The Thames and Severn Canal is a canal in Gloucestershire in the south-west of England, which was completed in 1789. It was conceived as part of a cargo route from Bristol and the Midlands to London, linking England's two largest rivers for better trade. The route climbs the steep Cotswold escarpment through the Golden Valley, tunnels underneath the summit of the Cotswold Edge, and emerges near the source of the Thames.
At its eastern end, it connects to the top of the navigable Thames at Inglesham Lock near Lechlade, while at its western end, it connects to the Stroudwater Navigation at Wallbridge near Stroud, and thence to the River Severn. It had one short arm (branch), from Siddington to the town of Cirencester. It includes Sapperton Tunnel, which when built was the longest canal tunnel in Britain, and remains the second-longest complete tunnel. There were always problems with water supply, as no reservoirs were built, while the summit section near the tunnel ran through porous limestone, and there were constant difficulties with leakage. Competition from the railways took much of the canal's traffic by the end of the 19th century, and most of the canal was abandoned in 1927, the remainder in 1941.
Since 1972, the Cotswold Canals Trust has been working to restore both the canal and the Stroudwater Navigation to navigably re-link the Thames and the Severn. A number of the structures have been restored, and some sections are now in water. A major step forward occurred in 2003, when a bid was made to the Heritage Lottery Fund for £82 million to restore both canals. The bid and the project had to be split into smaller sections, but £11.9 million was awarded in 2006 for Phase 1A, which with matched funding has restored from The Ocean at Stonehouse to Wallbridge on the Stroudwater Navigation, and from there to Stroud Brewery on the Thames and Severn Canal. The Phase 1B reconnection to the national waterways network at Saul Junction is expected to be completed by 2028, connecting the Severn with the Golden Valley for the first time in a century.
In 2010, British Waterways gave Inglesham Lock to the Trust, and the Inland Waterways Association mounted a national campaign to fund its restoration (and of canal above). To re-open the whole canal some major engineering obstacles will need to be overcome.
History Since 1730, when the first act of Parliament to authorize a canal from the River Severn to Stroud – the Stroudwater Navigation Act 1729 (3 Geo. 2. c. 13) – had been passed, the Stroudwater Navigation had been seen as part of a larger plan to link London and Bristol by waterway. No work took place immediately, but the Stroudwater was eventually opened in 1779, and within two years the shareholders commissioned a survey for a canal from Dudbridge to Cricklade, which would complete the link. It is likely that John Priddy – previously the engineer for the Stroudwater scheme – carried out the survey, but others were soon involved including Sir Edward Littleton, who was connected with the Staffordshire and Worcestershire Canal. Priddy suggested that there were better terminal points at Wallbridge and Lechlade. Robert Whitworth then surveyed two routes, the first as suggested by Priddy, and the second direct from the Severn to the Thames following the valley of the River Coln. The first route was chosen, based on excellent water supplies at Cirencester, although the estimates of the amount of water available proved to be wildly optimistic.
The estimated cost of the project was £127,916, most of which was promised within three weeks. The bill to authorise the canal passed through Parliament relatively easily, and became the (23 Geo. 3. c. 38) on 17 April 1783. The company could raise an initial £130,000, with an additional £60,000 if required. The canal was to be suitable for boats wide, and so could accommodate Thames barges, but not Severn trows. Josiah Clowes was appointed head engineer, surveyor and carpenter to the canal in 1783 to assist Whitworth. Clowes became resident engineer and was paid £300 per year. His work on the canal gave him a reputation that made him highly sought after in the last five years of his life. He left the construction of the canal shortly before its completion, to work on Dudley Tunnel.
There was great debate about the gauge of the tunnel required at Sapperton. Commissioners from the River Thames thought that it would have to be built for narrow boats, since the cost of a larger tunnel would be prohibitive. It was also going to be longer than any tunnel yet built. However, a decision was made that it would be built as a broad tunnel, wide and high, and so the company advertised for tunnellers. The tunnel was expected to take four years to complete when work began at the start of 1784, but it was not completed until April 1789.
The canal opened in stages as it was completed. The first from Wallbridge to Chalford opened in January 1785, and by mid-1786, the navigable section had reached the western portal of the tunnel, and 28 locks from Wallbridge. A wharf was built at Daneway Bridge, equipped with a warehouse and coalyard.
The tunnel was constructed from many workfaces, with 25 shafts sunk along its course to provide access. After completion there were problems, and the tunnel was shut for two and a half months during 1790 for further work to be carried out. The summit level and the branch to Cirencester were completed in 1787, and became operational as soon as the tunnel opened. The final section to the junction with the Thames at Inglesham, which descends through 16 locks, was finished in November 1789. The canal was completed at a cost of £250,000. With the Stroudwater Navigation, which had been completed in 1779, it completed a link between the River Severn in the west and the River Thames in the east.
