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Basingstoke Town CentrePhoto: Mr Ignavy · CC BY-SA 2.0
CHazard risk Grade
Flood & hazards in Basingstoke · Environment Agency

Surface water, more than the river, is Basingstoke’s flood risk: 4.3% of homes, against 1% 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. For hazard risk, Basingstoke grades C: #51 of 76 in Hampshire.

1947worst recorded flood0flood warnings since 200690%in a radon Affected Area
In brief

What stands out about Basingstoke’s hazards

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

Rain, more than the river4.3% of homes sit where heavy rain can flood the streets, against 1% at risk from rivers and the sea.Remembers 1947Floodwater covered 14 hectares of today’s Basingstoke in 1947; 168 of today’s households live inside past flood outlines.No flood warning since 2006The Environment Agency has 4 warning areas in Basingstoke and hasn’t had to issue a flood warning for any of them.Radon in parts49% of the city is in 1 km squares where 5% or more of homes may be above the radon action level.
By hazard

What Basingstoke faces

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

Rivers and the sea

1%of homes at high or medium risk
More than the typical UK town · more than 68% of towns
516 homes by the EA’s own count

Surface water

4.3%of homes at high or medium risk
More than 61% of UK towns
Rivers and sea: 1%

Past floods

1years with a recorded flood
Last recorded: January 1947
168 households inside past outlines

The River Loddon

1.21 mhighest in winter 2025–26 at Pyotts Bridge
13th-highest of 19 winters
Record 1.45 m, July 2007

Flood warnings

0flood warnings since 2006
49 flood alerts for the wider area
Never warned

Radon

90%of the city in a radon Affected Area
Highest band here: 5–10% of homes
49% in squares 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

Basingstoke grades C for hazard risk

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

Homes at high or medium flood risk (1%)Fewer than 32% 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 Basingstoke

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: 1947© OpenStreetMap contributors · EA NaFRA2
HighMediumLowrivers & seaHighMediumLowsurface waterBasingstoke’s built-up area

The river and sea risk follows the Pettys Brook, the River Loddon and the Groundwater. Surface-water risk is spread across the city, in dips, underpasses and along small streams, which is why more homes are exposed to it.

Rivers and the sea

1% of Basingstoke’s homes are at high or medium risk from rivers or the sea

The Environment Agency’s national map, allowing for defences. A further 0.9% are at low risk.

High risk0.9%of homes · 1 in 30 a year or more451 homes, EA count
Medium risk0.1%of homes · 1 in 30 to 1 in 10065 homes, EA count
Low risk0.9%of homes · 1 in 100 to 1 in 1,000463 homes, EA count
Where Basingstoke sits among 3,735 UK towns
35%None
23%Under 0.5%
9%0.5–1%Basingstoke
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; Basingstoke has more than 68% of towns.

Towns its size: 39th of 60 from the fewest homes at risk
#TownPeopleHigh or med.
1Oldham Greater Manchester110,7220%
2Birkenhead Merseyside109,8540%
3Kensington and Chelsea London143,348under 0.1%
…
37Blackburn Lancashire124,9580.9%
38Solihull West Midlands107,7541%
39Basingstoke Hampshire117,2111%
40Cheltenham Gloucestershire115,9411%
41Salford Greater Manchester108,4311.1%
…
59Lincoln Lincolnshire104,5536%
60Grimsby Lincolnshire85,9158.9%

UK towns of 82,000 to 164,000 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 4.3 times as many Basingstoke 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 water4.3%
Rivers and the sea1%
0%7%14% of homes

About 2.2% of homes are at high risk of surface-water flooding (a 1 in 30 chance or more each year) and 2.1% at medium risk: roughly 2,090 households. A further 4.2% face a low risk from surface water. That is more than 61% of UK towns.

~2,090
households at high or medium risk
4.2%
of homes at low risk
61%
of UK towns have a smaller share
57,888
addresses read on the map

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.

Flood history

Basingstoke has flooded in 1 recorded year since 1947

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

  1. 1947January 1947: River flooding recorded14 hectares inside today’s built-up area
The worst: 194714 ha

Floodwater covered 14 hectares of what is now Basingstoke in 1947, the largest flood the record holds here (January).

