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CHazard risk Grade
Flood & hazards in Barnet · Environment Agency

Surface water, more than the river, is Barnet’s flood risk: 12% of homes, against 1.2% 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 Barnet at C: #19 of 33 in London.

1992worst recorded flood4flood warnings since 20061.5%at low risk
In brief

What stands out about Barnet’s hazards

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

Rain, more than the river12% of homes sit where heavy rain can flood the streets, against 1.2% at risk from rivers and the sea.Remembers 1992Floodwater covered 35 hectares of today’s Barnet in 1992; 511 of today’s households live inside past flood outlines.The Silk Stream ran its 5th-highest in July 20251.77 m at Colindale on 19 July 2025, 66 cm under the record set in 1992.4 flood warnings since 2006For the parts of Barnet the Environment Agency warns directly; the most recent on 19 July 2025.
By hazard

What Barnet faces

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

Rivers and the sea

1.2%of homes at high or medium risk
More than the typical UK town · more than 71% of towns
1,894 homes by the EA’s own count

Surface water

12%of homes at high or medium risk
More than 94% of UK towns
Rivers and sea: 1.2%

Past floods

6years with a recorded flood
Last recorded: July 2021
511 households inside past outlines

The Silk Stream

1.64 mhighest in winter 2025–26 at Colindale
10th-highest of 36 winters
Record 2.43 m, September 1992

Flood warnings

4flood warnings since 2006
221 flood alerts for the wider area
Last warning 19 July 2025

Radon

0%of the borough 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

Barnet grades C for hazard risk

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

Homes at high or medium flood risk (1.2%)Fewer than 29% 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 Barnet

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: 1980Recorded flood: 1981Recorded flood: 1992Recorded flood: 2007Recorded flood: 2015Recorded flood: 2021© OpenStreetMap contributors · EA NaFRA2
HighMediumLowrivers & seaHighMediumLowsurface waterBarnet’s built-up area

The river and sea risk follows the Silk Stream; Dollis Brook; Deans Brook; Edgware Brook; Mutton Brook; Wealdstone Brook; Wembley Brook, the Ching Brook and the Cobbins 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

1.2% of Barnet’s homes are at high or medium risk from rivers or the sea

The Environment Agency’s national map, allowing for defences. A further 1.5% are at low risk.

High risk0.7%of homes · 1 in 30 a year or more1,047 homes, EA count
Medium risk0.6%of homes · 1 in 30 to 1 in 100847 homes, EA count
Low risk1.5%of homes · 1 in 100 to 1 in 1,0002,420 homes, EA count
Where Barnet sits among 3,735 UK towns
35%None
23%Under 0.5%
9%0.5–1%
11%1–2%Barnet
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; Barnet has more than 71% of towns.

Towns its size: 15th 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%
…
13Sheffield South Yorkshire500,5200.9%
14Cardiff South Glamorgan348,5110.9%
15Barnet London388,5721.2%
16Enfield London329,8221.3%
17Hillingdon London307,0891.3%
…
29Lewisham London300,7643.6%
30Nottingham Nottinghamshire299,7863.6%

UK towns of 272,000 to 544,000 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 9.7 times as many Barnet 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 water12%
Rivers and the sea1.2%
0%10.5%21% of homes

About 7.8% of homes are at high risk of surface-water flooding (a 1 in 30 chance or more each year) and 3.9% at medium risk: roughly 17,600 households. A further 9% face a low risk from surface water. That is more than 94% of UK towns.

~17,600
households at high or medium risk
9%
of homes at low risk
94%
of UK towns have a smaller share
196,479
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

Barnet has flooded in 6 recorded years since 1980, most of all in 1992

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

  1. 2021July 2021: River flooding recorded11 hectares inside today’s built-up area
  2. 2015August 2015: River flooding recorded6 hectares inside today’s built-up area
  3. 2007July 2007: River flooding recordedUnder 1 hectare inside today’s built-up area
  4. 1992January and September 1992: River flooding recorded35 hectares inside today’s built-up area
  5. 1981January 1981: River flooding recordedUnder 1 hectare inside today’s built-up area
  6. 1980January 1980: River flooding recordedUnder 1 hectare inside today’s built-up area
The worst: 199235 ha

Floodwater covered 35 hectares of what is now Barnet in 1992, the largest flood the record holds here (January and September).

