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Bletchley QueenswayPhoto: Tom walker · CC BY 3.0
B−Hazard risk Grade
Flood & hazards in Bletchley · Environment Agency

In Bletchley, heavy rain puts more homes at risk than rivers or the sea: 6.9%, against 0.2%

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. Bletchley grades B− for hazard risk: #26 of 39 in Buckinghamshire.

1947worst recorded flood22flood warnings since 20060.2%at low risk
In brief

What stands out about Bletchley’s hazards

From the Environment Agency’s maps and records and the BGS radon atlas, below.

Rain, more than the river6.9% of homes sit where heavy rain can flood the streets, against 0.2% at risk from rivers and the sea.Remembers 1947Floodwater covered 5 hectares of today’s Bletchley in 1947; 180 of today’s households live inside past flood outlines.22 flood warnings since 2006For the parts of Bletchley the Environment Agency warns directly; the most recent on 5 January 2025.Low radonEvery 1 km square over Bletchley is in the lowest radon band: under 1% of homes above the action level.
By hazard

What Bletchley faces

Each hazard against its own yardstick; meters run from low to high on that yardstick.

Rivers and the sea

0.2%of homes at high or medium risk
Fewer than the typical UK town · more than 49% of towns
34 homes by the EA’s own count

Surface water

6.9%of homes at high or medium risk
More than 82% of UK towns
Rivers and sea: 0.2%

Past floods

3years with a recorded flood
Last recorded: 1992
180 households inside past outlines

The River Ouzel

1.39 mhighest in winter 2025–26 at Bletchley
22nd-highest of 31 winters
Record 1.90 m, September 2024

Flood warnings

22flood warnings since 2006
16 flood alerts for the wider area
Last warning 5 January 2025

Radon

0%of the town in a radon Affected Area
Highest band here: Under 1% of homes
No square of 5% or more
Not on this page: coastal erosion, subsidence and shrink-swell ground (the British Geological Survey licenses it), groundwater flooding and reservoir failure.
Hazard risk Grade

Bletchley grades B− for hazard risk

Flood risk from rivers and the sea, against all UK towns.

Homes at high or medium flood risk (0.2%)Fewer than 51% of 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.

Flood map

Where the water goes in Bletchley

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.

Recorded flood: 1947Recorded flood: 1968Recorded flood: 1992© OpenStreetMap contributors · EA NaFRA2
HighMediumLowrivers & seaHighMediumLowsurface waterBletchley’s built-up area

The river and sea risk follows the River Ouzel and the Water Eaton Brook. Surface-water risk is spread across the town, in dips, underpasses and along small streams, which is why more homes are exposed to it.

Rivers and the sea

0.2% of Bletchley’s homes are at high or medium risk from rivers or the sea

The Environment Agency’s national map, allowing for defences. A further 0.2% are at low risk.

High riskunder 0.1%of homes · 1 in 30 a year or more5 homes, EA count
Medium risk0.2%of homes · 1 in 30 to 1 in 10029 homes, EA count
Low risk0.2%of homes · 1 in 100 to 1 in 1,00030 homes, EA count
Where Bletchley sits among 3,735 UK towns
35%None
23%Under 0.5%Bletchley
9%0.5–1%
11%1–2%
11%2–5%
5%5–10%
3%10–20%
2%20% +

Share of each UK town’s homes at high or medium risk from rivers and the sea. 35% of UK towns have none; Bletchley has more than 49% of towns.

Towns its size: 56th of 160 from the fewest homes at risk
#TownPeopleHigh or med.
1Smethwick West Midlands56,3430%
2Bootle Merseyside53,7220%
3Bloxwich West Midlands51,8910%
…
54Bebington Merseyside57,6070.2%
55Winchester Hampshire48,4860.2%
56Bletchley Buckinghamshire45,0180.2%
57Great Malvern Worcestershire33,1940.2%
58Barry South Glamorgan56,5890.2%
…
159Exmouth Devon35,5029.8%
160Caversham Berkshire33,03813%

UK towns of 32,000 to 63,000 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.

Surface water

Heavy rain puts about 36.2 times as many Bletchley 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.

Surface water6.9%
Rivers and the sea0.2%
0%10.5%21% of homes

About 4.3% of homes are at high risk of surface-water flooding (a 1 in 30 chance or more each year) and 2.6% at medium risk: roughly 1,220 households. A further 8.6% face a low risk from surface water. That is more than 82% of UK towns.

~1,220
households at high or medium risk
8.6%
of homes at low risk
82%
of UK towns have a smaller share
20,982
addresses read on the map

Our estimate: every address in the town (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.

