FRA Guidance Note 3: Development in Flood Zones 3 and 2
(Excluding Minor Extensions)

March 2007

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FRA Guidance Note 3: Development in Flood Zones 3 and 2 (Excluding Minor Extensions)

Environment Agency guidance on the requirements for undertaking a Flood Risk Assessment (FRA) for planning applications. This guidance note relates specifically to the commissioning and undertaking of flood risk assessment studies for development in Flood Zones 2 and 3 other than ‘minor’ extensions i.e. excluding householder extensions and non-domestic extensions with a footprint of less than 250m2, which are covered separately in FRA guidance note 2.

Prior to investing resources in completing a FRA, applicants are advised to contact the Local Planning Authority (LPA) and discuss how the flood risk Sequential Test as set out in Planning Policy Statement 25 (PPS25) will affect the proposed development. It is possible that the development will be inappropriate and be refused planning permission irrespective of any FRA. Advice on the evidence required to show that the Sequential and Exception Test has been properly applied is set out in the Sequential Test table within the Environment Agency's Standing Advice on development and flood risk and in the draft Practice Guide to PPS25. The Environment Agency may require evidence that the Sequential Test has been properly applied before commenting in detail on FRAs for development in this category.

Why is a FRA required?

In Flood Zone 3, the flood risk from rivers and the sea is classified as ‘high’, while in Flood Zone 2 it is said to be ‘low to medium’. This classification is simply based on the probability of flood events occurring and does not address the possible consequences including the effects of any flood defences in the area. A FRA is required to ensure that all aspects of flood risk are considered both to the proposed development itself and also the potential impact on people and property elsewhere within the catchment. The scale, nature and location of the proposed development will inform the scope of the FRA required.

What should be in the FRA?

The detail and technical complexity of a FRA will reflect the scale and potential significance of the development. FRAs can be of a relatively minor nature, evaluating a small development on a site at the margins of the flood plain, or conversely can comprise major basin-wide studies for significant infrastructure developments. On occasions, preliminary or scoping studies may be undertaken prior to a fuller assessment. The following list sets out the kind of information that should be submitted as a FRA for development in Flood Zones 2 and 3:

Plans

  • A location plan that includes geographical features, street names and identifies the catchment, watercourses or other bodies of water in the vicinity.
  • A plan of the site showing
    • existing site;
    • development proposals;
    • identification of any structures, which may influence local hydraulics. This will include bridges, pipes/ducts crossing the watercourse, culverts, screens, embankments, walls, outfalls and condition of channel.

Surveys

  • Site levels related to Ordnance Datum, both existing and proposed
  • Appropriate cross-section(s) of the site showing finished floor levels or road levels, or other relevant levels relative to the source of flooding, and anticipated water levels and associated probabilities.

Assessments

  • Consideration of whether the site falls within the functional flood plain as defined by the draft Practice Guide to Planning Policy Statement 25 (PPS25), and if so, demonstration that development meets the vulnerability criteria set out in table D1 PPS25.
  • Flood alleviation measures already in place, their state of maintenance and their performance.
  • Information about all potential sources of flooding that may affect the site – from rivers and the sea, streams, surface water run-off, sewers, groundwater, reservoirs, canals and other artificial sources or any combination of these.
  • The impact of flooding on a site including:
    1. the likely rate or speed of surface water run-off with which flooding might occur;
    2. the order in which various parts of the location or site might flood;
    3. the likely duration of flood events
    4. the economic, social and environmental consequences of flooding on occupancy of the site
    5. information on extent and depth of previous flood events or on flood predictions.
  • An assessment of how safe access and exit can be provided for routine and emergency access under both frequent and extreme flood conditions.
  • An assessment of how the layout and form of development can be used to reduce or minimise flood risk.
  • An assessment of the capacity of any drains or sewers, existing or proposed, on the site during various flood events.
  • An assessment of the volume of surface water run-off likely to be generated from the proposed development.
  • Proposals for surface water management according to sustainable drainage principles, with the aim of not increasing, and where practicable, reducing the rate of runoff from the site as a result of the development
  • The likely impact of any displaced water on third parties caused by alterations to ground levels or raising flood embankments.
  • The potential impact on fluvial or coastal morphology and the likely longer-term stability and sustainability of existing defences.
  • Estimates should be made of how climate change could affect the probability and intensity of flood events. The assessment should ensure that the development meets an acceptable standard of flood protection for the design life of the development. The hydrological analysis of flood flows and definition of defence standards needs to include the allowances for increased flows and sea level rise contained in DEFRA's project appraisal guidance for flood defence and in accordance with Appendix B of PPS 25 or the latest information from UKCIP.
  • The residual risks to the site after the construction of any necessary defences and the means of managing those.
  • Consideration of the proposal relative to any existing Strategic Flood Risk Assessment carried out by the local authority.

Exception Test requirements

In addition to the requirements listed above, when completing a FRA as part of meeting the requirements of the Exception Test, an assessment will be required of on and off site opportunities for reducing flood risk overall. This will include an appraisal of the strategic flood risk management measures to which the development can contribute.

For further information on the Exception Test contact the Local Planning Authority.

What is the Environment Agency’s Role?

We will usually provide comments at the planning application stage on Flood Risk Assessments covered by this guidance note. (unless indicated otherwise by Environment Agency Planning Liaison team in the area where the development is proposed). We have three main interests:

  • Ensuring that the calculation and design of the site drainage and flood risk management measures meet Environment Agency policies and plans where present, resulting in a contribution to sustainable development.
  • If the proposal is within the Byelaw Distance 2 of a Main River 3 or flood defence structure, or includes the diversion or culverting of an Ordinary Watercourse 4 then formal consent for the proposal may also be required from us.
  • Prior to carrying out a FRA, developers should contact the Environment Agency and other operating authorities (including the engineering department of the local authority or Internal Drainage Board as appropriate) to establish whether any information is available relating to flood risk at the site they propose to develop. It should be noted that, whilst we can provide information on flooding from rivers and the sea, we only record known problems relating to other sources. The absence of information in this respect does not mean that a site will not flood. Developers should also take full account of the local knowledge of flooding in the community and account for this within the FRA.

Sources of information:

  1. www.environment-agency.gov.uk For information on SUDS best practice, flood proofing and flood resilient construction methods, flood warning, Flood Map and contact details for local Environment Agency offices.
  2. www.ciria.org.uk Check ‘publications’ for details of relevant information
  3. www.ciwem.com/directory/ For information on consulting engineers who may be able to carry out FRAs. This is by no means a definitive list.
  4. www.hrwallingford.co.uk For information on an R&D project on flood risk assessment guidance for new development.

1 Flood Zone 2: 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.
Flood Zone 3: 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.

2 Byelaw distance varies across the country. To find out what distance applies in your area call 08708 506 506 and ask to speak to a member of the Development Control team in the area where the development is proposed.

3 Main Rivers are watercourses designated as such on Main River maps and are generally the larger arterial watercourses. Main Rivers are indicated with a red line as part of the Flood Zones held by the Local Planning Authority and on maps held by the Environment Agency.

4 An Ordinary Watercourse is any watercourse that doesn’t form part of a Main River


Published by the Environment Agency. © Crown Copyright 2007. This page last updated 3rd March 2007