Ice expert says Yukon break-up conditions tough to predict

While ice jams are a normal occurrence in the Yukon, each spring the risk they pose varies.

To understand more about Yukon's risk this year, Yukon Morning host Elyn Jones spoke to Benoit Turcotte, a senior researcher at YukonU Research Centre. He's alsoan expert on river ice.

In places like Dawson City, Mayo and Carmacks, spring breakup often means ice jams which can lead to flooding, said Turcotte.

"Each river has its own personality and it's very hard to predict what will exactly happen. Of course, the timing this year will probably be delayed," he said.

"We hope that it will be a smooth melt despite the fact that there's a lot of snow to melt and at specific locations."

A jam is when ice accumulation creates a "back water." Water levels rise upstream because there is less capacity for the river to drain.

Ice jams usually need a rise in runoff to take place, which pushes on the weaker ice cover, which accumulates against obstacles, he said.

Heavy engineering, like building a dam, can store all of the water to allow ice to melt in place downstream but it's not worth the economic, political or environmental price, he said.

The more reasonable option is to weaken the ice cover at specific locations by breaking it or drilling holes.

Ideal melt

In an ideal break up, the melt is gradual, and freezing at night reduces runoff, said Turcotte.

"Rain is not welcome. We would like partially sunny days, but especially freezing at night."

If there is melting during the day, which eases at night, that will be a more "gentle" melt than if Yukon experiences high temperatures.

Manipulating the melt is a 'dangerous task'

An ice jam could produce water levels to rise anywhere from 30 centimetres, like what is seen in downtown Whitehorse right now, up to 10 metres or more, said Turcotte.

But human intervention is somewhat ill-advised, he said.

"The science is not there, especially for large rivers," he said.

Breaking the ice up beforehand is a "dangerous task," said Turcotte.

"It could work, but it's risky. The best approach right now is to actually give forecasts so that people can prepare for it," he said.

Ice and snow pack influence breakup conditions

This year, there are locations where ice jams could be more frequent.

In Yukon, that includes the Klondike River where " there's always a small ice jam here and there, sometimes very large ice jams."

There was higher river ice formation in the fall and high rivers in the summer.

"They're really thick, so that doesn't help," he said.

There is considerable snow pack in southern Yukon, like the Liard River but in that region, ice jams are less likely, he said.

This spring, Turcotte anticipates high flow in small creeks and for southern lakes to have high water levels, a situation that Yukon Energy is taking very seriously, he said.

Turcotte said Whitehorse residents, for example, should be more worried about snow melt drainage than flooding from the Yukon River.

The Yukon Government has a team of forecasters to look out for potential flooding, he said.

"What I can see, and they would probably say the same thing, is that this year doesn't necessarily look good,"Turcotte said.

"People will hate me to say that, but to avoid significant ice jams, we need that cold weather to continue for a while and for spring to be delayed."