The locks on this canal were designed to carry the ‘short boats’ that had twice the capacity of the narrow boats used on other canals.
The locks therefore had to be wide enough to allow the 62 feet long, 14 feet wide boats through them. Most of the locks were also grouped together to give long runs between the locks although not all were staircase locks like this with no gap between each lock.
The boats were mainly used to carry bulk cargoes such as coal, stone and limestone. Commercial traffic ceased in 1964, but the locks are still used to carry leisure boats which have become very popular. Ironically the leisure craft are normally narrow boats, because there are links to other canals, and wider boats would not be able to pass through the locks on the other canals.
The construction of the canal was started in 1770 and the first section opened in 1774 and finally completed in 1816. These days no commercial traffic operates on the canal, but it is popular with leisure boaters and the canal never closed.
Staircase locks are used when there is a need to raise canal boats quickly over a short distance. Unlike normal locks there is no pound or stretch of water between the sets of gates and boats enter the next lock chamber immediately after negotiating the previous one.
Whether heading up or down, the top lock needs to be full, and the bottom lock empty. The boat needs to enter its nearer lock, equalise the levels, forward into the other lock, and operate that like a single lock.
Each of the three chambers have a wooden footbridge to allow boaters to access the paddles at both sides of the lock.
The locks on this canal are numbered from the Leeds end of the canal and for numbering purposes Kirkstall Forge Locks is considered to be locks 8, 9 and 10.
The lock is an English Heritage Grade II listed building with the following details. "Flight of 3 locks. 1770-1777. Dressed millstone grit walls ramped up to lower 2 lock gates with steps on each side, steel foot bridges have replaced single wooden bridge on downstream side of each gate. Overflow and side channel on S side. The Leeds and Liverpool Canal was built 1770-1816; the stretch from Leeds to Gargrave was completed by 1777."
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Most locks have overflow channels as described in the English Heritage listing. Depending on the lay of the land the channel may be completely open and visible, but if the space is limited it may be covered over underneath the tow path.
This lock has an unusual arrangement, as well as the normal channel, the side of the lock on the bottom chamber has a shallow depression, covered by cobble stones. It would appear that sometimes the normal overflow channel cannot cope and so this extra channel diverts any extra overflow that may occur during the operation of the lock.
Although lock gates are made of hard wood, on average they only have an operational life of 25 years. The gates on this lock were replaced in 2010, at a cost of £300,000. This website shows pictures of the new gates being fitted. It also indicates that "the construction of these locks is unusual with the stone walls built on wooden foundations, and have wooden flooring to the bottom of the lock chambers. As such, they are an important historical engineering structure and require high standards of conservation."
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