Flood risk assessment

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A flood risk assessment is an assessment of the risk of flooding, particularly in relation to residential, commercial and industrial land use.

England and Wales[edit]

In England and Wales, the Environment Agency requires a Flood Risk Assessment (FRA) to be submitted alongside planning applications in areas that are known to be at risk of flooding (within flood zones 2 or 3) and/ or are greater than 1ha in area, planning permission is not usually granted until the FRA has been accepted by the Environment Agency. Flood risk assessments are also relevant to the maintenance and insurance of existing buildings.[1]

PPS 25 - England only[edit]

Flood Risk Assessments are required to be completed according to the National Planning Policy Framework,[2] which replaces Planning Policy Statement PPS 25: Development and Flood Risk. The initial legislation (PPG25) was introduced in 2001 and subsequently revised.[3]

PPS 25 was designed to "strengthen and clarify the key role of the planning system in managing flood risk and contributing to adapting to the impacts of climate change."[4] and sets out policies for local authorities to ensure flood risk is taken into account during the planning process to prevent inappropriate development in high risk areas and to direct development away from areas at highest risk.

In its introduction, PPS25 states "flooding threatens life and causes substantial damage to property [and that] although [it] cannot be wholly prevented, its impacts can be avoided and reduced through good planning and management".[5]

Composition of an FRA[edit]

For a flood risk assessment to be written information is needed concerning the existing and proposed developments, the Environment Agency modeled flood levels and topographic levels on site. At its most simple (and cheapest) level an FRA can provide an indication of whether a development will be allowed to take place at a site.

An initial idea of the risk of flooding to a local area can be found on the Environment Agency flood map website. However, the Environment Agency use low resolution flood mapping to create this flood map as a cautious estimate of flood risk, and therefore on the more local scale this mapping may not be accurate.[citation needed]

Longer FRAs consist of a detailed analysis of available data to inform the Environment Agency of flood risk at an individual site and also recommend to the developer any mitigation required for a planning application to be submitted. More costly analysis of flood risk can be achieved through detailed flood modelling to challenge the agency's modelled levels and corresponding flood zones.

The FRA takes into account the risk and impact of flooding on the site, and takes into consideration how the development may affect flooding in the local area. It also includes provides recommendations as to how the risk of flooding to the site can be improved or improved following development.

As well as assessing the risk to the site posed by fluvial flooding, FRAs should also consider flooding from other sources including fluvial, groundwater, surface water runoff and sewer flooding. This is often required to be addressed up front in the planning and development process, as local planning authorities are increasingly less likely to consent major proposed developments without an adequate assessment of flood risk and a drainage strategy designed to minimize long term flood impacts.

Other uses[edit]

Assessments can also be used to provide insurers with a more detailed assessment of flood risk at a location, and can act as a means of reducing insurance premiums.[citation needed]

Northern Ireland[edit]

In 2006, the Planning Service, part of The Department of the Environment, published Planning Policy Statement 15 (PPS15): Planning and flood risk.[6] The guidelines are precautionary and advise against development in flood plains and areas subject to historical flooding. In exceptional cases a FRA can be completed to justify development in flood risk areas. Advice on flood risk assessment is provided to the Planning Service by the Rivers Agency, which is the statutory drainage and flood defence authority for Northern Ireland.

Republic of Ireland[edit]

In 2009, the Department of the Environment, Heritage and Local Government and Office of Public Works published planning guidelines requiring local authorities to apply a sequential approach to flood risk management.[7] The guidelines require that proposed development in flood risk areas must undergo a justification test, consisting of a flood risk assessment.

See also[edit]


  1. ^ Floodrisk Management Research Consortium
  2. ^ National Planning Policy Framework (https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/6077/2116950.pdf) "National Planning Policy Framework"
  3. ^ HMSO (2006, Revised 2010) Planning Policy Statement 25: Development and Flood Risk, TSO, London. ISBN 978-0-11-754099-6
  4. ^ Angela Smith MP (7 December 2006) Planning Policy Statement (PPS) 25: Flooding, Written Parliamentary Statement
  5. ^ Communities and Local Government (2006) Planning Policy Statement 25: Development and Flood Risk: Full Regulatory Impact Assessment
  6. ^ Department of the Environment (2006) Planning Policy Statement 15 (PPS 15): Planning and Flood Risk, The Planning Service, Belfast
  7. ^ Government of Ireland (2009) The Planning System and Flood Risk Management, The Stationery Office, Dublin ISBN 978-1-4064-2467-6

External links[edit]