What is a flood risk assessment?

A Flood Risk Assessment (FRA) is a technical report prepared by a qualified consultant that assesses the risk of flooding to a proposed development and from it. It must demonstrate that the development will be safe from flooding over its lifetime, will not increase flood risk elsewhere, and incorporates appropriate mitigation measures. It is required for planning applications in Flood Zones 2 and 3, and in some other circumstances.

How much does a flood risk assessment cost?

A basic FRA for a single residential property typically costs £500–£1,500. More complex assessments for larger sites or highly constrained flood zone 3 sites can cost £3,000–£10,000+. Your planning consultant or the Environment Agency's pre-application service can advise on the scope of FRA needed.

Can I build in Flood Zone 3?

Development is restricted in Flood Zone 3. Highly vulnerable uses (e.g., basements, essential infrastructure) are not permitted. More vulnerable uses (e.g., dwellings) require an Exception Test as well as a Sequential Test — the development must provide wider sustainability benefits, and the flood risk must be safely managed for the lifetime of the development. Councils and planning inspectors take flood risk in Zone 3 very seriously.

What is the Sequential Test?

The Sequential Test is a planning policy tool from the NPPF that requires councils and applicants to demonstrate that a proposed development could not be located on a site with a lower flood risk. If equally suitable lower-risk sites are available, the higher-risk site will fail the Sequential Test and permission is likely to be refused.

What is the difference between surface water flooding and river flooding?

River (fluvial) flooding occurs when rivers overflow their banks. Surface water (pluvial) flooding occurs when rainfall cannot drain away quickly enough — it often affects areas well away from rivers, including urban streets and gardens. Both types are assessed in flood risk assessments and on the Environment Agency's risk checker.

How to Check Flood Risk for Your Property or Planning Application

Flood risk is a material planning consideration. Before submitting a planning application — or buying a property — it is important to understand the flood zone your site falls within and whether a flood risk assessment is required. The Environment Agency provides free online flood maps for England.

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