SW1H: 57 of 91 postcodes stand below a spring high tide

The ground at 57 of SW1H's 91 postcodes (63%) is lower than an ordinary spring high tide at London Bridge (3.9 m above Ordnance Datum).

• Ground at eight in ten of its postcodes: between 2.7 m and 4.5 m, measured from Ordnance Datum; the middle one stands at 3.7 m.
• All 91 stand lower than the 1953 tide (5.41 m).
• 91 lie in the Environment Agency's Flood Zone 3 from the sea, mapped without defences.
• Mostly in Westminster; partly in Wandsworth.