Northfleet has some flood risk, mostly in small, specific places. Only a sliver of the town is in the river-and-sea flood zones. Rain is the bigger worry, and it is spread more widely. Only a handful of individual properties are rated high risk from the Thames itself. For a town on the estuary, the danger is mostly from the sky.
On the Environment Agency's river-and-sea mapping, about 3% of Northfleet's postcodes are in flood zone 3, the highest-probability band, and about 1% are in flood zone 2, the medium-probability fringe beyond it. The two bands do not overlap, so the zone 2 figure counts additional postcodes and does not include the zone 3 ones. Most of the town is higher up, away from the water.
Surface water is a separate problem. It comes from heavy rain that drains cannot cope with, and it follows streets and dips in the ground rather than the river. No separate surface-water percentage exists for Northfleet. It is counted in the combined postcode measure further down, and that combined measure is the one that turns up in far more of the town than the river zones do. About 2% of the area falls within the outlines of recorded historic floods. The last event on record is February 1953, when the sea came over the defences.
The Environment Agency also models how the zones would look with a climate-change allowance, and on that basis about 9% of Northfleet's postcodes would fall inside the flood zone. That is a modelled scenario for a future with more water in it, and it still leaves most of the town outside.
For insurance, the deciding factor is where your particular house is, and the town average will not settle it. A home in one of the few mapped zone 3 postcodes, or on a street with a surface-water rating, may pay more for cover or find fewer insurers willing to quote. Most homes higher up should see no flood loading at all. Before you commit to an address, get a building insurance quote for it. The insurer will put the postcode through its own flood model, so the quote tells you more than any map.
Counting every measure together, rivers, sea and surface water, about 14% of Northfleet's postcodes are rated high on at least one, 20% medium on at least one and 38% low on at least one. Because a postcode qualifies on whichever measure is worst, these shares are much bigger than the river-zone figures and measure something different. They are the broadest view of where water could cause trouble.
Counted as properties, the Environment Agency's rivers-and-sea assessment lists 710 properties in Northfleet postcodes that carry any risk at all. Six are rated high, none medium, one low and 449 very low, and none of the six high-risk properties is a home. Postcodes with no risk are left out of that list entirely. For the river, the honest number to quote is six buildings.
About 1% of postcodes fall inside the Environment Agency's high-risk flood extent with no defence modelled, and none fall inside it with a defence. In other words, where the model shows high risk, it also shows no defence in the way. "Defended" would only ever have meant a structure appears in the model, never that the house behind it stays dry, and here that question does not arise.
Where Northfleet postcodes are covered by the shoreline management plan, the stated policy is to hold the line over the next 20, 50 and 100 years. That means keeping the defences where they are now. It is a plan for those timescales, it depends on funding nobody has yet committed, and it says nothing about the condition of whatever defences stand there today.
The nearest long-running 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 there over those five decades, and it is the only record the gauge offers.
Flood risk in Northfleet is middling. The river threatens a few buildings and the rain threatens more streets, so how much it matters depends entirely on which house you pick.