Yes, and not at the margins. The town was put here because fast water was useful, for the crossing and for washing fleeces in the leats, and the water has not since been persuaded to go elsewhere. Getting on for a third of postcodes sit in the highest river flood band. Nearly one in five rates high on at least one flood measure. Two floods are on the formal record, which sounds reassuring until you notice where the buildings actually are.
The Environment Agency's river-and-sea mapping puts about 28% of the area's postcodes in flood zone 3, the highest-probability band, and about 2% in flood zone 2. Those two zones are exclusive bands rather than nested ones. Zone 2 is the additional medium-probability fringe lying beyond zone 3, so a small zone 2 alongside a large zone 3 is not a contradiction: in a valley this steep the ground goes from at-risk to comfortably clear in a short walk uphill. The practical version is that the risk here is concentrated near the Barle rather than smeared across the town.
Surface water is not broken out as its own share in this area's mapping, and in a valley town it is not really a separate story anyway, since rain off the hills and the river are using the same route. What is recorded separately is where water has actually been: about 4% of postcodes sit inside historic flood outlines. The most recent formally recorded event was in August 1952, logged as a main river flood caused by channel capacity being exceeded with no raised defences in place.
Looking forward rather than back, the Environment Agency also models a zone that allows for climate change, and about 15% of postcodes fall inside it. That figure is a modelled allowance rather than a prediction of any particular decade, but it is the one a buyer planning to hold a house for thirty years should be reading.
For insurance, this matters at the quote stage rather than the exchange stage. A property inside a high-risk zone can be harder to place, and premiums and excesses tend to reflect it. Flood Re, the industry scheme that helps insurers cover high-risk homes, does not apply to homes built since 2009, so a newer property near the water sits outside it. Getting an indicative quote for the exact address before instructing anyone is cheap, and finding out afterwards is not.
Taking every indicator together, including surface water, about 19% of postcodes carry a high rating on at least one measure, roughly 30% a medium one and about 38% a low one. Those bands overlap with the zone figures above rather than adding to them, and a single postcode can appear in more than one. It is a different lens on the same water, not extra water.
Counted as homes rather than postcodes, the Environment Agency's rivers-and-sea mapping lists 433 properties across the 24 postcodes that carry any risk at all. Of those, 30 are rated high, 70 medium, 62 low and 60 very low, with 12 of the high-rated ones residential. Postcodes with no risk do not appear in that list, so this is the exposed end of the town rather than the whole of it.
On whether anything stands between the water and the house, about 23% of postcodes sit inside a high-risk extent with no defence in the model, against about 8% inside a defended one. Defended means a defence exists in the modelling, not that the building behind it is safe, and the 1952 record explicitly notes there were no raised defences.
The nearest tide gauge, at Devonport, records sea level rising by about 2.35 millimetres a year across its 1962 to 2015 record. That is a measured historic rate at the coast rather than a forecast, and an inland Exmoor town is not going to be troubled by a tidal surge. Rivers are the hazard here, and they are fed from above.
Flooding is the weakest thing about Dulverton, and it is weak for a straightforward reason: the town is in the bottom of a valley with a fast river through the middle of it. Buy uphill, or buy the survey.