Mostly no, and the river is the smaller part of the risk. Hardly any postcodes fall in the river-and-sea flood zones. About one in eleven rates high on at least one flood measure once rain is counted. No flooding is on record. The risk is small across the town and real for the streets that carry it.
In the Environment Agency's river-and-sea flood zones, about 1% of Wallington's postcodes fall in zone 3, the highest-probability band, and about 4% in zone 2, the medium-probability fringe beyond it. The two bands do not overlap, so the town's river exposure is roughly 5% of postcodes in total. The River Wandle runs past the old village by Wallington Bridge, and it once turned the mills whose pond is now The Grange boating lake. These days it mostly decorates the park.
Surface water, the rain that has nowhere to go after a heavy downpour, is the risk the river zones leave out entirely. It is folded into the combined postcode measure further down, and on that measure the picture gets larger. A home outside the river zones can still sit on a street where the drains lose the argument.
The Environment Agency's climate-adjusted zone, which redraws the flood zones for the rainfall and river levels expected in future, takes in about 9% of Wallington's postcodes. That is a modelled scenario for planning purposes, and it moves the line on the map rather than any water.
For most homes in Wallington, flood risk should barely register on an insurance quote. For a property in zone 3 or on a high surface-water rating, the premium and the excess can look very different, and some insurers will ask questions others do not. Put the exact address into the Environment Agency's long-term flood risk service and get an indicative insurance quote early in the process, while walking away is still cheap.
On the combined measure, about 9% of Wallington's postcodes rate high on at least one flood indicator, about 15% medium and about 36% low, with surface water counted alongside rivers and sea. These bands overlap with the zone figures above and are a different yardstick, so they should never be added together. A postcode needs only one indicator to earn its rating.
Counted as properties, the Environment Agency's rivers-and-sea mapping lists 1,593 properties across the Wallington postcodes that carry any risk at all. Of those, 173 are at high risk, 164 of them homes, 21 at medium risk and 818 at low risk. Postcodes with no river-and-sea risk do not appear in that count. The question for a buyer is whether the house being viewed is one of the 173.
The modelled high-risk extent covers about 1% of postcodes with defences left out of the model and about 1% with them included. The defences in the model, in other words, do not shrink the high-risk share at all. "Defended" in a set of sales particulars describes a structure on a map; it says nothing about whether the water stops before the front door.
The nearest tide gauge to Wallington is at Portsmouth, where the sea rose about 2 millimetres a year across the record from 1962 to 2023. That is the rate measured at Portsmouth over those years and nothing more. A town whose nearest tide gauge is on another coast has other things to worry about.
The Environment Agency's records show no historic flooding in Wallington's postcodes. That is good news, and it means nobody has recorded a flood here, which falls short of proving the water has never come.
Wallington's flood risk is middling: low for the bulk of the town, concentrated and costly for the 173 properties that carry the high rating.