Comparative analysis

Chapter 3 - Justification for Inscription

1. Criteria under which inscription is proposed
2. Proposed statement of outstanding universal value
3. Comparative analysis
4. Authenticity

C. Comparative analysis

The earliest evidence of the development of canals dates back approximately 4 000 years to Egypt and the Middle East. The Grand Canal in China was built in the 4th century B.C.E., with several later extensions. Linking the Yangtze and Yellow rivers to Beijing, it is the longest canal in the world, the first summit level canal and had the first recorded pound lock. The Canal du Midi in France, built in the 17th century, is widely regarded as the first canal of the modern era. It was enormously influential in the design of subsequent canals in Europe, and is, at present, the only canal inscribed on the World Heritage List (although the four lift locks on the Canal du Centre in Belgium are also inscribed). Beginning in the middle of the 18 th century, there was a virtual explosion in canal building in Europe. By 1850, 6 500 km of canals had been constructed in England and Wales alone.

Worldwide, canals have been built for three main purposes – irrigation, water control and transportation. The Rideau Canal is a transportation canal. The engineering and construction techniques transferred to North America for the building of the Rideau Canal were based on European canalbuilding experience but were significantly adapted to meet the needs of the North American environment and the particular design requirements of a slackwater canal. For purposes of comparative analysis, it is most relevant to examine other transportation canals based on the European canal-building experience of the early 19th century, in particular those built in North America.

A Masterpiece of Human Creative Genius: The Rideau as a Slackwater Canal

Slackwater Canal Experience in Europe

The slackwater concept was used only to a limited degree in Europe. Typically, 18th and early-19 th century canals were excavated channels linked to natural navigable waterways, usually rivers. Locks were built in the excavated channels to overcome changes in elevation. While dams were used to control feeder channels to maintain water levels, they were rarely used to create the impoundments required for a slackwater canal. Even though slackwater systems could have been used to a greater extent, builders had the perception that it was more difficult to build and repair locks in natural or impounded watercourses. An additional factor that militated against more slackwater construction was the concern over fluctuations in water levels in slackwater systems, a problem not encountered to the same extent on excavated canals.

The most notable European slackwater system from the early-19th century canal-building era is the Gotä Canal in Sweden (1810–1832). The Gotä used slackwater techniques, with dams creating slackwater sections as part of its navigable route and reservoirs to control water levels. But, it also relied heavily on excavated channels, typical of the more common European canals. Forty-five percent of the total length of the Gotä is man-made. This is in contrast to the Rideau Canal, where only nine percent of the total length is excavated. Even though slackwater sections could have been used for a greater proportion of the length of the Gotä Canal, the builders demonstrated the same reluctance as other European canal builders to implement slackwater design and engineering. Their use of slackwater sections as the primary navigation route speaks to the ingenuity and confidence of the engineers of the Rideau Canal.

A comparison of the Gotä and the Rideau canals provides a perspective on these two slackwater canals from the early 19th century. Both the Gotä Canal and the Rideau Canal were remarkable engineering achievements in the tradition of European canal-building technology of the early 19th century. The builders of the Rideau Canal, however, while using this technology, adapted it and advanced it to create a remarkable slackwater canal system. Moreover, the Gotä Canal has, unlike the Rideau Canal, been modernized to a great extent. Only two of its fifty-eight locks are operated manually, while forty-four of the fortyseven locks on the Rideau are operated using authentic hand-powered winches.

Slackwater Canal Experience in North America

The European experience in canal development inspired a form of ‘canal mania’ in North America: approximately sixty-five canals were constructed before 1850, chiefly in the eastern United States of America. Most, however, represented a conventional application of European canal technology. American engineers demonstrated a caution similar to that of the European builders with respect to constructing a slackwater canal system. Consequently, no large-scale slackwater canals were built in the United States of America, although some canals used slackwater design for sections of their routes.

The most notable example was the Blackstone Canal, which was constructed from Providence, Rhode Island, to Worcester, Massachusetts, between 1824 and 1828. The Blackstone Canal was a towpath canal, suitable for small, heavily-laden barges, drawn between locks by horses. Forty-nine masonry locks, each 21,3 m long by 3,1 m wide, were built along its 72,4 km route.

There were some short slackwater sections on the Blackstone Canal, but its operators found that these were susceptible to flooding, freezing and low water, causing maintenance and operational difficulties. Clearly, the Blackstone lacked the sophistication of design to manage water flows that was developed for the Rideau Canal.

Due to the emergence of railways in the New England states, the canal closed in 1848 and was abandoned. Very little remains of its original works, much of the stone having been hauled away for other construction uses.

Another historically important American canal was the Schuylkill Canal, built from Philadelphia, Pennsylvania, 160 km along the Schuylkill River to the coal mining area of the Allegheny Mountains. The builders of the canal used excavated channels to bypass rapids and rocky shallows, but, in some locations, dams were built to create slackwater sections in the river. Completed in 1825, the Schuylkill was a towpath canal.

