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Up to Low likelihood
Properties in AL2 1DW sit in the Environment Agency's Low flood-likelihood band (worst property). The band is the worst found in the postcode — it describes the land around properties (defence-adjusted, rivers & sea), not any single address, and not today's conditions.
| Likelihood band | Annual chance | Properties | Of which homes |
|---|---|---|---|
| High | greater than 3.3% | 0 | 0 |
| Medium | 1% – 3.3% | 0 | 0 |
| Low | 0.1% – 1% | 1 | 0 |
| Very low | below 0.1% | 0 | 0 |
Over a 25-year mortgage, a property in a low-likelihood area has a 2–22% chance of flooding at least once.
AL2 1DW gets about 678 mm of rain a year on average (wettest month October, 74 mm; driest March, 40 mm). That is 42% drier than the UK as a whole, which averages 1,163 mm a year.
A thirty-year average for the surrounding area, not a measurement at this address and not a flood risk on its own: a dry area floods when a storm sits over it, and a wet one may drain away perfectly well. 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.
The ground here sits at about 74 m above sea level and falls 14 m across the surrounding 800 m. Surface water reaching this point runs off ground lying to the south-west, 11.7 m higher.
The river map has no watercourse within 1 km of the centre of AL2 1DW.
That means this spot is not on the river map, not that there is no water here: Ordnance Survey’s river map (OS Open Rivers) leaves out small streams, ditches and culverts. Contains OS data © Crown copyright and database rights 2026.
Because properties in the low likelihood band; 6 recorded flood outlines mapped nearby; 163 official warnings since 2006.
The map above shows the real EA rivers & sea likelihood cells around AL2 1DW. The small panels are illustrative previews of the report's per-layer map views — the full report draws each layer for real, plus recorded extents, defences and a building picker on an interactive map.
Warnings cover flood areas, not individual addresses.
| Date | Mapped flood extent | Approx. distance |
|---|---|---|
| Nov 2013 | Winter 2013/2014 | ~43.9 km |
| Feb 2009 | ea06FebruaryWinter2009 | ~1.5 km |
| Oct 2000 | 06OctoberAutumn2000 | ~2.1 km |
| Jan 1993 | 06OctoberAutumn1993 | ~4.5 km |
| Jan 1992 | 06SeptemberAutumn1992 | ~7.5 km |
| Jan 1987 | 06JulySummer1987 | ~9.6 km |
These are extents the Environment Agency has mapped, not a list of every flood. Records, not floods: no outline on the record is not evidence a place has not flooded. The full report tests whether any extent covered the exact spot.
2013-14 UK winter floods (2013, 18 warnings nearby) ▶ replay it here · Henk (2024, 3 warnings nearby) ▶ replay it here · Dennis (2020, 2 warnings nearby) ▶ replay it here · St Jude storm 2013 (2013, 1 warnings nearby) ▶ replay it here
| Gauge | River | Distance | Typical high | Highest on record |
|---|---|---|---|---|
| London Colney | River Colne | 1.6 km | 1.85 m | 2.72 m |
| Colney Street | River Ver | 3.3 km | 0.54 m | 0.56 m |
| Radlett | Radlett Brook | 5.1 km | 1.57 m | 1.60 m |
| North Mymms | Mimmshall Brook | 6.2 km | 1.50 m | 2.35 m |
Live levels, predictions and rain-response behaviour are on each gauge's page and in the property report.
2 mapped flood-defence assets within 500 m — nearest ~15 m (natural high ground). Defences reduce risk, never remove it.
The interactive flood-risk map with a building picker (your exact house, not the postcode), the 2050s climate view, surface-water and planning flood zones at your building, exact recorded-flood distances, year-by-year warning charts, watercourses including culverted streams, an insurance outlook with the Flood Re rules, and a printable document with every dataset receipt — start with the free preview, unlock for £19.
At-risk postcodes near AL2 1DW — all in the AL2 district.
© 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. Recorded Flood Outlines and warning history © Environment Agency copyright and/or database right 2025. Storm-overflow figures: EA Event Duration Monitoring (England); live overflow status © the water companies, incl. Dŵr Cymru Welsh Water and Scottish Water. Flood defences © Environment Agency (OGL v3). This page summarises public area-level data — it is not a flood-risk survey and not a substitute for the official GOV.UK service. All data sources & licences. More postcodes: the AL2 district.