Photo: John Sutton · CC BY-SA 2.0Heavy rain is Cambridge’s main flood risk: 12% of homes, against 1.3% from rivers or the sea
On the Environment Agency’s maps, which allow for flood defences, “high or medium” means at least a 1 in 100 chance of flooding from rivers or the sea in any year. Hazard risk puts Cambridge at C: #30 of 50 in Cambridgeshire.
What stands out about Cambridge’s hazards
From the Environment Agency’s maps and records and the BGS radon atlas, below.
What Cambridge faces
Each hazard against its own yardstick; meters run from low to high on that yardstick.
Rivers and the sea
Surface water
Past floods
Flood warnings
Radon
Cambridge grades C for hazard risk
Flood risk from rivers and the sea, against all UK towns.
The share of homes at high or medium risk from rivers and the sea, ranked against every UK town of 1,000 or more: fewer homes at risk is better. Towns with none at high or medium risk are ordered by their share at low risk, so they don’t all share one score. Surface water and radon aren’t graded: they are described below.
Where the water goes in Cambridge
Turn layers on and off. Blue is the risk from rivers and the sea; pink is where heavy rain collects. Both allow for flood defences.
The river and sea risk follows the River Cam and the Bin Brook. Surface-water risk is spread across the city, in dips, underpasses and along small streams, which is why more homes are exposed to it.
1.3% of Cambridge’s homes are at high or medium risk from rivers or the sea
The Environment Agency’s national map, allowing for defences. A further 1.8% are at low risk.
Share of each UK town’s homes at high or medium risk from rivers and the sea. 35% of UK towns have none; Cambridge has more than 72% of towns.
| # | Town | People | High or med. | |
|---|---|---|---|---|
| 1 | Camden London | 209,342 | 0% | |
| 2 | Westminster London | 203,571 | 0% | |
| 3 | Oldham Greater Manchester | 110,722 | 0% | |
| … | ||||
| 37 | Salford Greater Manchester | 108,431 | 1.1% | |
| 38 | Exeter Devon | 126,181 | 1.3% | |
| 39 | Cambridge Cambridgeshire | 152,742 | 1.3% | |
| 40 | Crawley West Sussex | 120,567 | 1.5% | |
| 41 | Maidstone Kent | 109,503 | 1.6% | |
| … | ||||
| 50 | Gloucester Gloucestershire | 118,562 | 4.5% | |
| 51 | Oxford Oxfordshire | 170,799 | 4.7% | |
UK towns of 107,000 to 214,000 people.
The Environment Agency’s Risk of Flooding from Rivers and Sea (NaFRA2, June 2026) counts each postcode’s homes by band; the shares weight those postcodes by Census 2021 households. The EA counts include homes built since 2021.
Heavy rain puts about 9.2 times as many Cambridge homes at risk as rivers and the sea do
Surface water is rain that falls faster than drains and the ground can take it. It is mapped separately from rivers and the sea, and it is not in the Hazard risk Grade.
About 7% of homes are at high risk of surface-water flooding (a 1 in 30 chance or more each year) and 5.1% at medium risk: roughly 6,750 households. A further 15% face a low risk from surface water. That is more than 95% of UK towns.
Our estimate: every address in the city (ONS NSUL) read on the Environment Agency’s Risk of Flooding from Surface Water map (NaFRA2, 2025), each postcode’s share weighted by its Census 2021 households. Neither agency publishes a count of homes for surface water, so treat it as a guide; one street can differ from the next.
Cambridge has flooded in 3 recorded years since 1947, most of all in 1947
Every flood the Environment Agency has mapped inside Cambridge’s built-up area, newest first. The record is fullest for big river floods; small and surface-water floods are often missing.
- 2001October 2001: River flooding recorded42 hectares inside today’s built-up area
- 1978May 1978: River flooding recorded7 hectares inside today’s built-up area
- 1947March 1947: River flooding recorded71 hectares inside today’s built-up area
Floodwater covered 71 hectares of what is now Cambridge in 1947, the largest flood the record holds here (March).