As built, the main line was just under long and had 44 locks. The branch to Cirencester added a further . The first from Wallbridge to Brimscombe, where there was a transhipment basin, was built with locks , enabling Severn trows to use it. Beyond that, the locks were and the boats used were Thames barges. The canal's summit, which is above sea level and long, includes the Sapperton Tunnel, at the time, the longest in England. Its length has only been exceeded by two other canal tunnels, at Standedge in the Pennines and at Strood in Kent.
Operation Until the summit level was completed, little thought seems to have been given to water supply. It was assumed that the River Frome, to the west of the tunnel, the River Churn which flows through Cirencester, and the River Coln, together with springs at Boxwell and a well near the source of the River Thames at Thames Head, would be sufficient. The original horse pump at Thames Head was replaced by a windmill, but Clowes found that he could not stop the summit pound from leaking. The flow on the River Churn was , whereas the calculated flow at the start of the project had been more than ten times this value. The summit level was losing around , largely because the underlying rock was porous limestone, and it was estimated that around half of the daily requirement could actually be supplied. The wells at Thames Head were extended and a Boulton & Watt steam engine was installed in 1792 to pump the water into the canal. An extra, shallow lock was built at Boxwell, which allowed the level of the canal to be dropped beyond it, and more water to be taken from Boxwell springs. The new arrangements were adequate, although some of the reason was the failure of traffic to develop to the levels anticipated.
Leakage was affected by springs breaking through the clay lining of the canal bed. In summer, when the springs receded, water was lost through these holes at a rate greater than the available supply. In one of the attempts to conserve water, the length of the locks was reduced by , giving them an unusual double-headed appearance. In a further attempt to prevent water loss, at King's Reach, the section immediately east of Sapperton Tunnel, the canal was lined with concrete rather than puddle clay. The concrete invert was thick, and A. Brome Wilson, the canal's engineer, used pipes to feed water from the underlying springs into the canal, but at a level above the waterline.
Neither of the river navigations to which the canal connected were satisfactory. In the west, the situation was remedied in 1827, on completion of the Gloucester and Sharpness Canal. On the Thames, there had been a proposal for a canal from Lechlade to Abingdon in 1784, and for a cut from Inglesham to Buscot in 1788, but neither had been built. Some improvements were made to the river after 1786, but the canal company encouraged the building of bypasses. The Wilts & Berks Canal was one Thames bypass, providing a link to the river at Abingdon, but did not initially connect to the Thames & Severn Canal. Although it was proposed in 1793, it was not opened until 1810, and the North Wilts Canal, which eventually provided the connecting link from Latton to Swindon for Thames & Severn traffic to bypass the upper river, was not completed until 1819. Even after this, vessels were restricted by the narrow 7ft width of the North Wilts, which was considerably smaller than the rest of the link between the Thames and the Severn, limiting income from cargo.
Ultimately, most of the Bristol to London trade used the Kennet and Avon Canal after it opened in 1810, as it provided a much shorter route than the Thames and Severn Canal. Similarly, the Midlands-London traffic that the proprietors had hoped to attract via the Severn found newer routes further east, such as the Grand Junction Canal, considerably more direct. Thus, the compromise alignment of the Thames & Severn found itself bypassed, with income mainly generated by carriage of Forest of Dean coal to places along the canal rather than the balanced trade of long-distance traffic between Thames and Severn that had been anticipated. Pleasure cruising, meanwhile, was firmly discouraged, with the proprietors setting a punitive toll of £1 per lock for such boats (equivalent to over £120 today).
Decline Railway competition began in 1836, when the Cheltenham and Great Western Railway proposed a line between Swindon and Cheltenham, via Gloucester. The canal company opposed the scheme, and received compensation of £7,500 from the railway company over the next four and a half years. The line opened to Kemble in 1841, and the tolls on the carriage of materials for the railway's construction improved the financial position of the canal for a short time. The railway company was then taken over by the Great Western Railway, who built a new tunnel at Sapperton, and opened the railway to Gloucester in 1845. Canal tolls were cut in an attempt to retain traffic, but toll revenue fell from £11,000 to £2,874 between 1841 and 1855. The Thames Commissioners were also in financial difficulties, and the Thames was almost unnavigable from Oxford to Lechlade after 1855. In 1866, plans to convert the canal to a railway were rejected by Parliament, but the Thames Commissioners were replaced by the Thames Conservancy, and most of the river was soon returned to a navigable state.