Canal
Canals or artificial waterways are
In most cases, a canal has a series of
A canal can cut across a drainage divide atop a ridge, generally requiring an external water source above the highest elevation. The best-known example of such a canal is the Panama Canal.
Many canals have been built at elevations, above valleys and other waterways. Canals with sources of water at a higher level can deliver water to a destination such as a city where water is needed. The Roman Empire's aqueducts were such water supply canals.
The term was once used to describe linear features seen on the surface of Mars, Martian canals, an optical illusion.
Types of artificial waterways
A navigation is a series of channels that run roughly parallel to the valley and stream bed of an unimproved river. A navigation always shares the drainage basin of the river. A vessel uses the calm parts of the river itself as well as improvements, traversing the same changes in height.
A true canal is a channel that cuts across a drainage divide, making a navigable channel connecting two different drainage basins.
Structures used in artificial waterways
Both navigations and canals use engineered structures to improve navigation:
- weirs and dams to raise river water levels to usable depths;
- looping descents to create a longer and gentler channel around a stretch of rapids or falls;
- locksto allow ships and barges to ascend/descend.
Since they cut across drainage divides, canals are more difficult to construct and often need additional improvements, like viaducts and aqueducts to bridge waters over streams and roads, and ways to keep water in the channel.
Types of canals
There are two broad types of canal:
- Waterways: canals and navigations used for carrying vessels transporting goods and people. These can be subdivided into two kinds:
- .
Importance
Historically, canals were of immense importance to commerce and the development, growth and vitality of a civilization. In 1855 the Lehigh Canal carried over 1.2 million tons of anthracite coal; by the 1930s the company which built and operated it for over a century ceased operation. The few canals still in operation in our modern age are a fraction of the numbers that once fueled and enabled economic growth, indeed were practically a prerequisite to further urbanization and industrialization. For the movement of bulk raw materials such as coal and ores are difficult and marginally affordable without water transport. Such raw materials fueled the industrial developments and new metallurgy resulting of the spiral of increasing mechanization during 17th–20th century, leading to new research disciplines, new industries and economies of scale, raising the standard of living for any industrialized society.
The surviving canals
Most
By the early 1880s, canals which had little ability to economically compete with rail transport, were off the map. In the next couple of decades, coal was increasingly diminished as the heating fuel of choice by oil, and growth of coal shipments leveled off. Later, after World War I when motor-trucks came into their own, the last small U.S. barge canals saw a steady decline in cargo ton-miles alongside many railways, the flexibility and steep slope climbing capability of lorries taking over cargo hauling increasingly as road networks were improved, and which also had the freedom to make deliveries well away from rail lined road beds or ditches in the dirt which could not operate in the winter.
The longest extant canal today, the Grand Canal in northern China, still remains in heavy use, especially the portion south of the Yellow River. It stretches from Beijing to Hangzhou at 1,794 kilometres (1,115 miles).
Construction
Canals are built in one of three ways, or a combination of the three, depending on available water and available path:
- Human made streams
- A canal can be created where no stream presently exists. Either the body of the canal is dug or the sides of the canal are created by making Canal de Briare and the Panama Canal.
- A canal can be constructed by dredging a channel in the bottom of an existing lake. When the channel is complete, the lake is drained and the channel becomes a new canal, serving both drainage of the surrounding polder and providing transport there. Examples include the Lage Vaart . One can also build two parallel dikes in an existing lake, forming the new canal in between, and then drain the remaining parts of the lake. The eastern and central parts of the North Sea Canal were constructed in this way. In both cases pumping stations are required to keep the land surrounding the canal dry, either pumping water from the canal into surrounding waters, or pumping it from the land into the canal.
- Canalization and navigations
- A stream can be Riparian zone restorationmay be required.
- Lateral canals
- When a stream is too difficult to modify with canalization, a second stream can be created next to or at least near the existing stream. This is called a Garonne Lateral Canal, Welland Canal and Juliana Canal.
Smaller transportation canals can carry barges or narrowboats, while ship canals allow seagoing ships to travel to an inland port (e.g., Manchester Ship Canal), or from one sea or ocean to another (e.g., Caledonian Canal, Panama Canal).