168 of Basingstoke’s households today live inside the outline of a recorded flood.

River levels

The River Loddon at Pyotts Bridge: highest 1.45 m, in July 2007

The highest level each winter (October to September) at the Environment Agency’s Pyotts Bridge gauge (Old Basing), since 1995. The river normally runs between 0.95 m and 1.35 m here.

Highest level each winter, metres
Winter 2006–07: highest 1.45 m · 1 days above the normal rangeWinter 2007–08: highest 1.15 m · 0 days above the normal rangeWinter 2008–09: highest 1.23 m · 0 days above the normal rangeWinter 2009–10: highest 1.26 m · 0 days above the normal rangeWinter 2010–11: highest 1.23 m · 0 days above the normal rangeWinter 2011–12: highest 1.29 m · 0 days above the normal rangeWinter 2012–13: highest 1.27 m · 0 days above the normal rangeWinter 2013–14: highest 1.37 m · 4 days above the normal rangeWinter 2014–15: highest 1.17 m · 0 days above the normal rangeWinter 2015–16: highest 1.27 m · 0 days above the normal rangeWinter 2016–17: highest 1.14 m · 0 days above the normal rangeWinter 2017–18: highest 1.16 m · 0 days above the normal rangeWinter 2019–20: highest 1.28 m · 0 days above the normal rangeWinter 2020–21: highest 1.25 m · 0 days above the normal rangeWinter 2021–22: highest 1.11 m · 0 days above the normal rangeWinter 2022–23: highest 1.17 m · 0 days above the normal rangeWinter 2023–24: highest 1.26 m · 0 days above the normal rangeWinter 2024–25: highest 1.24 m · 0 days above the normal rangeWinter 2025–26: highest 1.21 m · 0 days above the normal rangeRecord 1.45 m, 2007Top of normal range
2006–072025–26
The highest days on record
  • 25 November 19959.25 m
  • 27 September 19959.23 m
  • 18 March 19969.21 m
  • 28 April 19969.19 m
  • 19 September 19959.19 m
  • 7 September 19959.18 m

The River Loddon has topped its normal range on 5 days since 1995, most in the winters of 2013–14 and 2006–07. By its highest day, the winter of 2025–26 was the 13th-highest of the 19.

Environment Agency Hydrology API, Pyotts Bridge (station 2401TH), 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 Basingstoke · 0 warnings in 20 years

The Environment Agency has 4 flood warning areas and 1 alert area reaching into the city; warnings since the service began in 2006.

Now: no flood warnings or alerts for Basingstoke (checked 4 November 2026, 19:53). Check for flooding on GOV.UK →
Warnings and alerts each year for areas in Basingstoke
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)

None of Basingstoke’s 4 flood warning areas has had a flood warning since the service began in 2006.

Show the 5 warning and alert areas
AreaKindSince 2006Now
Groundwater flooding in the Basingstoke and Buckskin areasWarning area0None
Groundwater flooding in the Sherborne St John areaWarning area0None
Pettys Brook at ChinehamWarning area0None
River Loddon at Old BasingWarning area0None
Upper River LoddonAlert area46None

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

Parts of Basingstoke are in radon Affected Areas, up to the 5–10% 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).

