Flood Zone 1 is the lowest flood risk designation used by the Environment Agency in England. It encompasses all land where the annual probability of flooding from rivers or the sea is less than 0.1% — equivalent to less than a 1 in 1,000 chance in any given year.
Most of England falls within Flood Zone 1. Development in this zone is generally unconstrained from a fluvial and tidal flood risk perspective, and the Sequential Test is automatically passed.
However, a Flood Risk Assessment is still required for:
- Sites exceeding one hectare in area, to address surface water drainage and the impact of the development on runoff
- Sites identified by the LLFA or SFRA as being at risk from other sources such as surface water, groundwater, or sewers
- Sites where the vulnerability classification is “highly vulnerable” and local evidence suggests residual risk
Even in Flood Zone 1, surface water flood risk can be significant. Many urban sites experience pluvial flooding from intense rainfall that overwhelms existing drainage infrastructure. A properly designed surface water drainage strategy using SuDS remains essential.
For further information on how flood zones are defined and applied to planning decisions, see our Flood Zones Explained guide.