Plaistow has a real flood risk, and it shows up more on the maps than in the area's history. About one postcode in six falls inside the highest river-and-sea flood zone. Once climate change is allowed for, that becomes nearly two in three. Nothing in the modelling puts a defence between those postcodes and the water. Flooding has never been recorded here, so the risk exists on the map and not yet in anyone's memory.
On the Environment Agency's river-and-sea flood maps, about 16% of Plaistow's postcodes are in Flood Zone 3, the band with the highest probability. Another 2% are in Flood Zone 2, the medium-probability fringe outside it. The agency's separate count of properties at risk from rivers and the sea, which also looks at defences, rates none of Plaistow's properties as high or medium risk, 683 as low and about 3,290 as very low. These are two official measures of the same water, and they can give quite different answers. Plaistow has no river of its own on these maps, so the water they worry about would come from further away.
Surface water, meaning rain with nowhere to go, is not given a figure of its own here. It is included in the postcode-level measure further down. In a place this densely built, with this little open ground, the drains carry a lot of the load.
The Environment Agency also maps a flood zone that allows for climate change, and that one covers about 65% of Plaistow's postcodes. It is a modelled view of what might happen, not something that has already happened, and it covers a much larger area than today's zones.
Insurance follows the maps. A postcode in the highest zone can mean a higher premium or extra questions from the insurer, even when nothing has ever got wet. Two neighbouring streets can get very different quotes. One check is worth making for a specific home: put the exact address into the Environment Agency's long-term flood risk service and get a quote for buildings cover while the sale is still at an early stage.
At postcode level, Plaistow's figures count a postcode if any one of several measures flags it, rivers, sea and surface water included. On that wider count, about 15% of postcodes are rated high on at least one measure, 25% medium and 57% low. One bad indicator is enough to put a postcode in a band, so this count is wider than any single map.
The Environment Agency's modelled flood extents also show whether a defence is present. About 13% of Plaistow's postcodes are in the high-probability extent with no defence in the model, and none are in a defended high-probability area. Another 18% are in the low-probability extent with no defence. In the model, nothing stands between those postcodes and the water. A modelled defence would only change the odds anyway, so having none removes even that.
The nearest tide gauge with a long record is at Portsmouth, where the sea rose by about 2 millimetres a year between 1962 and 2023. That is the rate measured on the south coast over those years. Plaistow can only borrow it as a rough guide.
No historic flood outline in the Environment Agency's records covers any part of Plaistow. That is good news. It only shows that no flood has been recorded here, not that the ground has never been wet.
Flood risk is one of Plaistow's weaker points. The history is clean, but the zone maps, the climate-change mapping and the missing modelled defences all point the same way, and buyers and their insurers should take them seriously.