Photo: Stefan Czapski · CC BY-SA 2.0Surface water, more than the river, is Tower Hamlets’s flood risk: 7.7% of homes, against 0.5% 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 Tower Hamlets at C+: #12 of 33 in London.
What stands out about Tower Hamlets’s hazards
From the Environment Agency’s maps and records and the BGS radon atlas, below.
What Tower Hamlets 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
Tower Hamlets 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 Tower Hamlets
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 Lee and the River Thames. Surface-water risk is spread across the borough, in dips, underpasses and along small streams, which is why more homes are exposed to it.
0.5% of Tower Hamlets’s homes are at high or medium risk from rivers or the sea
The Environment Agency’s national map, allowing for defences. A further under 0.1% 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; Tower Hamlets has more than 58% of towns.
| # | Town | People | High or med. | |
|---|---|---|---|---|
| 1 | Southwark London | 307,076 | 0% | |
| 2 | Newham London | 351,065 | under 0.1% | |
| 3 | Wolverhampton West Midlands | 234,029 | under 0.1% | |
| … | ||||
| 11 | Lambeth London | 317,108 | 0.4% | |
| 12 | Luton Bedfordshire | 233,524 | 0.4% | |
| 13 | Tower Hamlets London | 311,072 | 0.5% | |
| 14 | Brighton and Hove East Sussex | 277,096 | 0.5% | |
| 15 | Bexley London | 246,074 | 0.6% | |
| … | ||||
| 39 | Nottingham Nottinghamshire | 299,786 | 3.6% | |
| 40 | Kingston upon Hull East Riding of Yorkshire | 270,816 | 6.3% | |
UK towns of 218,000 to 436,000 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 16.1 times as many Tower Hamlets 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 2.9% of homes are at high risk of surface-water flooding (a 1 in 30 chance or more each year) and 4.9% at medium risk: roughly 9,400 households. A further 13% face a low risk from surface water. That is more than 86% of UK towns.
Our estimate: every address in the borough (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.
Tower Hamlets has flooded in 2 recorded years since 1928, most of all in 1928
Every flood the Environment Agency has mapped inside Tower Hamlets’s built-up area, newest first. The record is fullest for big river floods; small and surface-water floods are often missing.
- 1947January 1947: River flooding recorded47 hectares inside today’s built-up area
- 1928January 1928: The sea came in166 hectares inside today’s built-up area
Floodwater covered 166 hectares of what is now Tower Hamlets in 1928, the largest flood the record holds here (January).
13,436 of Tower Hamlets’s households today live inside the outline of a recorded flood.
Since 1928, the largest recorded flood inside the borough covered 47 hectares.
No flood warning or alert is in force for Tower Hamlets · 0 warnings in 20 years
The Environment Agency has 7 flood warning areas and 4 alert areas reaching into the borough; warnings since the service began in 2006.
None of Tower Hamlets’s 7 flood warning areas has had a flood warning since the service began in 2006.
Show the 11 warning and alert areas
| Area | Kind | Since 2006 | Now |
|---|---|---|---|
| Tidal Thames from the Limehouse Basin to Blackfriars Bridge | Warning area | 0 | None |
| Lower River Lee at Hackney and Walthamstow | Warning area | 0 | None |
| Lower River Lee at Stratford | Warning area | 0 | None |
| Lower River Lee from West Ham and Canning Town | Warning area | 0 | None |
| Tidal Thames at the Isle of Dogs north of South Dock | Warning area | 0 | None |
| Tidal Thames at the Isle of Dogs south of South Dock | Warning area | 0 | None |
| Tidal Thames at Mill Meads and East Plaistow | Warning area | 0 | None |
| Tidal Thames riverside from the Thames Barrier to Putney Bridge | Alert area | 94 | None |
| Lower River Lee from Hoddesdon to Canning Town | Alert area | 17 | None |
| Tidal Thames in the boroughs of Tower Hamlets, City of London, City of Westminster, Ken and Chelsea | Alert area | 2 | None |
| Tidal Thames in the boroughs of Havering, Barking and Dagenham, and Newham | Alert area | 2 | 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.
Parts of Tower Hamlets are in radon Affected Areas, at the low end
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).
6% of Tower Hamlets’s built-up area is in a radon Affected Area (1% of homes or more above the action level).
The squares are indicative: each takes the highest band found anywhere inside it, so most homes in a coloured square are below it. Only a three-month test in the home gives a real answer.
BGS/UKHSA Indicative Atlas of Radon in Great Britain, version 3. Check an address at UKradon.org.
Flood risk in the places around Tower Hamlets
Share of homes at high or medium and at low risk from rivers and the sea. Tap a town for its page.
Lewisham, 4.5 miles south, has the most homes at risk around Tower Hamlets (3.6% at high or medium). City of London, Southwark and Islington have none.
Get ready for what Tower Hamlets 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.
- Tower Hamlets’s warning areas include Tidal Thames at the Isle of Dogs north of South Dock and Tidal Thames at the Isle of Dogs south of South Dock.
- 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.
- Test over three months, in a living room and a bedroom.
- Above 200 Bq/m³, a small sump and fan usually fixes it.
- New homes in radon areas are built with protection: basic from 3%, full from 10%.
- 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.
- Check radon for the address on UKradon.org (a small fee) or ask the seller for a test result.
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 Tower Hamlets
Does Tower Hamlets flood?
The last flood the Environment Agency recorded inside the borough was in January 1947. 0.5% 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 7.7% of homes are at high or medium risk from surface water, when heavy rain overwhelms the drains. Tower Hamlets grades C+ for hazard risk against UK towns.
Which parts of Tower Hamlets are at risk of flooding?
From rivers and the sea, the places the Environment Agency warns directly: Tidal Thames at the Isle of Dogs north of South Dock, Tidal Thames at the Isle of Dogs south of South Dock, Lower River Lee from West Ham and Canning Town and Tidal Thames from the Limehouse Basin to Blackfriars Bridge. Surface water can collect in low spots anywhere in the borough. Check a specific address on GOV.UK’s long-term flood risk service.
When did Tower Hamlets last flood?
The recorded flood outlines inside the borough run from 1928 to 1947 (2 years); the largest was in 1928.
Is Tower Hamlets at risk of surface water flooding?
About 2.9% of homes are at high risk and 4.9% at medium risk from surface water, against 0.5% 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 Tower Hamlets?
6% of the borough’s built-up area is in a radon Affected Area on the BGS/UKHSA atlas. Most homes are below it; a three-month test is the only way to know.
Are there flood warnings in Tower Hamlets now?
No flood warning or alert was in force near Tower Hamlets at 4 November 2026, 08:08. 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.