Flood risk assessment
Encyclopedia
A flood risk assessment is an assessment of the risk
Risk assessment
Risk assessment is a step in a risk management procedure. Risk assessment is the determination of quantitative or qualitative value of risk related to a concrete situation and a recognized threat...

 of flood
Flood
A flood is an overflow of an expanse of water that submerges land. The EU Floods directive defines a flood as a temporary covering by water of land not normally covered by water...

ing, particularly in relation to residential, commercial and industrial land use.

England and Wales

In England and Wales, the Environment Agency
Environment Agency
The Environment Agency is a British non-departmental public body of the Department for Environment, Food and Rural Affairs and an Assembly Government Sponsored Body of the Welsh Assembly Government that serves England and Wales.-Purpose:...

 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
Planning permission
Planning permission or planning consent is the permission required in the United Kingdom in order to be allowed to build on land, or change the use of land or buildings. Within the UK the occupier of any land or building will need title to that land or building , but will also need "planning...

 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.

PPS 25 - England only

Flood Risk Assessments are required to be completed according to Planning Policy Statement PPS 25: Development and Flood Risk. The initial legislation (PPG25) was introduced in 2001 and subsequently revised.

PPS 25
PPS 25
Planning Policy Statement 25, commonly abbreviated as PPS 25, is a document produced by the British Government and intended to set out policy on development and flood risk. PPS25 was published in December 2006 and has been supplemented with a Practice Guide in June 2008...

 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." 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".

Composition of an FRA

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.

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.

Other uses

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.

Northern Ireland

In 2006, The Department of the Environment, Planning Service published Planning Policy Statement 15 (PPS15): Planning and flood risk. 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. Advise on FRA is provided to Planning Service by Rivers Agency.

Republic of Ireland

In 2009, The Department of the Environment, Heritage and Local Government and Office of Public Works
Office of Public Works
The Office of Public Works is a State Agency of the Department of Finance in the Republic of Ireland...

published planning guidelines requiring Local Authorities to apply a sequential approach to flood risk management. The guidelines require that proposed development in flood risk areas must undergo a justification test, consisting of a Flood Risk Assessment.

External links

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