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Devizes Locks
Kennett & Avon Canal, west of Devizes, Wiltshire, UK
Devizes Locks
associated engineer
John Rennie snr
date  opened 28th December 1810
UK era  Georgian  |  category  Locks  |  reference  ST985615
ICE reference number  HEW 1078
photo  © Andrew Gritt and licensed for reuse under this Creative Commons Licence
The Devizes area has 29 of the 78 locks on the Kennett & Avon Canal, and they raise it some 72m in less than 4km distance. The picture shows the 16-lock flight at Caen Hill, where the gradient is 1 in 30. The locks, now a Scheduled Ancient Monument, have undergone extensive restoration.
The Kennett & Avon Canal lies between two river navigations the Avon Navigation from Bristol to Bath (opened in 1727) and Kennet Navigation from Newbury to Reading (1723). The Kennet and Avon Canal Act was passed on April 17th 1794 and the canal was completed when the Caen Hill Locks opened on 28th December 1810. Scotsman John Rennie (1761-1821) was its engineer, working on his first civil engineering project in England.
The canal covers 91km between Bath and Newbury, via Devizes and Hungerford, and has many notable engineering features along its course. The sequence of 29 locks at Devizes is impressive. Though Tardebigge on the Worcester & Birmingham Canal has the greatest number of locks in one flight (30 locks) in Britain, at Devizes the locks rise through a greater height over a lesser distance.
The locks at Devizes are all ascending the canal summit is to the east, at the Bruce Tunnel (SU236631) near Stibb Green. The first of the Devizes Locks is No.22 (ST965616) near Rowde and the last is No.50 (SU000617), 3.92km away and 72.2m higher, west of the A361 bridge over the canal. Locks No.46, 48 and 49 each have a rise of 2.5m. Locks No.29 to No.44 form the Caen Hill flight, set in a straight line 1.06km long and rising at a gradient of 1 in 30.
To prevent the canal running dry while the locks were in use, and causing flooding downstream as the locks emptied, balancing storage was required. Connecting side ponds of 0.3ha were constructed next to each of the Caen Hill locks on the north side of the canal. Widening the canal between locks provided extra capacity for the other Devizes Locks.
The lock chambers are mainly of brick, with some masonry. The bricks are made from clay dug from a pit on the south side of the canal between locks No.29 to No.35. Lock ponds are lined with a layer of puddle clay up to 1.2m thick
From 1803 to 1810, the completed stretches of canal either side of Devizes were connected by a two-track horse-drawn tramway with iron rails on timber sleepers. Rennie's resident engineer, John Blackwell (1775-1840), served as Superintending Engineer for the canal company for 34 years, until his death.
Gas lighting was installed in 1829 to allow movement along the canal at night, for which an extra charge was made one shilling (5p) per barge and sixpence (2.5p) per boat.
The locks closed in 1951, and were re-opened by Queen Elizabeth II on 8th August 1990 after major restoration work. In 1996, a pumping station was built to lift water from the foot of the locks to the top of the Caen Hill flight. The Kennett & Avon Canal is now owned by British Waterways.
Further restoration work was carried out on the Devizes Locks in 1999-2000, as part of a 29m scheme to upgrade the whole canal. Three of the Caen Hill lock ponds were relined the 1990 PVC lining was replaced by 750mm of puddle clay and the embankments between them were strengthened with clay cores.
In 2010, 16 new oak lock gates were fitted to the Caen Hill flight, replacing the ones installed in 1990. The wall between Lock No.28 and its side pond was rebuilt, as were the walls between Locks No.35-43. However, the old lock gates were re-used as bridges and gateways at the 2010 Glastonbury Festival.
Resident engineer: John Blackwell
Research: ECPK
reference sources   CEH W&WSmiles2

Devizes Locks