Yes, and more than most Surrey towns of its size. More than a quarter of its postcodes sit in the Thames's highest-risk zone. About a quarter have flooded on record. Defences barely shrink the modelled high-risk area. The higher ground towards Englefield Green is where the risk thins out.
On the Environment Agency's river-and-sea flood zones, about 29% of Egham's postcodes fall in Flood Zone 3, the high-probability band, and a further 18% in Flood Zone 2, the medium-probability fringe beyond it. Nearly half the town is in one zone or the other. Cooper's Hill rises beside the Thames floodplain, and much of Egham Hythe and the land around Runnymede lies on the flat below it. The meadow at Runnymede is a meadow because the Thames keeps it that way.
The record goes beyond the models. About a quarter of postcodes lie inside the Environment Agency's recorded historic flood outlines, and the agency logs 182 recorded flood events here, the most recent in January 2003, when a channel overtopped with no raised defences in the way. In the winter storms that began in 2013, the army was deployed to help with defences and damage around Runnymede and Egham Hythe after exceptional rain across the Thames Valley.
Allowing for climate change, the Environment Agency's adjusted flood zone covers about 60% of Egham's postcodes. That is the agency's planning view of where the river could reach as the climate shifts, and it takes in a good deal of the town that today's zones leave out.
For insurance, a home in Zone 3 or inside a historic outline will usually cost more to cover, and some properties with a flood claim behind them can be hard to insure at all. Ask the seller in writing whether the house took water in the 2013 storms and whether a past insurer has ever refused or loaded the flood cover, because the answer belongs in the price.
Counting postcodes across every measure the Environment Agency publishes, surface water included alongside rivers, about 29% of Egham's postcodes rate high on at least one, about 38% medium and about 50% low. A postcode only needs one measure to qualify, so these shares overlap and cannot be stacked into a single total.
In homes, the Environment Agency's rivers-and-sea mapping lists 293 Egham postcodes carrying some risk, covering 6,522 properties. Of those, 1,650 are at high risk, 1,747 at medium risk and 2,361 at low risk, with 23 at very low risk. Postcodes with no river or sea risk do not appear in the count at all, so these are the properties that made the list.
The model of the highest-risk flood extent puts about 28% of postcodes inside it without defences and about 28% with them. "Defended" here means a defence exists in the Environment Agency's model, and in Egham its presence changes the high-risk map by almost nothing. A buyer reading the word as reassurance has been given a word.
The nearest tide gauge is at Portsmouth, where the sea rose by about 2 millimetres a year across the record from 1962 to 2023. That is a measured past rate on the coast, a long way downriver, and Egham's flooding comes from the Thames and the rain.
Flood risk is the weak point in Egham's case, serious enough that the house's exact position on the slope matters as much as its price.