teddington_lock
Well-Known Member
You could lower the reaches a bit but nothing like the drawdown, the weirs are just overflows so a minimum amount is always there like the overflow in your bath. To expose the riverbed you need a plughole in the bottom which is what Richmond barrier is when the tide is out.
I suppose opening both end sluices on a lock might get rid of enough but it would take a long time.
I'm not sure I'd agree with this. Just using Teddington as an example , the fall on the weir is the same as the lock , 8'10"
If you opened Teddington weir you'd drop the level in the reach above by 8'10" which, if there was no water being fed from Molesey , would empty the reach ( which has an average depth of 6/7 feet ) fairly quickly.
The weirs aren't just 'overflows' ... The gates extend to the river bed, exactly the same as Richmond. Same goes for all the other weirs upstream.