Critères en vertu desquels l'inscription est proposée

1. Critères en vertu desquels l'inscription est proposée
2. Proposition de déclaration de valeur universelle exceptionnelle
3. Analyse comparative
4. Authenticité

A. Criteria under which inscriptions proposed

Criterion (i): The Rideau Canal is a masterpiece of human creative genius.

The Rideau Canal is a masterpiece of human creative enius, in its concept, design, and engineering. To build the canal, Lieutenant-Colonel John By, he canal’s principal designer, had two options. The conventional and proven option was to use excavated channels of considerable length to link existing waterways that were navigable, bypassing falls, rapids, swamps and rocky shallows. John By dismissed this approach as being too expensive and time-consuming, given the terrain, geology and configuration of the lakes and rivers. Through a fundamental stroke of creative genius, he envisioned another option to join the watersheds of the two river systems, the Rideau and the Cataraqui: a slackwater canal, executed on a monumental scale. His decision to build a slackwater canal was highly innovative – and technologically risky. The slackwater system was virtually untried at this time in Europe. Slackwater techniques on a limited scale had been attempted in North America, but none of these canals was near the complexity of what John By conceived for the Rideau Canal.

Navigation of the Rideau and Cataraqui rivers was impeded by numerous rapids and waterfalls. © Parks Canada

The slackwater design that John By envisioned for the Rideau Canal required a very large number of embankments and high dams in order to inundate shallows, swamps, and rapids, and thus create a series of impoundments of sufficient depth to allow navigation along the full length of the canal. This approach dramatically reduced the requirement for extensive excavated channels, thereby reducing costs and construction time. The Corps of Royal Engineers responded with designs for an ingenious system of engineering works, including seventyfour dams and forty-seven locks at twenty-four lockstations, allowing vessels to ascend 85 m to the summit of the canal from the Ottawa River, and then descend 50 m to Lake Ontario.

The lock, weir and 400-m-long earth embankment dam at The Narrows created a slackwater section allowing navigation to Newboro Lockstation. © Parks Canada

One of the problems that plagued slackwater canals and discouraged their use was the difficulty of controlling water levels on such a system. Once again, John By and his engineers created an imaginative and effective solution to the problem. They included in the plan for the canal a system of dams and embankments that created lakes to serve as reservoirs, allowing water to be stored to supply the canal during dry summer months. Conversely, during periods when excess water was in the system, such as in the spring or during heavy rainfalls, the reservoirs allowed water to be held back and released gradually, preventing damage to engineering works.

The genius of the slackwater canal solution to the construction of the Rideau Canal was equaled by John By’s foresight regarding the future dominance of steamboats as a mode of transportation. The specifications for the canal that he was given called for locks sufficient in size to accommodate Durham boats, flat-bottomed vessels propelled by sail or oars. Soon after his arrival in Canada, Lieutenant- Colonel By sought, and was given, authorization from his superiors to build locks to accommodate vessels using the newly emerging technology of steam power. The Rideau Canal became one of the first canals in the world designed specifically for steam-powered vessels.

Criterion (ii): The Rideau Canal exhibits an important interchange of human values, over a span of time or within a cultural area of the world, on developments in technology.

Building the Rideau Canal and its fortifications required adapting existing European technology to the North American environment and to the specific circumstances and geography of its setting. The experience gained in the engineering of canal works and fortifications for the Rideau Canal advanced these technologies to a new level.

The Transfer of Canal Technology

The concept of canals and their engineering principles and technology were well known in Europe prior to the construction of the Rideau Canal. Canals had emerged as important commercial transportation systems in the mid-18 th century, closely associated with the Industrial Revolution. The Rideau Canal was built using canal technology developed in Europe and transferred to North America. However, the existing European canal technology was adapted and advanced on the Rideau in order to build a slackwater system on a scale previously untried.

There were three areas of canal-building technology in which significant adaptation and technological advancement occurred during the building of the Rideau Canal – surveying methodology, lock engineering and dam engineering.

