Rivers and the sea are a small risk in Epsom, but surface water is a bigger one. Hardly any postcodes are in a river flood zone. About one in six is rated high risk on at least one flood measure. There is no recorded flood history. The danger in Epsom comes from water running off the ground after heavy rain, not from rivers bursting their banks.
On the Environment Agency's river-and-sea flood map, under 1% of Epsom's postcodes are in flood zone 3, the highest-probability band. About 2% are in flood zone 2, the medium-probability band beyond it. The two bands don't overlap, so together they cover only a sliver of the town. For flooding from rivers and the sea, Epsom has very little exposure.
Surface water is a different matter, and the river-and-sea zones leave it out entirely. Epsom grew up along the line where the chalk of the Downs meets the clay, and tributaries of the Hogsmill River rise at several points along that boundary. Heavy rain on clay has nowhere quick to drain to. A town built where water comes out of the ground will always have some on the surface.
The Environment Agency also publishes a version of its flood zones adjusted for climate change, and about 5% of Epsom's postcodes fall inside it. That is the agency's modelled view of how the zones could spread, which is not the same as a record of what has happened.
Insurers price each address, and many use surface-water mapping as well as the river zones, so the cost of cover can vary between neighbouring streets. Put the exact address into the Environment Agency's long-term flood risk service, check the surface-water result specifically, and get an insurance quote early, while you can still walk away.
The wider measure folds surface water in alongside rivers and the sea, which is why its figures run far higher than the zone shares. About 16% of Epsom's postcodes are rated high risk on at least one flood measure, 22% medium and 43% low. These bands overlap with the flood zones above, so don't add them together. Each figure is the share of postcodes where at least one type of flooding reaches that level.
Counting homes gives a clearer picture. The Environment Agency's rivers-and-sea mapping lists 1,797 properties in Epsom, all in the 63 postcodes that carry some risk; postcodes with none are left off the list. Of those properties, 96 are at high risk, 111 at medium risk and 365 at low risk. Sixty-three of the high-risk properties are homes.
About 1% of Epsom's postcodes fall in the high-risk flood extent when flood defences are left out of the model, and about 1% when they are included. That suggests defences make very little difference to how far the high-risk area reaches. "Defended" also means only that a defence appears in the model. It says nothing about whether the defence will stop water reaching a particular house. A seller who calls a property "defended" is quoting the model, not giving an assurance about the house.
The nearest tide gauge is at Portsmouth, where sea level rose by about 2 millimetres a year between 1962 and 2023. That is the rate measured at that gauge over that period. Epsom is a long way inland, and the sea is one of the few flood sources it can mostly ignore.
There is no historic flooding on record anywhere in Epsom. That is reassuring. It shows that nothing has been written into the records, which is not quite the same as nothing ever having happened.
Overall, flood risk is one of Epsom's weaker points. The rivers and the sea are barely a factor, but surface water reaches far enough across the town that every purchase needs its own check.