Yes, and the risk in Grays comes from above as well as from the river. About one in ten postcodes falls in the highest river-and-sea flood zone. Four in five rate high on at least one flood measure once rain is counted. The sea last came over in the middle of the last century. The Thames is the obvious worry, and the drains are the one buyers forget.
On the Environment Agency's river-and-sea mapping, about 9% of Grays postcodes are in Flood Zone 3, the highest-probability band. Another 11% are in Flood Zone 2, the medium-probability fringe outside it. Zone 2 is a separate band and does not include Zone 3. Most of the water's likely route is the riverside strip, where marshland, storage yards and the yacht club meet the Thames, and the river has first claim on that ground.
Surface water is the rain that cannot drain away fast enough, and the river-and-sea zones leave it out entirely. In a town as built-up as Grays, that is the risk that reaches streets nowhere near the water, and it is folded into the broader postcode measure further down this page.
Allow for the Environment Agency's climate-change projections and about 27% of postcodes fall inside the flood zones. That is the Agency's modelled future and should be read as a wider band the planners already have in mind.
Insurers price on the exact address and the measure they trust, and in a town with this much of its map coloured in, a quote can vary a great deal from one street to the next. An indicative insurance quote on a specific house is worth more than the town average, and it costs nothing to ask for one early.
Count every flood indicator the Environment Agency publishes, surface water included, and about 81% of Grays postcodes rate high on at least one, about 47% medium on at least one, and about 52% low on at least one. One postcode can turn up in several of those bands, because each counts any one of several measures. A postcode only has to fail one test to make that list, and in Grays most of them do.
Counting homes gives a different and smaller result. The Environment Agency's rivers-and-sea assessment lists 137 Grays postcodes carrying some risk, covering 4,404 properties. Of those, one property is at high risk, none at medium, one at low, and 3,130 at very low. Postcodes with no river or sea risk are not on that list at all. A share of postcodes can sound alarming while the count of homes says most of the river risk is very low.
The defences question is the useful one. On the Agency's flood-extent modelling, about 9% of Grays postcodes are inside the high-risk extent with no defence in the model, against well under 1% where a defence is modelled. A defence in the model means something is drawn on the map between the river and the house. Whether it is a wall, an embankment or a line on a plan is the question to put to a surveyor.
The nearest tide gauge in the record is at Dover, which measured sea level rising by about 2.2 millimetres a year between 1961 and 2010. That is what the gauge recorded over those years at a site well down the coast from the Thames. The Environment Agency holds 40 recorded flood events for the area, and the latest, in 1953, came from the sea.
Flood risk is the weakest point of Grays, mainly because of rain. Buyers who want a house here should rule out an address on the map before they start to like it.