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Flood Risk Assessment (FRA) – Northern Ireland (NI)

Flooding is a natural phenomenon which carries serious risks to human health and the built environment. To overcome these negative effects as far as is reasonable, the Rivers Agency of Northern Ireland has been tasked to ensure compliance with PPS15 guidance for all new planning applications. This ensures developments that are at risk from flooding or increase the risk of flooding elsewhere are prohibited. Local Planning Authorities may deem your site at risk of flooding and ask for a Flood Risk Assessment (FRA) in line with PPS15 before your development is allowed to proceed.

At OSM Environmental Consulting, we are experts in Flood Risk Assessment and frequently carry out FRAs across Northern Ireland for all scales of developments, including single dwellings, large scale housing projects, hydro-electric schemes, commercial / industrial developments and commercial sports grounds. We are trusted by authorities to provide scientifically accurate reports and respect our client’s project timelines when conducting FRAs. To view our latest projects, including Flood Risk Assessments, click here.

Headed by our Director and Flood Risk Assessment expert, Micheál O’Sullivan, the OSM Team have over 20 years’ experience of Flood Risk Assessments (FRA) and successfully complete all types of Flood Risk Assessments for a range of hydrological settings in Northern Ireland, including:

  • Developments in or near river floodplains (Fluvial Flood Risk Assessment)
  • Developments in close proximity to reservoirs or dams
  • Developments at risk of coastal flooding (Coastal FRA)
  • Developments at risk of surface water flooding(Drainage Assessments)

Speak directly with one of our Flood Risk Assessment team today.

What is a Flood Risk Assessment (FRA)?

Local Planning Authorities may ask for a Flood Risk Assessment (FRA) to be carried out on your site before development is allowed to go ahead if they deem your site to be at risk of flooding or likely to increase the risk of flooding to surrounding areas. These Flood Risk Assessments may require a desktop assessment, computer modelling or a mix of both to accurately assess your site’s risk of flooding.

Across Northern Ireland, most major watercourses have been ‘Modelled in Detail’ by DfI Rivers Agency in urban areas, meaning Flood Risk Assessments in Greater Belfast and other urban areas can normally be conducted by a simple desktop assessment. Outside of these areas, unique modelling of sites is usually required.

OSM Environmental Consulting tailor Flood Risk Assessments to the needs of each site, never tacking on unnecessary works for our clients. If modelling is required as part of a Flood Risk Assessment, OSM carry out this work in-house using Rivers Agency recognised software and industry-leading modelling techniques.  The Flood Risk Assessment team at OSM have extensive experience in Flood Risk modelling in a range of settings, including culverts, bridges, weirs and engineered watercourses.

All works are undertaken on a strictly confidential basis. If you would like any further information on our Flood Risk Assessment services, please do not hesitate to contact us.

Types of Flood Risk Assessment in Northern Ireland

The four main types of Flood Risk Assessment in Northern Ireland are:

  • Fluvial Flood Risk Assessments (river flooding)
  • Pluvial Flood Risk Assessments (surface water flooding)
  • Impounded Waterbodies FRA (reservoirs)
  • Coastal Flood Risk Assessments

Fluvial Flood Risk Assessment (River Flooding)

Fluvial flooding occurs when a river bursts its banks, resulting in flood waters flowing across what would normally be dry land.

OSM uses globally recognised technologies to assess whether this is likely to occur. Typically, a Flood Risk Assessment will be required as part of a planning application for your local Planning Authority when developing a site near a river or other watercourse.

Pluvial Flood Risk Assessment (Surface Water Flooding)

Pluvial (or Surface Water) Flooding occurs when heavy rainfall overwhelms drainage systems and the excess water cannot be absorbed, resulting in water flowing overland and collecting in large pools in dips in the ground.

A Pluvial Flood Risk Assessment (FRA) may be required by local planning authorities to ensure the natural or man-made drainage systems serving your site, or land downstream of it, are not overwhelmed during intense periods of rainfall. Pluvial flooding is a particular problem in urban areas (such as Belfast) which are often dominated by sealed or ‘non-permeable’ surfaces, such as roofs, roads and carparks. These surfaces stop water being absorbed into the ground as it would do naturally on non-developed ground.

When undertaking a Pluvial FRA, OSM use modelling to assess the level of water infiltration within your site and its surrounding area and recommend measures required to prevent or lessen the effects of pluvial flooding.

Impounded Water Body Flood Risk Assessment (Reservoirs)

Planning authorities in Northern Ireland require an Impounded Water Body Flood Risk Assessment (or Reservoir Flood Risk Assessment) for any new development within or near an area at risk of flooding from a ‘controlled’ (regulated) reservoir. Given the quantity of controlled reservoirs in Northern Ireland, the requirements for flood risk assessments for developments near these reservoirs have grown increasingly complex over the last decade.

To gain planning permission in such sites, an Impounded Water Body Flood Risk Assessment (or Reservoir Flood Risk Assessment) is required to demonstrate that by developing your site, there is no increase in the flood risk to your site or its surrounding areas. OSM extensive experience of conducting Reservoir FRAs and have successfully assessed most reservoirs in Northern Ireland, building up a positive relationship with the Rivers Agency in doing so.

Coastal Flood Risk Assessment NI

A Coastal Flood Risk Assessment is required in developments in low lying land close to the shoreline around Northern Ireland, putting it at risk during large scale coastal flooding, known as a ‘Q200 Coastal Flood Event’. Although coastal flooding is less frequent than river flooding, it causes sea water to flow rapidly inland, meaning coastal flooding poses a far greater risk to human health.

In a Coastal Flood Risk Assessment, OSM consider various elements of such a coastal flooding event, such as wave height and climate change, to assess the potential impact of coastal flooding to your site.