Yes, Buntingford has a real flood risk, and most of it comes from rain, not the River Rib. About three in ten postcodes rate high on at least one flood measure. The river-and-sea flood zones cover only a small part of the town and none of the highest band. The trouble is water falling on hard ground and heading downhill, which a river map doesn't show.
On the Environment Agency's river-and-sea mapping, about 7% of Buntingford's postcodes fall in Flood Zone 2 and none 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 outside it, so this is a town with a fringe and no core. The agency holds 13 recorded flood events, the latest in December 1968, when the main river overtopped a channel with no raised defences. The Rib gave the town its ford and has stayed in its banks for most of living memory.
Surface water is a different measure from the river zones. It tracks where heavy rain collects because drains and soil can't take it fast enough, and it can reach houses a long way from any watercourse. Buntingford's high readings come from these other measures, surface water among them, because the river-and-sea zones put none of the town at high probability. "Outside the flood zone" is true of almost every house here, but it only answers the question about the river, and here that's the smaller question.
Looking ahead, the Environment Agency's climate-change version of the river-and-sea zones covers about 8% of the town's postcodes, a little more than today's Zone 2.
Insurance follows the address-level risk. Insurers price from their own address-level mapping, which includes surface water, so a house well outside the river zones can still get a higher quote or an excess written for flood claims. The useful check is the Environment Agency's long-term flood risk service for the exact address, then an insurance quote while the purchase is still at the solicitor stage. Ask the seller whether water has ever come into the garden, garage or cellar after a storm.
Counting every postcode in Buntingford against several measures at once, rivers, sea and surface water included, about 31% rate high on at least one of them, about 32% medium and about 42% low. A postcode only has to rate high on one measure to count, which is why these shares are so much bigger than the river zones.
The agency also counts properties at risk from rivers and the sea, and lists only postcodes with some risk. Those listed postcodes hold 378 properties: 5 at high risk, 17 at medium, 50 at low and 9 at very low. Of the high-risk five, three are homes. That is a small number, and it is the river's count alone.
On defences, none of Buntingford's postcodes fall inside the agency's high-risk modelled flood extents, defended or undefended, and about 2% fall inside the low-risk extent with no defence in the model. "Defended" only means a defence appears in the agency's model, and it would be no reason to relax even where it applied. Here the question hardly comes up, because the river was never the main threat, and a river wall does nothing about a road full of rainwater.
Flood risk is Buntingford's weak point: the river behaves, but the rain decides which streets get wet, and a third of the town is on that list.