Yes, in the parts of Marlow closest to the Thames. About one postcode in eight is in the highest river flood zone. One in six rates high on at least one flood measure. The recorded floods run to fifty. The town grew up beside the river, and the risk lives on the same streets.
On the Environment Agency's river-and-sea mapping, about 12% of Marlow's postcodes are in flood zone 3, the highest-probability band, and another 12% are in flood zone 2, the medium-probability fringe beyond it. The two bands do not overlap. Marlow owed its early importance to being an inland port where the Reading road crossed the river, which is another way of saying it was built as close to the water as anyone could get.
The Environment Agency holds 50 recorded flood events for the area, the latest in February 2014, and its historic flood outlines touch about 7% of postcodes. Surface water, the rain that floods a road before any river rises, has no separate share in the agency's figures here; it is folded into the postcode ratings further down.
With the agency's climate allowance applied, the share of postcodes in a flood zone rises to about 25%. That is the agency's modelled view of a wetter future, and the extra postcodes in it are the ones nobody thinks to ask about yet.
For insurance, a home in or near the zones should expect underwriters to look harder, and premiums and excesses to reflect it. The word "riverside" in the particulars and the flood zone in the insurer's system describe the same feature from opposite ends of the transaction.
Counting every flood measure together, including surface water, about 16% of postcodes rate high on at least one, about 28% medium and about 51% low. Those bands overlap with the zone figures above, because a postcode can sit in zone 3 and also flood from rainfall, so the two sets of percentages should never be added together. A "low" rating here means a small chance in any given year, which is still a chance.
The Environment Agency's rivers-and-sea mapping counts 2,113 properties across the 133 postcodes that carry any risk at all. Of those, 146 are at high risk, 453 at medium, 1,183 at low and 39 at very low, and 116 of the high-risk properties are homes. Postcodes with no modelled risk do not appear in the count. A number of homes is more use to a buyer than any percentage: the question is whether the one being viewed is on the list, so put the exact address into the agency's long-term flood risk service and read the result in full.
About 12% of postcodes fall inside the high-risk flood extent with no defence assumed, and about 8% fall inside it even with defences counted in. "Defended" means the model includes a defence, which reduces the modelled extent without removing it. Marlow Rowing Club trains above and below Marlow Lock, and in a wet winter the water uses both stretches too.
The nearest tide gauge is at Portsmouth, which recorded sea level rising by about 2 millimetres a year between 1962 and 2023. Marlow is a long way inland and has a lock between it and anything tidal, so the gauge describes the coast far better than it describes the Thames here.
Flood risk is a weak point for Marlow, concentrated in the low streets by the river and serious enough there to shape what a buyer pays and insures. Higher up the town it matters far less, which is why the postcode decides the answer.