Flood risk maps compared: which one to use

Why there is more than one map

The Environment Agency publishes several flood datasets because they serve different people. Planners need a consistent view of where land is exposed regardless of existing defences. Householders and insurers want to know the realistic risk today. Researchers and surveyors want to know where flooding has actually happened. Each map is correct for its own purpose, and the confusion usually comes from reading one map as if it were another.

Flood Map for Planning

This is the map behind the flood zones. It shows Flood Zone 2 and Flood Zone 3 for rivers and the sea, with everything else being Flood Zone 1. It is used for planning applications and is described in the GOV.UK planning practice guidance. The key point is that it initially ignores flood defences, so it shows where water could go if defences were not there. Use it when you are asking a planning question: do I need a flood risk assessment, and will the council take a cautious view of building here? Our flood zones guide covers it in detail.

Risk of Flooding from Rivers and Sea (RoFRS)

This map sorts land into four bands: high (more than 1 in 30 each year), medium (between 1 in 100 and 1 in 30), low (between 1 in 1,000 and 1 in 100) and very low (less than 1 in 1,000). It takes the presence and condition of flood defences into account. Insurers, lenders and surveyors often look at this view because it is closer to the likely reality for a defended property. Use it when you want to know how likely river or sea flooding is today.

Risk of Flooding from Surface Water (RoFSW)

This uses the same four bands but for rainwater running over the ground. It is a separate layer and often shows a very different picture from the river and sea maps, because it follows slopes and hollows rather than watercourses. It is the only one of these maps that helps with the hillside street or the basement. See our surface water guide for how to read it.

Historic and recorded flood maps

The Historic Flood Map shows the extent of all known past flooding from rivers, the sea and groundwater, and the Recorded Flood Outlines dataset holds individual flood events with details such as date, source and cause where they are known. These look back rather than forward. They are valuable evidence because an actual flood is stronger than a model, but they have an important limit: the absence of a record does not prove a place has never flooded. Records depend on whether the event was reported and measured.

Why zones and bands can disagree

A common surprise is a property in Flood Zone 3 that the risk bands call low or very low. The reason is defences. The Flood Map for Planning deliberately ignores them, while RoFRS includes them. The reverse can also happen when defences are poor or when the models were updated at different times. Neither map is wrong. Zone 3 tells you the land is naturally floodplain. A low RoFRS band tells you defences currently reduce the chance. Both facts matter, because defences need funding and maintenance, and they can be overtopped in an extreme event.

A low band is a reduced chance, not a promise. Flood defences are designed to a standard of protection, and bigger events than the design standard can and do happen.

Which map for which job

• Planning an extension or new build: Flood Map for Planning, then ask the council.
• Checking likelihood today for a river or coastal home: Rivers and Sea risk bands.
• Hill, basement or street-drainage worries: Surface water bands.
• Evidence of past flooding: Historic and Recorded Flood Outlines, plus the seller’s answers and your conveyancer’s searches.
• Insurance questions: bands are a guide, but the insurer’s own model decides. See flood insurance.

Limits that apply to all of them

National flood maps are modelled at a broad scale, updated periodically, and cover England only. Wales, Scotland and Northern Ireland publish their own. They do not show every ditch or private drain, and they cannot see a blocked gully or a recently built wall. The GOV.UK long term flood risk service is the official place to view them, and our check pulls the same layers for one point so you can compare them side by side.

Check your own postcode

Our free check shows the flood zone, the river, sea and surface water bands, and recorded floods for any English postcode.

Check a postcode