Flood risk maps in the UK: what each one shows and how they differ

Most arguments about flood maps in the UK start with two people looking at two different maps. One says the house is in Flood Zone 3. The other says the risk is low. Both are reading official data correctly. The difference lies in what each flood risk map was built to do.

Three families of flood risk map

Across the four nations the official maps fall into three broad families.

Planning maps exist to steer new building away from places that flood. In England this is the Flood Map for Planning, run by the Environment Agency at flood-map-for-planning.service.gov.uk. In Wales it is the Flood Map for Planning published by Natural Resources Wales. These maps feed into decisions on planning applications and use flood zones, not risk bands.

Risk maps for the public exist to tell residents, buyers and businesses how likely their area is to flood today, with defences in place. In England this is the long term flood risk service on GOV.UK. In Wales it is the Flood Risk Assessment Wales map. They speak of high, medium, low and very low risk.

Hazard maps by source show where water from a given source could go at a given likelihood. SEPA’s flood maps for Scotland and the Department for Infrastructure’s Flood Maps NI work this way, with separate layers for rivers, the coast and surface water at high, medium and low likelihood.

The distinction is not academic. A planning map answers “should anyone build here?”. A risk map answers “how often might this area flood as things stand?”. A hazard map answers “where would water go in a flood of a given size?”. Using one to answer the other’s question produces the confusion described above.

England: flood zones for planning

The government’s planning guidance on flood risk and coastal change, last updated on 17 September 2025, sets out the flood zones in its Table 1:

The key instruction sits a few lines further on. Planners are told that, initially, “the presence of existing flood risk management infrastructure should be ignored, as the long-term funding, maintenance and renewal of this infrastructure is uncertain”. Only after that first step can the role of defences be considered within medium and high-risk areas.

This is a deliberate choice. It treats a flood wall as something that might not be maintained in 80 years, which is a reasonable view for a building expected to stand that long. It also means the planning flood zone describes the floodplain as nature drew it, not the protection that exists today.

The Flood Map for Planning has historically shown rivers and the sea only. In January 2025 the Environment Agency said the service would be updated on 25 March 2025 to display flood zones based on the new national assessment, add surface water risk and show how climate change may affect the extent of future flooding from rivers and the sea.

England: the long term flood risk map

The long term flood risk service draws on the National Assessment of Flood and Coastal Erosion Risk (NaFRA), last refreshed in December 2024. Unlike the planning map, the assessment accounts for existing defences and their current condition. It reports separate results for rivers and the sea, surface water, reservoirs and (where data exists) groundwater, and it rates an area, not an individual property.

Its bands are defined by annual chance: high is greater than 3.3% (1 in 30), medium between 1% and 3.3%, low between 0.1% and 1%, and very low less than 0.1%. The full detail, including the NaFRA 2024 figures and how to read a result, is in the guide to checking long term flood risk.

Note the mismatch with the planning zones. Planning’s “high probability” begins at 1 in 100 for rivers. The long term service’s “high” begins at 1 in 30. The same word covers two different thresholds on two official maps from the same agency.

England: surface water maps

Surface water flooding is the largest source of flood risk in England by property count. NaFRA 2024 puts about 4.6 million properties in areas at risk from surface water, against about 2.4 million for rivers and the sea. The surface water figure is 43% higher than in the previous assessment, which the Environment Agency attributes mainly to better modelling.

Surface water maps are the hardest to read well. They depend on how quickly drains and sewers can carry water away, on small changes in ground level and on the timing of intense rain. The 2024 assessment maps at 2-metre resolution, up from 50 metres, which makes the outlines far sharper than before. Sharp outlines on a screen can look like certainty. They are not; a kerb, a garden wall or a blocked gully can change where water goes.

Local councils, as lead local flood authorities, also hold information on surface water flooding, and GOV.UK directs people to their council for surface water and flash flooding questions.

Wales: two maps from Natural Resources Wales

Wales separates the two jobs cleanly.

The Flood Risk Assessment Wales map shows the risk of flooding from rivers, the sea, surface water and small watercourses, and reservoirs. It takes flood defences into account, shows where defences are and which areas benefit from them, and gives risk levels of high, medium, low or very low. Natural Resources Wales stresses two limits: it calculates risk “to land, not individual properties”, and the map “has no official status for planning purposes”. For reservoirs it gives no risk level, showing instead the worst-case area that could be flooded.