511 of Barnet’s households today live inside the outline of a recorded flood.

Since 1992, the largest recorded flood inside the borough covered 11 hectares.

River levels

The Silk Stream in July 2025 rose to its 5th-highest level since 1990

The highest level each winter (October to September) at the Environment Agency’s Colindale gauge (Hendon), since 1990. The river normally runs between 0.10 m and 1.25 m here.

Highest level each winter, metres
Winter 1990–91: highest 1.32 m · 1 days above the normal rangeWinter 1991–92: highest 2.43 m on 23 September 1992 · 3 days above the normal rangeWinter 1992–93: highest 1.66 m · 2 days above the normal rangeWinter 1993–94: highest 1.55 m · 3 days above the normal rangeWinter 1994–95: highest 1.24 m · 0 days above the normal rangeWinter 1995–96: highest 1.29 m · 1 days above the normal rangeWinter 1996–97: highest 1.73 m on 26 June 1997 · 1 days above the normal rangeWinter 1997–98: highest 0.80 m · 0 days above the normal rangeWinter 1998–99: highest 1.41 m · 2 days above the normal rangeWinter 1999–00: highest 1.49 m · 1 days above the normal rangeWinter 2000–01: highest 2.01 m on 30 October 2000 · 3 days above the normal rangeWinter 2001–02: highest 1.52 m · 2 days above the normal rangeWinter 2002–03: highest 1.13 m · 0 days above the normal rangeWinter 2003–04: highest 1.15 m · 0 days above the normal rangeWinter 2004–05: highest 0.86 m · 0 days above the normal rangeWinter 2005–06: highest 1.30 m · 1 days above the normal rangeWinter 2006–07: highest 1.70 m on 20 July 2007 · 1 days above the normal rangeWinter 2007–08: highest 1.29 m · 1 days above the normal rangeWinter 2008–09: highest 1.82 m on 27 June 2009 · 2 days above the normal rangeWinter 2009–10: highest 1.30 m · 1 days above the normal rangeWinter 2010–11: highest 1.37 m · 2 days above the normal rangeWinter 2011–12: highest 1.43 m · 1 days above the normal rangeWinter 2012–13: highest 1.24 m · 0 days above the normal rangeWinter 2013–14: highest 1.52 m · 2 days above the normal rangeWinter 2014–15: highest 2.20 m on 26 August 2015 · 2 days above the normal rangeWinter 2015–16: highest 1.65 m · 1 days above the normal rangeWinter 2016–17: highest 1.10 m · 0 days above the normal rangeWinter 2017–18: highest 0.93 m · 0 days above the normal rangeWinter 2018–19: highest 1.51 m · 1 days above the normal rangeWinter 2019–20: highest 1.39 m · 2 days above the normal rangeWinter 2020–21: highest 1.57 m · 4 days above the normal rangeWinter 2021–22: highest 1.16 m · 0 days above the normal rangeWinter 2022–23: highest 1.36 m · 2 days above the normal rangeWinter 2023–24: highest 1.55 m · 2 days above the normal rangeWinter 2024–25: highest 1.77 m on 19 July 2025 · 1 days above the normal rangeWinter 2025–26: highest 1.64 m · 2 days above the normal range’91–92’14–15’00–01Record 2.43 m, 1992Top of normal range
1990–912025–26
The highest days on record
  • 23 September 19922.43 m
  • 26 August 20152.20 m
  • 30 October 20002.01 m
  • 27 June 20091.82 m
  • 19 July 20251.77 m
  • 26 June 19971.73 m

The Silk Stream has topped its normal range on 47 days since 1990, most in the winters of 2020–21 and 1991–92. By its highest day, the winter of 2025–26 was the 10th-highest of the 36.

Environment Agency Hydrology API, Colindale (station 3829TH), 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 Barnet · 4 warnings in 20 years

The Environment Agency has 8 flood warning areas and 3 alert areas reaching into the borough; warnings since the service began in 2006.

Now: no flood warnings or alerts for Barnet (checked 5 November 2026, 13:56). Check for flooding on GOV.UK →
Warnings and alerts each year for areas in Barnet
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 Barnet, Dollis Brook from Barnet to Hendon, has not had a flood warning since 2006. Of the 4 warnings, 4 were for Silk Stream at Edgware and Colindale.

