Kempston's flood risk is modest overall but real in a few spots. The river zones cover only a sliver of the town. Measures that also count rainwater flag more of it. A small group of homes carries serious risk. For most buyers, flooding is a line in the survey. For the few homes in that group, it can decide the purchase.
On the Environment Agency's river-and-sea flood zones, about 1% of Kempston's postcodes are in zone 3, the highest-probability band. Another 3% are in zone 2, the medium-probability fringe that runs beyond it. The Great Ouse divides Kempston from Queen's Park, and on these maps it mostly stays within its banks.
Rainwater is the other half of the story. The Environment Agency holds 57 recorded flood events for the area, the most recent dated 1998, and about 4% of postcodes fall inside a recorded historic flood outline. The record doesn't say what caused the most recent one, so a river and a blocked drain look the same in it.
Add the Environment Agency's allowance for climate change and about 7% of postcodes fall inside the flood zones. That is the agency's modelled picture of a wetter future, and it is drawn more widely than today's map.
For most addresses, insurance should be routine. The homes in the high-risk band are where premiums and excesses can climb, and some insurers will ask more questions or decline. "Close to the river" sounds lovely in the particulars and reads differently to an underwriter. Get a buildings insurance quote on the exact postcode while the solicitor is still doing searches.
Count every measure the Environment Agency publishes, surface water included, and the picture widens. About 9% of Kempston's postcodes rate high on at least one measure, 18% medium and 43% low. A postcode only needs one of those measures to qualify, so this is the broad net, and it catches more than the river zones alone.
The river-and-sea mapping also counts individual properties, and only postcodes with some risk are listed. Across the 36 Kempston postcodes listed, 628 properties are counted. Of those, 46 are at high risk, 33 at medium, 215 at low and one at very low. Thirty-one of the high-risk properties are homes. On a town this size, that is a short list, and buyers with a house on it will want to know before they make an offer.
On defences, the high-risk share is about 1% of postcodes whether or not the model includes them, and the low-risk share without defences is about 3%. A defence showing up in the model only means something is there. It doesn't mean the house behind it stays dry, and the high-risk share doesn't shrink when defences are added.
The nearest tide gauge is at Portsmouth. It recorded sea level rising by about 2 millimetres a year between 1962 and 2023. That rate applies to the Solent, and Kempston's floods come from the Great Ouse and the rain, so the sea plays almost no part here.
Kempston's flood risk is middling: barely a factor on most streets, and a serious cost for the small number of homes the Environment Agency has marked.