Calgary issues boating advisory for the Bow River, parts of Banff under flood watch

The City of Calgary is issuing a boating advisory for the Bow River, and flood-watch advisories have gone into effect upstream of Banff including Lake Louise and the Pipestone River, but serious flooding 'highly unlikely' elsewhere, expert says.

Recent heat has led to rapid melting of snowpack in the mountains

Rafters float down the river in Calgary in August 2018. (Pat Fogg/CBC)

The City of Calgary issued a boating advisory for the Bow River Friday, as water levels have risen amid high temperatures and a rapidly melting snowpack in the mountains. 

Calgarians are advised against boating and all other watercraft activities on the Bow River due to higher expected flow rates and the current forecast. 

The city says it expects high flows to continue due to snow melt and the possibility of thunderstorms in the area throughout the weekend.

No flooding over riverbanks is expected.

Elsewhere, flood-watch advisories were put into effect on Friday morning for the Bow River upstream of Banff including Lake Louise and the Pipestone River, but an expert says it isn't the time to worry about serious flooding in Alberta — unless heavy rain occurs.

John Pomeroy, the Canada Research Chair in Water Resources and Climate Change, told the Calgary Eyeopener on Friday that temperatures in the Bow Valley reached about 30 C in the early days of June and caused snow to melt at a "remarkable rate."

Pomeroy said this helped raise water levels, which are up as much as a metre in the Bow River and Elbow River in the last week.

However, he said that snow melt would have to continue in conjunction with heavy rainfall in order for major flooding to occur.

"We get concerned if there's a forecast for hundreds of millimetres of rainfall coming at the same time this snow is melting, and that's what happened to us in [the floods of] 2013," Pomeroy said.

"We have some rain in the forecast … and that will increase stream flows for sure, but it's unlikely — highly unlikely — to trigger any flooding event."

Be cautious on the Bow, expert says

The heat wave most of Alberta experienced earlier in the week is expected to abate in the Bow Valley, where temperatures are expected to dip below 20 C on Saturday and stay there for about two weeks.

And although some rain is expected, the current forecast is for just 10 to 30 millimetres over the weekend, Pomeroy said, which doesn't represent a major flooding threat. 

Alberta Environment data suggests rivers will peak Friday or Saturday, but Pomeroy also warned Albertans that rivers will be cold and moving fast for some time, which means those looking to enjoy the weather with a float down the Bow should be cautious.

The Town of Banff also issued a warning that the banks of the Bow River are unsafe due to rising water levels and debris.

"You have to be extremely careful," Pomeroy said.

"The river's flow is turbulent, which means the velocities can increase dramatically over short distances, and typical velocities in rivers like the Bow right now are faster than humans can swim."

With files from the Calgary Eyeopener and Lucie Edwardson


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