Chorleywood's flood risk is modest, and almost all of it falls from the sky. No postcode is in a river or sea flood zone. About 6% of postcodes rate high for some kind of flooding. Nobody has recorded a flood here. In Chorleywood the gutters matter more than the riverbank.
The Environment Agency's river-and-sea mapping puts 0% of Chorleywood's postcodes in Flood Zone 3, the high-probability band, and 0% in Flood Zone 2, the medium-probability band beyond it. Those two zones measure rivers and the sea only, and for those sources the answer is plain.
Surface water is a different measure, and it is where Chorleywood's risk comes from. Heavy rain on hard ground and roads can pool in low spots whatever the nearest river is doing. One of the places nearby is called Chorleywood Bottom, and the old names were usually honest about which way the water runs.
The Environment Agency's climate-adjusted flood zone takes in about 1% of postcodes. That is the modelled zone redrawn for a wetter future. It shows where the edge of risk might move, and it says nothing about when.
Insurers price surface water as well as rivers, and they price it street by street. A house in a dip that has a high surface-water rating can face questions and premiums that a house further up the same road never will. Put the exact address into the Environment Agency's long-term flood risk service and read the surface-water result before you get an insurance quote.
The postcode measure combines several kinds of flooding, surface water included, and records the worst rating each postcode gets on any of them. On that basis, about 6% of Chorleywood's postcodes rate high on at least one measure, 8% medium and 19% low. A postcode only has to fail one test to be counted, so this is the widest net on the page.
The Environment Agency's rivers-and-sea property count is narrower still. Only two postcodes carry any river or sea risk at all, covering 45 properties. One of those properties is at high risk, none at medium and one at low, and none of the high-risk properties is a home. The count lists only postcodes that carry some risk, so the rest of the village is absent from it, which is good news.
The defences question hardly applies. The Environment Agency's modelled extents put 0% of postcodes in the high-risk area with a defence and 0% without one. In that model, a defence only means something is present. It says nothing about whether a house stays dry, and Chorleywood barely needs the distinction.
The nearest tide gauge to Chorleywood is in Portsmouth, where sea level rose about 2mm a year between 1962 and 2023. That is the rate measured on the south coast over those years. Having to borrow a gauge from Portsmouth says all you need to know about how much the sea matters here.
There is no recorded history of flooding in the area. That is reassuring, though records miss small and older events, so it does not prove that water has never come up a driveway.
On flooding, Chorleywood is middling. The rivers and sea leave it alone, while a minority of postcodes face a real surface-water risk that varies from street to street.