2016 had the most warnings (2). The most recent warning was on 19 July 2025.

Show the 11 warning and alert areas
AreaKindSince 2006Now
Silk Stream at Edgware and ColindaleWarning area4None
River Brent in the London Borough of BrentWarning area0None
Edgware Brook at StanmoreWarning area0None
Pymmes Brook at East BarnetWarning area0None
River Brent in the London Borough of BarnetWarning area0None
Dollis Brook from Barnet to HendonWarning area0None
Mutton Brook at Hampstead Garden SuburbWarning area0None
Deans Brook at EdgwareWarning area0None
Lower Lee tributariesAlert area115None
Silk Stream and the Deans, Edgware, Dollis, Mutton, Wembley and Wealdstone BrooksAlert area79None
River Brent from Hendon to BrentfordAlert area27None

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

Barnet 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).

TQ1793: Under 1% of homes above the action levelTQ1794: Under 1% of homes above the action levelTQ1891: Under 1% of homes above the action levelTQ1892: Under 1% of homes above the action levelTQ1893: Under 1% of homes above the action levelTQ1894: Under 1% of homes above the action levelTQ1990: Under 1% of homes above the action levelTQ1991: Under 1% of homes above the action levelTQ1992: Under 1% of homes above the action levelTQ1993: Under 1% of homes above the action levelTQ1994: Under 1% of homes above the action levelTQ1995: Under 1% of homes above the action levelTQ2089: Under 1% of homes above the action levelTQ2090: Under 1% of homes above the action levelTQ2091: Under 1% of homes above the action levelTQ2092: Under 1% of homes above the action levelTQ2093: Under 1% of homes above the action levelTQ2094: Under 1% of homes above the action levelTQ2095: Under 1% of homes above the action levelTQ2187: Under 1% of homes above the action levelTQ2188: Under 1% of homes above the action levelTQ2189: Under 1% of homes above the action levelTQ2190: Under 1% of homes above the action levelTQ2191: Under 1% of homes above the action levelTQ2192: Under 1% of homes above the action levelTQ2193: Under 1% of homes above the action levelTQ2194: Under 1% of homes above the action levelTQ2195: Under 1% of homes above the action levelTQ2196: Under 1% of homes above the action levelTQ2286: Under 1% of homes above the action levelTQ2287: Under 1% of homes above the action levelTQ2288: Under 1% of homes above the action levelTQ2289: Under 1% of homes above the action levelTQ2290: Under 1% of homes above the action levelTQ2291: Under 1% of homes above the action levelTQ2292: Under 1% of homes above the action levelTQ2293: Under 1% of homes above the action levelTQ2294: Under 1% of homes above the action levelTQ2295: Under 1% of homes above the action levelTQ2296: Under 1% of homes above the action levelTQ2297: Under 1% of homes above the action levelTQ2385: Under 1% of homes above the action levelTQ2386: Under 1% of homes above the action levelTQ2387: Under 1% of homes above the action levelTQ2388: Under 1% of homes above the action levelTQ2389: Under 1% of homes above the action levelTQ2390: Under 1% of homes above the action levelTQ2391: Under 1% of homes above the action levelTQ2392: Under 1% of homes above the action levelTQ2393: Under 1% of homes above the action levelTQ2394: Under 1% of homes above the action levelTQ2395: Under 1% of homes above the action levelTQ2396: Under 1% of homes above the action levelTQ2397: Under 1% of homes above the action levelTQ2484: Under 1% of homes above the action levelTQ2485: Under 1% of homes above the action levelTQ2486: Under 1% of homes above the action levelTQ2487: Under 1% of homes above the action levelTQ2488: Under 1% of homes above the action levelTQ2489: Under 1% of homes above the action levelTQ2490: Under 1% of homes above the action levelTQ2491: Under 1% of homes above the action levelTQ2492: Under 1% of homes above the action levelTQ2493: Under 1% of homes above the action levelTQ2494: Under 1% of homes above the action levelTQ2495: Under 1% of homes above the action levelTQ2496: Under 1% of homes above the action levelTQ2497: Under 1% of homes above the action levelTQ2498: Under 1% of homes above the action levelTQ2585: Under 1% of homes above the action levelTQ2586: Under 1% of homes above the action levelTQ2587: Under 1% of homes above the action levelTQ2588: Under 1% of homes above the action levelTQ2589: Under 1% of homes above the action levelTQ2590: Under 1% of homes above the action levelTQ2591: Under 1% of homes above the action levelTQ2592: Under 1% of homes above the action levelTQ2593: Under 1% of homes above the action levelTQ2594: Under 1% of homes above the action levelTQ2595: Under 1% of homes above the action levelTQ2596: Under 1% of homes above the action levelTQ2597: Under 1% of homes above the action levelTQ2686: Under 1% of homes above the action levelTQ2687: Under 1% of homes above the action levelTQ2688: Under 1% of homes above the action levelTQ2689: Under 1% of homes above the action levelTQ2690: Under 1% of homes above the action levelTQ2691: Under 1% of homes above the action levelTQ2692: Under 1% of homes above the action levelTQ2693: Under 1% of homes above the action levelTQ2694: Under 1% of homes above the action levelTQ2695: Under 1% of homes above the action levelTQ2696: Under 1% of homes above the action levelTQ2788: Under 1% of homes above the action levelTQ2789: Under 1% of homes above the action levelTQ2790: Under 1% of homes above the action levelTQ2791: Under 1% of homes above the action levelTQ2792: Under 1% of homes above the action levelTQ2793: Under 1% of homes above the action levelTQ2794: Under 1% of homes above the action levelTQ2795: Under 1% of homes above the action levelTQ2796: Under 1% of homes above the action levelTQ2890: Under 1% of homes above the action levelTQ2891: Under 1% of homes above the action levelTQ2892: Under 1% of homes above the action levelTQ2893: Under 1% of homes above the action levelTQ2894: Under 1% of homes above the action levelTQ2895: Under 1% of homes above the action levelTQ2896: Under 1% of homes above the action levelTQ2992: Under 1% of homes above the action levelTQ2993: Under 1% of homes above the action levelTQ2994: Under 1% of homes above the action level© OpenStreetMap contributors · BGS/UKHSA
Under 1%
Share of the borough’s area in each band
Under 1% of homes100%

