Benson has some flood risk, mostly along its edges, and most of the village stays dry. A small share of postcodes are in the high-risk river zone. About one in eight are high risk on at least one measure. The Thames and a chalk brook meet at the village's edge. Whether a house floods depends on which end of the village it is in.
The Environment Agency's river-and-sea flood zones cover about 3% of Benson's postcodes in zone 3, the highest-probability band, and about 1% more in zone 2, the medium-probability ring around it. The two bands do not overlap. Together they amount to a thin strip along the water, where Ewelme Brook meets the Thames by Benson Lock. Two of the places nearest the river are called Preston Crowmarsh and Rokemarsh, and the people who named them were not being poetic.
The river zones leave out rain that has nowhere to drain. Surface water collects in dips, gardens and roads well away from any river, and the Agency maps it separately, so a house outside both zones can still flood from the sky.
The Agency's flood zone with a climate change allowance covers about 4% of postcodes. That is a modelled band for a wetter future, and it moves the edges of the strip, not the middle of the village.
Insurers look at the exact house and how close it is to the water, not the village name. A house in or next to the river zone is more likely to bring questions, exclusions or a higher premium, while most homes on higher ground should insure normally. The Agency's long-term flood risk checker, searched by the exact address for both river and surface water, will show which kind of house you are looking at before the insurer does.
A wider measure scores each postcode on several kinds of flooding at once, rivers, sea and surface water included, and records its worst result. On that measure about 12% of Benson's postcodes rate high on at least one, about 15% medium and about 26% low. A postcode only needs one bad result to count, so this measure runs higher than the river zones on purpose.
Counted as buildings, the Environment Agency's rivers-and-sea mapping lists 15 Benson postcodes with some risk, holding 367 properties. Of those, 38 are at high risk, 22 medium and 54 low, and 32 of the high-risk properties are homes. Postcodes with no river risk at all are left out of these counts, so the 367 are the riverside part of the village, and most of Benson is not in them.
On defences, the Agency's high-probability extent covers about 3% of postcodes when defences are modelled and about 3% when they are not. The defences in the model do not take a single postcode out of that zone, and the Agency's only recorded flood here, in December 1947, came when the main river overtopped a channel with no raised defences. Do not assume a defence is protecting a house.
The nearest tide gauge, at Portsmouth, recorded sea level rising about 2 millimetres a year between 1962 and 2023. Benson is a long way inland, and its flooding comes from the Thames and the brook, not the sea.
Benson's flood risk is middling. Most of the village is fine, and the risk is real but small, concentrated on the houses nearest the water.