Yes. Bishop's Stortford has a real flood risk, and most of it comes from rain rather than the river. Only a small share of the town is in the main river flood zones. More than four in ten postcodes carry a high flag on at least one flood measure. Floods have been recorded here more than a hundred times. The river gets the blame, but more of the risk comes from rainwater running down the valley sides.
On the Environment Agency's river-and-sea mapping, about 1% of the town's postcodes are in Flood Zone 3, the highest-probability band. About 7% are in Flood Zone 2, the medium-probability band. The two bands are counted separately, so the zone 2 figure covers the area beyond zone 3 and does not include it. By that measure, the river is a problem for a narrow strip of the town.
Rainfall is the bigger concern. The town climbs out of the Stort valley on both sides, so heavy rain that falls on the higher edges runs down towards the middle. The Environment Agency holds 103 recorded flood events here, and about 6% of postcodes fall within an area that has flooded before. The most recent recorded flood was in October 2001, when the main river rose over its banks at a point with no raised defences. Samuel Pepys came through in May 1668 and wrote that the roads were so full of water they could hardly be passed. The water has been arriving here for a long time.
Looking ahead, the Environment Agency's climate-adjusted mapping puts about 10% of the town's postcodes in the flood zones once a wetter future is allowed for, compared with about 7% in zone 2 and about 1% in zone 3 today.
For insurance, a high flag on the postcode can mean a higher premium, a larger excess or fewer insurers willing to quote. The most useful check is to get a buildings insurance quote on the exact postcode early in the purchase, because that tells you what the risk costs before you have spent money on surveys and solicitors. In the parish of Thorley there is a hamlet called Thorley Wash, which is not a name you would choose for selling houses.
The postcode indicators combine several kinds of flooding, surface water included, and a postcode counts if it reaches a level on any one of them. On that basis, about 43% of the town's postcodes reach a high level on at least one measure, about 32% a medium level and about 51% a low level. The higher figures come from counting rainwater as well as rivers, and in this town that makes a big difference.
The Environment Agency's rivers-and-sea mapping also counts properties, which is a more useful number for a buyer than a share of postcodes. Of about 2,200 properties in the 102 postcodes that carry some river or sea risk, 170 are at high risk, 52 at medium, 762 at low and 5 at very low. That covers only the postcodes with some river or sea risk, so homes elsewhere in the town are not counted at all.
About 2% of the town's postcodes are in high-risk river flood areas where the model shows no defence, and about 2% are in high-risk areas where it does. A defence in the model means a wall or embankment is shown on the map. It does not mean the water will stay out.
Flood risk is Bishop's Stortford's weak point. Most of the risk comes from rainwater rather than the river, so it pays to check any street on the valley floor, whatever it is called.