FloodRadar
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Over Wallop, Hampshire
Up to Low likelihood
Properties in SO20 8HU 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 | 1 |
| 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.
SO20 8HU gets about 842 mm of rain a year on average (wettest month November, 99 mm; driest May, 50 mm). That is 28% 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), 1.0 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 69 m above sea level and falls 20 m across the surrounding 800 m. Surface water reaching this point runs off ground lying to the north-north-east, 16.8 m higher.
The river map has no watercourse within 1 km of the centre of SO20 8HU.
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; 194 official warnings since 2006.
The map above shows the real EA rivers & sea likelihood cells around SO20 8HU. 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 |
|---|---|---|
| Feb 2014 | River Test Aerial Photography | ~11.9 km |
| Jan 1995 | Winter1995_Wallop Brook_Aerial(14) | ~0.6 km |
| Jan 1995 | Winter1995_Wallop Brook_Aerial(11) | ~1.1 km |
| Jan 1995 | Winter1995_Wallop Brook_Aerial(10) | ~1.0 km |
| Jan 1995 | Winter1995_Wallop Brook_Aerial(20) | ~1.4 km |
| Jan 1995 | Winter1995_Wallop Brook_Aerial(15) | ~0.7 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, 44 warnings nearby) ▶ replay it here · Henk (2024, 7 warnings nearby) ▶ replay it here · Herminia (2025, 2 warnings nearby) ▶ replay it here · Jocelyn (2024, 2 warnings nearby) ▶ replay it here
| Gauge | River | Distance | Typical high | Highest on record |
|---|---|---|---|---|
| Stockbridge Main | River Test | 7.8 km | 34.45 m | 34.63 m |
| Stockbridge Side | River Test | 7.9 km | 35.38 m | 0.75 m |
| Idmiston | River Bourne | 8.4 km | 0.60 m | 0.94 m |
| Shipton Bellinger | River Bourne | 8.7 km | 0.30 m | 0.95 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 ~12 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 SO20 8HU — all in the SO20 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 SO20 district.