Old Basing's flood risk is low, and it sits in a few specific spots. No part of it lies in the highest-risk river zone. A thin fringe sits in the medium-risk zone. Rainwater running off the land is the bigger variable than the river. For most homes here, flooding is a box to tick, not a reason to walk away, provided the box is ticked for the exact address.
On the Environment Agency's river-and-sea flood maps, about 4% of Old Basing's postcodes fall in flood zone 2, the medium-probability band, and none fall in flood zone 3, the high-probability band. The two zones don't overlap: zone 2 is the fringe beyond zone 3, so here the fringe exists without the core. The same 4% or so of postcodes sits on land with a recorded history of flooding. Four flood events are on the record, the most recent in 1947, when a main river overtopped a channel with no raised defences. That's a long time without a repeat, and still a reason to know where the river runs before buying next to it.
Surface water is a different kind of risk, and the river maps don't show it. It comes from heavy rain that the ground and drains can't take quickly enough, and it can reach streets nowhere near a river. The postcode measure further down includes it, which is why it gives a wider figure than the river zones alone.
Looking ahead, the Environment Agency's climate-adjusted flood zone covers about 4% of postcodes, the same share as today's zone 2. On that measure, the modelled future footprint of river flooding in Old Basing is no bigger than the present one.
For insurance, a low-risk area generally means standard cover at ordinary prices for most homes. Homes in the handful of flagged postcodes are the exception, and a buyer there should get an insurance quote before instructing a solicitor, not after. A premium that looks wrong is the cheapest flood survey there is.
Counting every measure together, including surface water, about 5% of Old Basing's postcodes rate high on at least one flood indicator, about 7% medium, and about 21% low. These bands overlap with the river zones above rather than adding to them, and they cast a wider net because surface water is in the mix. One in five postcodes showing at least some risk is the figure to hold on to, and a low rating on one indicator is the most common result by a distance.
Counting homes rather than postcodes is more useful. The Environment Agency's rivers-and-sea mapping lists 103 properties in the Old Basing postcodes that carry any risk at all: 6 at high risk, 1 at medium and 5 at low. Of the high-risk properties, 3 are homes. Postcodes with no river or sea risk don't appear in that count at all, so the total is the at-risk slice of the village, not all of it.
On whether anything stands between the water and the house, the modelled high-risk flood extent covers 0% of Old Basing's postcodes, defended or undefended. There is no high-risk river extent here for a defence to protect. That's a statement about the model's high-risk band, not a guarantee for any single property, and the handful of homes flagged at high risk on the property count still need checking individually.
The nearest tide gauge, at Portsmouth, recorded sea level rising by about 2 millimetres a year over its record from 1962 to 2023. That's a measured historic rate, not a forecast, and for an inland village like Old Basing it's background rather than a threat.
Flood risk is one of Old Basing's better points: low across most of the village and concentrated in a small number of identifiable homes. The buyers who need to take it seriously are the ones looking at those homes, and the checks will tell them if they are.