Long Term Flood Risk Map: What It Shows and How to Read It

The long term flood risk map is the Environment Agency's public service for England. It shows the chance of flooding at a location from rivers and the sea, surface water, reservoirs and, where the data exists, groundwater, reported in four bands from Very Low to High. It is built for householders, buyers and owners who want to understand present-day risk, and it takes existing flood defences into account. That last point causes most of the confusion, because the map planning applications are decided against makes the opposite assumption and deliberately ignores every defence.

People searching for the Environment Agency long term flood risk map, or for its older name Check Your Long Term Flood Risk, land on the same service. This article covers what each band means in numbers, how defences change the answer, what the December 2024 NaFRA2 update did to the results, and where the map stops being the right tool.

The Environment Agency's 2024 national assessment put around 6.3 million properties in England at risk of flooding, 4.6 million of them from surface water alone.

What the long term flood risk map is

The long term flood risk map is the mapping behind Check your long term flood risk, the Environment Agency service published at gov.uk as Check the long term flood risk for an area in England. Enter a postcode or click a point and it returns a risk band for each source of flooding it models, plus a short explanation and links to flood warnings for the area. It is free and needs no account. England only.

The service answers one question. Over a long period, how likely is flooding here? What it does not do, deliberately, is answer that question at the scale of a single property. The Environment Agency states plainly that it does not assess how likely it is that an individual property will flood, and it excludes flooding from blocked drains and burst pipes.

• Rivers and the sea. Fluvial and tidal flooding, modelled with existing defences and their condition taken into account.
• Surface water. Rainfall that overwhelms the ground and the drainage network before it reaches a watercourse. This is the source that affects most properties in England.
• Reservoirs. The worst-case extent if a large reservoir were to fail. It carries no probability band, because reservoir failure is not assigned an annual chance.
• Groundwater. Shown only where the Environment Agency holds usable data, so a blank result is not the same as no risk.

If the reason you are looking at the map is a planning application, read the section on what you cannot use it for first. For everything else the map is a reasonable starting point, and Unda's own postcode flood risk map draws on the same national datasets if you prefer a single screen. Where the answer needs to satisfy a planning officer, you need a flood risk assessment for planning instead, and the two are not interchangeable.

What do High, Medium, Low and Very Low actually mean?

Each band is a range of annual chance, not a verdict. High means a 3.3% or greater chance of flooding in any given year, which is one year in thirty. Medium is less than 3.3% but at least 1%, or between one year in a hundred and one in thirty. Low is less than 1% but at least 0.1%, between one year in a thousand and one in a hundred. Very Low is less than 0.1%, or under one year in a thousand.

Two things follow. Very Low is not zero. A site at 0.09% a year still carries roughly a one in forty-five chance of flooding at least once across a twenty-five year mortgage term, and a Low band at the top of its range is closer to one in five over the same period. Our explainer on flood return periods and annual probability sets out the arithmetic.

A Very Low band means under 0.1% a year. That is a small chance of flooding, not no chance.

And the bands are wide. A property at 1.1% and a property at 3.2% both read as Medium; the second is roughly three times as likely to flood in any given year as the first, and nothing on the screen says so. The same four bands are used for rivers and the sea and for surface water, so a result reading Low for rivers and Medium for surface water is telling you the surface water case is the stronger of the two. Reservoir results sit outside this scale entirely.

Does the long term flood risk map account for flood defences?

Yes. This is the single most consequential thing to understand about it. The Risk of Flooding from Rivers and Sea dataset that sits behind the service assigns each cell a category taking into account flood defences and their condition. A town behind a raised embankment therefore reads better on this map than the ground level alone would suggest, because the model has credited the embankment.

For a homeowner asking what their present-day exposure looks like, that is the right approach. It is the wrong approach for anything that has to hold for the lifetime of a new building, because defences can be overtopped by an event larger than their design standard, they can fail, and they need maintenance funding that is not guaranteed for a hundred years. The land behind a defence is described as benefiting from it, not as removed from the floodplain.

This is why a site can sit in Flood Zone 3 and still read Low on the public service. Neither result is wrong. They answer different questions, which is also why a site stays in a flood zone after new defences are built.

How to read the four flood sources separately

The service reports each source on its own, and the sources behave differently enough that an averaged impression of the site is misleading.

• Rivers and the sea. The best-modelled source, defended, and the one the planning system has mapped longest.
• Surface water. Modelled at 2m grid resolution in the current surface water flood risk map, and the source that has moved most as the modelling has improved. Surface water flooding is local, fast and often unrelated to the nearest watercourse.
• Groundwater. Reported where data exists. Groundwater flooding is slow, persistent and hard to defend against, and a blank result means no data rather than no risk. Our guide to checking groundwater and water table maps covers what to do when the layer is empty.
• Reservoirs. A worst-case extent with no annual chance attached, shown so that people know they are downstream of a large reservoir.

A property can be Very Low for rivers and High for surface water. In urban England that combination is common, and it is the one most often missed by a reader who takes the first band as the answer.

What NaFRA2 changed, and why your risk band may have moved

The second National Flood Risk Assessment, published on 17 December 2024, rebuilt the national picture, and its results are what the public service now shows. The headline totals rose sharply: 2.4 million properties at risk from rivers and the sea, 4.6 million from surface water, and around 6.3 million in total once the overlap between the two is removed.

Surface water risk rose 43% on the previous assessment, which the Environment Agency attributes to improvements in its data, modelling and use of technology rather than to a physical change on the ground.

Rivers and sea totals stayed broadly stable, but the number of properties in the highest risk categories rose by 88%. Looking further out, the assessment puts around 8 million properties, roughly one in four, at risk by the middle of the century once climate change is allowed for.

