Flood zones and what they mean

Flood zones give you one type of flood risk information for the planning process.

They are based on a location's chance of flooding from rivers or the sea in any year. They do not take into account:

  • other sources of flooding
  • future flood risk from rivers or the sea

This means a site in flood zone 1 could still flood now or in the future.

To get a more complete picture of a location's risk, you should check the long term flood risk for an area .

Flood zone 1

Locations in flood zone 1 have a low probability of flooding. This means in any year land has a less than 0.1% chance of flooding from rivers or the sea.

Some flood zone 1 developments need a flood risk assessment as part of their planning application. Find out when you need a flood risk assessment for development in flood zone 1.

Flood zone 2

Locations in flood zone 2 have a medium probability of flooding. This means in any year land has between a 1% and 0.1% chance of flooding from rivers and between a 0.5% and 0.1% chance of flooding from the sea.

Flood zone 2 developments need a flood risk assessment as part of their planning application.

Flood zone 3

Locations in flood zone 3 have a high probability of flooding. This means in any year land has a 1% or more chance of flooding from rivers, or a 0.5% or more chance of flooding from the sea.

Flood zone 3 developments need to submit a flood risk assessment as part of their planning application.

Flood defences

There are flood defences in part or all of the location you selected.

Flood defences:

  • reduce the probability of flooding from a specific source (a river or the sea)
  • do not completely stop the chance of flooding because there may be a flood that is bigger than the one the defence is designed to protect against (this is called overtopping), or the defence can fail
  • may provide reduced protection over time because of climate change increasing flood risk in the future

There are different types of flood defence. They include:

  • culverts
  • embankments
  • flood walls

You can view a complete list of flood defences, called asset categories, on environment.data.gov.uk.