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Egham, Surrey
Up to Low likelihood
Properties in TW20 8BT 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% | 35 | 35 |
| 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.
TW20 8BT gets about 645 mm of rain a year on average (wettest month October, 70 mm; driest March, 41 mm). That is 45% 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), 1.5 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 16 m above sea level and falls 3 m across the surrounding 800 m. The ground contributing surface water to this point lies to the west-south-west.
Two mapped watercourses are about the same distance from the centre of TW20 8BT: the River Thames (about 820 m) and County Ditch (about 860 m), so this page cannot say which one is nearer to you.
Distances along the river are from the point on each watercourse nearest the centre of TW20 8BT. 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.
Because properties in the low likelihood band; 3 recorded flood outlines mapped nearby; 376 official warnings since 2006.
The map above shows the real EA rivers & sea likelihood cells around TW20 8BT. 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 | ~2.2 km |
| Dec 2012 | ea06DecemberWinter2012 | ~1.0 km |
| Dec 2002 | 06JanuaryNewYear2003 | ~0.8 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, 79 warnings nearby) ▶ replay it here · Henk (2024, 11 warnings nearby) ▶ replay it here · Dennis (2020, 5 warnings nearby) ▶ replay it here · Conall (2024, 4 warnings nearby) ▶ replay it here
| Gauge | River | Distance | Typical high | Highest on record |
|---|---|---|---|---|
| Staines | River Thames | 1.1 km | 4.00 m | 4.96 m |
| Hythe End | Colne Brook | 1.4 km | 2.20 m | 3.32 m |
| Staines Trading Estate | River Colne | 1.4 km | 2.00 m | 1.67 m |
| Knowle Green | River Ash | 2.2 km | 0.81 m | 1.16 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 |
|---|---|---|---|---|
| Chertsey Stw | Bourne (north) | 2.9 km | 104 (2024) | 1,913 |
| Windsor | Thames | 4.9 km | 133 (2024) | 1,735 |
Official annual EDM figures — a water-quality signal for local watercourses, not a property flood-risk factor.
2 mapped flood-defence assets within 500 m — nearest ~459 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 TW20 8BT — all in the TW20 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. 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. 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 TW20 district.