When do you need a flood risk assessment?

In the UK, a site-specific Flood Risk Assessment is a statutory requirement under the NPPF for any development that meets specific environmental or physical criteria. The primary objective is to ensure the development is safe for its lifetime and does not increase flood risk to third parties.

According to Environment Agency guidance, you must submit an FRA for:

• All developments in Flood Zones 2 or 3, including extensions and changes of use.

• Developments with a site area of 1 hectare or more.

• Any site in Flood Zone 1 identified by the Lead Local Flood Authority (LLFA) as having critical drainage problems.

• Sites in Flood Zone 1 where government mapping identifies a risk of flooding from surface water.

• Sites in Flood Zone 1 where the SFRA shows an increased risk from climate change, groundwater or reservoirs.

• Any change of use that increases the vulnerability classification (e.g., converting a commercial unit into a residence) in a flood-risk area.