SU5847: 5–10% of homes above the action levelSU5848: 5–10% of homes above the action levelSU5947: 5–10% of homes above the action levelSU5948: 5–10% of homes above the action levelSU5949: 5–10% of homes above the action levelSU5950: 5–10% of homes above the action levelSU5951: 5–10% of homes above the action levelSU5952: 5–10% of homes above the action levelSU6047: 5–10% of homes above the action levelSU6048: 5–10% of homes above the action levelSU6049: 5–10% of homes above the action levelSU6050: 5–10% of homes above the action levelSU6051: 5–10% of homes above the action levelSU6052: 5–10% of homes above the action levelSU6053: 3–5% of homes above the action levelSU6148: 5–10% of homes above the action levelSU6149: 5–10% of homes above the action levelSU6150: 5–10% of homes above the action levelSU6151: 5–10% of homes above the action levelSU6152: 5–10% of homes above the action levelSU6153: 3–5% of homes above the action levelSU6154: 3–5% of homes above the action levelSU6249: 5–10% of homes above the action levelSU6250: 5–10% of homes above the action levelSU6251: 5–10% of homes above the action levelSU6252: 3–5% of homes above the action levelSU6253: 3–5% of homes above the action levelSU6254: 3–5% of homes above the action levelSU6349: 5–10% of homes above the action levelSU6350: 5–10% of homes above the action levelSU6351: 5–10% of homes above the action levelSU6352: 3–5% of homes above the action levelSU6353: 3–5% of homes above the action levelSU6354: 3–5% of homes above the action levelSU6355: 3–5% of homes above the action levelSU6450: 3–5% of homes above the action levelSU6451: 3–5% of homes above the action levelSU6452: 3–5% of homes above the action levelSU6453: 3–5% of homes above the action levelSU6454: 3–5% of homes above the action levelSU6455: Under 1% of homes above the action levelSU6551: 3–5% of homes above the action levelSU6552: 3–5% of homes above the action levelSU6553: 3–5% of homes above the action levelSU6554: Under 1% of homes above the action levelSU6555: Under 1% of homes above the action levelSU6556: Under 1% of homes above the action levelSU6653: 3–5% of homes above the action levelSU6654: 3–5% of homes above the action levelSU6655: Under 1% of homes above the action levelSU6656: 3–5% of homes above the action levelSU6755: 3–5% of homes above the action levelSU6756: 3–5% of homes above the action level© OpenStreetMap contributors · BGS/UKHSA
Under 1%3–5%5–10%
Share of the city’s area in each band
Under 1% of homes10%
3–5% of homes42%
5–10% of homes49%

90% of Basingstoke’s built-up area is in a radon Affected Area (1% of homes or more above the action level), and 49% in squares of 5% or more, mostly on the south-west side of the city.

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.

Neighbours

Flood risk in the places around Basingstoke

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

Old Basing: Hazard risk B−Oakley: Hazard risk ABramley: Hazard risk CSherfield on Loddon: Hazard risk B−Tadley: Hazard risk B+Hook: Hazard risk C−Odiham: Hazard risk C+Old BasingOakleyBramleySherfield on LoddonTadleyHookOdihamBasingstoke
ABCD
TownPeopleHigh or mediumLowHazard
Basingstoke117,2111%0.9%C
Old Basing3,8340.2%under 0.1%B−
Oakley5,2640%0%A
Bramley4,7300.9%2.7%C
Sherfield on Loddon1,3850.3%2.2%B−
Tadley14,7670%0.2%B+
Hook9,0622.8%0.2%C−
Odiham5,0910.5%0.5%C+

Hook, 6.3 miles east, has the most homes at risk around Basingstoke (2.8% at high or medium). Oakley and Tadley have none.

Be ready

Get ready for what Basingstoke 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.
  • Basingstoke’s warning areas include Groundwater flooding in the Basingstoke and Buckskin areas and Pettys Brook at Chineham.
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.
Radon
  • 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%.
UKradon ↗
Before you buy or rent in Basingstoke
  • 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.
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 Basingstoke

Does Basingstoke flood?

The last flood the Environment Agency recorded inside the city was in January 1947. 1% 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 4.3% of homes are at high or medium risk from surface water, when heavy rain overwhelms the drains. Basingstoke grades C for hazard risk against UK towns.

Which parts of Basingstoke are at risk of flooding?

From rivers and the sea, the places the Environment Agency warns directly: Groundwater flooding in the Basingstoke and Buckskin areas, Pettys Brook at Chineham, River Loddon at Old Basing and Groundwater flooding in the Sherborne St John area. 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 Basingstoke last flood?

The recorded flood outlines inside the city run from 1947 to 1947 (1 years); the largest was in 1947.

Is Basingstoke at risk of surface water flooding?

About 2.2% of homes are at high risk and 2.1% at medium risk from surface water, against 1% 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 Basingstoke?

90% of the city’s built-up area is in a radon Affected Area on the BGS/UKHSA atlas, and 49% is in 1 km squares where 5% or more of homes may be above the action level. Most homes are below it; a three-month test is the only way to know.

Are there flood warnings in Basingstoke now?

No flood warning or alert was in force near Basingstoke at 4 November 2026, 19:53. 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.