Bexley has a middling flood risk, and almost none of it comes from a river or the sea. The river flood zones barely touch the place. Rain is the bigger worry. About one postcode in seven rates high on at least one flood measure. The danger here arrives from above, in an ordinary heavy shower, and gets nowhere to go.
On the Environment Agency's river-and-sea flood zones, about 1% of Bexley's postcodes are in Flood Zone 3, the highest-probability band, and about 2% are in Flood Zone 2, the medium-probability fringe that lies beyond it. Those are separate bands, so the second figure sits outside the first. For a village built along a river valley, that is a small footprint on the map that most buyers are told about.
Surface water is the measure that changes the picture. It covers what happens when rain falls faster than drains, gardens and gutters can take it, and it pays no attention to where the river is. In Bexley it accounts for most of the risk that the river zones leave out, which is why a house well away from any water can still be the one with a problem.
The Environment Agency's climate-adjusted mapping widens the river-and-sea zone to about 5% of postcodes. That is its modelled allowance for a wetter future, and it is still a small share of the place.
For insurance, a home outside the river zones usually gets ordinary cover at ordinary prices, while one with a surface-water history can find the questions get longer and the quotes less friendly. Put the exact address into the Environment Agency's long-term flood risk service and ask for an indicative buildings quote early, because the flood answer in Bexley changes from one road to the next.
Across Bexley's postcodes, about 14% rate high on at least one flood measure, about 19% medium and about 43% low. That count takes the worst result from several measures at once, surface water included, so it runs well above the river-and-sea zones and describes a different question. "Low" on any of them still means a chance, only a small one in a given year.
Counted in homes, the Environment Agency's rivers-and-sea mapping lists 968 properties across the postcodes where it finds any risk at all. Of those, 19 are at high risk, 56 at medium, 170 at low and 133 at very low. Postcodes with no river or sea risk do not appear in that list at all, so the 968 are the homes the mapping has an opinion about, which in Bexley is a short list.
Whether anything stands between the river and the house makes little difference on the Environment Agency's model. About 1% of postcodes sit in the high-probability flood extent with defences left out, and the same share with defences counted. "Defended" there only means a defence exists in the model, and in Bexley the model draws the same line either way.
The nearest tide gauge with a long record is at Dover, where the sea rose by about 2.2 millimetres a year between 1961 and 2010. That is what the gauge measured over that half-century, and the fact that the nearest one is at Dover says plenty about how far Bexley is from the coast.
Flood risk in Bexley is middling, made almost entirely of rain on the streets and very little of rivers or sea. The exact address decides which side of that a buyer ends up on.