Flood history

Bletchley has flooded in 3 recorded years since 1947, most of all in 1947

Every flood the Environment Agency has mapped inside Bletchley’s built-up area, newest first. The record is fullest for big river floods; small and surface-water floods are often missing.

  1. 19921992: River flooding recordedUnder 1 hectare inside today’s built-up area
  2. 1968July 1968: River flooding recorded5 hectares inside today’s built-up area
  3. 19471947: River flooding recorded5 hectares inside today’s built-up area
The worst: 19475 ha

Floodwater covered 5 hectares of what is now Bletchley in 1947, the largest flood the record holds here.

180 of Bletchley’s households today live inside the outline of a recorded flood.

Since 1947, the largest recorded flood inside the town covered 5 hectares.

River levels

The River Ouzel at Bletchley: highest 1.90 m, in September 2024

The highest level each winter (October to September) at the Environment Agency’s Bletchley gauge (Water Eaton), since 1990. The river normally runs between 0.22 m and 0.68 m here.

Highest level each winter, metres
Winter 1992–93: highest 1.51 m · 42 days above the normal rangeWinter 1993–94: highest 1.56 m · 54 days above the normal rangeWinter 1996–97: highest 0.59 m · 0 days above the normal rangeWinter 1997–98: highest 1.59 m · 13 days above the normal rangeWinter 1998–99: highest 1.39 m · 42 days above the normal rangeWinter 1999–00: highest 1.52 m · 22 days above the normal rangeWinter 2000–01: highest 1.67 m · 65 days above the normal rangeWinter 2001–02: highest 1.40 m · 18 days above the normal rangeWinter 2002–03: highest 1.80 m on 2 January 2003 · 34 days above the normal rangeWinter 2003–04: highest 1.16 m · 14 days above the normal rangeWinter 2004–05: highest 1.38 m · 2 days above the normal rangeWinter 2005–06: highest 0.57 m · 0 days above the normal rangeWinter 2006–07: highest 1.82 m on 21 July 2007 · 47 days above the normal rangeWinter 2007–08: highest 1.69 m · 39 days above the normal rangeWinter 2008–09: highest 1.61 m · 20 days above the normal rangeWinter 2009–10: highest 1.61 m · 32 days above the normal rangeWinter 2010–11: highest 1.32 m · 12 days above the normal rangeWinter 2011–12: highest 1.68 m · 16 days above the normal rangeWinter 2012–13: highest 1.55 m · 45 days above the normal rangeWinter 2013–14: highest 1.77 m on 7 February 2014 · 54 days above the normal rangeWinter 2014–15: highest 1.07 m · 12 days above the normal rangeWinter 2015–16: highest 1.43 m · 18 days above the normal rangeWinter 2016–17: highest 1.19 m · 9 days above the normal rangeWinter 2017–18: highest 1.35 m · 26 days above the normal rangeWinter 2018–19: highest 0.70 m · 2 days above the normal rangeWinter 2019–20: highest 1.57 m · 43 days above the normal rangeWinter 2020–21: highest 1.89 m on 4 October 2020 · 74 days above the normal rangeWinter 2021–22: highest 1.53 m · 23 days above the normal rangeWinter 2022–23: highest 3.98 m on 8 February 2023 · 28 days above the normal rangeWinter 2023–24: highest 1.82 m on 5 January 2024 · 74 days above the normal rangeWinter 2025–26: highest 1.39 m · 28 days above the normal range’22–23’20–21Record 1.90 m, 2024Top of normal range
1992–932025–26
The highest days on record
  • 8 February 20233.98 m
  • 4 October 20201.89 m
  • 23 September 19921.83 m
  • 5 January 20241.82 m
  • 21 July 20071.82 m
  • 2 January 20031.80 m

The River Ouzel has topped its normal range on 908 days since 1990, most in the winters of 2020–21 and 2023–24. By its highest day, the winter of 2025–26 was the 22nd-highest of the 31.

Environment Agency Hydrology API, Bletchley (station E21505), daily maximum level; the record and normal range from the EA’s stage scale. Live river levels are on GOV.UK’s Check for flooding.

Flood warnings

No flood warning or alert is in force for Bletchley · 22 warnings in 20 years

The Environment Agency has 2 flood warning areas and 1 alert area reaching into the town; warnings since the service began in 2006.

Now: no flood warnings or alerts for Bletchley (checked 6 November 2026, 00:52). Check for flooding on GOV.UK →
Warnings and alerts each year for areas in Bletchley
06
07
08
09
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
Flood warning (flooding expected)Flood alert (flooding possible)

Of the 22 warnings, 12 were for River Ouzel at Bletchley and Caldecotte and 10 for Water Eaton Brook at Water Eaton. 2024 had the most warnings (14).

