TW3: 7.9 m clear of the highest tide in the London Bridge ledgers

The lowest postcode in TW3, TW3 2JX, stands 7.9 m above the highest tide in the London Bridge ledgers (5.41 m, 1 February 1953). The highest, TW3 4AZ, stands 22 m above it.
- Ground at eight in ten of its postcodes: between 17 m and 24 m, measured from Ordnance Datum; the middle one stands at 20 m.
- None lies in the Environment Agency's Flood Zone 3 from the sea.
- Mostly in Hounslow; partly in Richmond upon Thames.