Yes, Lechlade-on-Thames has a real flood risk, and it comes from the rivers that made the town. Three rivers meet around it. About one postcode in six is rated high on at least one flood measure. In the high-risk modelling, the defences make no difference at all. Boats can get up the Thames as far as Lechlade, and in a wet season the river has been known to keep going.
In the Environment Agency's river-and-sea flood zones, about 4% of the area's postcodes are in Zone 3, the highest-probability band, and another 12% are in Zone 2, the medium-probability fringe beyond it. The town is built on alluvium and river gravels on flat, low ground, where the Leach and the Coln join the Thames. The Environment Agency has 16 flood events on record, the most recent in July 2007, when the main river overflowed its channel at a point with no raised defences.
There's no separate surface-water figure for the area here. Surface water is included in the postcode measure further down, alongside rivers and sea.
Allowing for climate change, the Environment Agency's projected flood zone takes in about 19% of the area's postcodes. That's the agency's planning allowance for a wetter future, and it covers more ground than today's zones.
Insurance is where this turns into money. Homes in or near a modelled flood extent usually get more questions from insurers, higher premiums or higher excesses, and some policies come with conditions. Get an insurance quote for the exact address early, while you can still walk away from the offer, because two houses on the same street here can be quoted very differently.
On a wider measure that includes surface water as well as rivers and sea, and counts a postcode if any of several flood indicators applies, about 17% of postcodes rate high, 12% medium and 44% low. That's the broadest view and it covers more of the town, because it captures water that gathers in streets and gardens as well as water coming over a riverbank.
Counting homes instead of postcodes, the Environment Agency's rivers-and-sea mapping lists 294 properties in the postcodes that carry any risk at all. Of those, 71 are at high risk, 5 at medium risk, 64 at low risk and 23 at very low risk, and 59 of the high-risk properties are homes. Postcodes with no risk on that mapping don't appear in the count at all, so these numbers describe the exposed edge of the town.
The Environment Agency's high-risk extent covers about 13% of the town's postcodes without defences and still about 13% with defences included. "Defended" in the model only means a defence exists somewhere on the map, and here, including the defences leaves the high-risk area exactly the same size. Anyone told a riverside house is "defended" should ask what that defence actually does, because the model says it doesn't shrink the high-risk area at all.
The nearest tide gauge is at Portsmouth, where sea level rose by about 2 millimetres a year over its record from 1962 to 2023. For an upper-Thames town that far inland, the threat comes from rain and rivers, and the tide plays almost no part.
On flood risk, Lechlade-on-Thames is below average, with a high-risk area the defences don't shrink and a river that has come over its banks within living memory. The risk varies house by house, and for the homes closest to the water it's the first thing to check.