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C−Hazard risk Grade
Flood & hazards in Croydon · Environment Agency

In Croydon, heavy rain puts more homes at risk than rivers or the sea: 9.5%, against 1.9%

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. Croydon grades C− for hazard risk: #27 of 33 in London.

1968worst recorded flood3flood warnings since 200665%in a radon Affected Area
In brief

What stands out about Croydon’s hazards

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

Rain, more than the river9.5% of homes sit where heavy rain can flood the streets, against 1.9% at risk from rivers and the sea.Remembers 1968Floodwater covered 2 hectares of today’s Croydon in 1968; 44 of today’s households live inside past flood outlines.The River Wandle ran its highest in February 20260.29 m at Waddon Ponds on 6 February 2026, 14 cm under the record set in 2000.3 flood warnings since 2006For the parts of Croydon the Environment Agency warns directly; the most recent on 27 September 2024.
By hazard

What Croydon faces

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

Rivers and the sea

1.9%of homes at high or medium risk
More than the typical UK town · more than 77% of towns
3,484 homes by the EA’s own count

Surface water

9.5%of homes at high or medium risk
More than 91% of UK towns
Rivers and sea: 1.9%

Past floods

2years with a recorded flood
Last recorded: September 1968
44 households inside past outlines

The River Wandle

0.29 mhighest in winter 2025–26 at Waddon Ponds
Highest of 12 winters
Record 0.43 m, December 2000

Flood warnings

3flood warnings since 2006
134 flood alerts for the wider area
Last warning 27 September 2024

Radon

65%of the borough in a radon Affected Area
Highest band here: 5–10% of homes
14% 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

Croydon grades C− for hazard risk

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

Homes at high or medium flood risk (1.9%)Fewer than 23% 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 Croydon

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: 1965Recorded flood: 1968© OpenStreetMap contributors · EA NaFRA2
HighMediumLowrivers & seaHighMediumLowsurface waterCroydon’s built-up area

The river and sea risk follows the River Wandle, the River Ravensbourne and the Chaffinch Brook. Surface-water risk is spread across the borough, in dips, underpasses and along small streams, which is why more homes are exposed to it.

Rivers and the sea

1.9% of Croydon’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 risk1.4%of homes · 1 in 30 a year or more2,614 homes, EA count
Medium risk0.5%of homes · 1 in 30 to 1 in 100870 homes, EA count
Low risk0.9%of homes · 1 in 100 to 1 in 1,0001,557 homes, EA count
Where Croydon sits among 3,735 UK towns
35%None
23%Under 0.5%
9%0.5–1%
11%1–2%Croydon
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; Croydon has more than 77% of towns.

Towns its size: 22nd of 30 from the fewest homes at risk
#TownPeopleHigh or med.
1Southwark London307,0760%
2Newham London351,065under 0.1%
3Newcastle upon Tyne Tyne and Wear286,4720.2%
…
20Brent London340,6111.5%
21Waltham Forest London278,1291.6%
22Croydon London389,2421.9%
23Manchester Greater Manchester470,3951.9%
24Greenwich London288,1172%
…
29Lewisham London300,7643.6%
30Nottingham Nottinghamshire299,7863.6%

UK towns of 272,000 to 545,000 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 5.1 times as many Croydon 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 water9.5%
Rivers and the sea1.9%
0%10.5%21% of homes

About 5.2% of homes are at high risk of surface-water flooding (a 1 in 30 chance or more each year) and 4.3% at medium risk: roughly 14,510 households. A further 8.6% face a low risk from surface water. That is more than 91% of UK towns.

~14,510
households at high or medium risk
8.6%
of homes at low risk
91%
of UK towns have a smaller share
197,257
addresses read on the map

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.

Flood history

Croydon has flooded in 2 recorded years since 1965, most of all in 1968

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

  1. 1968September 1968: River flooding recorded2 hectares inside today’s built-up area
  2. 1965November 1965: River flooding recorded1 hectare inside today’s built-up area
The worst: 19682 ha

Floodwater covered 2 hectares of what is now Croydon in 1968, the largest flood the record holds here (September).

44 of Croydon’s households today live inside the outline of a recorded flood.

River levels

The River Wandle in February 2026 rose to its highest level since 2013

The highest level each winter (October to September) at the Environment Agency’s Waddon Ponds gauge (Beddington), since 2013. The river normally runs between 0.00 m and 0.32 m here.

