SHIP CANALS Ship canals, from an engineering point of view, chiefly differ from barge canals in the magnitude of the works they involve, but there is no definite line of distinction. For instance, the so called Marseille-Rhone ship canal has approximately the same limiting structural dimensions as the New York State barge canal. Speaking generally, ship canals accommodate ocean going ships, within the limits of their dimensions, while barge canals are restricted, normally, to inland navigation craft and special types of coasting vessels. The terminal works of a ship canal, e.g., sea approaches, locks, etc., are usually such as commonly form part of dock and harbour (q.v.) works.
Ship canals have mostly been constructed either to shorten the voyage between two seas by cutting through an intervening isthmus, or to convert important inland places into sea-ports. An early example of the first class is afforded by the Caledonian canal (q.v.) opened in 1822, while among later ones may be mentioned the Suez, Kiel and Panama canals (qq.v.). One of the earliest examples of the second class is the small ship canal between Sharpness and Gloucester, completed in 1827, and among later ones are the Manchester ship canal (q.v.) and the canal from Zeebrugge on the North Sea to Bruges (q.v.).
Isthmian canals may be either open cuttings, like the Suez canal, or locked canals as at Panama. Many have been enlarged since their first construction; and this in the case of a simple cutting can be effected by degrees and in stages ; as for instance in the Suez canal, whose dimensions have been increased by dredging and in other ways from a depth of 26f t. and bottom width of 72ft. to minima of 391f t.
and 148ft. respectively. Further enlargement, sanctioned in 1921, to a minimum depth of 42ift.
and a minimum width of 197ft.
(at a depth of 33ft.) was still in progress in 1928 (fig. 7). Locked canals, if they have to be en larged, present a different prob lem, of which the North Sea Amsterdam ship canal furnishes an example. This canal, which is 153-m. in length from Ymuiden on the North Sea to Amsterdam, was constructed between 1865 and 1876 to supersede the Great North Holland canal made early in the 19th century from the Texel Roads to Amsterdam. Origi naily it had a depth of 23ft., bottom width of 882ft., and an entrance lock 394x6oft. internally. In 1896 a second sea lock, 738x8 2 f t. and 33ft. deep over the sill at mean tide level, was constructed to meet the increased dimensions of shipping, and the entrance channel and canal section were enlarged. In 1921 further enlargement was undertaken ; and the building of a new lock, the largest in the world (1928), was begun in the following year. It is 1,315ft. long, 164ft. wide and Soft. deep over the entrance sill at mean tide level. The harbour and canal have been deepened to 4of t. and the canal widened to 246f t. at the bottom.
The new lock (completed 1928) is, in fact, considerably larger than is necessary for the near future ; but its dimensions will allow the harbour to be deepened and the section of the canal to be still further increased.
The Cronstadt canal (1878-84), connecting the roadstead of Cronstadt with the port of Leningrad (Petrograd), is a channel 28f t. deep. It is dredged through the Neva bay and protected by lateral moles or embankments on either side for a great part of its length of about 18 miles.
The Corinth canal cut through the Isthmus of Corinth, which connects the Morea to the mainland of Greece, is four miles long and is without locks. The canal passes through high land, mostly rock, and the deepest cutting is 285 feet. A small difference in tidal ranges at the two ends causes a current through the canal which rarely exceeds two knots. The bottom width is 72ft. and the depth 261ft. below mean sea level. The cut was actually commenced in the time of Nero whose work was incorporated in the canal when it was completed between 1882 and Belgium possesses several ship canals of moderate dimensions; the oldest is the Ghent-Terneuzen canal connecting the city of Ghent with the river Scheldt at Terneuzen, about 12m. above Flushing. Originally constructed during the years 1825-27, when Belgium was united with Holland, half of its length of 18 miles is now in Dutch and the other half in Belgian territory. It has been enlarged and now has a depth of 28if t. with bottom width of 164ft., except in the Dutch section which is narrower but of the same depth. At Terneuzen there are three sea locks and near the Dutch frontier three regulating locks which are only used for flood water control. The canal is at one level throughout. Ships drawing 26-27ft. can navigate up to Ghent where an extensive and well equipped inland port has been con structed. The Roupel ship canal, between a tributary of the Scheldt and Brussels, where an inland harbour has been built, was opened in 1922. This waterway, 2om. long, has a minimum bottom width of 66f t. and a depth of 21 feet. The three locks are 3 74x5 2 1f t. internally. Ships drawing 18f t. can pass by the canal from the sea up to Brussels.
The Bruges ship canal (1896-1907) begins in the harbour of Zeebrugge, on the Belgian coast, which was constructed at the same time. It connects this port with the city of Bruges, 6-1m. distant, where basins and quays for sea-going ships have been built. The entrance lock at Zeebrugge is 518x651f t. internally and is closed by rolling caissons; the canal is 72ft. wide at the bottom, 229ft. at water level and 28ft. deep. The basins at Bruges are in communication with the canal system of Belgium.
