Properties at Risk of Flooding 2120
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TotalMetadata
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- Summary information
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Title
Properties at Risk of Flooding in WalesLast update
August 2024Next update
July 2026Publishing organisation
Welsh GovernmentSource 1
National Flood Risk Assessment data, Natural Resources WalesContact email
stats.environment@gov.walesDesignation
NoneLowest level of geographical disaggregation
Local authoritiesGeographical coverage
WalesLanguages covered
English and WelshData licensing
You may use and re-use this data free of charge in any format or medium, under the terms of the Open Government License - see http://www.nationalarchives.gov.uk/doc/open-government-licenceGeneral description
The Flood Risk Assessment Wales (FRAW) modelling, together with the latest National Receptor Database 2023 (NRD 2023) are used to determine the number of properties (residential and non-residential) at risk of flooding from Rivers, the Sea and Surface Water and Small Watercourses in Wales. The information is for Present Day risk (2024) and Climate Change risk (2120) and includes both the presence and removal of flood defences within the modelling (defended and undefended scenarios).Data collection and calculation
The chance of flooding is set out in three risk categories:High Risk; Greater than or equal to 1 in 30 (3.3%) chance in any given year
Medium Risk; Less than 1 in 30 (3.3%) but greater than or equal to 1 in 100 (1%) chance in any given year for rivers and surface water flooding and less than 1 in 30 (3.3 per cent) but greater than or equal to 1 in 200 (0.5 per cent) for the sea.
Low Risk; Less than 1 in 100 (1%) for rivers and surface water flooding and 1 in 200 (0.5 per cent) for the sea but greater than or equal to 1 in 1,000 (0.1%) chance in any given year.
FRAW typically includes flooding from rivers with a catchment size greater than 3 square kilometres, and flooding from the sea (both along the open coast and tidal estuaries). Smaller watercourses with a catchment size smaller than 3 square kilometres are represented in the FRAW Surface Water data and maps.
The assessment takes into account the location and standard of protection afforded by flood defences and adjusts the risk categorisation accordingly from an initial, ‘undefended’ scenario.
Climate change uplift values are based on the guidance available at the time of the original FRAW project which was completed in 2019. The uplift values are very similar or identical to current Welsh Government guidance, using a “Central Estimate”. Typical values for Sea level rise are approximately 1.1m across Wales, a 20% to 30% increase in River flows based on River Basin Catchments and a 20% increase to rainfall for the Surface Water and Small Watercourse mapping.
For the Climate Change Defended scenario, an assumption has been made that the existing standard of protection of the flood defences keeps pace with climate change.
Data reference periods
2024 onwardsRounding applied
None.Statistical quality
FRAW typically includes flooding from rivers with a catchment size greater than 3 square kilometres, and flooding from the sea (both along the open coast and tidal estuaries). Smaller watercourses with a catchment size smaller than 3 square kilometres are represented in the FRAW Surface Water data and maps.The assessment takes into account the location and standard of protection afforded by flood defences and adjusts the risk categorisation accordingly from an initial, ‘undefended’ scenario.
Some properties in Wales may be affected by more than one source of flooding, therefore when counting properties at risk, you need to be careful the same property isn’t counted more than once. For example, if a property is affected by all three sources of flooding, when reporting by flood sources it will be counted as one property for rivers, one for the sea and one for surface water & small watercourse. However, if you are counting the total number of properties in Wales at flood risk, using the sum of all three sources, the same property could be counted 3 times.
The property counts provided are a snapshot in time based on 2024 datasets. They are subject to change year on year, as data and methodology improves over time. This may cause counts to increase or decrease between individual releases. When we count buildings or properties, this may include multiple buildings at the same address.