Highest level each winter, metres
Winter 2013–14: highest 0.15 m · 0 days above the normal rangeWinter 2014–15: highest 0.09 m · 0 days above the normal rangeWinter 2015–16: highest 0.18 m · 0 days above the normal rangeWinter 2016–17: highest 0.19 m · 0 days above the normal rangeWinter 2017–18: highest 0.23 m on 17 June 2018 · 0 days above the normal rangeWinter 2018–19: highest 0.10 m · 0 days above the normal rangeWinter 2019–20: highest 0.22 m · 0 days above the normal rangeWinter 2021–22: highest 0.11 m · 0 days above the normal rangeWinter 2022–23: highest 0.16 m · 0 days above the normal rangeWinter 2023–24: highest 0.17 m · 0 days above the normal rangeWinter 2024–25: highest 0.25 m on 23 May 2025 · 0 days above the normal rangeWinter 2025–26: highest 0.29 m on 6 February 2026 · 0 days above the normal range’25–26’24–25’17–18Record 0.43 m, 2000Top of normal range
2013–142025–26
The highest days on record
  • 6 February 20260.29 m
  • 19 March 20260.28 m
  • 11 March 20260.26 m
  • 23 May 20250.25 m
  • 27 February 20260.23 m
  • 17 June 20180.23 m

The River Wandle has topped its normal range on 0 days since 2013. By its highest day, the winter of 2025–26 was the highest of the 12.

Environment Agency Hydrology API, Waddon Ponds (station 4139TH), 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 Croydon · 3 warnings in 20 years

The Environment Agency has 5 flood warning areas and 2 alert areas reaching into the borough; warnings since the service began in 2006.

Now: no flood warnings or alerts for Croydon (checked 5 November 2026, 17:09). Check for flooding on GOV.UK →
Warnings and alerts each year for areas in Croydon
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)

The warning area covering the most of Croydon, Groundwater flooding in South East London, has not had a flood warning since 2006. Of the 3 warnings, 3 were for Chaffinch Brook and St James Stream at Elmers End.

2024 had the most warnings (2); 2021 the most alerts (16). The most recent warning was on 27 September 2024.

Show the 7 warning and alert areas
AreaKindSince 2006Now
Chaffinch Brook and St James Stream at Elmers EndWarning area3None
Groundwater flooding in South East LondonWarning area0None
Groundwater flooding in the Caterham Bourne catchmentWarning area0None
River Wandle at Beddington ParkWarning area0None
Norbury Brook at Thornton Heath and Streatham ValeWarning area0None
Ravensbourne area in the London Boroughs of Lewisham, Bromley, Greenwich and CroydonAlert area85None
River Wandle area in the London Boroughs of Wandsworth, Merton, Lambeth, Croydon and SuttonAlert area44None

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 Croydon 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).

TQ2857: 1–3% of homes above the action levelTQ2858: 1–3% of homes above the action levelTQ2859: 1–3% of homes above the action levelTQ2957: 1–3% of homes above the action levelTQ2958: 1–3% of homes above the action levelTQ2959: 1–3% of homes above the action levelTQ2960: 1–3% of homes above the action levelTQ2961: 1–3% of homes above the action levelTQ2962: 1–3% of homes above the action levelTQ2967: Under 1% of homes above the action levelTQ2969: Under 1% of homes above the action levelTQ3057: 1–3% of homes above the action levelTQ3058: 1–3% of homes above the action levelTQ3059: 1–3% of homes above the action levelTQ3060: 1–3% of homes above the action levelTQ3061: 1–3% of homes above the action levelTQ3062: 1–3% of homes above the action levelTQ3063: 1–3% of homes above the action levelTQ3064: 1–3% of homes above the action levelTQ3065: 1–3% of homes above the action levelTQ3066: Under 1% of homes above the action levelTQ3067: Under 1% of homes above the action levelTQ3068: Under 1% of homes above the action levelTQ3069: Under 1% of homes above the action levelTQ3070: Under 1% of homes above the action levelTQ3157: 1–3% of homes above the action levelTQ3158: 1–3% of homes above the action levelTQ3159: 1–3% of homes above the action levelTQ3160: 1–3% of homes above the action levelTQ3161: 1–3% of homes above the action levelTQ3162: 1–3% of homes above the action levelTQ3163: 3–5% of homes above the action levelTQ3164: 3–5% of homes above the action levelTQ3165: 1–3% of homes above the action levelTQ3166: Under 1% of homes above the action levelTQ3167: Under 1% of homes above the action levelTQ3168: Under 1% of homes above the action levelTQ3169: Under 1% of homes above the action levelTQ3170: Under 1% of homes above the action levelTQ3171: Under 1% of homes above the action levelTQ3257: 1–3% of homes above the action levelTQ3258: 1–3% of homes above the action levelTQ3259: 1–3% of homes above the action levelTQ3260: 1–3% of homes above the action levelTQ3261: 3–5% of homes above the action levelTQ3262: 3–5% of homes above the action levelTQ3263: 3–5% of homes above the action levelTQ3264: 3–5% of homes above the action levelTQ3265: 1–3% of homes above the action levelTQ3266: Under 1% of homes above the action levelTQ3267: Under 1% of homes above the action levelTQ3268: Under 1% of homes above the action levelTQ3269: Under 1% of homes above the action levelTQ3270: Under 1% of homes above the action levelTQ3271: Under 1% of homes above the action levelTQ3357: 3–5% of homes above the action levelTQ3358: 3–5% of homes above the action levelTQ3359: 3–5% of homes above the action levelTQ3360: 3–5% of homes above the action levelTQ3361: 5–10% of homes above the action levelTQ3362: 5–10% of homes above the action levelTQ3363: 3–5% of homes above the action levelTQ3364: 3–5% of homes above the action levelTQ3365: 1–3% of homes above the action levelTQ3366: Under 1% of homes above the action levelTQ3367: Under 1% of homes above the action levelTQ3368: Under 1% of homes above the action levelTQ3369: Under 1% of homes above the action levelTQ3370: Under 1% of homes above the action levelTQ3459: 3–5% of homes above the action levelTQ3460: 3–5% of homes above the action levelTQ3461: 5–10% of homes above the action levelTQ3462: 5–10% of homes above the action levelTQ3463: 5–10% of homes above the action levelTQ3464: 5–10% of homes above the action levelTQ3465: 5–10% of homes above the action levelTQ3466: Under 1% of homes above the action levelTQ3467: Under 1% of homes above the action levelTQ3468: Under 1% of homes above the action levelTQ3469: Under 1% of homes above the action levelTQ3559: 3–5% of homes above the action levelTQ3560: 3–5% of homes above the action levelTQ3561: 5–10% of homes above the action levelTQ3562: 5–10% of homes above the action levelTQ3563: 3–5% of homes above the action levelTQ3564: 5–10% of homes above the action levelTQ3565: 5–10% of homes above the action levelTQ3566: Under 1% of homes above the action levelTQ3567: Under 1% of homes above the action levelTQ3568: Under 1% of homes above the action levelTQ3661: 3–5% of homes above the action levelTQ3662: 3–5% of homes above the action levelTQ3663: 3–5% of homes above the action levelTQ3664: 3–5% of homes above the action levelTQ3665: Under 1% of homes above the action levelTQ3666: Under 1% of homes above the action levelTQ3667: Under 1% of homes above the action levelTQ3761: 3–5% of homes above the action levelTQ3762: 3–5% of homes above the action levelTQ3763: 3–5% of homes above the action levelTQ3764: 3–5% of homes above the action levelTQ3765: Under 1% of homes above the action levelTQ3766: Under 1% of homes above the action levelTQ3861: 3–5% of homes above the action levelTQ3862: 3–5% of homes above the action levelTQ3863: 3–5% of homes above the action levelTQ3864: 3–5% of homes above the action levelTQ3960: 3–5% of homes above the action levelTQ3961: 3–5% of homes above the action levelTQ3962: 3–5% of homes above the action level© OpenStreetMap contributors · BGS/UKHSA
Under 1%1–3%3–5%5–10%
Share of the borough’s area in each band
Under 1% of homes35%
1–3% of homes28%
3–5% of homes23%
5–10% of homes14%