Sweden possesses an abundance of lakes and rivers but, on account of the uneven nature of the country, the rivers generally are not naturally navigable and some of them have been canalized. The canal system dating, for the most part, from the middle of the 19th century, is extensive. In general the locks measure I I 7x24f t.x l oft. deep, but in some cases they are smaller. Three of these canals have been reconstructed as ship canals since the beginning of the 2oth century.
The Trollhatte ship canal, completed in 1916, connects Gotten burg and the Kattegat with Lake Vannern in southern Sweden and is, for the most part, the canalized Gota river. It is remark able for a flight of three contiguous locks overcoming a total rise of 77 feet. The canal is 52 miles long and the locks are 321-ix 45 f t. internally with a depth of 18f t. The Gota canal, connecting Lakes Vannern and Vattern with the Baltic, having locks of less dimensions than those of the Trollhatte, enables small vessels to cross Sweden from Gottenburg to the Baltic.
The Sodertalje canal between Lake Malaren and the Baltic was reconstructed in 1924, the one lock being 45ox67ft. and 27ft. deep. The canal itself was deepened in 1924 to take ships drawing about 2of t. and will be further enlarged, if required, up to the capacity of the lock.
The Hammarby canal, a short cut, completed in 1926, between Stockholm and Lake Malaren, one of the larger Swedish lakes, has one lock with internal dimensions 358x57ft.x2oift. deep. The locks on the Sodertalje and Hammarby canals are interesting as having balanced sector gates of a novel type, which uphold moderate heads of water on either side.
The Marseille-Rhone ship canal, commenced before the War but only partially completed in 1928, does not accommodate large sea-going vessels, but is designed to open up the port of Marseille to barge traffic on the Rhone and the inland navigation system of France generally. It also places Marseille in direct inland water communication with the >?tang de Berre, an inland lake over 7o sq.m. in area, capable of considerable industrial development. The total length of the waterway is about 48m. and it extends from the harbour of Marseille to Arles on the Rhone, passing through the mountainous district of Nerthe by a tunnel at Rove, thence through the Mang de Berre to Port-de-Bouc where it con nects with an old barge canal to Arles which was being enlarged in 1928. The canal is level throughout, but has two regulating locks and one, at Arles, between the river and the canal. These are 525ft. long and 52ft. wide. The waterway, normally 75ft. wide at bottom, is I of t. deep in the completed sections. The Rove tunnel, nearly 4-im. in length, cut through rock, has a width of 72ft. and a height of 37ft. above the water level, the depth of water in the tunnel being 13 feet. The cross section is larger than that of any other tunnel in the world (fig. 8).
The Lake Washington ship canal, eight miles long, extending from Puget sound to Lake Washington, was opened in 1916. The sea entrance at Seattle has two locks, the larger of which has a usable length of 8 2 5f t., with intermediate gates, and is 8oft. wide. The depth over the sill varies from 25 to 44ft. according to the state of the tide. Flood water is provided for by the construction of a dam with movable crest gates.
The Cape Cod canal, connecting Cape Cod bay on the east, with Buzzards bay on the west of the Cape Cod isthmus, is Tim. in length with dredged approaches which make the total length of the cut 13 miles. Its construction was begun in 1909 and the waterway was first opened to traffic in 1914, since when the works have been completed to give a depth of 25ft. at low water. There is at present no regulating lock on the canal ; and on account of the difference in sea levels at the two ends there is at times a considerable current flowing through it. It provides a shorter route than the exposed open sea route between New York and Boston.
For the St. Mary's Falls canal, or, more correctly, canals, connecting Lakes Superior and Huron at Sault Ste. Marie, and, the new Welland ship canal connecting Lakes Erie and Ontario in Canada, see GREAT LAKES. The canal itself is excavated to 25ft. depth with provision for a depth of 3of t. later. The cost of the new waterway was about $1I0,000,000.
The project for cutting a ship canal through the upper Florida peninsula, initiated by the state legislature in 1933, was approved early in September 1935 by President Roosevelt and $5,000,000 of PWA funds were allotted for the purpose.
The most generally useful works in French are Paul Vidal, Rivigires Canalisees; and O. Jacquinot and F. Galliot, Canaux, both volumes in section Navigation Interieure of the series "Encyclopedie de Genie Civil" (1922). For U.S.A. waterways see the Annual Reports of Chief of Engineers U.S. Army and the Reports of the Commissioner on Inland Waterways, etc. (Washington, 1909-13) .
See also the Reports, etc., of the Royal Commission on Canals, including vol. iv. which is a valuable report by Sir W. H. Lindley on Continental Waterways and Proceedings Inst. C.E. The Reports of the International Navigation Congresses (1885 et seq.) contain valuable papers, particularly those of the Milan (1908) , Philadelphia (1912) and London (1923) congresses. Exhaustive bibliographies have been issued by the I.N.C. Bureau, Brussels, at intervals since 1908.
(N. G. G.)