rationalskepticism.org

Alan B wrote:

TopCat wrote:All rivers, as they discharge into the sea, are at sea level. If the sea level rises, the point at which the river level is at sea level will move upstream.

This happens twice a day, of course, as the tide comes in. Take the Thames for instance. The river flows upstream while the tide is coming in, until the most downstream permanent lock*. Hence the term tideway, in relation to the Thames. Teddington (a couple of miles from where I live) is in West London, a long way from the estuary. Yet downstream from Teddington, the river flows in the upstream direction while the tide is coming in.

If the downstream flow is sufficient, then of course it will overflow the banks. This happens frequently at Richmond, in past winters making an ice rink out of Old Deer Park.

So as sea level rises due to global warming (and there's no 'may be' about it, OP) then such floods will become more likely.

However, by far the largest contributory factor, as several have said, is simply the volume of water which cannot be contained by the channel. All the serious flooding on the Thames (Chertsey and Staines, for instance, which are upstream of the tideway) in recent years has been caused by this.

Teddington has seen very high water levels recently, but it has (just) avoided being actually flooded, despite the fact that the weir can allow a lot of water to bypass the lock.

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* there is also a lock at Richmond. However, it isn't permanently raised, so it doesn't stop the Thames being tidal as far upstream as Teddington.

This is what I remember, being an ex-Londoner. The Thames flowing backwards or at least stationary at Woolwich.