The most recent warning was on 5 January 2025.

Show the 3 warning and alert areas
AreaKindSince 2006Now
River Ouzel at Bletchley and CaldecotteWarning area12None
Water Eaton Brook at Water EatonWarning area10None
River Ouzel in Central Bedfordshire, Buckinghamshire and Milton KeynesAlert area16None

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.

Radon

Bletchley 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).

SP8432: Under 1% of homes above the action levelSP8433: Under 1% of homes above the action levelSP8434: Under 1% of homes above the action levelSP8531: Under 1% of homes above the action levelSP8532: Under 1% of homes above the action levelSP8533: Under 1% of homes above the action levelSP8534: Under 1% of homes above the action levelSP8535: Under 1% of homes above the action levelSP8630: Under 1% of homes above the action levelSP8631: Under 1% of homes above the action levelSP8633: Under 1% of homes above the action levelSP8634: Under 1% of homes above the action levelSP8635: Under 1% of homes above the action levelSP8730: Under 1% of homes above the action levelSP8731: Under 1% of homes above the action levelSP8732: Under 1% of homes above the action levelSP8733: Under 1% of homes above the action levelSP8734: Under 1% of homes above the action levelSP8735: Under 1% of homes above the action levelSP8831: Under 1% of homes above the action levelSP8832: Under 1% of homes above the action levelSP8833: Under 1% of homes above the action levelSP8834: Under 1% of homes above the action levelSP8835: Under 1% of homes above the action levelSP8932: Under 1% of homes above the action levelSP8933: Under 1% of homes above the action level© OpenStreetMap contributors · BGS/UKHSA
Under 1%
Share of the town’s area in each band
Under 1% of homes100%

Every 1 km square over Bletchley 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.

Neighbours

Flood risk in the places around Bletchley

Share of homes at high or medium and at low risk from rivers and the sea. Tap a town for its page.

Newton Longville: Hazard risk B−Stoke Hammond: Hazard risk B−Milton Keynes: Hazard risk B−Woburn Sands: Hazard risk AStewkley: Hazard risk AAspley Guise: Hazard risk AHeath and Reach: Hazard risk B−Newton LongvilleStoke HammondMilton KeynesWoburn SandsStewkleyAspley GuiseHeath and ReachBletchley
ABCD
TownPeopleHigh or mediumLowHazard
Bletchley45,0180.2%0.2%B−
Newton Longville1,8770.1%0.6%B−
Stoke Hammond1,1550.3%1.1%B−
Milton Keynes197,3280.2%0.7%B−
Woburn Sands4,3150%0%A
Stewkley1,4210%0%A
Aspley Guise2,1140%0%A
Heath and Reach1,4510.3%0.3%B−

Woburn Sands, Stewkley and Aspley Guise have none.

Be ready

Get ready for what Bletchley faces

Free warnings, what to do in a cloudburst, and what to check before you move.

Get the warnings
  • Sign up free for Environment Agency flood warnings by text, call or email.
  • Floodline: 0345 988 1188, 24 hours.
  • Bletchley’s warning areas include River Ouzel at Bletchley and Caldecotte and Water Eaton Brook at Water Eaton.
Sign up ↗
In a cloudburst
  • 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.
When the river rises
  • 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.
Before you buy or rent in Bletchley
  • 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.
How to read these numbers

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.

Check the long-term flood risk for an address on GOV.UK →

Questions about flooding and hazards in Bletchley

Does Bletchley flood?

The last flood the Environment Agency recorded inside the town was in 1992. 0.2% 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 6.9% of homes are at high or medium risk from surface water, when heavy rain overwhelms the drains. Bletchley grades B− for hazard risk against UK towns.

Which parts of Bletchley are at risk of flooding?

From rivers and the sea, the places the Environment Agency warns directly: River Ouzel at Bletchley and Caldecotte and Water Eaton Brook at Water Eaton. Surface water can collect in low spots anywhere in the town. Check a specific address on GOV.UK’s long-term flood risk service.

When did Bletchley last flood?

The recorded flood outlines inside the town run from 1947 to 1992 (3 years); the largest was in 1947. Flood warnings have been issued for parts of the town since 2006, most recently on 5 January 2025.

Is Bletchley at risk of surface water flooding?

About 4.3% of homes are at high risk and 2.6% at medium risk from surface water, against 0.2% 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 Bletchley?

Not by the atlas: every 1 km square over Bletchley 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 Bletchley now?

No flood warning or alert was in force near Bletchley at 6 November 2026, 00:52. 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 Hydrology API (daily maximum river level) and flood-monitoring stage scales · 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.