For most homes, only a little, and the risk that exists sits in pockets. Rivers barely touch the map. Surface water is the bigger nuisance. A few hundred properties carry a rating at all. The honest answer depends on the exact address, and "the area is fine" is not an address.
On river and sea flooding, the Environment Agency's flood zones cover very little of the area. About 2% of postcodes sit in flood zone 3, the highest-probability band, and a further 2% sit in flood zone 2, the medium-probability fringe beyond it. Those are two separate bands, not one inside the other. For a place threaded by the Basingstoke Canal and within reach of the Wey Navigation, that is a small footprint.
Surface water is where the picture widens, because rain does not need a river to cause trouble. It pools where drains and gradients send it, which is why a house well away from any water can still carry a rating. The recorded history is thin but not blank: the Environment Agency holds 25 recorded flood events for the area, covering about 1% of it, and the most recent dates to 12 December 1974, when an ordinary watercourse overflowed because its channel could not carry the water and no raised defences stood in the way. Half a century without a repeat is reassuring, and it is also exactly the kind of fact that makes buyers stop checking.
Looking ahead, the Environment Agency's climate-adjusted zones put about 6% of postcodes inside the future flood extent, up from the combined zone figures above. That is a modelled allowance for wetter conditions, not a prediction that any given street will flood.
Insurance follows the address, not the area. A house outside every indicator should see no flood loading on its premium, while one inside a high-risk pocket can find cover dearer, more restricted or subject to a larger excess. Get a quote on the specific property before you instruct a solicitor, because finding out after exchange is an expensive way to learn.
At postcode level, and folding surface water in with rivers and sea, about 9% of postcodes rate high on at least one flood measure, 17% rate medium on at least one, and 36% rate low on at least one. These bands overlap with each other and with the zone figures, so they cannot be added together or read as the same measure. They are the broadest net, and the reason a postcode can look clear on the river map and still show up here.
Counted as properties rather than postcodes, the Environment Agency's rivers-and-sea mapping lists 1,111 properties across the 38 postcodes that carry any risk at all. Of those, 101 are at high risk, 146 at medium risk and 243 at low risk, and 88 of the high-risk properties are homes. Postcodes with no river or sea risk do not appear in this count, so it describes the exposed corners, not the whole place.
Defences make less difference to the modelled picture than buyers tend to assume. The share of postcodes inside the high-probability flood extent is about 2% whether or not defences are included in the model. "Defended" means a defence is present in the model, not that any property behind it is safe, and it should never be read as a guarantee.
The nearest tide gauge is at Portsmouth, where sea level rose at a measured rate of about 2 millimetres a year across its record from 1962 to 2023. That is a historic rate recorded on the coast, and for an inland place like this one it is context rather than a threat on the doorstep.
Flood risk here is middling: low for most of the map, real for a small number of streets, and serious for the few homes sitting in the high-risk pockets. Check the exact address before you fall for the house, not after.