Whiteley is at modest flood risk, almost entirely from surface water rather than rivers or the sea. Effectively no postcode here sits in the highest river or coastal flood zone. About one in five postcodes carry some high surface-water risk. Another one in eight sit at medium surface-water risk. The danger is what lands on the ground here, not what arrives from elsewhere.
On the river-and-sea side, the formal flood zones contain barely any of the town. About one in a hundred postcodes sit in the medium river-or-sea flood zone, and none sit in the higher one. There is no river floodplain inside Whiteley, and the coast, though within driving distance, is not the immediate threat at street level. The historic-flood record for the town itself is effectively empty.
The surface-water picture is harder. About one in five postcodes carry some high surface-water flood risk, and another one in eight carry medium. About three in ten carry some low risk. That is the number that drives the overall flood rating for the town, and it is also the kind of risk that is hardest to manage at street level. When estates are built quickly on what used to be farmland, the drainage either keeps up or it does not, and the rain a system copes with on an average October day is not the rain that overwhelms it on an unusual one. Surface-water risk is concentrated in pockets rather than spread evenly, so two streets a hundred metres apart can have different profiles altogether.
Looking forward, the climate-adjusted river-or-sea flood zone covers about one in fifty postcodes once a climate assumption is built into the projection. That is a small share, but it is a doubling of the headline figure. The surface-water picture is the one more likely to shift as more frequent intense rainfall meets drainage designed for last century's storms.
For insurance, surface-water risk is the kind that insurers price for. Homes in postcodes flagged for high surface-water risk often see modestly higher premiums or a specific excess for flood claims. Flood Re, the industry pool that subsidises cover for at-risk homes, does not apply to properties built since 2009, and the newer parts of Whiteley's stock fall outside it. Anyone buying a newer house in a high surface-water postcode should price flood cover separately during conveyancing rather than assume the standard premium applies. The cheap version of the policy is sometimes the one that excludes the most likely claim.
So, is Whiteley at risk of flooding? Yes, from surface water rather than from rivers or the sea, and at a level high enough to be worth checking street by street before buying. The river-and-sea answer is benign; the surface-water answer is the one that drives the dial.