Does AL3 flood?

Yes — parts of the AL3 district carry real flood risk: 8 of its 31 at-risk postcodes reach the Environment Agency's High likelihood band. The AL3 postcode district covers Watling, Redbourn, Verulam, close to Markyate, Harpenden, Upper Lee, and surrounding villages in parts of Hertfordshire and Luton.

31 postcodes in the AL3 district appear in the Environment Agency's rivers-and-sea flood-risk dataset — worst bands: 8 high, 6 medium, 13 low, 4 very low. A postcode not listed here has no properties in any recorded risk band (which is good news, but never proof it cannot flood).

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Which AL3 postcodes are at risk?

AL3 4HJ up to High AL3 4SJ up to High AL3 6LB up to High AL3 7LA up to High AL3 7NH up to High AL3 8HA up to High AL3 8HB up to High AL3 8JH up to High AL3 8JG up to Medium AL3 8JP up to Medium AL3 8LG up to Medium AL3 8LJ up to Medium AL3 8LY up to Medium AL3 8NL up to Medium AL3 4SF up to Low AL3 4SG up to Low AL3 4SP up to Low AL3 7LG up to Low AL3 7LT up to Low AL3 7PD up to Low AL3 7QG up to Low AL3 8EX up to Low AL3 8FH up to Low AL3 8JL up to Low AL3 8JN up to Low AL3 8PL up to Low AL3 8PY up to Low AL3 4SD up to Very low AL3 7LH up to Very low AL3 8JR up to Very low AL3 8JW up to Very low

Rivers and flooding history near AL3

The rivers that matter here, each monitored live on FloodRadar:

Harpenden on the River Lee — 5.4 km away, highest on record 1.69m
Luton East Hyde on the River Lee — 5.6 km away, highest on record 2.77m
Gadebridge Park on the River Gade — 6.8 km away, highest on record 0.41m
Hemel Hempstead, Two Waters Road on the River Bulbourne — 8.4 km away, highest on record 1.19m

29 official flood warnings and alerts have been raised within ~10 km of the district's centre since 2006 (2 at warning level or above), most recently 19 December 2024. Warnings cover flood areas, not individual addresses.

Recorded flood extents near the district (Environment Agency record):

January 2021 flooding — about 2.6 km from the centre
Winter 2013/2014 (2013) — about 42.6 km from the centre
October 1993 flooding — about 2.5 km from the centre
June 1993 flooding — about 4.6 km from the centre

Records, not floods: no outline on the record is not evidence a place has not flooded.

🏠 Buying or renting in AL3? The full property flood-risk report covers any postcode here — the official likelihood band, every recorded flood nearby with distances, warning history year by year, how the local rivers behave, and an insurance outlook, print-ready for £19. See what's in the report →

Flood risk in nearby postcode districts

AL2 AL4 AL1 AL5 AL6 AL8 AL9 AL10

Band = the worst likelihood band of any property in that postcode (EA Risk of Flooding from Rivers & Sea, defence-adjusted, area-level). Check any postcode in detail — or get the full £19 property report — at the property flood-risk report. © 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.