Features
At their simplest, canals consist of a trench filled with water. Depending on the
Canals need to be level, and while small irregularities in the lie of the land can be dealt with through cuttings and embankments, for larger deviations other approaches have been adopted. The most common is the
Prior to the development of the pound lock in 984 AD in China by Chhaio Wei-Yo[2] and later in Europe in the 15th century, either flash locks consisting of a single gate were used or ramps, sometimes equipped with rollers, were used to change the level. Flash locks were only practical where there was plenty of water available.
Locks use a lot of water, so builders have adopted other approaches for situations where little water is available. These include
To cross a stream, road or valley (where the delay caused by a flight of locks at either side would be unacceptable) the valley can be spanned by a
Another option for dealing with hills is to tunnel through them. An example of this approach is the Harecastle Tunnel on the Trent and Mersey Canal. Tunnels are only practical for smaller canals.
Some canals attempted to keep changes in level down to a minimum. These canals known as contour canals would take longer, winding routes, along which the land was a uniform altitude. Other, generally later, canals took more direct routes requiring the use of various methods to deal with the change in level.
Canals have various features to tackle the problem of water supply. In cases, like the Suez Canal, the canal is open to the sea. Where the canal is not at sea level, a number of approaches have been adopted. Taking water from existing rivers or springs was an option in some cases, sometimes supplemented by other methods to deal with seasonal variations in flow. Where such sources were unavailable,
Where large amounts of goods are loaded or unloaded such as at the end of a canal, a canal basin may be built. This would normally be a section of water wider than the general canal. In some cases, the canal basins contain wharfs and cranes to assist with movement of goods.
When a section of the canal needs to be sealed off so it can be drained for maintenance stop planks are frequently used. These consist of planks of wood placed across the canal to form a dam. They are generally placed in pre-existing grooves in the canal bank. On more modern canals, "guard locks" or gates were sometimes placed to allow a section of the canal to be quickly closed off, either for maintenance, or to prevent a major loss of water due to a canal breach.
Canal falls
A canal fall, or canal drop, is a vertical drop in the canal bed. These are built when the natural ground slope is steeper than the desired canal gradient. They are constructed so the falling water's kinetic energy is dissipated in order to prevent it from scouring the bed and sides of the canal.[3]: 643
A canal fall is constructed by cut and fill. It may be combined with a regulator, bridge, or other structure to save costs.[3]: 643–4
There are various types of canal falls, based on their shape. One type is the ogee fall, where the drop follows an s-shaped curve to create a smooth transition and reduce turbulence. However, this smooth transition does not dissipate the water's kinetic energy, which leads to heavy scouring. As a result, the canal needs to be reinforced with concrete or masonry to protect it from eroding.[3]: 644
Another type of canal fall is the vertical fall, which is "simple and economical". These feature a "cistern", or depressed area just downstream from the fall, to "cushion" the water by providing a deep pool for its kinetic energy to be diffused in. Vertical falls work for drops of up to 1.5 m in height, and for discharge of up to 15 cubic meters per second.[3]: 646
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A canal boat traverses the longest and highest aqueduct in the UK, at Pontcysyllte in Denbighshire, Wales
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The Corinth Canal seen from the air
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Miami and Erie Canal Lock in Ohio, United States
History
The transport capacity of pack animals and carts is limited. A mule can carry an eighth-ton[4] [250 pounds (113 kg)] maximum load over a journey measured in days and weeks,[4] though much more for shorter distances and periods with appropriate rest.[4] Besides, carts need roads. Transport over water is much more efficient and cost-effective for large cargoes.
Ancient canals
The oldest known canals were
In
In the 5th century BC,
There was little experience moving bulk loads by carts, while a pack-horse would [i.e. 'could'] carry only an eighth of a ton. On a soft road a horse might be able to draw 5/8ths of a ton. But if the load were carried by a barge on a waterway, then up to 30 tons could be drawn by the same horse.
