

A Flood Risk Assessment is typically required where a proposed development site is at risk of flooding, at present or sometime in the future. This includes Critical Drainage Areas and Surface Water Flooding.
The National Planning Policy Framework sets strict tests to protect people and property from flooding which all local planning authorities are expected to follow. Where these tests are not met, national policy is clear that new development should not be allowed. The mains steps to be followed are set out below which, in summary, are designed to ensure that if there are better sites in terms of flood risk, or a proposed development cannot be made safe, it should not be permitted.
The policies are based on the Environment Agency’s maps of flood risk zones. These cover all of England and Wales and map areas prone to flooding in terms of the following.
Zone 1 – Low Probability (Little or No Risk)
This zone comprises land assessed as having a less than 1 in 1000 annual probability of river or sea flooding in any year. There are no development constraints.
Zone 2 – Medium Probability (Low to Medium Risk)
This zone comprises land assessed as having between a 1 in 100 (1%) and 1 in 1000 (0.1%) annual probability of river flooding or between a 1 in 200 and 1 in 1000 annual probability of sea flooding in any year.
Zone 3a – High Probability (High Risk)
This zone comprises land assessed as having a 1 in 100 or greater annual probability of river flooding or a 1 in 200 or greater annual probability of flooding from sea in any year.
Zone 3b – Functional Floodplain
This zone comprises land where water has to flow or be stored in times of flood. The annual probability that such land will flood will be 1 in 20 or greater.
Flood Risk Zones 3a and 3b are not separately mapped by the Environment Agency (EA). The advice of the EA is that it is the responsibility of the applicant to determine whether a site is in Zone 3a or 3b in the course of preparing a flood risk assessment.