Traffic And Other Considerations

Traffic

The main types of cargo carried through the canals have been mentioned in connection with the special cargo vessels. Many other types also are carried and the total quantities may be seen from the table of Canal Cargoes for the year 1953. (Table 4).

Fig. 35 Graph Showing Total Traffic Through the St. Lawrence Canals, 1931-1953

Fig. 35 shows the total traffic through the canals since 1931. From 1931 to the beginning of World War II the volume was generally increasing but fell off very steeply in 1939-1940. This was due largely to the sudden loss of the European wheat markets and traffic fell to its lowest level in 1944.

War Service

During this period many of the canal vessels were transferred to duties in the coasting and other trades. Many canallers were also requisitioned by the Ministry of Shipping and sent overseas, most of these being bulk carriers which were used for the carriage of bauxite from the West Indies to Canada.

At one period in the war the East coast and Gulf of St. Lawrence became so hazardous for these vessels that the bauxite was shipped in barges via the New York State Barge Canal to Oswego and thence by canaller to Port Alfred on the Saguenay River in Quebec for processing at Arvida.

Although few canallers were designed for open sea work they were very successful in the wartime bauxite trade and carried large quantities of this vital material.

Several canallers were operated as military supply vessels in Europe and one of these, the Waterloo, was eventually scuttled to block an entrance during a raid on an enemy port.

After the war the grain trade returned to normal and the total traffic figures again began to increase, a further impetus being given by the opening of the Labrador iron ore trade.

Ice Conditions

There are two main restrictions to ship traffic along the St. Lawrence route, the first being the lock dimensions already referred to and the second the short navigation season. The whole navigation system on the river and the lakes is, of course, subject to this same latter difficulty but in the case of the canal route the situation is aggravated by the numerous locks. The St. Lawrence canal system has a total of 22 locks between Montreal and Lake Ontario, each of which becomes a major problem when ice begins to form in the canals. Some time before the ice on the open water is thick enough to hinder navigation, slush and small pieces are carried into the locks by the movement of the vessels. This ice collects in the vee behind the gates which cannot then be fully opened into their recesses until the ice has been removed. A second difficulty is the ice which forms on the faces of the gates themselves, caused by thin streams of water flowing down as the gates are opened. This ice prevents the gates from closing watertight and must be chipped off by hand before the locks can be filled.

In the Spring when the ice is beginning to break up, pieces of ice, moved by the ships, create similar conditions so that the canal has to be fairly clear before traffic can commence.

These complications result in a shorter navigation season than on the lakes or in the Gulf. The canal system usually closes between the 5th and 10th of December and reopens about the 20th of April, leaving a season 15 to 20 days shorter than on the upper lakes. These dates vary by a few days each year according to the particular conditions which apply.

The closing of the season often develops into a race against the ice and a sudden drop in temperature may catch vessels in the canals. Typical of this condition was the end of the 1955 season which was unseasonably cold and serious ice jams occurred in the Lachine canal, with the result that a few days before the closing date over 60 ships, including many ocean-going vessels, were waiting to pass through the locks. A fortunate rise in temperature allowed the ice to be cleared and the ships passed into open water.

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This paper was presented at a meeting of the Society of Naval Architects and Marine Engineers and is reproduced with permission.