688 of Cambridge’s households today live inside the outline of a recorded flood.
Since 1947, the largest recorded flood inside the city covered 42 hectares.
No flood warning or alert is in force for Cambridge · 0 warnings in 20 years
The Environment Agency has 6 flood warning areas and 2 alert areas reaching into the city; warnings since the service began in 2006.
None of Cambridge’s 6 flood warning areas has had a flood warning since the service began in 2006.
Show the 8 warning and alert areas
| Area | Kind | Since 2006 | Now |
|---|---|---|---|
| Low lying areas close to the River Cam at Chesterton and Fen Ditton | Warning area | 0 | None |
| Wider area at risk from the River Cam at Chesterton and Fen Ditton | Warning area | 0 | None |
| Low lying areas close to Bin Brook at Newnham | Warning area | 0 | None |
| Wider area at risk from Bin Brook at Newnham | Warning area | 0 | None |
| Low lying areas close to the River Cam at Grantchester and Chesterton | Warning area | 0 | None |
| Wider area at risk from the River Cam at Grantchester and Chesterton | Warning area | 0 | None |
| Lower River Cam in Cambridgeshire | Alert area | 99 | None |
| Bin Brook in Cambridgeshire | Alert area | 20 | None |
Environment Agency Historic Flood Warnings (first issues only, not updates; “flood watch” counted as an alert before 2011) and the real-time flood-monitoring API. Sign up for free warnings on GOV.UK or call Floodline, 0345 988 1188.
Cambridge is in the lowest radon band
Radon is a natural radioactive gas from the ground; long exposure raises the risk of lung cancer. The atlas gives the chance that a home in each 1 km square is above the UK action level (200 Bq/m³).
Every 1 km square over Cambridge is in the lowest band: fewer than 1 in 100 homes are expected to be above the action level.
BGS/UKHSA Indicative Atlas of Radon in Great Britain, version 3. Check an address at UKradon.org.
Flood risk in the places around Cambridge
Share of homes at high or medium and at low risk from rivers and the sea. Tap a town for its page.
| Town | People | High or medium | Low | Hazard |
|---|---|---|---|---|
| Cambridge | 152,742 | 1.3% | 1.8% | C |
| Milton | 4,150 | under 0.1% | under 0.1% | B |
| Girton | 4,384 | 2.1% | 0.4% | C− |
| Histon and Impington | 7,781 | under 0.1% | 1.2% | B |
| Fulbourn | 3,737 | 0% | 0% | A |
| Great Shelford and Stapleford | 6,159 | 0.4% | 0.6% | C+ |
| Hauxton | 1,322 | 0.2% | 0% | B− |
| Harston | 1,827 | 0% | 0% | A |
Girton, 3.1 miles north-west, has the most homes at risk around Cambridge (2.1% at high or medium). Fulbourn and Harston have none.
Get ready for what Cambridge faces
Free warnings, what to do in a cloudburst, and what to check before you move.
- Sign up free for Environment Agency flood warnings by text, call or email.
- Floodline: 0345 988 1188, 24 hours.
- Cambridge’s warning areas include Wider area at risk from the River Cam at Chesterton and Fen Ditton and Low lying areas close to the River Cam at Grantchester and Chesterton.
- Surface water rises in minutes, often with no warning issued: stay out of underpasses and dips.
- Keep the gullies and drains outside your home clear of leaves.
- Report a blocked road drain to the council.
- Never walk or drive through floodwater: 30 cm of moving water can float a car.
- Move valuables, papers and medicines upstairs.
- Turn off gas, electricity and water if you’re told to.
- Check the address on GOV.UK’s long-term flood risk service: it gives rivers and sea and surface water separately.
- Ask whether the home has flooded or had a flood insurance claim; the TA6 property form asks the seller.
- Homes built before 2009 can get flood cover through Flood Re, the government-backed scheme; newer homes can’t.
