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Up to Medium likelihood
Properties in HP18 9EW sit in the Environment Agency's Medium 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% | 1 | 1 |
| Low | 0.1% – 1% | 0 | 0 |
| Very low | below 0.1% | 0 | 0 |
Over a 25-year mortgage, a property in a medium-likelihood area has a 22–57% chance of flooding at least once.
HP18 9EW gets about 625 mm of rain a year on average (wettest month November, 67 mm; driest March, 39 mm). That is 46% 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), 1.9 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 66 m above sea level and falls 17 m across the surrounding 800 m. Surface water reaching this point runs off ground lying to the west-north-west, 14.4 m higher.
The river map has no watercourse within 1 km of the centre of HP18 9EW.
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 medium likelihood band; 2 recorded flood outlines mapped nearby; 147 official warnings since 2006.
The map above shows the real EA rivers & sea likelihood cells around HP18 9EW. 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 | ~27.2 km |
| Jan 1992 | 06SeptemberAutumn1992 | ~2.7 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, 2 warnings nearby) ▶ replay it here · Bram (2025, 1 warnings nearby) ▶ replay it here · Herminia (2025, 1 warnings nearby) ▶ replay it here · Bert (2024, 1 warnings nearby) ▶ replay it here
| Gauge | River | Distance | Typical high | Highest on record |
|---|---|---|---|---|
| Thame Bridge | River Thame | 4.3 km | 2.25 m | 2.99 m |
| Cuddington | River Thame | 6.2 km | 2.09 m | 2.59 m |
| Wheatley | River Thame | 7.2 km | 5.75 m | 6.11 m |
| Lower Arncott | River Ray | 11.1 km | 2.00 m | 2.98 m |
Live levels, predictions and rain-response behaviour are on each gauge's page and in the property report.
| Overflow | Discharges into | Distance | Spills | Hours |
|---|---|---|---|---|
| Worminghall Stw | Worminghallbrook | 2.0 km | 93 (2024) | 1,215 |
| Shabbington Wwtw | Shabbington Brook | 2.1 km | 67 (2024) | 998 |
| Long Crendon Wwtw | Crendon Stream | 3.1 km | 19 (2024) | 84 |
| Thame Wastewater Treatment Works | Lashlake Stream | 4.8 km | 105 (2024) | 1,608 |
Official annual EDM figures — a water-quality signal for local watercourses, not a property flood-risk factor.
6 mapped flood-defence assets within 500 m — nearest ~25 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 HP18 9EW — all in the HP18 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 HP18 district.