Bromley has some flood risk, and most of it comes from rain, with hardly any from rivers. Very few postcodes are in a river flood zone. About one in five rates high on at least one flood measure. The last recorded river flood was decades ago. The rain that falls on Bromley itself is the bigger problem than any river.
The Environment Agency's river-and-sea flood zones cover very little of Bromley. About 1% of the area's postcodes are in zone 2, the medium-probability band, and about half of 1% are in zone 3, the high-probability band. Zone 2 is the outer fringe beyond zone 3, so the two figures are separate bands that do not overlap. The agency has 12 recorded flood events in the area, the latest on 19 September 1968, when a main river overtopped its channel and no raised defences stood in the way.
Surface water is a different story. When the postcode ratings include surface water alongside rivers and the sea, about 20% of Bromley's postcodes come out at high risk on at least one measure. That is water from heavy rain collecting on roads and in low gardens, and a river does not need to be anywhere nearby. A seller can truthfully say a house is "not in a flood zone" and still leave the surface-water question unanswered.
The Environment Agency's climate-adjusted mapping, which looks ahead to a wetter future, puts about 2.5% of postcodes in the river-and-sea flood zones. That is a modelled future scenario, more than today's figure but still small. The extra risk Bromley faces from climate change shows up mainly in its rainfall.
For most homes in Bromley, flood risk will not change what insurance costs. For homes in the minority that rate high for surface water, it can, and insurers price the exact property instead of the town. Getting a quote on the specific address early in the process is the quickest way to find out whether a particular house is one of them.
At postcode level, about 20% of Bromley's postcodes rate high, 22% medium and 37% low on at least one of several measures. One bad measure is enough to put a postcode in a band, so these shares mix surface water, rivers and the sea, and the bands overlap with the zone figures above. The two sets of figures should not be added together.
Counting homes is more useful than counting postcodes. The Environment Agency's rivers-and-sea mapping lists only the 27 postcodes in Bromley that carry any river or sea risk, covering 755 properties. Of those, 27 properties are at high risk, 64 medium, 100 low and 4 very low. Only six of the high-risk properties are homes.
The Environment Agency's model puts about 0.6% of postcodes inside the high-risk flood extent with no defence present, and the same 0.6% inside it with a defence present. "Defended" means a wall or embankment appears in the model. Whether that defence will hold in a given flood is a separate question, and the model does not answer it.
The nearest tide gauge is at Portsmouth, where sea level rose by about 2 millimetres a year between 1962 and 2023. That is a measurement taken on the south coast over those years. Bromley's own flood risk depends far more on local rainfall than on the Channel.
Rivers pose almost no risk in Bromley, but surface water reaches enough streets that flooding is one of its weaker points. Check the exact address and its surface-water rating first.