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Does Radlett flood? 24 postcodes in Radlett are in the Environment Agency's rivers-and-sea flood-risk data (10 High, 7 Medium likelihood) — the breakdown is further down this page.
Conditions are worth watching: the Environment Agency has a Flood Alert in force for Tidal Thames riverside from Putney Bridge to Teddington Weir — flooding is possible from 02:15 AM to 04:15 AM on Saturday 10th October. Flooding is possible — be prepared and keep an eye on updates.
Updated 2026-10-09 22:01:32 UTC · Official GOV.UK warnings · Flood preparation & help guide
Radlett is a large village in Hertfordshire, England, between Elstree and St Albans on Watling Street, with a population of 10,060. It is in the council district of Hertsmere in the south of the county, and forms part of the civil parish of Aldenham. Radlett is located just inside the M25 motorway between Watford and Borehamwood.
Ordnance Survey places 24 postcodes in Radlett in the Environment Agency's rivers-and-sea flood-risk dataset (Risk of Flooding from Rivers and Sea). Each postcode is counted once, under the worst band any of its properties reaches; together they hold 216 properties in the EA dataset's likelihood bands.
| EA likelihood band | Postcodes (worst band) | Properties in the EA dataset | of which homes |
|---|---|---|---|
| High | 10 | 33 | 26 |
| Medium | 7 | 77 | 53 |
| Low | 2 | 47 | 30 |
| Very low | 5 | 59 | 44 |
| All bands | 24 | 216 | 153 |
This dataset covers flooding from rivers and the sea only — one of five flood sources. Surface water, groundwater, sewers and reservoirs are assessed separately, so a postcode missing from it is not proof that a place cannot flood. The band describes the land around properties (allowing for defences), not any single address and not today's conditions.
Bushey · Potters Bar · Barnet
Flood-risk bands: © Environment Agency copyright and/or database right 2025. All rights reserved. Some features of this map are based on digital spatial data from the Centre for Ecology & Hydrology, © NERC (CEH). © Crown Copyright and Database Rights 2025 OS AC0000807064. This product is produced in part from PAF® and Multiple Residence Data, the copyright in which is owned by Royal Mail Group Limited and/or Royal Mail Group plc. All rights reserved. Licence number AC0000807064.
Place names: Contains OS data © Crown copyright and database rights 2026. Contains Royal Mail data © Royal Mail copyright and database right 2026. Contains National Statistics data © Crown copyright and database right 2026. Licensed under the Open Government Licence v3.0.
The nearest watercourse on the river map is Tykes Water, about 10 m from the middle of Radlett's gauges. It flows into the Brook about 490 m downstream.
A gauge downstream shows water that has already passed this point; one upstream sees it first. Distances along the river are from the point on Tykes Water nearest the middle of Radlett's gauges. From Ordnance Survey’s river map (OS Open Rivers), which leaves out small streams, ditches and culverts, so a nearer one may exist. This describes where water goes on the map; it says nothing about flooding at any address. Contains OS data © Crown copyright and database rights 2026.
Radlett is monitored by 1 Environment Agency river level station on the Radlett Brook, in Hertfordshire. Water levels are updated every 15 minutes, providing real-time flood monitoring for the area.
The Radlett Brook is monitored by 1 station (Radlett). Each station records water levels continuously, with data synced to FloodRadar every 5 minutes.
There are 8 Environment Agency flood warning areas within 10km of Radlett. When the EA issues a flood warning for any of these areas, it will appear on this page. These include: The Radlett Brook at Radlett; The Radlett and Borehamwood Brooks at Borehamwood; The River Colne at London Colney including Colney Street and Broad Colney; The Upper River Colne and Radlett Brook at Colney Heath, London Colney, Borehamwood and Radlett.
There is 1 storm overflow within 5km of Radlett. None of the 1 with a reporting monitor is currently discharging. Enable "Sewage" on the map above to see their locations.
It has its own page of live status and past discharges:
If flooding is forecast in Radlett, call Floodline on 0345 988 1188 for the latest information. Move valuables upstairs, turn off gas and electricity if safe to do so, and avoid walking or driving through flood water. Sign up for flood warnings on any station page above to receive email alerts when water levels rise. For emergency numbers, a preparation checklist and insurance guidance, see our flood help & preparation guide.
Radlett gets about 699 mm of rain a year on average (wettest month October, 78 mm; driest March, 42 mm). That is 40% drier than the UK as a whole, which averages 1,163 mm a year. See the rain gauges →
A thirty-year average for the area, not a forecast and not a flood risk on its own. Source: Met Office HadUK-Grid 1991–2020 (5 km grid), 2.3 km away. Average rainfall: HadUK-Grid v1.3.2, Met Office. Contains public sector information licensed under the Open Government Licence v3.0.
Floods whose mapped extent (EA Recorded Flood Outlines) reached within ~5 km of the town centre — most recent first. These are records of mapped extents, not a full list of floods. See them on the map →
Records, not floods: no outline on the record is not evidence a place has not flooded.
Current verdict: Watch. Conditions are worth watching: the Environment Agency has a Flood Alert in force for Tidal Thames riverside from Putney Bridge to Teddington Weir — flooding is possible from 02:15 AM to 04:15 AM on Saturday 10th October. Flooding is possible — be prepared and keep an eye on updates.
Radlett has river level monitoring on Radlett Brook — 1 monitoring station in total.
Use the GOV.UK Check for Flooding service (check-for-flooding.service.gov.uk) or call Floodline on 0345 988 1188 (24 hours). You can also set up free FloodRadar email or browser alerts from any station page above.
Follow official advice: move valuables and vehicles to safety, never walk or drive through flood water, turn off gas and electricity if safe, and check on vulnerable neighbours. See our flood preparation guide at floodradar.co.uk/flood-help.
Yes — the Environment Agency's Recorded Flood Outlines dataset shows 6 recorded flood extents around the town centre since 1703, most recently in 1992. That is a count of mapped extents, not of separate floods. Records, not floods: no outline on the record is not evidence a place has not flooded. See the flood history link below.
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