65% of Croydon’s built-up area is in a radon Affected Area (1% of homes or more above the action level), and 14% in squares of 5% or more, mostly on the south-east side of the borough.

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 Croydon

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

Sutton: Hazard risk C+Warlingham: Hazard risk AWhyteleafe: Hazard risk D−Merton: Hazard risk C−Chipstead and Woodmansterne: Hazard risk ABromley: Hazard risk C−Caterham: Hazard risk ASuttonWarlinghamWhyteleafeMertonChipstead and WoodmansterneBromleyCaterhamCroydon
ABCD
TownPeopleHigh or mediumLowHazard
Croydon389,2421.9%0.9%C−
Sutton208,8580.5%2.1%C+
Warlingham8,9180%0%A
Whyteleafe3,17413%0%D−
Merton214,9311.7%4.6%C−
Chipstead and Woodmansterne4,5230%0%A
Bromley325,4692%0.6%C−
Caterham22,7570%0%A

Whyteleafe, 4.6 miles south, has the most homes at risk around Croydon (13% at high or medium). Warlingham, Chipstead and Woodmansterne and Caterham have none.

Be ready

Get ready for what Croydon 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.
  • Croydon’s warning areas include Groundwater flooding in South East London and Groundwater flooding in the Caterham Bourne catchment.
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 Croydon
  • 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 Croydon

Does Croydon flood?

The last flood the Environment Agency recorded inside the borough was in September 1968. 1.9% 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 9.5% of homes are at high or medium risk from surface water, when heavy rain overwhelms the drains. Croydon grades C− for hazard risk against UK towns.

Which parts of Croydon are at risk of flooding?

From rivers and the sea, the places the Environment Agency warns directly: Chaffinch Brook and St James Stream at Elmers End, Groundwater flooding in South East London, Groundwater flooding in the Caterham Bourne catchment and River Wandle at Beddington Park. 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 Croydon last flood?

The recorded flood outlines inside the borough run from 1965 to 1968 (2 years); the largest was in 1968. Flood warnings have been issued for parts of the borough since 2006, most recently on 27 September 2024.

Is Croydon at risk of surface water flooding?

About 5.2% of homes are at high risk and 4.3% at medium risk from surface water, against 1.9% 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 Croydon?

65% of the borough’s built-up area is in a radon Affected Area on the BGS/UKHSA atlas, and 14% 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 Croydon now?

No flood warning or alert was in force near Croydon at 5 November 2026, 17:09. 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.