The Flood Map for Planning supports Technical Advice Note 15 (TAN15) on development, flooding and coastal erosion. It indicates the potential extent of flooding “assuming no defences are in place” and includes the effects of climate change over the next century. It shows:

• Rivers Flood Zone 2: 0.1% to 1% (1 in 1,000 to 1 in 100) annual chance, including climate change;
• Rivers Flood Zone 3: more than 1% (1 in 100) annual chance, including climate change;
• Sea Flood Zone 2: 0.1% to 0.5% (1 in 1,000 to 1 in 200) annual chance;
• Sea Flood Zone 3: more than 0.5% (1 in 200) annual chance;
• zones for surface water and small watercourses.

Natural Resources Wales updates the planning map twice a year, in late May and late November. The latest update listed was on 21 May 2026.

Building climate change into the Welsh planning zones is a real difference from the English approach. A Welsh Zone 3 tells a developer what the floodplain is expected to look like later in the century, not only today.

Scotland: SEPA flood maps

The Scottish Environment Protection Agency publishes flood maps at map.sepa.org.uk/floodmaps for river, coastal and surface water flooding, with present-day maps and future flood maps that take account of projected climate change.

SEPA uses likelihood, defined by return period:

• High likelihood: a flood event is likely to occur in the defined area on average once in every ten years (1:10).
• Medium likelihood: on average once in every 200 years (1:200).
• Low likelihood: on average once in every thousand years (1:1000).

Scotland’s “high” is therefore a 10% annual chance, three times the English threshold of 3.3%. A reader moving between Carlisle and Dumfries who trusts the word rather than the number will misjudge the risk.

Northern Ireland: Flood Maps NI

The Department for Infrastructure publishes Flood Maps NI, an interactive viewer that shows areas that have flooded from rivers and the sea in the past and those that may be prone to flooding now and in the future, with the location of flood defences and the areas they benefit. The maps are available for the present day and a climate change epoch of 2080.

Its probability levels differ by source:

AEP stands for annual exceedance probability, the chance that a given flood level is exceeded in a single year. The Department states that the indicative flood maps “cannot be used to predict the flood risk to a particular property or specific point location”.

Common misreadings, and a worked example

Five mistakes come up again and again.

1. Treating a flood zone as a risk rating. Flood zones ignore defences at first; risk ratings include them. Neither is wrong.
2. Comparing labels across borders. “High” means more than 3.3% a year in England’s long term service, 10% for rivers in Scotland and Northern Ireland, and at least 1% for rivers in the English planning zones.
3. Reading only the rivers layer. Surface water affects far more properties in England than rivers and the sea do.
4. Reading the map as a property survey. Every agency says its maps describe areas or land, not individual buildings.
5. Assuming a map is permanent. England’s ratings changed in January 2025 when new data went live, and the Welsh planning map changes twice a year.

A worked example: a semi-detached house in an English market town sits 200 metres from a river, behind an embankment built after an earlier flood. On the Flood Map for Planning the plot falls in Flood Zone 3, because the embankment is ignored in that first step. On the long term flood risk service the rivers and sea band reads “low”, because the embankment is included and is in good condition. The surface water band reads “medium”, because the street sits in a shallow dip.

Each map is telling the owner something real. If the owner wants to build a rear extension, the planning authority will apply the Zone 3 rules and is likely to ask for a flood risk assessment. If the owner wants to know how likely it is that water reaches the house next winter, the long term result is the better guide, and the surface water band, not the river, is the one to watch. If the owner is asking an insurer for a quote, the insurer will use its own model, which may agree with neither. The guide to home insurance in flood risk areas explains how Flood Re can change the price for eligible homes.

When a map looks wrong

Maps can be wrong in the detail. A model may miss a recently raised wall or misread a ground level. The mapping agencies take evidence: Natural Resources Wales, for example, publishes a process for challenging its flood maps. Surveyed levels, photographs of past events and records of defences carry the most weight.

There is a tension the agencies do not hide. Finer maps help planners and emergency services, but they also put individual streets into higher bands overnight, with consequences for sale prices and insurance quotes that the maps were never designed to carry. The Environment Agency’s own statement that NaFRA was not developed or tested for insurance underwriting is, in effect, an admission that its data travels further than its purpose.

For the wider picture of who maps flood risk in each nation and how the UK pays for flood losses, see the UK flood risk overview. How other European countries spread the same costs, often through compulsory schemes, is compared on the schemes hub.