Navigating Planning - When you need a Flood Risk Assessment

National Planning Policy requires flood risk to be taken into account as part of the planning process, it’s a material planning consideration and likely to be a validation requirement. You don’t even need to build anything - a change of use can make the site a more vulnerable class of development.

But when do you need a Flood Risk Assessment?

Sites in Flood Zone 1

For sites in Flood Zone 1 an FRA is needed where it is more than 1 hectare in size.

Where it is less than 1 hectare in size and possibly at risk from sources of flooding other than rivers and the sea, such as a sewer, surface water or a nearby reservoir, an FRA will be required.

Sites in Flood Zone 2 or 3

If your site is in flood zone 2 or 3 and is any size, you will need an FRA.

Flood zone 2 is categorized as having a medium probability of flooding - Land having between a 1% and 0.1% annual probability of river flooding; or land having between a 0.5% and 0.1% annual probability of sea flooding.

Flood Zone 3 is classed as having a high probability of flooding - Land having a 1% or greater annual probability of river flooding; Land having a 0.5% or greater annual probability of sea flooding, or functional floodplain.

Where to start

The first step is defining your site. Assess flood mapping, strategic flood risk documents and other records. From there it can be determined what risks are present, and what assessment you may need.

Feeling stuck? Get in touch.