Redbridge carries a middling flood risk, and almost none of it comes from the river. The official river flood zones barely touch the area. Even so, about one postcode in eight rates high on some flood measure. That gap belongs to heavy rain and the low corners of streets the river maps never mention. A buyer here should worry less about rising water and more about where the rain has nowhere to go.
On the Environment Agency's river-and-sea mapping, about 1% of the area's postcodes fall in flood zone 3, the highest-probability band, and none at all in zone 2, the medium-probability fringe drawn outside it. None of the properties the agency lists as at risk from rivers and the sea is in its high band. "Not in a flood zone" will be true of almost every house for sale here, and it answers the river question only.
Surface water is a separate risk, and a separate map. It comes from rain falling faster than the drains can take it, and it pays no attention to how far a house is from a river, with water about 550 metres from a typical front door here. The Environment Agency maps it street by street, so the useful check is the agency's long-term flood risk service for the exact address, which shows the surface-water rating alongside the river one.
The Environment Agency also models the river zones with an allowance for a wetter climate. On that version, about 2% of the area's postcodes fall inside the zone. That is a small rise on today's map, and still small.
Insurers price the exact address, using their own maps, not the neighbourhood's reputation. A house well clear of every flood measure should be insured like any other London semi. One of the few addresses with a high surface-water rating can still find the quote a good deal higher, or the excess larger, however dry the street looked on the day of the viewing.
Counting every measure together, including surface water as well as rivers and the sea, about 12% of the area's postcodes rate high on at least one, about 14% medium and about 30% low. A postcode only needs one measure against it to appear in those shares. That makes them the widest net on this page, and the reason they run well ahead of the river-zone share.
The Environment Agency's modelling also asks whether defences change the picture. About 1% of postcodes are inside the high-risk flood extent with defences ignored, and about 1% with them included. Wherever defences are in the model, they make no difference to that share here. "Defended" in this modelling only means a defence is on the map. It says nothing about whether it would hold.
The Environment Agency's historic flood outlines, the record of where water has actually been mapped, cover none of the area's postcodes. Its event records do hold eight floods logged for the area. The most recent was in December 1987, when a main river overtopped a channel that had no raised defences. A blank map of past flooding is a good sign. It is still only a record of what someone measured and wrote down.
Flooding in Redbridge is a middling worry: the river barely features, and the risk that does exist turns up in rain-soaked corners on a handful of streets. Most buyers will never think about it, and the few on the wrong postcodes will think about it whenever it rains.