Greenhithe has a middling flood risk, and almost all of it sits along the Thames frontage. Most of the village is outside the river-and-sea flood zones. A small slice is in the highest zone. A climate-adjusted map roughly doubles the exposure. The village is named after a landing place, and the water still remembers where that was.
The Environment Agency's river-and-sea mapping puts about 5% of the Greenhithe area's postcodes in Flood Zone 3, the highest-probability band, and about 13% more in Flood Zone 2, the medium-probability fringe that lies beyond it. The two bands do not overlap, so together they describe the low ground by the river and the reclaimed land where the old wharves shipped chalk. The higher streets further from the water sit outside both.
Surface water, which comes from heavy rain running off roads and roofs rather than from the river, is not part of that zone map. It is folded into the wider postcode measure below, so a street outside the river zones can still collect rainwater in a downpour.
The Environment Agency also publishes a version of its zones adjusted for climate change, and on that map about 25% of the area's postcodes fall inside a flood zone. That is a modelled look ahead, built on assumptions about future sea levels and rainfall, and it is the map that insurers and planners increasingly read alongside the current one.
On insurance, homes in Flood Zone 3 by the river can expect closer questions and a higher premium, and some newer builds may fall outside the government-backed scheme that helps older flood-risk homes find cover. Get a buildings insurance quote on the exact address early, while the survey is still being booked, because a cheap flat with expensive cover is a different flat.
Counting every measure together, river, sea and surface water, about 9% of postcodes in the Greenhithe area rate high on at least one of them, about 14% medium and about 32% low. A postcode only needs one high reading to count, so these shares are wider than the flood zones above and should not be added to them. The Environment Agency's property-level count for rivers and sea is reassuring by comparison: of 898 properties in the at-risk postcodes, none rated high, one medium, one low and 408 very low.
On the question of defences, the Environment Agency models about 1% of the area's postcodes inside the high-probability flood extent with no defence in place, and none inside it with a defence. A defence appearing in that model means a wall or barrier exists on paper, which is useful to know and says nothing about how it will cope on a bad night. The Environment Agency has 27 recorded flood events in its history for the area, and the latest, in February 1953, came from the sea overtopping the defences that were there at the time.
The nearest tide gauge with a long record is at Dover, where the sea rose by about 2 millimetres a year between 1961 and 2010. That is what was measured at Dover over those 50 years, and the Thames at Greenhithe has its own tides and its own defences.
Greenhithe's flood risk is middling. Most homes will never notice it, and the ones on the riverside need a proper check and an insurance quote in hand.