— technology historian Ronald W. Clark referring to transport realities before the industrial revolution and the Canal age.[4]
Hohokam was a society in the North American Southwest in what is now part of Arizona, United States, and Sonora, Mexico. Their irrigation systems supported the largest population in the Southwest by 1300 CE.[14] Archaeologists working at a major archaeological dig in the 1990s in the Tucson Basin, along the Santa Cruz River, identified a culture and people that may have been the ancestors of the Hohokam.[15] This prehistoric group occupied southern Arizona as early as 2000 BCE, and in the Early Agricultural Period grew corn, lived year-round in sedentary villages, and developed sophisticated irrigation canals.[14] The large-scale Hohokam irrigation network in the Phoenix metropolitan area was the most complex in ancient North America. A portion of the ancient canals has been renovated for the Salt River Project and now helps to supply the city's water.
The Sinhalese constructed the 87 km (54 mi) Yodha Ela in 459 A.D. as a part of their extensive irrigation network which functioned in a way of a moving reservoir due to its single banking aspect to manage the canal pressure with the influx of water. It was also designed as an elongated reservoir passing through traps creating 66 mini catchments as it flows from Kala Wewa to Thissa Wawa. The canal was not designed for the quick conveying of water from Kala Wawa to Thissa Wawa but to create a mass of water between the two reservoirs, which would in turn provided for agriculture and the use of humans and animals.[16] [17] They also achieved a rather low gradient for its time. The canal is still in use after renovation.
Middle Ages
In the
In Britain, the Glastonbury Canal is believed to be the first post-Roman canal and was built in the middle of the 10th century to link the River Brue at Northover[18] with Glastonbury Abbey, a distance of about 1.75 kilometres (1,900 yd).[19] Its initial purpose is believed to be the transport of building stone for the abbey, but later it was used for delivering produce, including grain, wine and fish, from the abbey's outlying properties. It remained in use until at least the 14th century, but possibly as late as the mid-16th century.[20]
More lasting and of more economic impact were canals like the Naviglio Grande built between 1127 and 1257 to connect Milan with the river Ticino. The Naviglio Grande is the most important of the lombard "navigli"[21] and the oldest functioning canal in Europe.
Later, canals were built in the Netherlands and Flanders to drain the polders and assist transportation of goods and people.
Canal building was revived in this age because of commercial expansion from the 12th century. River navigations were improved progressively by the use of single, or
To break out of the limitations caused by river valleys, the first
Africa
In the
Early modern period
Around 1500–1800 the first summit level canal to use pound locks in Europe was the Briare Canal connecting the Loire and Seine (1642), followed by the more ambitious Canal du Midi (1683) connecting the Atlantic to the Mediterranean. This included a staircase of 8 locks at Béziers, a 157 metres (515 ft) tunnel, and three major aqueducts.
Canal building progressed steadily in Germany in the 17th and 18th centuries with three great rivers, the
The oldest canal in the European settlements of North America, technically a mill race built for industrial purposes, is Mother Brook between the Boston, Massachusetts neighbourhoods of Dedham and Hyde Park connecting the higher waters of the Charles River and the mouth of the Neponset River and the sea. It was constructed in 1639 to provide water power for mills.
In Russia, the Volga–Baltic Waterway, a nationwide canal system connecting the Baltic Sea and Caspian Sea via the Neva and Volga rivers, was opened in 1718.
Industrial Revolution
The modern canal system was mainly a product of the 18th century and early 19th century. It came into being because the Industrial Revolution (which began in Britain during the mid-18th century) demanded an economic and reliable way to transport goods and commodities in large quantities.
By the early 18th century, river navigations such as the
The claim for the first pure canal in Great Britain is debated between "Sankey" and "Bridgewater" supporters.[26] The first true canal in what is now the United Kingdom was the Newry Canal in Northern Ireland constructed by Thomas Steers in 1741.
The Sankey Brook Navigation, which connected St Helens with the River Mersey, is often claimed as the first modern "purely artificial" canal because although originally a scheme to make the Sankey Brook navigable, it included an entirely new artificial channel that was effectively a canal along the Sankey Brook valley.[26][27] However, "Bridgewater" supporters point out that the last quarter-mile of the navigation is indeed a canalized stretch of the Brook, and that it was the Bridgewater Canal (less obviously associated with an existing river) that captured the popular imagination and inspired further canals.[26][27]
In the mid-eighteenth century the
The new canals proved highly successful. The boats on the canal were horse-drawn with a towpath alongside the canal for the horse to walk along. This horse-drawn system proved to be highly economical and became standard across the British canal network. Commercial horse-drawn canal boats could be seen on the UK's canals until as late as the 1950s, although by then diesel-powered boats, often towing a second unpowered boat, had become standard.
