Yes, Wandsworth Town has a real flood risk, and most of it lies along the Thames and the Wandle, the two rivers that built the place. About one postcode in seven is in the highest river flood zone. About a quarter are rated high risk on at least one measure once rainwater is counted too. On the climate-adjusted maps the zone grows to over a third of the area. Most homes here are on dry ground, but the wet ground includes the riverside flats that sell the area.
On the Environment Agency's river-and-sea flood map, about 14% of Wandsworth Town's postcodes fall in Flood Zone 3, the highest-probability band, and a further 17% are in Flood Zone 2, the medium-probability fringe beyond it. The two bands don't overlap, so between them they cover the low ground near the water. The old wharves where coal was unloaded beside the gasworks are now lined with apartment blocks, and the river has the same view of them it had of the barges.
Surface water is a separate risk. It comes from heavy rain that the drains and pavements can't clear, and it can reach streets well away from either river. The Environment Agency maps it separately, and it is included in the postcode measure further down, not in the zone figures above.
The Environment Agency also maps how the river zone would look under its climate allowance, and on that basis about 36% of postcodes fall within it. That is the modelled scenario for a warmer future, and it changes the map more than it changes this year's weather.
For insurance, a home in Flood Zone 3 or near the riverside will usually face more questions, a higher premium or a larger excess than the same flat up the hill. Get an indicative buildings quote for the exact address early, while walking away still costs nothing.
Counting all the flood indicators together, including surface water, about 26% of postcodes are rated high risk on at least one of them, about 33% medium on at least one, and about 46% low on at least one. A postcode can appear in more than one band, because each one only needs a single measure to qualify.
In terms of actual homes, the Environment Agency's rivers-and-sea mapping counts 10,103 properties in the postcodes it lists, and only postcodes with some risk are listed at all. Of those, 366 properties are at high risk, 1,278 at medium, 6,052 at low and 120 at very low. Most of the exposed homes are in the lowest band, and the high-risk group is small enough to come down to particular streets and particular buildings.
Then there is the question of whether anything stands between the water and the front door. About 3% of postcodes fall inside the modelled high-risk flood area with no defence counted, and about 4% fall inside it with a defence present in the model. A defence in the model is something the Environment Agency has taken into account. It doesn't mean the water stops there. Of the 20 floods on record for the area, the most recent came off the main river in January 1928, and it happened when the water overtopped the defences.
The nearest tide gauge in the national record is at Portsmouth, where the sea rose by about 2 millimetres a year between 1962 and 2023. That is the rate measured at that gauge over those years, and the Thames at Wandsworth Bridge never figures in it.
Flood risk is a real weakness for Wandsworth Town. It is concentrated, mapped and heaviest on the riverside, so it matters a lot for some homes and very little for others.