One day, unless climate change is reversed or our flood defences are improved, much of riverside London will be submerged. Several historic and highly populated areas of the capital are at risk, being not far above current sea level, which ultimately may not be enough to hold back the tide.
So I thought I'd have a look on an Ordnance Survey map to see just how low certain parts of London are. I'm using spot heights, precise locations at which height above sea level is stated. They're fairly rare on the map, but they're more accurate than contours. Here are the really low ones.
On the eastern edge of London, where the A13 makes a break for Thurrock, London is only one metre above sea level. The precise spot is beside an electricity pylon at the point where the A13 viaduct swings across the Chunnel-bound railway. If this area ever flooded road traffic would continue to flow but High Speed One might be in trouble. Wennington Marshes are of course unpopulated, other than by a bird reserve, with the village of Wennington sensibly set back along the 5m contour a few hundred metres beyond. But even a one metre rise in sea level, unchecked, would start to shrink London's land area as the Thames marshes inexorably widened.
Also 1m: I can only find two other places in London with a spot height of 1m, both near Erith. One's on the Belvedere Industrial Estate, where several livelihoods would be affected (but no homes). Crucially the river wall is higher than this (a spot height beside Crossness Pumping Station reads 6m). The other's on the Darent Industrial Park, near Crayford Ness (behind the Darent Flood Barrier).
Well that got very serious very quickly. A spot height on the Ordnance Survey map shows that Downing Street is only 2m above sea level at its junction with Horse Guards Road, just behind the Foreign Office. Horseguards Parade is just up the road. St James's Park is immediately opposite (with a lake that one day risks becoming rather larger). Whitehall is clearly an area that the UK government would protect at all costs against the onslaught of rising sea level, but this gives some idea of the scale of the problem London might be up against.
n.b. Buckingham Palace is above the 5m contour, and Hyde Park Corner is at 13m, while Piccadilly Circus and St Paul's Cathedral are comfortably above 30m. Almost all of the City and most of the West End is perfectly safe, but low-lying Westminster is not.
Also 2m: Industrial estates on Ferry Lane, Rainham, beside Rainham Marshes Also 2m: Entrance to the former Ford motor works, Dagenham, off Ripple Road Also 2m: The Thames View estate, Barking Riverside, at the junction with River Road Also 2m:Barking Road, East Ham, near the North Circular (a mile and a half from the Thames, courtesy of the River Roding) Also 2m: The shopping centre on Pier Road, North Woolwich, near King George V station Also 2m:North Woolwich Road through Silvertown, close to Pontoon Dock station Also 2m:Freemasons Road, Canning Town, close to the A13 (a full mile from the Thames, because south Newham is really floodable) Also 2m: Beside the Twelvetrees gasholders, to the west of West Ham station (much of the Newham side of the Lea is low-lying) Also 2m:Thames Barrier Control Centre, Charlton (reassuringly) Also 2m:Thames Road, Barnes Cray, where the railway to Dartford crosses the road to Dartford
You might expect Thamesmead to be low-lying, given it was built across the Plumstead and Erith marshes, a huge estuary-side expanse previously uninhabited. But low-lying Abbey Road lies on its southern edge, fairly near Abbey Wood station, with well over a mile of densely populated housing between the spot height and the river. Thamesmead's flood defences are of course substantial, because the GLC wouldn't have built an enormous housing estate here otherwise, but tens of thousands of people live here only a few metres above sea level. The monks knew what they were doing when they established Lesnes Abbey on the steep ridge immediately behind.
Also 3m:The Oval, Kennington. Yes, that is the cricket ground in south London, the 3m spot height specifically amid the clump of gasholders at the Vauxhall End. The largest flood risk zone in central London covers much of northern Lambeth, Southwark and Lewisham, with Bermondsey one of the areas to suffer most the last time the Thames broke its banks. It's a shame the OS have no other spot heights across this contour-free zone, but it spreads a lot further than you might think.
I wasn't expecting to find a 4m spot height as far upriver as this, but there it is on Peterborough Road between the Hurlingham Club and Wandsworth Bridge. Even Fulham Palace Road only gets a 6, and there are two other 6m spot heights even further inland at Turnham Green and Acton Green. Fulham and Chiswick are unexpected suburbs to be at genuine risk of flooding, given that so many downriver are not, but borough evacuation plans confirm the local peril.
I can't find any 5m spot heights on the current Ordnance Survey map, but 5m contours run through such spots as Stratford town centre, the Millennium Dome, Camberwell Church Street and Wandsworth Road station. We may be centuries off those being submerged, or they may already be in their last hundred years as physical locations above the waterline. Best take climate change seriously, else large parts of London may require cripplingly expensive protection or be irretrievably lost.