Why doesn’t the N.W.T. bomb ice to prevent floods?

In 1951, a man in Hay River, N.W.T., drowned after the town experienced devastating flooding.

The cause of the flooding was the same thing that caused the 2022 floods: ice jams. But a 1988 report by the federal government details that a flood prevention measure that had been used the previous three years wasn’t used in 1951. This was the practice of ice blasting, using explosives to blow up river ice and prevent jamming.

“Because of the flooding in 1951, an extensive blasting program was undertaken in the spring of 1952,” the report said.

The first mention of blasting in the report is in the 1940s, but it’s unclear when exactly it was discontinued — it’s not currently used by the N.W.T.

However, it is still used in several other jurisdictions, including Ottawa.

Blasting on the Rideau River

Bryden Denyes is the area manager for roads services with the city of Ottawa.

He’s been in charge of Ottawa’s blasting program for eight years. This takes place in the spring and is done to protect 900 homes along the Rideau River — in comparison, the N.W.T. has nine communities at risk of flooding, including the territory’s second-largest, Hay River.

Denyes said they locate areas where ice could potentially jam, often near bridges.

“So a shallow area with, say, a natural pinch point where the shoreline narrows is an area we definitely watch because you can have, potentially, some ice jams there depending on the thickness of the ice and how fast the flow is,” he said.

Denyes said in all the years he’s run the program, there’s never been flooding from ice jams, just some due to sheer volume of water.

The task can be dangerous, involving explosives and ice, but Denyes said the staff monitor the ice and ensure the blasting is done proactively and not in a manner that could damage infrastructure.

“Our staff are trained specifically how to deal with these explosives,” Denyes said.

In terms of environmental impact, Denyes said the city works with conservation partners to ensure it isn’t detrimental to ecosystems. He added the city is also trying to use less explosives and more mechanical tools to break up the ice, including an amphibious excavator.

CBC News reached out to the federal Fisheries Department on the risks of blasting in the N.W.T., but didn’t receive a response.

Unpredictability

The Rideau River is significantly smaller than many of the rivers that present flood risks to the N.W.T., but Denyes said he believes blasting can be used on any size of river — it’s a matter of having the right tools and training to complete it.

“You have to really have that knowledge of what that river system is, the infrastructure you’re dealing with, and really you’re looking at your flows, how thick your ice is,” he said.

Jay Boast, a spokesperson for the Department of Municipal and Community Affairs, said in an email, “due to the unpredictability of ice and flooding in the N.W.T., flood mitigation tactics would have to be community specific and would require feasibility studies prior to initiating a measure like blasting.”

He said currently the N.W.T. “is focusing on better understanding flood risk to N.W.T. communities through flood mapping efforts.”