In their laboratory simulator - one of kind in Canada - the Polytechnique Montréal team reproduces the conditions under which ice forms and ice jams build up  (Photo : Professor Shakibaeinia' laboratory)

Every spring (and sometimes even during winter!) thaw conditions cause ice jams to form on rivers throughout Québec. The phenomenon can have dramatic consequences for shoreline residents, synonymous as it often is with flooding. Solutions for mitigating the impacts of ice jams do exist, and a team at Polytechnique Montréal is testing them using digital tools and an ice-behaviour simulator, an apparatus found nowhere else in the country.

When the thermometer reads minus 15 or 20 degrees Celsius, it can be difficult to imagine winter ever ending… but spring does eventually get here! Other seasonal certainties include one less likely to be cause for rejoicing: springtime water levels rising.

Melting snow and ice cause rivers to swell, and most of the time, the phenomenon is spread out over months, and so has few adverse impacts. Yet the results are far different when the spring thaw takes just a few days. In the latter case, ice that’s been forming all winter long breaks up abruptly, and large chunks float downstream along watercourses; when they encounter an obstacle, ice blocks accumulate, and presto – you’ve got an ice jam.

Ice jams behave like regular dams do, they hold back water. The usual outcome is that the river breaches its banks upstream from the jam. Flooding can also occur downstream if the jam suddenly clears and a large volume of water is released all at once. This is what happened in the Beauce region of Québec in the spring of 2019.

So, controlling ice-jam formation can eliminate a whole host of worries.

Searching for the best solution

Through the years, various strategies have been developed and adopted to prevent drifting ice from accumulating and forming jams near inhabited areas. For example, natural as well as artificial structures that are obstacles to ice can be altered, or simply removed from rivers. The pillars of new river-intermingling structures are designed to deflect ice and prevent it from accumulating.

In some locations, ice-control structures resembling dams are built upstream from inhabited areas to control river flow at critical points, and the height of the ice-control structure is raised or lowered depending on the season. Nets can also be added, which hold back ice while letting water flow past. These structures also keep frazil ice (loose, needle-like ice crystals that are all mixed up and don’t float) and solid ice upstream from municipalities, away from critical infrastructure.

How can optimum locations to build such structures be determined? What design should they be to effectively control ice at the lowest cost? These are the sorts of questions being tackled by Ahmad Shakibaeinia, Associate Professor of Civil, Geological and Mining Engineering at Polytechnique Montréal.

In his laboratory in the main building at Polytechnique Montréal, Professor Shakibaeinia and his team are helping municipalities, government departments, and companies they work with to make the best possible decisions to manage the formation of ice jams along Québec’s rivers.

There are no workspaces or electronic assemblies in this lab: it looks more like a warehouse space, and among other things it’s home to a huge refrigerated container capable of producing temperatures as low as minus 23 degrees Celsius. Inside is an ice-jam simulator, consisting of a long steel channel and a transparent polymer (plexiglass).

“This apparatus is unique in Canada,” Professor Shakibaeinia proudly explains. “It allows us to conduct experiments on ice formation and breakup by reproducing the conditions in the watercourses we study.”

The first step of the process is the behaviour of ice at a given location is modelled using a computational tool developed by the Polytechnique team. It considers a range of variables including ice thickness, fragment size, river flow and dimensions, and physical constraints about the riverbed area, in order to establish the likelihood of ice jam formation.

“We then use the simulator to validate our modelling. Once a model is validated, we turn to the simulator to look at how the ice behaves in the presence of ice-control structures,” explains Professor Shakibaeinia, who is also the holder of the Tier 2 Canada Research Chair in Computational Hydrosystems.

A high-speed camera system tracks and captures the movements of each fragment of ice along the water’s surface. This data enables the team to determine what proportion of ice is held back by the control structure. Additional tools measure the force applied to structures introduced into the simulator, while others measure the volume of water flowing out from it.

“By working this way, we can determine, for example, the optimum distances at which to place the piers of an ice control structure, and the optimum water flow for containing an ice jam at that location,” Professor Shakibaeinia adds, pointing out that the project is being conducted in collaboration with a team led by Professor Tadros Ghobrial (Civil and Water Engineering at Université Laval).

 

Learn More

Professor Ahmad Shakibaeinia expertise
Tier 2 Canada Research Chair in Computational Hydrosystems website
Experimental and Numerical Engineering Water Flow Group (GENIE-EAU) website
Department of Civil, Geological and Mining Engineering website