Blasting Day on the Rideau River

It was “blasting day” at the mouth of the Rideau River today — an annual river-clearing effort designed to prevent spring flooding. All that was missing was Wile E. Coyote, the Roadrunner and the ACME-brand dynamite.

Every year, the city has to proactively clear the frozen ice on the Rideau River as an anti-flooding effort. To do so, they first blow up the ice by dropping explosives into it near the Rideau Falls, and then drop an “amphibious excavator” — a machine that is like a floating backhoe — into the river to clear the rest of the ice.

“It’s really important to get the ice out, because it eliminates ice jams,” explains Bryden Denyes, area roads manager with the city. “When you have an ice jam, that’s what bucks up the flow of water and creates flooding.”

A small crowd had gathered on the Sussex Drive Bridge on Saturday morning to watch the explosions. After several hours of preparation, the charges were set off, which broke loose large chunks of ice, which floated towards, and then over, the Rideau Falls. Over the day, crews would repeat this basic explosion-ice drift pattern until all the ice between the falls and the Minto Bridges are cleared.

Denyes says the city is planning to have its amphibious excavator in the water by Monday, if all goes well. The amphibious excavator will work its way up up the Rideau River, to Billings Bridge.

The whole blasting rigamarole takes on some extra importance this year. As many in the city may have noticed, there’s a lot of snow outside. All of that snow eventually becomes water in the spring. The risk equation is fairly simple: all that water poses a serious risk of flooding in the spring.

Hence the early efforts to break up the ice on the river. The city has to try to balance the need to break it up earlier than the first major melt, but not so far out that they have to spend a lot of time and effort having staff out “in steel-hulled boats to ensure that the water does stay moving,” says Denyes.

“We don’t want to wait too long,” says Denyes. “If we have a very fast melt, it’s extremely dangerous.”

Flooding risk is higher in years when the snow has more water content in it. “From what I understand, water content is fairly high in the snow, and we have a lot of snow on the ground this year,” says Denyes. However, it depends on a lot of other factors, too — namely, the speed at which the snow and ice melts and runs off into the river.

Asked how the explosions are created — more specifically, this reporter asked if the explosions were performed with red sticks of ACME dynamite, a là the Looney Tunes — Denyes said that the city uses “a special gel explosive” that “is designed for minimal environmental impact.”