Finchley has a moderate flood risk, and nearly all of it falls out of the sky. The rivers barely come near it. Hardly any postcodes are in a river flood zone. About one in seven is flagged high on at least one flood measure. The brooks run along the edges, and the rain lands everywhere in between.
On the Environment Agency's river-and-sea mapping, under 1% of Finchley's postcodes are in flood zone 3, the highest-probability band, and under 1% more are in flood zone 2, the medium-probability fringe beyond it. Finchley is on a plateau. Dollis Brook marks the western edge and Mutton Brook the southern one, and the two join to become the River Brent somewhere that is no longer Finchley.
Surface water is a different matter. Rain that falls on a plateau, on roads and roofs, has to find a drain. When the drains are full it stands in the street until they empty. The river zones account for almost none of Finchley's flood flags, so most of the risk here comes down to what happens in a heavy downpour.
The Environment Agency also maps the zones with an allowance for climate change. On that version, under 1% of postcodes fall inside. That is a modelled look ahead, and the river picture barely moves on it.
A home in one of the few river-zone postcodes can expect an insurer to ask questions. A home on a street prone to surface water can expect the same once a claim has been made on it. Get an insurance quote for the exact address early on, and ask the seller directly whether water has ever come into the house or the garden. Insurers ask that question too, and it is cheaper to hear the answer before exchange.
The postcode-level indicators count a postcode if any one of several flood measures flags it, surface water included. On that count, about 14% of Finchley's postcodes rate high on at least one measure, about 10% medium and about 19% low. The zone map is clean. The indicators are less so, because they count the rain.
Counted in buildings, the Environment Agency's rivers-and-sea mapping lists 176 properties in Finchley across the only nine postcodes carrying any river risk at all. Four of those properties are at high risk, two of them homes. Another 43 are at medium risk and seven at low. Every other postcode in Finchley is left off that list entirely.
In the Environment Agency's modelled flood extents, under 1% of postcodes sit in the high-risk area with no defence in the model, and under 1% with one. "Defended" means only that the model includes a flood defence. It says nothing about whether that defence keeps a particular house dry, and the figures here are too small to read much into either way.
The nearest tide gauge to Finchley is in Portsmouth, where the sea rose by about 2 millimetres a year between 1962 and 2023. That is the rate measured at that gauge over those years. The fact that the nearest gauge is on the south coast tells you how little the sea features in Finchley's flood questions.
The Environment Agency has no recorded flooding anywhere in Finchley. That is reassuring. A record only shows the floods somebody wrote down, but a blank page is still a better start than a full one.
Finchley's flood risk is middling. It barely touches the river maps, and the rain is the one thing a buyer here needs to ask about.