The practical consequence is that a band can change without anything happening at the property. If your result moved between 2024 and 2025, the most likely explanation is better modelling, not a new hazard. Our NaFRA2 explainer covers the methodology change in more detail.

Why the long term flood risk map and the Flood Map for Planning disagree

The two Environment Agency services are built for different users and make opposite assumptions about defences. The Flood Map for Planning, often shortened to FMfP, shows the undefended floodplain and divides it into Flood Zones, because planning policy needs to know what the land would do if the defences were not there. The long term service shows defended, present-day risk in probability bands, because a householder wants to know their actual exposure now.

Read that table twice if a site has just produced two contradictory answers. The climate change allowance row is the one people miss: the planning map is deliberately the more conservative of the two. A Flood Zone 3 designation and a Low band are entirely compatible, and a house can be in a flood zone having never flooded. What matters is which question you are being asked to answer.

What you cannot use the long term flood risk map for

Five things, and a planning officer will pick up on all of them.

1. Redefining a flood zone. Flood zones come from the Flood Map for Planning. A screenshot showing Low risk does not move a boundary. There is a formal Environment Agency map challenge route, and it needs modelled evidence.
2. Passing the sequential test. The test weighs all sources of flooding, including surface water with climate change, and the September 2025 planning practice guidance update carried that position into what is now Policy F5. Sequential and exception test reports are prepared against the planning evidence base, not the public map.
3. Avoiding a flood risk assessment. Policy F4 requires an assessment wherever the strategic flood risk assessment or the Flood Map for Planning shows risk from any source. A Flood Zone 1 site with mapped surface water risk can now need one.
4. Evidencing that the risk is acceptable. Local planning authorities and the Environment Agency want modelled flood levels, finished floor levels, safe access and egress, and breach or overtopping analysis. That work draws on Environment Agency Products 4 to 7 and site survey, not a band.
5. Standing in for a defended-site case. Even though the map credits defences, it cannot tell you their standard of protection, their condition assessment, or what happens when they are overtopped. That needs hydraulic modelling.

The rule of thumb is simple. If a decision-maker will read it, use the Flood Map for Planning and a site-specific assessment, following the Environment Agency's own planning guidance. If you are deciding something for yourself, it is a fair place to start.

What changed on 28 May 2026

On 28 May 2026 the Environment Agency added surface water climate change extents and banded depth layers to the Flood Map for Planning. Version 4.0 of its Product Suitability for Planning Diagram, published the same month, sets out which datasets do which job, and the accompanying guidance states that planners no longer need to refer to the surface water information on Check your long term flood risk.

That closed a gap that had caused genuine difficulty. Until then, surface water was mapped properly only on the public service, so applicants used the public service, then found that the answer it gave them was not one a planning authority would accept. The surface water data on the planning map now uses an upper-end climate allowance for the 2070s, against the central 2050s allowance used on the public service, so the planning extents are the more conservative of the two by design. The May 2026 update is covered in full separately.

Long term flood risk or live flood warnings? Two different services

Check your long term flood risk and Check for flooding are separate Environment Agency services, and people land on the wrong one all the time. The long term service answers what could happen over decades. Check for flooding answers what is happening today: current flood warnings and alerts, the five-day national flood forecast, and live readings from river, sea, groundwater and rainfall gauges.

A property with a Very Low long-term band can still be under a flood warning tomorrow, and a High band means nothing about whether a warning is in force right now.

Use the long term service for buying, insuring, planning ahead and understanding a place. Use Check for flooding, sign up for flood warnings, or call Floodline on 0345 988 1188, when weather is coming. The Met Office issues the weather warnings; the Environment Agency and the Flood Forecasting Centre handle the flood side.

What the map means when you are buying, selling or insuring

For a property transaction the map is a screening step, not an answer, and it is worth being clear with yourself about which it is.

• Buying. Check all four sources. Reading the rivers band alone is the commonest mistake, and a Medium or High surface water band on a property nowhere near a watercourse is the classic surprise it produces. That combination is worth a site-level look before exchange.
• Insurance. Insurers use their own models and their own data, so the public band tells you which way a quote is likely to go rather than what it will say. Flood Re exists for eligible homes where the market price is unaffordable.
• Selling. Flood history is a separate matter from flood risk. The TA6 form asks what has actually happened to the property, and the map does not answer that.
• Conveyancing. A search report is not a flood risk assessment, and a conveyancing flood report will not satisfy a planning authority.

Where the stakes justify it, a flood risk survey for a property purchase measures ground and threshold levels at the address and tells you what the 2m grid cannot. Mapped risk and measured risk diverge more often than people expect, and the difference is usually a few hundred millimetres of ground level.

Where the long term flood risk map runs out

It is a national screening product, and every limitation follows from that. Current modelling resolves to 2m grid squares, with some areas still carried at the older 50m resolution; neither knows where your door threshold sits, what your private drainage does, or that the ground falls half a metre between the pavement and the back wall. Nor does it show flood depth in the way a hydraulic model does, or account for a blocked culvert or a trash screen carrying debris in the middle of an event.

That is not a criticism. No national dataset surveys 25 million addresses. It does mean that a result sitting close to a band boundary, or one that flatly contradicts what a site visibly does in heavy rain, is a prompt to look properly. It is not a conclusion. We have written at length on how accurate flood maps really are, including a case where measured levels put a mapped High risk plot at Low risk at the building itself.

The long term flood risk map is a good public service being asked, fairly often, to do a job it was never built for. Both flood risk maps are right about the question they were built to answer. Read the bands as ranges, remember that this one credits the defences, and treat a result near a boundary as a question rather than an answer. If the result has to persuade a local planning authority, that is a different piece of work, and our consultants prepare site-specific flood risk assessments for planning across England and Wales. Call 01293 214444 or email enquiries@unda.co.uk.

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