Rivers and the sea aren't a flood risk in Caterham, but heavy rain can be. No postcodes fall in the river-and-sea flood zones. About one in eight is rated high risk on at least one measure. There's no recorded flooding on file. Any flood here would come from a downpour, not a river.
In the Environment Agency's river-and-sea flood zones, 0% of Caterham's postcodes are in Zone 3, the highest-probability band, and 0% are in Zone 2, the medium-probability band around it. The two zones don't overlap, and in Caterham both are empty. This measure is separate from any surface-water figure, and the two shouldn't be mixed.
Surface water is where the real risk is. The town centre sits at the bottom of a dry valley, on chalk capped in large part by clay and gravel. In the lower spots the soil drains poorly. When a summer storm drops more rain than the drains and the ground can take, the water runs downhill and pools at the lowest point. The valley shape decides where that happens.
The Environment Agency's climate-adjusted mapping, which looks ahead to wetter conditions, puts 0% of postcodes in the future river-and-sea flood zones. It doesn't cover surface water.
For insurance, the lack of river-and-sea risk counts in a buyer's favour, and most postcodes should be straightforward to insure. The exceptions are homes on the surface-water flow paths, which insurers price one address at a time. A house on the flat part of the valley floor can quote differently from one a street up the slope, even if the estate agent calls them the same neighbourhood.
On the postcode-level indicators, which combine surface water with rivers and the sea, about 12% of Caterham's postcodes are rated high risk on at least one measure. Another 12% are rated medium and about 27% low. These bands count a postcode if it's flagged on any one measure. They overlap with the flood-zone figures above and can't be added to them.
The modelled flood extents put 0% of postcodes in the high-risk river-and-sea area, with or without defences. So there's no case here of a flood defence being the only thing between a house and the water. Even where a defence exists, the model only shows that it's there. It doesn't show that the house behind it is safe.
The nearest tide gauge is at Portsmouth. Over its record from 1962 to 2023, the sea there rose by about 2 millimetres a year. That's a measured past rate, not a forecast. For a town on high ground this far inland, it's background information, not a risk.
There's no recorded historic flooding in the area. That's reassuring, but it only means no flood has been recorded. A brief flash flood on a residential street can come and go without ever reaching the records.
Before you commit to a particular house:
- Put the exact address into the Environment Agency's long-term flood-risk checker, and look at the surface-water result, not only the river-and-sea one.
- Ask the seller directly whether water has ever come onto the property or into the house, and get the answer in writing through the property information forms.
- Get an indicative insurance quote for the address before you instruct a solicitor.
- On the viewing, look at which way the ground slopes and whether the house sits at the low point of the street.
Caterham's flood risk is middling. Rivers and the sea pose no threat, but surface water puts a minority of streets at real risk, and those are the ones to check.