What this data can and can’t tell you
- Defences are counted. Both agencies’ maps allow for flood defences and the chance they are overtopped or fail, so a town behind a defence scheme can show few homes at high risk and many at low risk.
- Surface water is our estimate. Neither agency publishes a count of homes at risk from surface water, so we read each address on the map. A flat on a hill and a basement in a dip can share a postcode.
- Past floods are what was recorded. The flood outlines come from surveys, aerial photographs and reports; many small floods, and most surface-water floods, were never mapped.
- One town, many streets. Risk is street by street. Check a specific address on GOV.UK’s long-term flood risk service before you buy or rent.
Questions about flooding and hazards in Cambridge
Does Cambridge flood?
The last flood the Environment Agency recorded inside the city was in October 2001. 1.3% of homes are at high or medium risk from rivers and the sea on the Environment Agency’s maps, which allow for flood defences. About 12% of homes are at high or medium risk from surface water, when heavy rain overwhelms the drains. Cambridge grades C for hazard risk against UK towns.
Which parts of Cambridge are at risk of flooding?
From rivers and the sea, the places the Environment Agency warns directly: Wider area at risk from the River Cam at Chesterton and Fen Ditton, Low lying areas close to the River Cam at Grantchester and Chesterton, Low lying areas close to the River Cam at Chesterton and Fen Ditton and Wider area at risk from the River Cam at Grantchester and Chesterton. Surface water can collect in low spots anywhere in the city. Check a specific address on GOV.UK’s long-term flood risk service.
When did Cambridge last flood?
The recorded flood outlines inside the city run from 1947 to 2001 (3 years); the largest was in 1947.
Is Cambridge at risk of surface water flooding?
About 7% of homes are at high risk and 5.1% at medium risk from surface water, against 1.3% at high or medium risk from rivers and the sea. Surface water floods come with little warning, and the agencies don’t issue warnings for them.
Is radon a problem in Cambridge?
Not by the atlas: every 1 km square over Cambridge is in the lowest band, where fewer than 1 in 100 homes are expected to be above the action level.
Are there flood warnings in Cambridge now?
No flood warning or alert was in force near Cambridge at 10 November 2026, 12:27. Live warnings are on GOV.UK’s Check for flooding service and Floodline, 0345 988 1188.
Contains Environment Agency information © Environment Agency and/or database right 2026. Contains British Geological Survey materials © UKRI 2026.
Sources: Environment Agency Risk of Flooding from Rivers and Sea, postcodes in areas at risk (June 2026); Natural Resources Wales Flood Risk Assessment Wales (May 2026); ONS Census 2021 households by postcode · Environment Agency Risk of Flooding from Surface Water (NaFRA2, 2025) and Natural Resources Wales Flood Risk Assessment Wales surface water and small watercourses, read at every address (ONS National Statistics UPRN Lookup, September 2026) and weighted by Census 2021 households by postcode · Environment Agency Recorded Flood Outlines and Natural Resources Wales historic flood map, inside the ONS 2022 built-up-area boundary · Environment Agency real-time flood-monitoring API · Environment Agency Historic Flood Warnings (January 2006 to June 2026) and flood warning and alert areas · BGS/UKHSA Indicative Atlas of Radon in Great Britain, version 3, by 1 km square · TownRatings grades: our own summary of the data, ranked against UK towns only. All under the Open Government Licence v3.0.
Contains public sector information licensed under the Open Government Licence v3.0. Contains HM Land Registry data © Crown copyright and database right 2026. Contains OS data © Crown copyright and database right 2026 (ONS boundaries). Northern Ireland: Source: NISRA; contains Land & Property Services data and Ordnance Survey of Northern Ireland information, © Crown copyright, licensed under the Open Government Licence v3.0. Scotland: contains National Records of Scotland data, Registers of Scotland data and SEPA data, © Crown copyright / © SEPA 2025, licensed under the Open Government Licence v3.0.