Understanding your flood risk results

Your flood risk results

This page helps you understand your flood risk results from the Flood Risk Assessment Wales map and the Check your flood risk by postcode service. 

Both services use the same flood risk information. They show risk to a general area, not to individual properties.

You should use this information to find out about flood risk in your area and to take appropriate action. This page shows you how you can prepare your property for flooding.  

As well as flood risk, the Flood Risk Assessment Wales (FRAW) map shows other information, including:

This page helps you understand your flood risk results and explains how you can prepare your property.  

Types of flood risk

We show flood risk for three different types of flooding:

  • rivers
  • the sea
  • surface water and small watercourses

The risk levels are high, medium, low or very low.

The risk levels do not take into account

  • the failure of flood defences
  • blockage of river channels, structures and other drainage systems

This could increase the risk and extent of flooding in an area.

We do not provide a risk level for flooding from reservoirs. We show the worst-case scenario for the area that could be flooded if a large reservoir were to fail and release the water it holds.

Read more about flooding from reservoirs

Flooding can be caused by other sources that are not shown in the Flood Risk Assessment Wales map. For example from overwhelmed or blocked sewers and drains, or groundwater from underground aquifers.

We also can not show the risk of flooding from underground mine systems. It is almost impossible to predict where this may happen because of the complexity of underground workings.

Flood risk from the sea

Flood risk from the sea is made up of two main elements – elevated sea level (known as Extreme Sea Level) and wave overtopping (where waves crash over coastal walls, defences and high ground). Wave overtopping is more likely to be an issue in exposed coastal locations.

Due to the complexities in calculating wave overtopping, our flood risk maps have historically only displayed the risk from Extreme Sea Levels. However, we are gradually adding new wave overtopping information to our flood risk maps. This will continue over the next 5years on a risk based approach.

The areas where we currently show the combined risk from both Extreme Sea Levels and wave overtopping are:

  • the Caldicott and Wentlooge Levels in south east Wales
  • from the Point of Ayr to Pensarn along the north Wales coast
  • between Borth and Llandanwg in west Wales.

For more information contact enquries@naturalresourceswales.gov.uk

The definition of flood risk

Flood risk is the likelihood of a flood occurring. We calculate this as the chance that a location will flood in any one year.

If a location has a 1% chance of flooding each year, there is a 1 in 100 chance of flooding in any year.

This doesn’t mean that if a location floods one year, it will not flood for the next 99 years. It also doesn’t mean if it hasn’t flooded for 99 years, it will flood this year.

The lower the percentage, the less chance there is of flooding in any one year; the higher the percentage then the more chance there is of flooding in any one year.

This chance is always there – this year, next year and in the future.

Creating our flood risk information

We use computer models to help predict the risk of flooding from rivers, the sea, and from surface water and small watercourses. We also use models to map the flood extents in the Flood Risk Assessment Wales map. This ensures our information is based on clear, scientific evidence, and is not subjective.

The risk assessment uses national-scale modelling or where available, more detailed, ‘local’ model data, to ensure we show the best information available.

In most cases, our modelling does not include the risk from wave action in coastal areas. We are continually improving our modelling information and may include wave action to update our risk assessment in the future.

The models use information, methodology and guidance available at the time they are created. This represents a ‘snap-shot’ in time and our assessment of risk could change in the future as things change.

Due to the limitations and uncertainties in modelling and mapping flood risk, we cannot guarantee the accuracy for a given area.

In particular, flooding from surface water and small watercourses is difficult to predict due to uncertainties in the location, topography and volume of water. The mapped extents should be considered a broad indicator of an area's risk.

There may be topographical features not reflected in our modelling that could greatly affect the severity of flooding within an area. Alternatively, topographical features may currently be included in our modelling but change over time and this could alter the level of flood risk in the future.

Representing buildings in our flood models

The computer models we use represent buildings in different ways. Our national-scale modelling represents buildings by raising them above the surrounding ground level.

This means that the flood extents in the Flood Risk Assessment Wales map may reach the edge of a building outline but the building itself is not shown as flooded. This does not mean the building will not flood and the risk should be considered in any assessment.

Flood defences

The flood risk assessment takes into account the presence of flood defences. However, the surface water and small watercourses map does not show the accumulation of water behind raised flood defences if it can not drain into a river or the sea.

It is important to remember that flood defences can fail or be overtopped during extreme flooding conditions.

More information about flood defences

Flood risk is for an area, not individual properties

We calculate the risk of flooding to land, not individual properties.

The information we provide is an indicator of an area's flood risk. It is not suitable for identifying whether an individual property, including any land linked to the property, such as a garden or driveway will flood.

This is because we don’t hold information about individual property construction that might affect whether flooding of a certain depth could enter and cause damage.

For example, one property might be raised above the road with steps leading up to the front and back doors, while the one next door is below road level, with steps down to it. We do not have this level of detail.

Not all properties and associated land shown at risk may flood but you should take responsibility to protect your property from possible flooding.

