Буде каналы: Корнуоллдың ең ерекше су жолы

Canal in Cornwall, England

The Bude Canal was a canal built to serve the hilly hinterland in the Cornwall and Devon border territory in the United Kingdom, chiefly to bring lime bearing sand for agricultural fertiliser. The Bude Canal system was one of the most unusual in Britain. It was remarkable in using inclined planes to haul tub boats on wheels to the upper levels. There were only two conventional locks, in the short broad canal section near the sea at Bude itself. It had a total extent of 35 mile (56 km), and it rose from sea level to an altitude of 433 feet (132 m). The design of the canal influenced the design of the Rolle Canal.

The coastal area at Bude has sand unusually rich in minerals, and the poor agricultural land of the locality was found to benefit considerably from application of the sand. In the pre industrial age, actually transporting it was difficult, even to land relatively close to the coast. Several schemes were put forward for canals to bring the sand to the countryside, and these proposals did not lack ambition. One early scheme, conceived by Cornish engineer John Edyvean, aimed at distributing Welsh coal from the port as far inland as Calstock on the River Tamar. It gained parliamentary approval for construction in 1774, but financial problems and the Napoleonic Wars frustrated the proposal. In 1818, the West Country canal engineer James Green produced a report for canal's backers, and an Act of Parliament was obtained for this more moderate proposal in 1819. After some difficulties in the construction phase, the canal was completed, and opened on 8 July 1823. Its cost was £118,000.

The unusual feature of the canal was the six inclined planes. The tub boats had wheels, and on the inclined planes they were pulled up the slopes with the wheels running in channel rails (like a squat letter "U" in section). There were two sets of rails, one for each direction, but it does not appear that a counterbalancing system was used (in which a boat coming down would balance one being pulled up). The tub boats were hauled up and let down the inclined planes by chains, which were operated in most cases by waterwheels; the transit took five minutes or so. There were standby steam engines at some of the inclined planes. However the Hobbacott Inclined Plane (both the steepest and that allowing the greatest height difference) used a different system of harnessing water power: water filled a very large bucket, and it was simply the weight of the water that pulled the ascending tub boat up the incline. The bucket operated in a deep vertical shaft, and at the bottom a plug was opened and the water ran to waste along an adit which connected to the lower level of the canal; the descending bucket pulled an empty bucket up in the same operation. The full bucket had to be heavy enough to pull a loaded tub boat up the 1 in 41/2 gradient as well as overcoming friction, and Green calculated that a weight of about fifteen tons was necessary. This was successful, and the bucket raised a boat up the plane in about four minutes, which was about one half of the time taken when the standby steam engine was used.

On Monday 10 March 2008, a powerful storm wrenched one of the lock gates off its fixings. Contractors removed the gate the following morning, and four tonne concrete pipes were placed in the canal basin to dissipate the power of waves coming in from the sea. A temporary dam was constructed at Falcon Bridge, and a team of anglers and staff from the Environment Agency rescued the fish population before it was swept out to sea. Beyond the dam, the loss of water was contained, with levels only dropping by about , but at the lower end of the canal water continued to flow out until it was practically empty, revealing some interesting finds in the mud, including a shotgun. The North Cornwall District Council used the opportunity to repair the canal walls and dredge the basin. During the course of the dredging, over of silt were removed. It was originally intended to refill the basin gradually after 8 July 2008, but a period of intense rainfall prior to that date resulted in a surge of water passing down the canal, which damaged the coffer dam protecting the empty section from the watered section. Consequently, the basin refilled in a single day.