Flood risk in KT3 (Kingston upon Thames)
Of the 751 postcodes in KT3 – covering Kingston upon Thames and Merton – 11 (1.5%) have their centre in Flood Zone 3 and 67 (8.9%) in Flood Zone 2, on the Environment Agency’s Flood Map for Planning.
The Zone 3 share is well below the England average of 5.6%, and well below the Kingston upon Thames figure of 6.5%.
Most of the district is in Flood Zone 1, but the postcodes in Zones 2 and 3 tend to cluster along rivers, streams and low-lying ground – so it’s worth checking the exact postcode rather than relying on the district picture.
Flood zones only cover rivers and the sea, and ignore flood defences. Surface water from heavy rain can affect any street, including in Zone 1.
Flood zones by postcode sector
Each sector is the first part of the postcode plus the first digit after the space. KT3 6 has the highest share in Flood Zone 3 (3.6% of its postcodes).
| Sector | Postcodes | Zone 3 | Zone 2 | Breakdown |
|---|---|---|---|---|
| KT3 3 | 236 | 0% | 3.8% | |
| KT3 4 | 161 | 3.1% | 13% | |
| KT3 5 | 183 | 0% | 3.3% | |
| KT3 6 | 166 | 3.6% | 19% | |
| KT3 9 | 5 | 0% | 0% |
Main rivers in Kingston upon Thames
River Thames – Kingston and Surbiton (non-tidal)
Hogsmill River – Ewell, Berrylands and Kingston
Beverley Brook – New Malden and the eastern edge
More on the area in our Kingston upon Thames flood risk guide.
How these figures are worked out
We took the centre point of every live postcode in KT3 from OS Code-Point Open and tested it against the Environment Agency’s Flood Map for Planning, as published in the flood-risk-zone dataset (version of 5 November 2026). A postcode counts once, whether it has one home or forty, and a postcode whose centre is just outside a zone still counts as Zone 1. Updated November 2026.
For one address, the free postcode check looks at the zones around the postcode, and the full report adds surface water, reservoirs, recorded floods and defences.