If you live in a second floor flat, flooding might not reach your home. But it could still affect your surrounding area, for example:

  • you might not be able to get into or out of your home
  • your car might get caught in the flood (it only takes two feet of water to float a car)
  • your garden, driveway, parking area may flood
  • your power, gas or water supplies might be interrupted

Flood results within 10 metre radius

Our flood risk results in Check your flood risk by post code are for an area within 10 metres of the address selected in the post code search bar.

To do this, we draw an imaginary line 10 metres away from the main building outline and identify the highest risk level within the search radius using information contained within the Flood Risk Assessment Wales map. Multiple buildings at the same address are not selected.

The search radius could include gardens, other parts of the property or where a car is parked on a street. Properties with large garden or boundaries may have a flood risk beyond the 10 metre search area and this can be viewed in our Flood Risk Assessment Wales map.

If a building is near a river, it may have a reduced risk of flooding if there is a flood defence providing some protection. However, beyond that flood defence and within 10 metres of the property there could be a high risk of flooding and this is displayed in the risk rating.

The risk to multiple buildings at an address or within the wider area can be viewed in our Flood Risk Assessment Wales map.

Recorded flooding

We record historical flooding from rivers, the sea and, in some locations, from surface water and small watercourses . However, this is only in locations where we are aware of flooding and have reasonable confidence in the records. 

Our Check your flood risk tool lets you know if we have a record of flooding within an area.

You can also view historical flooding on a map by ticking the ‘Recorded flood extents’ layer in the FRAW map. The map provides additional information of when the flooding was recorded.

 If an area is shown as having flooded in the past: 

  • it doesn’t mean that flooding will occur in the same way in the future as there may have been changes in the area affecting the pattern of flooding.
  • it doesn't mean that properties in that area flooded internally

Similarly, if an area shows no recorded flooding: 

  • it doesn't mean it has never flooded (there may be no records or unreliable records)
  • it doesn’t mean it won't flood in the future

As more data on historic flooding comes to light, and as flood incidents occur, then we will record this where adequate information is available.

Other organisations such as the local authority may hold further information about flood risk and historic flooding records. Contact the local authority for any historic flood information for surface water and small watercourses.

Flood risk can change over time

Your address might be shown as at risk of flooding but you’ve lived there for many years and it hasn’t flooded during that time.

This is because flood risk is not the same as whether an area has flooded before. Flood risk can change over time and might increase or decrease with changing land use.

Flood risk might increase with:

  • heavier or longer periods of rain
  • more impenetrable surfaces like tarmac
  • fewer trees and vegetation
  • climate change

Flood risk might decrease with:

  • flood defences
  • managing the environment to give better natural protection from flooding

Updating our flood risk information

Your risk result represents the best information currently available to us and may differ to information provided by other organisations. It reflects a snapshot in time and may not take account local changes, for example a change in ground levels as a result of new development.

We will take account of evidence from others on flood risk when we update our maps and include this information if it meets agreed quality standards.

We aim to update our flood risk information for rivers and sea every six months, in May and November. This will include any new information available to us.

This includes any new information that might change your flood risk, such as the construction of new flood defences.

We update the risk of flooding from surface water and small watercourses less frequently. This is due to the complexity of the modelling process and the availability of new topographical information.

More about our flood risk management programme

The ‘Risk level under review’ layer in the FRAW map shows locations where information may change within the next 6 months, as new information becomes available. In some cases, the risk level under review may be shown for longer than 6 months if the information has not been made available during this time.  

For more information about 'Risk level under review', contact DataDistribution@naturalresourceswales.gov.uk

Flood risk insurance and mortgages

When they set their prices, insurers and mortgage providers will consider the flood risk to a property. They will always consider the overall risk. This will include the risks from:

  • subsidence
  • historic mining
  • crime rates
  • previous insurance claims

They will not consider flood risk in isolation. Generally, the price of insurance policies reflects the risk of a claim.

We don’t have a role in deciding insurance cover or setting premiums. Insurers will use:

  • publicly available flood maps
  • flood maps purchased from the private sector which can provide information on flood risk to individual properties
  • independent surveys

Insurers are free to use our data but we advise them that:

  • it is not property-specific
  • it gives the flood risk to an area of land only

If insurers use our data, it is only as part of a much wider assessment of risk. Their assessment of risk may include all buildings and land within the property boundary.

The difficulty in securing insurance for a home can have a negative impact on the prospects of obtaining a mortgage. If you find it difficult to get property and/or contents insurance for your home, or it is unaffordable, try using the BIBA and ABI Flood Insurance Directory.

This Directory has been created by the British Insurance Brokers Association (BIBA), the Association of British Insurers (ABI) and Flood Re to help Customers find home insurance in flood risk areas. FloodRe is a scheme to make insurance more affordable for homes that are at risk of flooding.

If you are still experiencing problems please contact the National Flood Forum to get insurance advice.

View more information about preparing for flooding.

Contact us

Contact us if

  • you think the flood risk for your address is wrong for flooding from rivers or the sea. You might be able to challenge the flood risk we give for your area
  • you would like further information about the risk information in the Flood Risk Assessment Wales map

Contact your local authority if you think the flood risk for your address is wrong for flooding from surface water and small watercourses.


Please read the Disclaimer for our flood and coastal erosion risk mapping to learn about our liabilities for displaying risk results for a location. 

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