Dursley floods in a few places, and most of the town stays dry. Very few postcodes are in the river flood zones. A few dozen homes carry a high rating from the river. Rainwater reaches more streets than the river ever does. The sea doesn't come into it.
The Environment Agency's river-and-sea mapping puts about 2% of Dursley's postcodes in Flood Zone 2 and about 1% in Flood Zone 3. The two zones don't overlap. Zone 3 is the high-probability core, and Zone 2 is the medium-probability fringe beyond it, so the outer band can be the larger of the two and here it is. By that measure, this is a hillside town with a small wet edge.
Surface water is a separate problem from the rivers. The Environment Agency doesn't publish a standalone surface-water figure for the town, but surface water counts in the combined postcode measures further down, and those measures pick up far more of the town than the river zones do.
With the Environment Agency's allowance for a changing climate, the river-and-sea zone grows to cover about 3% of Dursley's postcodes. That's a model of how the zone spreads as rainfall changes. It gives no date for anything to flood.
Insurance follows the address. A house in one of the rated postcodes can face higher premiums or a narrower choice of insurer, and some homes will need cover through specialist schemes. A house on the slopes of Stinchcombe Hill is unlikely to cost more to insure because of flooding. Get a quote on the actual property while your offer is still negotiable. Waiting until the survey comes back is too late.
Count every postcode that rates high, medium or low on at least one flood measure, with rivers, sea and surface water all included, and the share widens. About 7% of Dursley's postcodes rate high on at least one measure, about 12% medium and about 28% low. A postcode only needs to trip one wire to count, so these shares run well above the zone figures. They're a broader net, measuring a different thing.
Counted in properties, the Environment Agency's rivers-and-sea mapping lists 208 properties across the nine Dursley postcodes that carry any risk at all. Postcodes with no risk aren't listed. Of those 208, 52 are rated high, 24 medium and 35 low, and all 52 high-risk properties are homes. Check whether the house you're looking at is in one of those nine postcodes. Spend the time on that question before you think about curtains.
Defences make little difference to the modelled picture. The high-risk extent covers the same small share of postcodes, about 1%, whether or not the model includes a defence. "Defended" in that model means a defence is drawn on the map, and it says nothing about whether water reaches a particular kitchen. Any particulars that use the word as a selling point are making an engineering claim the map doesn't support.
Shoreline management plans cover even this inland stretch, because the nearest coast is about 7 kilometres away, with most postcodes about 8 kilometres out, along the water beyond the Severn's banks. The policy for the next twenty years is managed realignment, which means letting the shoreline move back in a planned way. For the fifty and hundred-year horizons it's hold the line. Those are stated intentions, they depend on money nobody has committed, and they say nothing about what stands on the shore today.
The nearest long-running tide gauge is at Portsmouth, where the sea rose by about 2 millimetres a year between 1962 and 2023. That's the rate measured at that gauge over those years, on a different coast, and it's a fair measure of how far down Dursley's list of worries the sea comes.
Flood risk in Dursley is middling. Most of the town is dry, and the danger is concentrated in a few postcodes where it's serious enough to change what a buyer pays and how they insure.