The canal boats could carry thirty tons at a time with only one horse pulling[28] – more than ten times the amount of cargo per horse that was possible with a cart. Because of this huge increase in supply, the Bridgewater canal reduced the price of coal in Manchester by nearly two-thirds within just a year of its opening. The Bridgewater was also a huge financial success, with it earning what had been spent on its construction within just a few years.
This success proved the viability of canal transport, and soon industrialists in many other parts of the country wanted canals. After the Bridgewater canal, early canals were built by groups of private individuals with an interest in improving communications. In Staffordshire the famous potter
The new canal system was both cause and effect of the rapid industrialization of
For each canal, an Act of Parliament was necessary to authorize construction, and as people saw the high incomes achieved from canal tolls, canal proposals came to be put forward by investors interested in profiting from dividends, at least as much as by people whose businesses would profit from cheaper transport of raw materials and finished goods.
In a further development, there was often out-and-out speculation, where people would try to buy shares in a newly floated company to sell them on for an immediate profit, regardless of whether the canal was ever profitable, or even built. During this period of "canal mania", huge sums were invested in canal building, and although many schemes came to nothing, the canal system rapidly expanded to nearly 4,000 miles (over 6,400 kilometres) in length.[28]
Many rival canal companies were formed and competition was rampant. Perhaps the best example was Worcester Bar in Birmingham, a point where the Worcester and Birmingham Canal and the Birmingham Canal Navigations Main Line were only seven feet apart. For many years, a dispute about tolls meant that goods travelling through Birmingham had to be portaged from boats in one canal to boats in the other.[30]
Canal companies were initially chartered by individual states in the United States. These early canals were constructed, owned, and operated by private joint-stock companies. Four were completed when the
Power canals
A power canal refers to a canal used for
19th century
Competition, from railways from the 1830s and roads in the 20th century, made the smaller canals obsolete for most commercial transport, and many of the British canals fell into decay. Only the
In the United States, navigable canals reached into isolated areas and brought them in touch with the world beyond. By 1825 the Erie Canal, 363 miles (584 km) long with 36 locks, opened up a connection from the populated Northeast to the Great Lakes. Settlers flooded into regions serviced by such canals, since access to markets was available. The Erie Canal (as well as other canals) was instrumental in lowering the differences in commodity prices between these various markets across America. The canals caused price convergence between different regions because of their reduction in transportation costs, which allowed Americans to ship and buy goods from farther distances much cheaper. Ohio built many miles of canal, Indiana had working canals for a few decades, and the Illinois and Michigan Canal connected the Great Lakes to the Mississippi River system until replaced by a channelized river waterway.
Three major canals with very different purposes were built in what is now Canada. The first Welland Canal, which opened in 1829 between Lake Ontario and Lake Erie, bypassing Niagara Falls and the Lachine Canal (1825), which allowed ships to skirt the nearly impassable rapids on the St. Lawrence River at Montreal, were built for commerce. The Rideau Canal, completed in 1832, connects Ottawa on the Ottawa River to Kingston, Ontario on Lake Ontario. The Rideau Canal was built as a result of the War of 1812 to provide military transportation between the British colonies of Upper Canada and Lower Canada as an alternative to part of the St. Lawrence River, which was susceptible to blockade by the United States.
In France, a steady linking of all the river systems – Rhine, Rhône, Saône and Seine – and the North Sea was boosted in 1879 by the establishment of the Freycinet gauge, which specified the minimum size of locks. Canal traffic doubled in the first decades of the 20th century.[32]
Many notable sea canals were completed in this period, starting with the Suez Canal (1869) – which carries tonnage many times that of most other canals – and the Kiel Canal (1897), though the Panama Canal was not opened until 1914.
