Didcot carries more flood risk than its river maps suggest. Only a sliver of the town is in the river flood zones. About one postcode in six is flagged high on at least one flood measure. No past flooding is recorded. The zone map shows the river side of the risk, and the rest comes from elsewhere.
About 3% of Didcot's postcodes are in the Environment Agency's river-and-sea flood zone 2, and about 1% are in zone 3. The two bands are separate. Zone 3 is the higher-probability core, and zone 2 is the medium-probability fringe beyond it. The Thames runs past Appleford-on-Thames and Sutton Courtenay to the north, and the town itself keeps mostly clear of it.
Surface water is where the gap opens. Rain that has nowhere to go appears in the wider flood indicators and barely registers on the river zones. Ladygrove was built on former marshland north of the railway, and a buyer there should look up the exact address on the Environment Agency's long-term flood risk service, with the surface-water layer switched on.
When the Environment Agency adds its climate-change allowance to the river and sea modelling, about 5% of postcodes fall in the flood zone. That is the agency's planning projection for a wetter future, and it is a model rather than a record of anything that has happened.
For insurance, a postcode with a high rating on any measure can mean higher premiums or more questions from the insurer, even where the river zones are clear. A quote on the specific house is a better guide than the town-wide picture.
Taking all the indicators together, including surface water alongside rivers and the sea, about 17% of Didcot's postcodes rate high on at least one, about 22% rate medium on at least one and about 44% rate low on at least one. A postcode only needs to trip one measure to be counted, so these shares overlap with each other and with the zone figures above. The difference between about 1% in zone 3 and about 17% flagged high is the whole story of flooding in Didcot.
Counted by property, the Environment Agency's rivers-and-sea mapping lists 957 properties in the postcodes that carry any risk at all. Of those, 170 are at high risk, 162 of them homes. Another 2 are at medium risk and 459 at low risk. Postcodes with no river or sea risk are left out of the count entirely.
About 1% of postcodes are in the high-risk river extent with no defence modelled, and about 1% are in it with a defence present. "Defended" means only that a defence exists in the Environment Agency's model. The water does not consult the model before deciding what to do.
The nearest tide gauge is Portsmouth, which recorded sea level rising by about 2 millimetres a year between 1962 and 2023. That is the rate measured there over that period. Portsmouth being the closest gauge tells you how far Didcot is from the sea.
No past flooding is recorded across the area's postcodes. That is good news, though a clean record only covers events that were written down, and it says nothing about the rain to come.
Didcot's flood risk is a real weak point, much of it surface water rather than river. Anyone buying here should check the flood picture for the exact house as seriously as the price.