A Slippery History of Controlling Ice in the Great Lakes-St. Lawrence Basin

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Frazil is a fun word. It kind of sounds like Fraggle Rock (which reminds me of its awesome theme song) or Miss Frizzle from The Magic School Bus. But dealing with frazil ice was no fun for twentieth-century engineers designing public works on big rivers in northern North America.

“Frazil” takes its name from the old French word “fraisil,” referring to an accumulation of cinders. These fine ice spicules, discoids, or plates suspended in turbid supercooled water can form frazil slush or flocs that interfere with infrastructure, such as hydro dams or navigation locks .[1]

Ice on the St. Lawrence River in the 1950s (c) Dumas Collection, St. Lawrence University

The first studies of frazil ice anywhere seem to have taken place in the St. Lawrence River near Montreal in the middle of the nineteenth century.[2] Even though they were at the global forefront of ice science, controlling ice formation would prove to be an enduring challenge for hydraulic engineers designing water megaprojects in the Great Lakes-St. Lawrence basin.[3]

Ice bridge at Niagara Falls around the turn of the twentieth century © Library and Archives Canada

Niagara Falls has long been famous for its ice. Floes from Lake Erie would float down the Niagara River, plunge over the falls, and form into a thick mass at the base of the cataract. This “ice bridge” could be 40-60 feet thick. People from both sides of the Niagara border would congregate on the bridge for parties and festivities. Then, in 1912, the ice bridge broke free and several people perished. The transnational ice parties were consequently prohibited.

Historically, ice formation downstream in the St. Lawrence also had both benefits and drawbacks. It helped mobility in some ways (e.g., crossing the river over the ice) but impeded it in others, such as halting vessel navigation in winter. Ice also conflicted with the development of industrial and water power intakes.

As plans emerged over the first half of the twentieth century for hydro-electric developments in both rivers, as well as a deep waterway system in the St. Lawrence, engineers worried about how they could keep ice away from the hydro intakes in the winter and maximize the navigation season for the Seaway. The dams and control works were therefore designed in ways that could actually control the way that ice formed – or didn’t form.

Frazil ice was a particular concern. Many different theories were propounded to explain frazil ice. In 1928 McGill University professor H. T. Barnes, reputedly the first Canadian to focus on the science of river ice, published a book titled Ice Engineering which forwarded what became regarded as leading explanations for not only frazil ice but other gelid processes such as anchor ice.

But ice problems persisted, particularly as the number and size of hydro-electric plants in the region increased. Ice interfered with the hydropower intakes above Niagara Falls, and sometimes the ice wreaked havoc with the power stations in the gorge below the Falls. Ice took out the famed Honeymoon Bridge in 1938.

Beginning in the 1950s, decades of planning and binational negotiations came to fruition: construction finally began on the St. Lawrence Seaway and Power Project, as well as the Niagara remedial works and new power generating stations. and Many Canadian and American engineers, bureaucrats, and officials from Ontario Hydro, the Power Authority of the State of New York, and the U.S. Army Corps of Engineers worked on both. These technocrats changed and revised their blueprints and plans, and then revised them again and again, preoccupied by figuring out how to deal with, or diminish, ice.

Winter Construction on St. Lawrence Seaway and Power Project in the 1950s © Dumas Collection, St. Lawrence University

Revising engineering plans for hydraulic works in ways that accommodated seasonal ice formation speaks to the hybridity inherent in such designs. Organic elements were accommodated and factored into their “disguised design.”  They were incorporated as part of the infrastructure: i.e., the new envirotechnical systems they were creating would not work properly without ice formation or normal weed growth.

One of the major engineering advances associated with these huge undertakings was the extensive use of high-precision scale hydraulic models. These were particularly useful when it came to planning for ice control. In the models, for example, paraffin blocks were used to simulate ice. These would remain “the most credible engineering tool” for studying riverine ice formation until perhaps the 1990s, when computer modeling surpassed them.

Niagara model at U.S. Army Corps of Engineers Waterways Experiment Station in Vicksburg, Mississippi © International Joint Commission

 To deal with the many cases where they had only approximate knowledge of environmental conditions, engineers used the qualifying phrase “as nearly as may be” as a stand-in, or a sort of wild-card variable. When certain aspects of the project, such as ice formation, seemed beyond expert control, planners would ignore the problem and disclaim responsibility, labelling it an “Act of God.”

By the late 1950s, both the Niagara and St. Lawrence megaprojects were operational. But, in a subversion of  experts’ tendency to think they could control nature, both undertakings had problems with ice formation soon after their respective openings. (Here it seems apt to tweak an old aphorism: the best laid plains of ice and men often go awry). Immediately upon the creation of the St. Lawrence power reservoir, there were problems with ice congealing into “hanging dams,” a mass of ice composed chiefly of slush or broken ice deposited under an ice cover in a region of low flow velocity. These hanging dams reduced power output from the generating stations.

Robert Moses and other PASNY officials at site of St. Lawrence construction © New York Power Authority (formerly Power Authority of the State of New York (PASNY))

In the winter of 1961-62, unusually high ice levels caused significant problems for the power intakes at the Niagara power stations. Ice also caused almost $3 million dollars in shoreline damage that year.[7] Ontario Hydro and PASNY received permission to dredge and excavate high spots, shoals, and islands on which ice hung up, totaling about 161,000 cubic yards, and they bought ice breaking boats to ply the upper river.[8]

But it was apparent that more effective measures were needed to keep ice from blocking the power intakes at Niagara. Plans were developed for an ice boom to be set up at the mouth of the Niagara River.  It was approved in 1965 on a trial basis, and when it proved successful, it became permanent. (Ice booms were also installed across the St. Lawrence). Interestingly, since the boom at the mouth of the Niagara causes large ice fields to congeal in eastern Lake Erie, people subsequently complained that this prolonged the fields in the spring, thus affecting the local climate around Buffalo.

