Only from the rain, and not much from that. Rivers and the sea don't reach it. A small minority of postcodes carry a high surface-water rating. No flooding is on record. On the North Downs the water comes down from the sky, and nobody here needs to worry about a riverbank.
The Environment Agency's river-and-sea flood zones leave Warlingham out entirely. None of the area's postcodes are in flood zone 3, the highest-probability band, and none are in flood zone 2, the medium-probability fringe beyond it. For a village on the scarp slope of the Downs, that is about as surprising as finding no lifeboat station.
Surface water is the risk that matters here. Heavy rain on chalk and tarmac has to go somewhere, and on a hillside it gathers in the dips, the lower roads and the bottoms of drives. A small number of streets carry nearly all of it, and the rest of the village is high and dry.
The Environment Agency's climate-adjusted mapping, which looks ahead to wetter conditions, still puts none of the area's postcodes in its river-and-sea zones. Even a wetter future doesn't bring a river up this hill.
For insurance, being clear of the river-and-sea zones helps most homes here. Insurers still look at surface-water ratings for the exact property, though, so a house in one of the low spots can be quoted differently from its neighbour further up the slope. The simplest check is to put the exact address into the Environment Agency's long-term flood risk service and get an indicative buildings quote while the sale is still negotiable.
Looking postcode by postcode, about 6% of Warlingham's postcodes are rated high on at least one flood measure, about 9% medium and about 25% low. These ratings include surface water as well as rivers and the sea, so they overlap the zone figures above and shouldn't be added to them. In practice, the postcodes rated high are there because of rain running off the hill.
The modelled flood extents put none of the area's postcodes in a high-probability river or sea extent, with or without defences. With no water in that model to hold back, the defended-or-undefended question has nothing to answer.
The nearest tide gauge is at Portsmouth, where sea level rose by about 2 millimetres a year between 1962 and 2023. That rate was measured on the south coast, a long way south of the Downs and a long way below them, and it tells a Warlingham buyer almost nothing about their own house.
The Environment Agency has no historic flooding on record anywhere in the area. That is reassuring, though it only tells you about floods that were recorded. A blocked drain on a stormy night can still put water in a garage without anyone writing it down.
Warlingham's flood risk is middling at worst, and it all comes from rain running downhill. That makes a property's place on the slope matter more than anything about the village as a whole.