Mostly not, but the River Wey runs straight through the middle of town. Only a small share of the town falls in the river's highest-risk zone. More postcodes pick up a warning once rainwater is counted. The sea is too far away to matter. Whether flooding matters to you depends on your street, not the town.
The Environment Agency's river-and-sea flood zones put 2% of Farnham's postcodes in zone 3, the band with the highest probability of flooding. Another 7% sit in zone 2, the medium-probability fringe beyond zone 3. The two bands don't overlap. Together they follow the valley of the north branch of the Wey, which is where the town grew up and where some of its oldest streets still sit. Most of Farnham is on higher ground and is not in either zone.
Rivers aren't the only source. Heavy rain that can't drain away fast enough can flood a street a long way from the Wey. The Environment Agency has 67 recorded flood events in the area. The most recent recorded event was in December 1968, when an ordinary watercourse overflowed its channel with no raised defences in the way. Surface water is counted in the postcode-level measures further down, and that is where it shows up most.
Allowing for climate change, the Environment Agency's future flood zone covers 10% of the area's postcodes. That is a planning allowance for the river's reach in a wetter future, not a forecast that any particular street will flood.
Flood risk reaches your finances through insurance. A home in or near a flood zone can cost more to insure, carry a higher excess, or need specialist cover, and that is worth knowing before you make an offer, not after. Get an indicative quote on the exact address early, because the price of cover says more than any sales listing will.
At postcode level, 13% of Farnham's postcodes rate high on at least one flood measure, 13% rate medium and 26% rate low. These figures include surface water as well as rivers, and they overlap with the zone figures above, so the two should never be added together. A postcode rated high on one measure can be fine on every other, which is why the individual address matters more than the town.
The Environment Agency's rivers-and-sea mapping also counts individual properties, and only postcodes carrying some risk appear in it at all. Across the 90 listed postcodes there are 1,663 properties. Of those, 79 are rated high risk, 168 medium and 635 low. For a town of this size that's a short list, and the homes on it are concentrated rather than spread across the town.
In the high-risk river extent, 2% of postcodes fall in areas with no modelled defence, and another 2% fall in areas where a defence is present in the model. A defence in the model means something stands between the river and the house on paper. It doesn't mean the house stays dry, and defences can be overtopped or fail.
The nearest tide gauge, at Portsmouth, recorded sea level rising at about 2 millimetres a year over its record from 1962 to 2023. That's a measured historical rate on the coast. For an inland town on a river, sea level is background information rather than a threat.
Before instructing a solicitor on a Farnham home:
- Put the exact address into the Environment Agency's long-term flood risk service and check rivers and surface water separately.
- Get an indicative buildings insurance quote on that address before committing to survey costs.
- Ask the seller directly whether the property has ever flooded or made a flood claim.
- Check whether the home sits in the low ground near the Wey or up the slopes on either side.
Farnham's flood risk is middling: low across most of the town, but concentrated enough along the river and in the rainwater hotspots that checking the individual address is essential.