Surveying Methodology

The Corps of Royal Engineers brought European surveying methodologies to North America for the construction of the Rideau Canal. The adaptations they made in the application of the transferred technologies, to meet the exigencies of particular local conditions, was an outstanding technological advancement.

The Royal Engineers developed truly innovative methods for orienting a survey and taking levels.

First, a directional fire technique was adopted, enabling the surveyors to orient a survey over great distances in the dense forest. Second, they used compass traverses rather than conventional theodolite traverses, which were impossible in the forest. Third, so-called ‘flying levels’ were taken of the rise or fall of the land, based on the vertical position of a light placed at an established height on the leveling staff. And fourth, with the impossibility of running theodolite traverses, crosssections of the terrain were mapped using a grid survey on compass bearings. These maps allowed the canal to be routed to take advantage of the natural terrain, thereby minimizing tree clearing, excavation and embanking work.

These innovations eliminated a great deal of difficult, costly and time-consuming labour in clearing away forest growth to obtain clear sight lines. They enabled canal works, stretching throughout a 202-km-long wilderness corridor, to be laid out in a remarkably short period of time during the winter of 1826 and spring of 1827.

Lock Engineering

The second important area of the transfer of European technology where the Royal Engineers took an established technology to a new level was in lock engineering. Engineering principles transferred from Europe were used for the construction of the Rideau. The lock-building achievement on the Rideau was, however, the design and construction of locks capable of withstanding the unprecedented force of water pressure resulting from the high lifts and large lock chambers required for a slackwater canal built for steamboats.

The Rideau was one of the first canals designed to accommodate steamboats. © Parks Canada

Typically, locks on European canals had a lift of 2,4 m to 3,0 m. To overcome the terrain on the route of the Rideau Canal, John By was faced with the choice of building numerous locks with low lifts or fewer locks with high lifts. To minimize costs and construction time, he opted for high lifts and, therefore, fewer locks. For example, rather than construct six locks or more at Jones Falls, to overcome a rise of 18,4 m, four locks were constructed, with a maximum lift of 4,6 m. In addition, to accommodate steamboats, the lock chambers had to be significantly larger than those employed up to that time on European and North American canals. The locks on the Rideau Canal were 37,8 m long and 9,1 m wide. In comparison, the contemporary Blackstone Canal in the United States of America had locks 21,3 m long and 3,1 m wide.

The locks of the Rideau Canal were significantly larger than those found in Europe at the time. © Parks Canada

The large size of the lock chambers of the Rideau Canal required the design of massive lock gates. © Parks Canada

The force of water pressure created by the high lifts and large size of the locks required engineering advancements in design and construction. Lock walls, gates, sluice tunnels and wing walls were all designed and constructed to carry significantly greater force than in earlier canals. In later years, these advancements in lock engineering were applied elsewhere in the construction of locks, such as those built on the St. Lawrence River in the late 1840s.

Dam Engineering

The third major area of technology transfer where John By and his engineers took an established technology to new levels during the design and construction of the Rideau Canal was in the engineering of dams. The slackwater system used for the canal required a large number of dams to inundate shallows and rapids. Individually, and as a system, these dams represented a considerable advancement in dam-building technology.

The Jones Falls Stone Arch Dam was an astounding feat of engineering. © Parks Canada

The massive Jones Falls Stone Arch Dam well illustrates the adaptation and advancement of European dam-building technology to meet the challenges of the Rideau Canal. To deal with the deep gorge, falls and rapids at Jones Falls required a dam with a span 107 m, to a height of 19 m, double the height of any dam in North America at the time. John By’s design integrated stone masonry dam technology with the technology of clay core earth dams, to cope with the incredible stresses on a structure of this scale. The Jones Falls dam’s international importance was recognized in the International Canal Monuments List, prepared under the auspices of The International Committee for the Conservation of Industrial Heritage (TICCIH).

