Yes, in parts, and you can find out exactly which parts. Brentford is named after a crossing over a river. About one postcode in seven is in the Environment Agency's highest river-and-sea flood zone. A few hundred homes are rated high risk. Most of the town is outside the flood zones, and the risk is concentrated in the low ground by the water.
On the Environment Agency's river-and-sea mapping, about 15% of Brentford's postcodes are in flood zone 3, the highest-probability band. Another 6% are in flood zone 2, the medium-probability fringe just outside it. The two bands don't overlap, so the second figure adds to the first. The town grew up where the Brent meets the Thames, and the low ground near both rivers is where the flood zones are.
Surface water, from heavy rain that can't drain away fast enough, is a different risk with a different map. In Brentford it is not split out on its own; it is counted in the postcode measure below together with rivers and sea.
When the Environment Agency adds its allowance for climate change, about 23% of postcodes fall inside the flood zone. That figure is the agency's planning allowance for a wetter future, not a record of anything that has happened yet.
Insurance follows the address. A flat on an upper floor and a ground-floor home by the river can sit in the same postcode and get very different quotes. It is worth getting an indicative buildings-insurance quote for the exact property before paying for a survey, because the quote is where the mapping becomes a cost you actually pay.
On a wider measure that includes surface water as well as rivers and the sea, about 11% of postcodes are rated high risk on at least one flood measure. About 18% are rated medium and about 39% low. Those shares overlap with the flood-zone figures above and use a different method, so the two sets should never be added together.
Counted as properties, the Environment Agency's rivers-and-sea assessment lists 2,202 properties across the 80 Brentford postcodes that carry any risk. Postcodes with no risk are left out of the count entirely. Of those properties, 347 are rated high risk, 304 of them homes, 73 are medium, 1,332 are low and 166 are very low. A count of homes is more useful to a buyer than a share of postcodes, because it tells you how many front doors are affected.
On the question of defences, about 3% of postcodes are in the high-risk extent with no defence present in the model, and about 3% are in it with one. A defence in the model means a wall or embankment appears on the Environment Agency's map. It says nothing about whether that defence will hold, and a buyer who hears the word "defended" during a sale is being given less than it sounds like.
The nearest tide gauge in the national record is at Portsmouth, which measured sea level rising by about 2 millimetres a year between 1962 and 2023. That is the rate measured at Portsmouth over those years, a long way down the coast from the Thames at Brentford.
No historic flooding is recorded in the area. That is good to know, but it only means no flooding has been recorded, not that none has happened, and it should not count for more than the flood zones do.
Brentford's flood risk is middling. Most addresses are fine, and a few hundred homes by the water carry real risk that is mapped property by property.