Flood Risk Assessment Wales provides a national assessment of risk flooding from Rivers, the Sea and Surface Water and Small Watercourses (replacing the Risk of Flooding Rivers and Sea, or RoFRS, dataset).

The assessment takes into account flood defences and combines new, national-scale modelling with detailed local-scale models to categories risk into 3 bands, labelled ‘High’, ‘Medium’ and ‘Low’ risk.

For Rivers and Surface Water and Small Watercourses: 

  • ‘High’ risk means that each year, this area has a chance of flooding of greater than 1 in 30 (3.3%)
  • ‘Medium’ risk means that each year, an area has a chance of flooding of between 1 in 100 (1%) and 1 in 30 (3.3%).
  • ‘Low’ risk means that each year, an area has a chance of flooding of between 1 in 1000 (0.1%) and 1 in 100 (1%).

For the Sea:   

  • ‘High’ risk means that each year, this area has a chance of flooding of greater than 1 in 30 (3.3%)
  • ‘Medium’ risk means that each year, an area has a chance of flooding of between 1 in 200 (0.5%) and 1 in 30 (3.3%).
  • ‘Low’ risk means that each year, an area has a chance of flooding of between 1 in 1000 (0.1%) and 1 in 200 (0.5%)

The risk assessment takes into account the effect of flood defences where we have information. Flood defences reduce, but do not completely stop the chance of flooding as they can be overtopped or fail.

Flood risk information for each source has been created as ‘onion-skins’, i.e. with no overlapping data between individual risk bands. These risk bands should be combined and displayed a single layer for each flood source.

If data is displayed in map form to others, appropriate map scales should be used given the indicative nature of the modelling.  It should be shown with a maximum zoom scale of 1:5,000 and that base mapping of 1:10,000 is used to give context.

The flood mapping is based on areas at risk of flooding and is not specific to individual properties. NRW doesn’t hold information about an individual property’s construction that might affect whether flooding of a certain depth could enter a property and cause damage. As such, our information has been produced to identify general areas potentially at risk of flooding for further investigation.

Spatial resolution of the data:                                                                            National scale modelling undertaken at 2m grid resolution.                              Local scale modelling undertaken at different resolutions, typically between 2m – 10m.

More information is available in the FRAW (2019) project report and NRWs Understanding your flood risk results webpage (https://naturalresources.wales/flooding/managing-flood-risk/understanding-your-flood-risk-results?lang=en) for more information on our flood risk data and how it should be used.

An online version of the map is available here.

The Risk Level Under Review identifies locations where our risk assessment is under review over the next 6 months due to the availability of new, local-scale model information.

Attribution Statement                                                                                     

Contains Natural Resources Wales information © Natural Resources Wales and database right. All rights reserved. Some features of this information are based on digital spatial data licensed from the UK Centre for Ecology & Hydrology © UKCEH. Defra, Met Office and DARD Rivers Agency © Crown copyright. © Cranfield University. © James Hutton Institute. Contains OS data © Crown copyright and database right.

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  • Flood Risk Assessment Wales - Flood Risk from Rivers

  • Flood Risk Assessment Wales - Flood Risk from the Sea

  • Flood Risk Assessment Wales - Flood Risk from Surface Water and Small Watercourses

  • nrw_risk_levels_under_review

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Environmental resources, protection and conservation. Examples: environmental pollution, waste storage and treatment, environmental impact assessment, monitoring environmental risk, nature reserves, landscape

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