Cirencester has a middling flood risk, and most of it follows the River Churn down the eastern side of town. About one postcode in twelve is in the highest river flood zone. About one in ten scores high on at least one flood measure. Around fifty properties are rated high risk from rivers. For most of the town, a flood is something that happens on the news.
The Environment Agency's river-and-sea flood zones put about 8% of Cirencester's postcodes in Flood Zone 3, the highest-probability band. Another 6% are in Flood Zone 2, the medium-probability fringe just beyond it. The two bands do not overlap. Together they follow the Churn, which runs roughly north to south through the eastern side of town on its way to join the Thames near Cricklade. The Agency has six recorded floods on file, the most recent in July 2007, when the main river simply ran out of channel and there were no raised defences in its way.
The flood zones only measure water coming out of rivers and the sea. Rain that has nowhere to go is a separate risk, and it is picked up only by the wider postcode measure further down this page. Of the postcodes with a recorded history of flooding, the share in Cirencester is about 1%.
The Environment Agency also publishes a climate-adjusted version of the zones, which allows for heavier rain in the decades ahead. On that version, about 16% of postcodes fall inside. Those are the same streets as today plus the next row back, and they are the margin to think about if you plan to stay a long time.
For insurance, homes on the higher ground away from the Churn should be routine to cover. Homes inside the river zones are where premiums, excesses and the number of willing insurers start to vary. One part of town is called Watermoor, and buyers will draw their own conclusions from the name. The Environment Agency's long-term flood risk check for the exact address will tell you whether they were right, and an insurance quote on the same address will tell you what it costs.
A second measure scores every postcode on several kinds of flooding at once, surface water included, and rates it by its worst result. On that basis, about 10% of Cirencester postcodes come out high risk on at least one measure, 21% medium and 40% low. Because it counts any measure that fires, it always looks bigger than the river zones alone.
Counted as properties, the Environment Agency's rivers-and-sea mapping lists 50 at high risk, 437 at medium risk, 766 at low risk and 258 at very low risk. That is out of about 1,990 properties in the 95 postcodes that carry any risk at all, and 42 of the high-risk properties are homes. Postcodes with no risk are left off the list completely, so the rest of the town does not appear in those totals.
On the Agency's modelled flood extents, about 8% of postcodes are in the high-risk area if no defences are assumed. When the defences the Agency knows about are put into the model, about 6% are still inside. A defence in the model is a structure on a map. It does not mean the water will stay out of a particular kitchen.
The nearest tide gauge is at Portsmouth, where sea level rose by about 2 millimetres a year between 1962 and 2023. Cirencester is a long way inland, so the sea is the one flood risk it can safely leave to other people.
Flood risk in Cirencester is middling. It is real along the Churn and a minor issue for most of the rest of the town, so which side of the river a home is on matters more than the town's overall figures.