Every 1 km square over Barnet 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 Barnet

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

Brent: Hazard risk CBorehamwood: Hazard risk B+Elstree: Hazard risk AHaringey: Hazard risk CCamden: Hazard risk AHarrow: Hazard risk CIslington: Hazard risk ABrentBorehamwoodElstreeHaringeyCamdenHarrowIslingtonBarnet
ABCD
TownPeopleHigh or mediumLowHazard
Barnet388,5721.2%1.5%C
Brent340,6111.5%2.1%C
Borehamwood39,7600%0.1%B+
Elstree1,7370%0%A
Haringey264,0690.8%2.9%C
Camden209,3420%0%A
Harrow260,5341.3%1.8%C
Islington216,3090%0%A

Brent, 4.4 miles south-west, has the most homes at risk around Barnet (1.5% at high or medium).

Be ready

Get ready for what Barnet 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.
  • Barnet’s warning areas include Silk Stream at Edgware and Colindale and Dollis Brook from Barnet to Hendon.
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 Barnet
  • 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 Barnet

Does Barnet flood?

The last flood the Environment Agency recorded inside the borough was in July 2021. 1.2% 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 12% of homes are at high or medium risk from surface water, when heavy rain overwhelms the drains. Barnet grades C for hazard risk against UK towns.

Which parts of Barnet are at risk of flooding?

From rivers and the sea, the places the Environment Agency warns directly: Silk Stream at Edgware and Colindale, Dollis Brook from Barnet to Hendon, River Brent in the London Borough of Barnet and Pymmes Brook at East Barnet. 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 Barnet last flood?

The recorded flood outlines inside the borough run from 1980 to 2021 (6 years); the largest was in 1992. Flood warnings have been issued for parts of the borough since 2006, most recently on 19 July 2025.

Is Barnet at risk of surface water flooding?

About 7.8% of homes are at high risk and 3.9% at medium risk from surface water, against 1.2% 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 Barnet?

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

No flood warning or alert was in force near Barnet at 5 November 2026, 13:56. 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.