From an anthropogenic perspective, the primary benefit of reducing ice in these rivers was to prevent ice buildup at the water intakes for the hydro power plants. But messing with ice processes isn’t so hot from nature’s point of view. The removal of solid ice cover can disrupt a river’s chemical processes and ecosystem, and unnatural ice breakup can cause land scarring and other shoreline impacts. And there are other biophysical repercussions – ice cover prevents evaporation, for example.

In the decades after the St. Lawrence Seaway was opened, there were subsequent experiments and technological innovations to reduce ice formation and extend the winter navigation season for shipping. These included consideration of “ice bubblers” that were meant to prevent ice from freezing up shipping channels. Such engineering efforts did help reduce ice problems, although the St. Lawrence works remain vulnerable to above-average ice buildups. The Seaway is now effectively closed for only a few months, starting at the end of December.

Largely as a direct result of research and experiments on, and experience with, the St. Lawrence and Niagara rivers, the scientific understanding of many key principles of freshwater ice mechanics was well advanced by the 1960s, and was pushed even further during the 1970s. However, knowledge gaps and deficiencies persist when it comes to the formation and control of river ice. This is still a relatively inexact science even in the twenty-first century, with the unknowns and the knowns pretty much even.

Some of this material is taken from an article I’m working on concerning water and engineering uncertainty. I’ll admit, however, that this post is a kind of test to see whether I have enough on this subject to produce a full research article or book chapter focused primarily on ice. I know there is a rich historiography on ice in glacial and polar regions (which a chat with fellow NiCHE editor Tina Adcock made abundantly clear), but are there historians or historical geographers out there who have worked on controlling ice, particularly as it pertains to water control works, at more “temperate” latitudes?  Were these engineers truly global pioneers when it came to controlling ice? I’m also fishing for contemporary engineers or scientists to talk to, or collaborate with, who have expertise is in this area.

Finally, I’m wondering who else is working on “wintry” and “cold” topics? As has been pointed out by a number of Canadianists in various contexts (and highlighted by the “A Cold Kingdom” series here on The Otter) there has been, and remains, a noteworthy lack of theorizing about the importance and centrality of winter. While there are certainly exceptions, given the significance of winter in Canada – and the ever-rising interest in climate history among Canadian historians – it’s a little shocking that this topic has not garnered more attention among Canadian historians.[9] I’m thinking we need a conference and/or an edited collection on winter – indeed, some of us here at NiCHE have been starting to brainstorm such a project, so get in touch if this might be something you’d be interested in contributing to.


[1] B. Michel, “History of research on river and lake ice in Canada,” IAHR International Symposium on Ice, Quebec, 1981: Proceedings (July 27-31, 1981), 1-10.

[2] S. Beltaos and B.C. Burrell, “Hydrotechnical advances in Canadian rivers ice science and engineering during the 35 past years,” Canadian Journal of Civil Engineering, 42 (2015), 588.

[3] Michel, “History of research on river and lake ice in Canada”; Beltaos and Burrell, “Hydrotechnical advances in Canadian rivers ice science and engineering during the 35 past years.”

[4] IJC, Canadian Section, docket 68-2-5:1-9– St. Lawrence Power Application. Executive Session 1957/04 & 1957/10, IJC, St. Lawrence Power Development, Semi-Annual Meeting (Washington), April 9, 1957.

[5] This definition of “hanging dams” is taken from H.R. Kivisild, “River and lake ice terminology,” Ice and its action on hydraulic structures; I.A.H.R. Symposium Proceedings (September 8-10, 1979), 11.

[6] James L. Wuebben, ed., “Winter Navigation on the Great Lakes: A Review of Environmental Studies,” CRREL Report 95-10 (U.S. Army Corps of Engineers: Cold Regions Research and Engineering Laboratory, May 1995).

[7] Power Authority of the State of New York (PASNY), 1963 Annual Report.

[8] International Joint Commission (IJC), IJC Semi-Annual Meeting, Niagara Reference (1950) (Dockets 64, 74, and 75), October 3, 1963.

[9]  For example, mid-twentieth century historians, especially those of the Laurentian thesis vintage, invoked Canada’s forbidding size and climate, as has the CanLit crowd (e.g., the hostility thesis) and others, to explain Canada’s “character” with reference to its physical setting and vis-a-vis “the North”. Many historians have also focused on the Arctic and northern regions of Canada, such as the recent Ice Blinkthough the cold is arguably often taken as a given and not really probed. Some of the contributions to the 2016 Moving Natures collection get into wintry considerations (to her credit, I clearly remember Merle Massie admonishing us to pay attention to seasonality), as have several posts that have ran on The Otter in the past (such as this one and this one). And while I was putting this post together, the following exchange took place on Twitter: https://twitter.com/sandycassels/status/969236080238125056.




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Daniel is an Associate Professor in the School of the Environment, Geography, and Sustainability at Western Michigan University. He is an editor for The Otter-La loutre and is part of the NiCHE executive. A transnational environmental historian who focuses on Canadian-American border waters and energy issues, particularly in the Great Lakes-St. Lawrence basin, Daniel is the author or co-editor of six books on topics such as the St. Lawrence Seaway, border waters, IJC, and Niagara Falls. His book "Natural Allies: Environment, Energy, and the History of US-Canada Relations" was published in summer 2023. His newest book, an environmental history of Lake Ontario, will be published in September 2024. He is now working on a book about Lake Michigan and eventually hopes to eventually write a book on the environmental history of the Great Lakes. Website: https://danielmacfarlane.wordpress.com Twitter: @Danny__Mac__

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