Northwood does carry a flood risk, and it comes from the sky. Rivers and the sea barely touch the town. Rain is the problem. Close to three in ten postcodes rate high on at least one flood measure, and almost all of that is water with nowhere to drain.
On the Environment Agency's river-and-sea flood zones, Northwood hardly appears. None of its postcodes fall in Flood Zone 3, the highest-probability band, and under 1% sit in Flood Zone 2, the medium-probability fringe beyond it. For a town with no river worth mapping running through it, that is about as clean as the river-and-sea map gets.
Surface water is a different matter. Northwood is built on ridges and folds of land, and heavy rain runs off the high ground and gathers wherever the roads and gardens dip. That kind of flooding has nothing to do with being near a river, which is why buyers who check the river map and stop there come away with the wrong answer.
The Environment Agency's climate-adjusted mapping, which models how the river-and-sea zones could extend under future climate allowances, puts about 1% of Northwood's postcodes inside them. It is a modelled scenario, and on that scenario the rivers stay a minor concern.
What this means for insurance is mostly about the surface-water side. River-and-sea risk at these levels should rarely trouble an insurer, but a home in a dip that floods from rainfall can still face higher premiums or a closer look at underwriting. The useful check here is the Environment Agency's long-term flood-risk service for the exact address, with the surface-water layer switched on, followed by an indicative insurance quote on that address.
The postcode-level picture is where the risk shows. Counting a postcode if it rates on any one of several flood measures, surface water included, about 29% of Northwood's postcodes rate high on at least one, about 23% rate medium and about 45% rate low. Those categories pick up rain as well as rivers, so they sit far above the flood-zone shares without contradicting them.
Counted in homes, the Environment Agency's rivers-and-sea mapping lists only three postcodes in Northwood carrying any river or sea risk at all, covering 60 properties. One of those properties is at high risk, none at medium and 12 at low, and none of the high-risk properties is residential. Postcodes with no river or sea risk do not appear in that count at all.
On the defences question, none of Northwood's postcodes fall inside a high-risk river or sea flood extent, defended or undefended. Under 1% sit in the low-risk extent with no defence modelled. "Defended" in this mapping only means a defence exists in the model, and here there is nothing much for one to hold back.
The nearest tide gauge is at Portsmouth, where the measured sea level rose by about 2 millimetres a year across its record from 1962 to 2023. That is the rate recorded on the south coast, and it tells you roughly how much Northwood needs to think about the sea.
No historic flooding is recorded in the Environment Agency's outlines for the area. That is good news about the record, and it reflects what was mapped, so it cannot vouch for every garden or basement on every slope.
Flood risk in Northwood is a real weakness, and nearly all of it is rainwater. The river map flatters the town, and the surface-water figures are the ones a buyer should take seriously.