Yes, and the town has known it since the Iron Age. Glastonbury sits on a dry point in a drained marsh. Roughly a fifth of postcodes carry a high rating on at least one flood measure. Fewer than one in a hundred sits in the highest river-and-sea zone. The hill is fine. The flat ground that makes the hill look like a hill is a different conversation.
On the Environment Agency's river-and-sea flood zones, about 8% of the area's postcodes fall in zone 2 and under 1% in zone 3. Those are exclusive bands rather than nested ones. Zone 3 is the higher-probability core, and zone 2 is the medium-probability fringe sitting beyond it, which is why the smaller number is the more serious one. Anyone reading zone 2 as the bigger worry has the map upside down.
Those zones only describe water arriving from a river or the sea. They say nothing about rain landing on ground with nowhere to drain, which on the Somerset Levels is the failure mode that actually turns up. About 13% of Glastonbury's postcodes sit inside the Axe Brue Internal Drainage Board area, a body that exists because this landscape only stays dry through active management. Roughly 9% of the area carries a recorded historic flood.
With a climate allowance applied, the share of the area inside a modelled flood zone comes out at about 2%. That is a forward-looking adjustment to the mapping rather than a prediction about any particular house, and it is a modest number in a place where the surrounding moors flood in winter often enough that the town briefly looks like an island again.
For insurance, the town-level numbers are close to useless. Insurers price the address, and in a settlement built around a hill the difference between a comfortable premium and an awkward one can be two streets and four metres of elevation. Get an indicative quote on the specific property before instructing a solicitor rather than after, because the answer occasionally reshapes the offer.
On the postcode indicators, which fold surface water in alongside rivers and sea, about 18% of Glastonbury postcodes rate high on at least one measure, around 21% rate medium and roughly 36% rate low. Those bands overlap with the flood-zone shares rather than adding to them, and they cover a wider set of ways water can reach a doorstep.
Counted as homes rather than postcodes, the Environment Agency's rivers-and-sea mapping lists 826 properties across the 38 postcodes that carry any risk at all. Of those, 88 sit at high risk, 375 at medium, 4 at low and 1 at very low. Eight of the high-risk properties are residential. Postcodes carrying no risk never appear on that list, so this describes the affected slice of the town rather than the town.
Whether anything stands between the water and the house is the question most flood write-ups quietly skip. No Glastonbury postcodes sit inside a high-risk undefended extent, and under 1% sit inside a high-risk defended one. Defended means the model includes a defence, not that the property is safe. The Environment Agency records 43 historic flood events here, the most recent in March 2009, from a main river, caused by overtopping of defences. Defences were present that time too.
The nearest tide gauge is at Portsmouth, where the 1962 to 2023 record shows sea level rising by about 2mm a year. That is a measured historic rate at a gauge a long way from Somerset, and it matters here only at one remove. Glastonbury's flooding does not arrive from the sea. It arrives from rivers, from rain, and from a water table that has been held down by drainage engineering for eight centuries and requires continued attention to stay there.
Flooding is one of the harder things to like about living here. Most of the town is dry, a real portion of it is not, and the line between the two is drawn postcode by postcode rather than at the town sign. Check the address, not the reputation.