Tooting does have a real flood risk, and most of it comes from rain. Only a few postcodes fall in the river flood zones. Once surface water is counted, about one in five rate high on at least one measure. There's no recorded history of flooding in the area. In Tooting the risk comes from above.
In the Environment Agency's river-and-sea flood zones, about 4% of Tooting's postcodes are in Zone 3, the highest-probability band. Another 3% are in Zone 2, the medium-probability fringe outside it. The two bands don't overlap, so Zone 2 is the extra strip beyond Zone 3 and doesn't include it. A listing that says "Flood Zone 1" answers the river question, and in Tooting the river was never the main question.
Surface water is a different measure and a different problem. It happens when heavy rain falls faster than drains and gardens can take it away, and the river-and-sea zones don't model it at all. In a place this built up, with flats packed into Edwardian streets, rain has fewer places to go. That's why the postcode measures further down come out higher than the zone figures.
The Environment Agency also models what its flood zones could look like once a climate-change allowance is added. On that projection, about 21% of Tooting's postcodes fall inside the zone. It's a planning scenario for the decades ahead, and it shows how much bigger the problem gets when the rain gets heavier.
Insurers price flood risk by address, and in a place where much of the risk is surface water, two homes on the same street can get noticeably different quotes. Get a buildings insurance quote on the exact address while your offer can still change. A basement flat at the bottom of a slope and a top-floor flat in the same building are, to an insurer, two different risks.
Across Tooting's 949 assessed postcodes, about 19% rate high on at least one of several flood measures, about 27% rate medium on at least one, and about 55% rate low on at least one. Surface water is counted alongside rivers and sea. Because each postcode is scored on several measures, one postcode can show up in more than one of those shares.
Counted as homes and other properties, the Environment Agency's rivers-and-sea mapping lists about 3,550 properties in Tooting postcodes that carry some risk. Postcodes with no risk aren't listed at all. Of those properties, 41 are at high risk, 33 of them residential. About 1,130 are at medium risk, about 1,090 at low risk and 48 at very low risk. The medium band is where most of Tooting's river exposure is.
On defences, about 4% of postcodes are inside the modelled high-risk extent with no defence present, and about 3% are inside it with a defence present in the model. A defence in the model means something was built to hold water back. It says nothing about whether that defence will hold for a particular house, and it does nothing about rain that never gets near a river.
The nearest tide gauge is at Portsmouth, which measured sea level rising by about 2 millimetres a year between 1962 and 2023. For a place as far inland as Tooting, the sea is the least of its flood worries.
There's no recorded historic flooding in the area. That's reassuring, but a clean record only means nothing was written down.
Flood risk is one of Tooting's weak points, and nearly all of it comes from heavy rain with nowhere to drain.