The canal was an immediate commercial success but declined in the late 19th century with the introduction of railways to the area. The State of Pennsylvania acquired the canal in 1931 but saw no economic value in it. Many sections were drained and abandoned. Only a few are still evident today.

In Canada, an early canal project that used elements of slackwater design was the first Welland Canal, built from Lake Ontario to Lake Erie between 1824 and 1829. The route of the canal followed Twelve Mile Creek from Lake Ontario and connected to the Welland River through a series of locks. It then joined the Niagara River above Niagara Falls before reaching Lake Erie.

The use of slackwater design was undertaken to a limited degree on the Welland. Ultimately, however, the slackwater components were abandoned in favour of a series of excavated channels. There are, now, no intact remains of the original slackwater works, and the canal’s original line has been abandoned.

The Blackstone, the Schuylkill and the Welland canals are examples of early North American attempts to use slackwater canal-building techniques. None of them, however, was a fully functioning slackwater system. None advanced canal technology as did the Rideau, through its creative and ingenious slackwater engineering.

In considering European and North Americanexamples of the same time period, it is quite clear that no other canal is comparable to the Rideau Canal as a slackwater system. The Gotä Canal was a project of comparable scale but depended much more heavily on conventional excavated channel sections than did the Rideau and has been largely modernized. The Blackstone, Schuylkill and the Welland canals had only limited slackwater elements and have little historic authenticity today. The Rideau Canal is clearly the most outstanding surviving example in the world of an early-19 th century slackwater canal, and the best preserved.

The Transfer of Canal Technology to North America

The International Canal Monuments List identifies seven canals as being of technological significance worldwide: “These are the most influential waterways in this document. All are landmarks in the world history of canals.” (p. 65) The Erie Canal in the United States of America and the Rideau Canal in Canada are listed among these landmarks, which also include the Grand Canal in China, the Canal du Midi in France, and the Bridgewater, Ellesmere and Birmingham canals in Great Britain.

The Canal du Midi in Languedoc, France was designed with curved walls to resist the pressure of the earth and allow a larger number of boats into the lock. © Parks Canada

According to the authors of the list, the Erie Canal “was significant for being the product of the intercontinental transfer of technology.” (p. 65) Located between Albany and Buffalo, New York, it was considered a triumph of early engineering in the United States of America and one of the most ambitious construction projects of 19th century North America. Built as an excavated towpath canal, the first Erie Canal was completed in 1825. It included eighteen aqueducts to carry the canal over ravines and rivers, and eighty-three locks with a rise of 177,7 m from the Hudson River to Lake Erie.

Like the Erie Canal, the Rideau Canal is recognized in the International Canal Monuments List as demonstrating the “intercontinental transfer of technology and the adaptation of advanced, highly financed engineering to the circumstances of a developing country.” (p. 56) Unlike the Erie, however, the Rideau Canal is a well-preserved example of this early-19th century transfer of technology. Ten years after it was built, the Erie was enlarged, a process that altered the size of the locks and widened and deepened the excavated channel. The Erie Barge Canal, built between 1903 and 1918, bypassed the first and second Erie Canals. While some sections of the original canal have been preserved, the overall authenticity of the original line of the Erie Canal is severely impaired and most of its original engineering structures have disappeared.

A comparison of the two canals resulted in the conclusion by the authors of the list that, “the differing states of preservation of the waterways may well mean that the Rideau, rather than the original Erie Canal, is selected as an illustration of this process of intercontinental transfer and development.” (p. 57) In addition, they observed that the Rideau Canal “is particularly important in international terms because it is the only canal dating from the great North American canalbuilding era of the early nineteenth century that remains operational along its original line with most of its original structures intact.” (p. 70)

A Technological Ensemble which illustrates a Significant Stage in Human History

The Rideau Canal is a rare example of a canal that was built primarily for military purposes. Many canals in Europe and North America had some form of military use during their history. The Gotä Canal, discussed earlier, included military components and was viewed as having strategic importance in the defence of Sweden. For the most part, however, canals were built primarily for commercial purposes.

The idea that a canal could serve as an effective and secure military supply route began with the Royal Military Canal in Great Britain. This canal was constructed between 1804 and 1809 during the Napoleonic Wars, along the Romney Marsh in Kent. This 45,1-km excavated canal was considered a third line of defence against the possible invasion of south-eastern England, the Royal Navy and the system of Martello towers along the coastline being the two main lines of defence. The level of importance that British authorities assigned to the Royal Military Canal is questionable. Along its length, the canal was protected by nothing more than earthworks and defensible ‘station houses’. Its construction, however, signaled that British military and government leaders had grasped the concept of the use of canals as part of a defensive system. This understanding of the strategic role of canals was transferred to Canada for the construction of the Rideau Canal in the 1820s. It was envisioned by strategists as a major component in the defence of British North America against an attack from the United States of America. In contrast to the Royal Military Canal, it was heavily fortified with blockhouses, defensible lockmaster’s houses, Fort Henry and four Martello towers. The willingness of the British to invest enormous financial resources in the construction and defence of the Rideau Canal clearly demonstrates its fundamental importance in the on-going rivalry for control of the northern half of North America.