In the 19th century, a number of canals were built in Japan including the
A major question was how to connect the Atlantic and the Pacific with a canal through narrow
The second choice for a Central American canal was a
Twenty years later, an expansionist United States, that just acquired colonies after defeating Spain in the 1898
Modern uses
Large-scale ship canals such as the Panama Canal and Suez Canal continue to operate for cargo transportation, as do European barge canals. Due to
The narrow early industrial canals, however, have ceased to carry significant amounts of trade and many have been abandoned to navigation, but may still be used as a system for transportation of untreated water. In some cases railways have been built along the canal route, an example being the Croydon Canal.
A movement that began in Britain and France to use the early industrial canals for pleasure boats, such as hotel barges, has spurred rehabilitation of stretches of historic canals. In some cases, abandoned canals such as the Kennet and Avon Canal have been restored and are now used by pleasure boaters. In Britain, canalside housing has also proven popular in recent years.
The Seine–Nord Europe Canal is being developed into a major transportation waterway, linking France with Belgium, Germany, and the Netherlands.
Canals have found another use in the 21st century, as
Canals are still used to provide water for agriculture. An extensive canal system exists within the Imperial Valley in the Southern California desert to provide irrigation to agriculture within the area.
Cities on water
Canals are so deeply identified with
Other cities with extensive canal networks include:
Liverpool Maritime Mercantile City was a UNESCO World Heritage Site near the centre of Liverpool, England, where a system of intertwining waterways and docks is now being developed for mainly residential and leisure use.
Boats
Inland canals have often had boats specifically built for them. An example of this is the British narrowboat, which is up to 72 feet (21.95 m) long and 7 feet (2.13 m) wide and was primarily built for British Midland canals. In this case the limiting factor was the size of the locks. This is also the limiting factor on the Panama canal where Panamax ships were limited to a length of 289.56 m (950 ft) and a beam of 32.31 m (106 ft) until 26 June 2016 when the opening of larger locks allowed for the passage of larger New Panamax ships. For the lockless Suez Canal the limiting factor for Suezmax ships is generally draft, which is limited to 16 m (52.5 ft). At the other end of the scale, tub-boat canals such as the Bude Canal were limited to boats of under 10 tons for much of their length due to the capacity of their inclined planes or boat lifts. Most canals have a limit on height imposed either by bridges or by tunnels.
Lists of canals
- Africa
- Bahr Yussef
- El Salam Canal Egypt
- Ibrahimiya Canal Egypt
- Mahmoudiyah CanalEgypt
- Suez Canal Egypt
- Asia
- Europe
- North America
- Canals of Canada
- Canals of the United States
Lists of proposed canals
- Eurasia Canal
- Istanbul Canal
- Nicaragua Canal
- Salwa Canal
- Thai Canal
- Sulawesi Canal
- Two Seas Canal
- Northern river reversal
- Balkan Canal or Danube–Morava–Vardar–Aegean Canal
- Iranrud
See also
- Beaver, a non-human animal also known for canal building
- Canal elevator
- Calle canal
- Canal & River Trust
- Canal tunnel
- Environment Agency
- Horse-drawn boat
- Irrigation district
- Lists of canals
- List of navigation authorities in the United Kingdom
- List of waterways
- List of waterway societies in the United Kingdom
- Mooring
- Navigation authority
- Proposed canals
- Roman canals – (Torksey)
- Volumetric flow rate
- Water bridge
- Waterscape
- Water transportation
- Waterway restoration
- Waterways in the United Kingdom
- Weigh lock
References
Notes
- ^ Thompson, Kristi. "Glossary". www.usbr.gov. US Bureau of Reclamation. Retrieved 15 September 2017.
- ^ Hadfield 1986, p. 22.
- ^ ISBN 978-93-525-3377-0. Retrieved 31 July 2023.
- ^ ISBN 0-670-80483-5(1985) 352 pages, Viking Penguin, Inc, New York,
quotation p. 87: "There was little experience moving bulk loads by carts, while a packhorse would [sic, meaning 'could' or 'can only'] carry only an eighth of a ton. On a soft road a horse might be able to draw 5/8ths of a ton. But if the load were carried by a barge on a waterway, then up to 30 tons could be drawn by the same horse. - ^ Rodda 2004, p. 161.
- ^ Hadfield 1986, p. 16.
- ^ Needham 1971, p. 269.
