A very nice feature of the locks on the Worcester & Birmingham Canal are the stairs at the bottom gate, but as usual when thinking about the process of turning a lock, I have to scratch my head when considering all the implications.
Exiting a lock going uphill
If you’re going up a canal, it’s relatively easy for a boat crew to get back on the boat after turning a lock. Let’s pretend a boat, Clarissa, is exiting the lock and another boat, Tubby, is waiting to enter to enter the lock and go downhill. After closing the uphill paddles and opening the gate, the crew of Clarissa can re-board while the boat is in the lock, because there’s no need to close the gates. (It would be pretty rude to close the uphill gates after leaving because the crew of the Tubby would have to reopen them.)
Of course, if there were no boat waiting to enter to go downhill, the boat crew of the Clarissa should close the uphill gates after the boat has exited, which will require the Clarissa to nudge back to the mooring or towpath so that the crew may re-board.
Entering a lock going uphill
On many canals, going uphill requires that most boats would have to moor to let the crew off before entering a lock. Admittedly most crew members will just step off the boat without actually mooring if the downhill gates are open and if there is no queue to go uphill. On the Worcs & B’ham, however, there’s need to stop at the mooring (unless there’s a queue) because of the stairs. The Clarissa can simply stop at the stairs, the crew can get off and the boat can proceed. See the exception to this at the bottom of this post.
Exiting a lock going downhill
Also on many canals, the Tubby would need to pull over to the mooring to allow the crew to re-board even if there were no need to close the downhill gates (because another boat going uphill is waiting to enter the lock). On the Worcs & B’ham, however, regardless of whether the downhill gates need to be closed, the crew of the Tubby can re-board using the stairs. There’s plenty of room for the boat to pull forward and stop and allow the crew to re-board. If the gates are closed, the crew would need to re-board by the rear of the boat. If the gates remain open, the crew could re-board from the front of the boat.
I’ve read that the Worcester & Birmingham Canal originally had problems with shoddy construction, but overall I was impressed with the locks. I can’t recall if every lock had a diversion weir, but I think most do. The downhill gates were also all mitered gates and I didn’t notice any leaking gates in May 2017.
To help with visualization, I’m including the lock flowchart from my book, Narrowboating for Beginners.
Exception: If the Tubby is going uphill and the lock is flooded, it probably would be just as well to let the crew off at the mooring. Although the crew could get off via the stairs, the first thing they would do is open the downhill paddles and the wash would push the Tubby away from the gates.