Uxbridge has a real flood risk, but most of it comes from rain, not the rivers. Barely any of the town is in the river flood zones. More than a quarter of postcodes still carry a high flag on at least one measure. Water running off roofs and roads is what drives that number. On a quick look at the maps the town seems safe, and the wider indicators say otherwise.
The town is named after Wixan's Bridge, so water has been part of it from the start, though the River Colne and the Frays River mostly keep it to the western edge. On the Environment Agency's river-and-sea mapping, about 5% of Uxbridge postcodes are in Flood Zone 2, the medium-probability band, and about 1% are in Flood Zone 3, the high-probability band. The two are separate bands, so the Zone 2 figure covers the fringe beyond Zone 3 and does not include it. The agency has three recorded flood events here, the most recent in December 1988, when a main river overflowed its channel with no raised defences to stop it.
Surface water is where most of the risk is. Rain falling on a built-up town has to go somewhere, and when the drains can't keep up it pools on roads, in dips and against back doors well away from any river. That is why the wider indicators look so different from the zone map, and why a house that is nowhere near the Colne can still flood.
The Environment Agency also models river and sea flood zones with an allowance for climate change. On that version, about 10% of Uxbridge postcodes fall inside the zones. It shows where the agency's planners expect the edges to move. It says nothing about when.
For insurance, the gap between the measures matters. A house outside the river zones may still have a surface-water flag, and insurers look at the specific address, whatever the town looks like overall. Surface-water risk varies from street to street, so the Environment Agency's long-term flood-risk check for the exact address is worth more than any description of the street in the sales particulars.
Across the measures together, about 27% of Uxbridge postcodes are rated high on at least one, whether river, sea or surface water. About 30% are rated medium on at least one, and about 45% low on at least one. A postcode can appear in more than one of these bands, because each one counts any measure that reaches that level.
Counting buildings gives a more useful figure. The Environment Agency's river-and-sea mapping lists 4,375 properties in Uxbridge postcodes that carry some risk. Of these, 637 are at high risk, 42 at medium, 1,121 at low and 270 at very low, and 115 of the high-risk properties are homes. Only postcodes with some modelled risk are included, so the rest of the town does not appear in the count at all.
Whether anything holds the water back does not change the picture much. About 1% of Uxbridge postcodes are inside the high-probability river flood extent without defences, and about the same 1% with defences included. A defence that is in the model has not shrunk the at-risk area, and a modelled defence does not mean a house is dry.
The nearest tide gauge is Portsmouth. It measured sea level rising by about 2 millimetres a year between 1962 and 2023. For a town up the Colne valley on the edge of London, that is one of the few numbers on this page that nobody here needs to worry about.
Flood risk is a weak point for Uxbridge. The rivers are mostly contained, but rainwater across a quarter of the postcodes makes it a check every buyer here should make.