- ISBN 978-1-57607-112-0. Retrieved 15 February 2013.
the world's largest artificial waterway and oldest canal still in existence
- ^ Herodotus VII, 22
- JSTOR 30073214.
- ^ Moore, Frank Gardner (1950): "Three Canal Projects, Roman and Byzantine", American Journal of Archaeology, Vol. 54, No. 2, pp. 97–111 (99–101)
- ^ Froriep, Siegfried (1986): "Ein Wasserweg in Bithynien. Bemühungen der Römer, Byzantiner und Osmanen", Antike Welt, 2nd Special Edition, pp. 39–50 (46)
- ^ Schörner, Hadwiga (2000): "Künstliche Schiffahrtskanäle in der Antike. Der sogenannte antike Suez-Kanal", Skyllis, Vol. 3, No. 1, pp. 28–43 (33–35)
- ^ a b "The Hohokam". Arizona Museum of Natural History, City of Mesa. Archived from the original on November 30, 2012. Retrieved November 30, 2012.
- ^ 2007-036 General COP Treatment Plan; Pueblo Grande Museum Project 2007–95; City of Phoenix Project No. ST87350010; p. 9 Cultural Context Archived March 24, 2014, at the Wayback Machine
- ^ "Yoda Ela – An Ancient Engineering Marvel".
- ISBN 9788120613638.
- ^ specifically from (51°08′18″N 2°44′09″W / 51.1384°N 2.7358°W), Start point at River Brue
- ^ Details text and data with cites from Glastonbury Canal (medieval).
- ^ Gathercole, Clare (2003). An archaeological assessment of Glastonbury (PDF). English Heritage Extensive Urban Survey. Taunton: Somerset County Council. pp. 19–20. Archived from the original (PDF) on 15 July 2011. Retrieved 2 February 2010.
- ^ Calvert 1963, p. .
- ^ The International Canal Monuments List (PDF), archived from the original (PDF) on 10 August 2013, retrieved 8 October 2008
- ^ https://www.sahistory.org.za/sites/default/files/file%20uploads%20/general_history_africa_iv.pdf pages 193-194
- ^ David Cornforth (February 2012). "Exeter Canal and Quayside – a short history". www.exetermemories.co.uk. Retrieved 14 September 2013.
- ^ Exeter history by www.exeter.gov.uk, .pdf file Exeter Ship Canal, The First Four Hundred Years Archived 19 September 2015 at the Wayback Machine, accessdate=13 September 2013
- ^ ISBN 978-1-85501-695-8
- ^ a b c Rolt, Inland Waterways
- ^ a b c Reader's Digest Library of Modern Knowledge. London: Reader's Digest. 1978. p. 990.
- ISBN 978-0-7153-8079-6.
- ISBN 978-0-7153-4660-0.
- ^ Lowell National Historical Park – Lowell History Prologue, retrieved 8 October 2008
- ^ Edwards-May 2008, p. .
- ^ Hadfield 1986, p. 191.
- ^ "Panama Canal Opens $5B Locks, Bullish Despite Shipping Woes". The New York Times. Associated Press. 26 June 2016. Retrieved 26 June 2016.
Bibliography
- Calvert, Roger (1963), "Inland Waterways of Europe", The Geographical Journal, 129 (4), George Allen and Unwin: 515, JSTOR 1794678
- Edwards-May, David (2008), European Waterways - map and concise directory, 3rd edition, Euromapping
- ISBN 978-0-7153-8555-5
- Needham, J. (1971), Science and Civilisation in China, C.U.P. Cambridge
- Rodda, J.C. (2004), The Basis of Civilization - Water Science?, International Association of Hydrological Sciences
External links
- British Waterways' leisure website – Britain's official guide to canals, rivers and lakes
- Leeds Liverpool Canal Photographic Guide
- Information and Boater's Guide to the New York State Canal System Archived 24 July 2008 at the Wayback Machine
- "Canals and Navigable Rivers" by James S. Aber, Emporia State University
- National Canal Museum (US)
- London Canal Museum (UK)
- Canals in Amsterdam
- Canal du Midi
- Canal des Deux Mers
- Canal flow measurement using a sensor.
- New International Encyclopedia. 1905. .