East Dulwich has a real flood risk, and it comes from the sky. No river or sea threatens it. About three in ten postcodes rate high on at least one flood measure. The cause is rain that has nowhere to go. A buyer asking about the Thames is asking about the wrong water.
On the Environment Agency's river and sea mapping, none of East Dulwich's postcodes, 0%, are in flood zone 3, the highest-probability band, and 0% are in flood zone 2, the medium-probability band beyond it. The river-and-sea answer is about as clean as an answer in London gets.
Surface water is the other half of the picture, and the flood zones don't measure it at all. It is the water that collects when a heavy downpour arrives faster than the drains, the gardens and the paved-over front yards can take it. In a dense, built-up area of Edwardian and older streets, there is a lot of hard surface for it to run across.
The forward look on the main risk is clean too. The Environment Agency's climate-adjusted flood zones, which allow for wetter weather to come, put 0% of East Dulwich's postcodes inside them, so the river-and-sea answer holds even on the cautious version of the map.
For insurance, the zone maps help and the surface-water readings work against them. Insurers price by address and use their own models, and a postcode that rates high for surface water can attract a higher premium or questions about past claims even when the nearest river is miles off. The practical step here is to get an indicative buildings insurance quote on the exact address early in the process, because that quote is where the surface-water rating turns into money.
The postcode-level picture combines several flood measures, rivers, sea and surface water among them, and records the worst rating any of them gives. On that basis about 30% of East Dulwich's postcodes rate high on at least one measure, about 30% rate medium, and about 40% rate low. With the river and sea zones empty, those high readings are almost entirely the rain's doing.
On whether anything stands between the water and the house, the modelled flood extents have little to say: 0% of postcodes fall inside a high-risk extent, either with a defence present in the model or without one. That reflects the absence of any river or sea extent here, and it tells a buyer nothing about surface water, which no wall or embankment is built to stop.
The nearest tide gauge in the national record is at Portsmouth, where sea level rose about 2 millimetres a year between 1962 and 2023. That is the rate measured on the south coast over those years, and it is the clearest reminder of how far East Dulwich is from the sea.
No recorded flooding appears in the area, with 0% of it covered by historic flood outlines. That is reassuring about rivers and the sea. It says less about surface water, because a flooded basement or a garden under water after a storm rarely makes it into the official outlines.
The river and the sea give East Dulwich no trouble, but surface water marks out about three in ten postcodes as high risk, and that makes the flood picture here poor for a buyer.