CALGARY—Springtime in southern Alberta means flood season, and starting Tuesday, Calgary will be in the period of highest risk.

For now, the outlook is good, said Frank Frigo, the City of Calgary’s leader of watershed analysis. But that doesn’t rule out a huge, sudden storm — such as the one that led to widespread flooding in 2013.

“Things can change very fast,” Frigo said. “There’s not a lot of certainty.”

Read more:

‘Many millions of dollars’: Southern Alberta begins to tally flood damage

Alberta government pledges $13.5 million for Calgary flood protection

Tsuut’ina concerned Bragg Creek berming will flood land, impact water quality

Though the fact that Calgary exists along the banks of the Bow and Elbow rivers means risk is a constant, Calgary’s official flood season, when the city has historically received its largest rainfalls, lasts from May 15 to July 15.

With long-term forecasts showing a drier, more sweltering summer than average, wildfire risk may be more top of mind. The general trends, however, aren’t a guarantee. Rainfall in Calgary is notoriously hard to predict, Frigo said, due to the city’s proximity to the Rockies.

Usually, issues are caused by a combination several factors, such as heavy snowmelt, ice jams or a burst of rain that overwhelms storm systems. Because the Bow and the Elbow both flow through a steep drop from their source in the mountains towards Calgary, their water levels can swell rapidly.

This year’s higher-than-normal snowpack, a sudden rise in temperatures in Calgary last week and flooding in British Columbia and elsewhere in Alberta may have rattled nerves. However Frigo said the process is still fairly slow and not a cause for concern. River flows upstream of Calgary are higher than usual but still within an average range.

In fact, having more snowmelt flow slowly down from the mountains as the region heats up could be a good thing, Frigo said. Knowing more supply will be coming later allows city staff to lower water levels in reservoirs more aggressively, giving the city a greater capacity to handle runoff from a surprise storm.

“Right now, nothing that we can see is terribly concerning,” Frigo said.

Just in case, however, Frigo and the City of Calgary are constantly monitoring water levels and shifting forecasts. Frigo also suggests Calgarians check maps to know the chances of a flood in their neighbourhood — riverside areas such as Mission and Sunnyside, for example, are higher risk — and make sure they have emergency plans ready.

Revised estimates from the city in 2017 found damages from a flood on the Bow similar in scale to the one on the Elbow in 2013 would likely hit about $2.4 billion.

Loading... Loading... Loading... Loading... Loading... Loading...

The city and the province have invested millions on flood mitigation measures in Calgary, including a barrier to protect part of the downtown and stormwater sewer improvements.

Last month, the Alberta government pledged another $13.5 million to fortify the city. And this week, a city council committee approved a plan that would call for another large reservoir project upstream on the Bow River. Speaking to the committee, Frigo said the city aims to be ready for the effects of climate change.

According to University of Calgary climatologist Shawn Marshall, those effects have already begun. Though the city may not experience 2013-level floods every year, Calgarians can expect them to become more common over time.

“These extreme events are going to get more extreme,” Marshall said. “It’ll come back one of these years.”

With files from Matt McClure

Emma McIntosh is an investigative, environment and justice reporter based in Calgary. Follow her on Twitter at @EmmaMci

Read more about: