Yes, and almost all of it is rainwater with nowhere to go. The rivers barely reach the estate. Surface water reaches most of it. Six in ten postcodes rate high on at least one flood measure. The risk is in the drains, which most buyers do not think to look at.
The Environment Agency's river-and-sea flood zones hardly touch Becontree. About 2% of the area's postcodes are in flood zone 3, the highest-probability band, and about 1% more are in zone 2, the medium-probability band just outside it. The two zones do not overlap, so the totals do not double-count. The estate's bricks came up the Thames by barge, and on the river mapping very little water is expected to make the same trip.
The real exposure is surface water: heavy rain that falls faster than the drains can carry it away and collects in roads, gardens and the lowest houses. That risk comes from the shape of the streets and the capacity of the drains, and it does not show up in the river-and-sea zones at all. An estate built quickly on flat former market gardens, covered in roofs and tarmac, gives the rain very little ground to soak into.
The zone the Environment Agency draws for future climate change takes in about 29% of the area. That is its modelled view of where river and sea flooding could reach as conditions change, and it is a much bigger figure than the present-day 2%.
Insurers price surface-water risk as well as river risk, so a house that sits well outside the river zones can still get an expensive premium or a high excess if its postcode rates badly for rainfall. Get a quote on the specific address early, and run it through the Environment Agency's long-term flood risk service, which shows surface water separately.
Across Becontree's postcodes, about 62% rate high on at least one of several flood measures, surface water included, about 62% rate medium on at least one, and about 74% rate low on at least one. A postcode can appear in more than one of those bands, because each one counts any measure that puts it at that level. That is why the bands add up to well over 100%, and it is how a place with almost no river risk ends up with a postcode map that looks this bad.
The Environment Agency's property-level mapping for rivers and sea lists 1,349 properties, and it only includes postcodes that carry some risk in the first place. Of those, two are at high risk, both of them homes, none are at medium risk, 79 are at low risk and 545 are at very low risk. Counted by property, the river and sea threat amounts to two houses.
About 2% of Becontree's postcodes fall inside the high-probability river-and-sea flood extent with no defence in the model, and none fall inside it with a defence. The low-probability undefended extent covers about 3%. Nothing in the model stands between those few postcodes and the water. Where defences have existed, they are not foolproof: the Environment Agency has 35 recorded flood events here, and the most recent, in December 1974, happened when a defence on a main river failed.
The nearest tide gauge is at Dover, which recorded sea level rising by about 2.2 millimetres a year between 1961 and 2010. That is the rate measured at Dover over those years.
Flood risk in Becontree is poor. River and sea flooding barely registers, but surface water affects so much of the estate that very few addresses are free of it.