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West Somerset Council

Flood Zones

The Local Planning Authority will make a decision on whether a development is suitable, helped in this respect by the Environment Agency, who provide advice.

Is my proposed development at risk of flooding?

A flood map is available on the Environment Agency website which provides a guide as to whether  your location is at risk of flooding from rivers and seas at either low, moderate or significant level. 

There are three flood zones, which are:

ZONE 1 - LOW PROBABILITY
 
  • This zone comprises land assessed as having a less than 1 in 1000 annual probability of river or sea flooding in any year (<0.1%), ignoring the presence of defences.
  • All uses of land are appropriate in this zone.
Flood Risk Assessment (FRA) 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 an FRA. 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 techniques.
ZONE 2 - MEDIUM PROBABILITY
  • This zone comprises land assessed as having between a 1 in 100 and 1 in 1000 annual probability of river flooding (1% – 0.1%) or between a 1 in 200 and 1 in 1000 annual probability of sea flooding (0.5% – 0.1%) in any year.
  • The water-compatible, less vulnerable and more vulnerable uses of land and essential infrastructure (Table D.2) are appropriate in this zone. Subject to the Sequential Test being applied, the highly vulnerable uses in Table D.2 are only appropriate in this zone if the Exception Test (para. D9.) is passed. 
Flood Risk Assessment (FRA) requirements
  • All development proposals in this zone should be accompanied by an FRA.
  • 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 techniques.
ZONE 3a - HIGH PROBABILITY
  • 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.
  • The water-compatible and less vulnerable uses of land in Table D.2 are appropriate in this zone. The highly vulnerable uses in Table D.2 should not be permitted in this zone. The more vulnerable and essential infrastructure uses in Table D.2 should only be permitted in this zone if the Exception Test (see para. D9) 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 (FRA) requirements
  • All development proposals in this zone should be accompanied by an FRA.
  • Policy aims - in this zone, developers and local authorities should seek opportunities to:
    i. 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 techniques;
    ii. relocate existing development to land in zones with a lower probability of flooding; and
    iii. 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.
ZONE 3b - THE FUNCTIONAL FLOODPLAIN
  • 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 flood plain and its boundaries accordingly, in agreement with the Environment Agency. 
  • Only the water-compatible uses and the essential infrastructure listed in Table D.2 that has to be there should be permitted in this zone.  It should be designed and constructed to: (i) remain operational and safe for users in times of flood; (ii) result in no net loss of floodplain storage; (iii) not impede water flows; and (iv) not increase flood risk elsewhere. Essential infrastructure in this zone should pass the Exception Test.
Flood Risk Assessment (FRA) Requirements
  • All development proposals in this zone should be accompanied by an FRA.
  • Policy aims - in this zone developers and local authorities should seek to:  (i) reduce the overall level of flood risk in the area through the layout and form of the development and appropriate application of sustainable drainage techniques; and (ii) relocate existing development to land with a lower probability of flooding.
The Sequential Test

Development should, where possible, be in areas with a low probability of flooding (flood zone 1).  Therefore, where an application for development is received within flood zone 2 or 3, the sequential test is undertaken by the Local Planning Authority to demonstrate that there are no reasonably available sites in areas with a lower probability of flooding that would be appropriate to the type of development proposed. 

If there is no reasonably available site in flood zone 1 the flood vulnerability of the proposed development (Table D.2, Annex D) would be taken into account in locating development in flood zone 2 and then flood zone 3.  Within each flood zone new development would be directed to sites at the lowest probability of flooding as indicated within the Strategic Flood Risk Assessment. 

Whilst the sequential test is undertaken by the Local Planning Authority this is based on evidence provided by the applicant/agent within the required flood risk assessment.

Flood Risk Assessments

An FRA varies in complexity and scope depending upon the type of development, the use of the development and the flood zone.  The Environment Agency provides advice to applicants and agents on what is required