To establish the impoundments of water that were required for the Rideau Canal’s slackwater system, sets of dams were often required at lockstations. The engineering of such dam systems involved the use of earth embankment dams, stone masonry dams and stone masonry water control weirs in combination. The system of dams at Kingston Mills illustrates John By’s mastery of traditional European dam building technology and his advancement of it. He achieved the impoundment of the 15.6-km stretch of water above Kingston Mills through a system of dams that included two earth embankments dams, 1,4 km in total length, a 120-m long stone masonry arch dam, natural geological features, a water control weir, and the upper lock.

The Transfer of Military Technology

The construction of the Jones Falls dam was a complex feat of engineering. © Parks Canada

The slackwater system often entailed the construction of a system of dams, as at Kingston Mills. © Parks Canada

The fortifications built at Kingston to defend the mouth of the Rideau Canal represent the transfer of European military technology to North America. Fort Henry was, however, a considerable advance over earlier fortifications built in British North America. Major citadels built in the 1820s at Halifax and Quebec City conformed to the traditional Vauban design of fortification. For Fort Henry, engineers abandoned this approach, adapting newer Prussian thinking to create a fortification that was unique in British North America. The result was a powerful and compact fort, well suited to the topography of Point Henry.

The four Martello towers, built between 1846 and 1848 to protect Kingston Harbour and the entrance to the canal, were designed by Lieutenant-Colonel W. Holloway of the Corps of Royal Engineers. Martello towers had been adapted by the British from round tower fortifications found on the European continent, and built to protect the English coastlines during the period of the Napoleonic Wars. They extended their use to British North America, eventually building twelve towers in total, the last being the four in Kingston.

Fort Henry was innovative in design and planned to be a self-defending redoubt. © Parks Canada

Murney Tower, with ditch, counterscarp, glacis and caponiers, was a small self-contained fortress. © Parks Canada

The Kingston towers were the culmination of decades of British development of round masonry tower design and construction. All incorporated significant innovative structural and external features to address defensive weaknesses previously associated with this type of fortification. Of the four, Murney is the best example of the final phase in this process of evolution. Like traditional Martello towers, it consisted of two floors with a gun platform protected by a high parapet. It was, however, surrounded by a deep ditch with a dry masonry counterscarp. Tower and ditch were protected by a rubble-filled glacis. Four massive caponiers projected from the base of the tower, enabling defenders to fire in to the ditch. All the Kingston towers were innovative in design and of a high quality of construction. Murney is, however, regarded as the most sophisticated Martello tower to be built in British North America.

Criterion (iv): The Rideau Canal is an outstanding example of a technological ensemble which illustrates a significant stage in human history.

The Rideau Canal was built at a time when two powers, Great Britain and the United States of America, vied for the control of the northern portion of the North American continent. This significant stage in human history resulted in the creation of two distinct political and cultural entities, Canada and the United States of America. One of very few canals in the world built primarily for strategic military purposes, the Rideau Canal and its associated defensive works were critical elements in the global strategy developed by Great Britain immediately after the Napoleonic Wars in Europe and the War of 1812 in North America. The two wars demonstrated to British political and military leaders the importance of a military defensive system to protect their far-flung global interests.

The view from Fort Henry of the naval dockyards, the entrance to the Rideau Canal and the town of Kingston. © Parks Canada

In North America, the key to the defence of Canada lay in a transportation route from Montréal to Lake Ontario, more secure than the St. Lawrence River, to supply the vital naval base at Kingston. When the British Government examined the defence of British North America, two Canadian projects were sanctioned: the Rideau Canal and the Kingston harbour fortifications.

This was the context for the British decision to invest enormous financial resources in the construction of the Rideau Canal and its associated fortifications. At stake was the future security and expansion of British political and commercial interests on the North American continent. This was also the context for approval of locks large enough to accommodate steam-powered vessels. As historian Robert Passfield remarks, “steamboat navigation provided the British forces with a speed of movement superior to that enjoyed by the Americans. Had the Rideau Canal not been completed, or had it been constructed as a small gunboat canal, the whole of the military’s efforts at engineering the defence of Canada would have been undermined.”

The blockhouse built to protect the locks at Merrickville. © Parks Canada

The ultimate success of this strategy was fundamental to the growth of colonial Canada and, subsequently, its development as an independent nation, spanning the northern half of the continent.