Flood Zones

October 13, 20120 Comments

What flood zone is my house in?

One of the most frequently asked questions encountered by our team is – “What flood zone is my house in?”

For individual’s concerned about the risk of flooding to their property or to one they plan to purchase, please read our information on Flood risk assessments for property sales and purchases

The definitions of flood zones below are taken from the government’s technical guidance to the National Planning Policy Framework. This is essential reading for anyone planning on developing a new property.

Definition of Flood Zones

Flood Zone 1 – Low Probability

Definition

This zone comprises land assessed as having a less than 1 in 1,000 annual probability of river or sea flooding (<0.1%).

Appropriate uses

All uses of land are appropriate in this zone.

Flood risk assessment requirements

For development proposals on sites comprising one hectare or above the vulnerability to flooding from other sources as well as from river and sea flooding, and the potential to increase flood risk elsewhere through the addition of hard surfaces and the effect of the new development on surface water run-off, should be incorporated in a flood risk assessment. This need only be brief unless the factors above or other local considerations require particular attention.

Policy aims

In this zone, developers and local authorities should seek opportunities to reduce the overall level of flood risk in the area and beyond through the layout and form of the development, and the appropriate application of sustainable drainage systems.

Flood Zone 2 – Medium Probability

Definition

This zone comprises land assessed as having between a 1 in 100 and 1 in 1,000 annual probability of river flooding (1% – 0.1%), or between a 1 in 200 and 1 in 1,000 annual probability of sea flooding (0.5% – 0.1%) in any year.

Appropriate uses

Essential infrastructure and the water-compatible, less vulnerable and more vulnerable uses, are appropriate in this zone. The highly vulnerable uses are only appropriate in this zone if the Exception Test is passed.

Flood risk assessment requirements

All development proposals in this zone should be accompanied by a flood risk assessment.

Policy aims

In this zone, developers and local authorities should seek opportunities to reduce the overall level of flood risk in the area through the layout and form of the development, and the appropriate application of sustainable drainage systems.

Flood Zone 3a – High Probability

Definition

This zone comprises land assessed as having a 1 in 100 or greater annual probability of river flooding (>1%), or a 1 in 200 or greater annual probability of flooding from the sea (>0.5%) in any year.

Appropriate uses

The water-compatible and less vulnerable uses of land are appropriate in this zone. The highly vulnerable uses should not be permitted in this zone. The more vulnerable uses and essential infrastructure should only be permitted in this zone if the Exception Test is passed. Essential infrastructure permitted in this zone should be designed and constructed to remain operational and safe for users in times of flood.

Flood risk assessment requirements

All development proposals in this zone should be accompanied by a flood risk assessment.

Policy aims

In this zone, developers and local authorities should seek opportunities to:

  • reduce the overall level of flood risk in the area through the layout and form of the development and the appropriate application of sustainable drainage systems;
  • relocate existing development to land in zones with a lower probability of flooding; and
  • create space for flooding to occur by restoring functional floodplain and flood flow pathways and by identifying, allocating and safeguarding open space for flood storage.

Flood Zone 3b – The Functional Floodplain

Definition

This zone comprises land where water has to flow or be stored in times of flood. Local planning authorities should identify in their Strategic Flood Risk Assessments areas of functional floodplain and its boundaries accordingly, in agreement with the Environment Agency. The identification of functional floodplain should take account of local circumstances and not be defined solely on rigid probability parameters. But land which would flood with an annual probability of 1 in 20 (5%) or greater in any year, or is designed to flood in an extreme (0.1%) flood, should provide a starting point for consideration and discussions to identify the functional floodplain.

Appropriate uses

Only the water-compatible uses and the essential infrastructure listed in table 2 that has to be there should be permitted in this zone. It should be designed and constructed to:

  • remain operational and safe for users in times of flood;
  • result in no net loss of floodplain storage;
  • not impede water flows; and
  • not increase flood risk elsewhere.

Essential infrastructure in this zone should pass the Exception Test.

Flood risk assessment requirements

All development proposals in this zone should be accompanied by a flood risk assessment.

Policy aims

In this zone, developers and local authorities should seek opportunities to:

  • reduce the overall level of flood risk in the area through the layout and form of the development and the appropriate application of sustainable drainage systems;
  • relocate existing development to land with a lower probability of flooding.
What flood zone is my house in?

To find out which flood zone your house resides in according the above definitions, you will need to visit the Environment Agency’s website here and enter your postcode into the box on the right hand side of the screen.

HOWEVER

Please be aware that the above information constitutes the Environment Agency’s definition of flood zones (as set out in the Government’s National Planning Policy Framework) and, as such, only pertains to river and coastal flooding.

If you are looking for a flood risk assessment to assist property sales and purchases, please contact our team. Use our free quotation form to get in touch.

Filed in: FRA NewsPlanning & property

About the Author ()

James Hubbard is part of Ambiental's technical team and takes responsibility for managing the company website.

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