Alberta will build a major reservoir in Springbank to protect Calgary from Elbow River flooding, the province has announced.

The move is sure to upset area landowners opposed to the project, but was welcomed by Calgary Mayor Naheed Nenshi.

"It's a good day," the mayor told reporters at a press conference announcing the project's selection. "We are very, very supportive of the creation of the Springbank off-stream reservoir."

Environment Minister Shannon Phillips also announced "local mitigation" further upstream from the Springbank project to help protect the communities of Bragg Creek and Redwood Meadows.

Costs

The province is committing $297 million, in total, to mitigation projects on the Elbow River.

Nenshi said the Springbank reservoir is expected to "attenuate" 81 per cent of the water that Calgary saw from that waterway during the 2013 flood.

Combined with upgrades to the Glenmore Reservoir the city also has planned, the mayor said the reservoir would protect Calgary from a 2013-level event on the Elbow in the future.

Springbank vs. McLean Creek

A dry dam farther west at the confluence of McLean Creek and the Elbow River had also been under consideration.

The plan was favoured by some Springbank residents who are unhappy about the prospect of using private land for a project they say wouldn't even protect Bragg Creek and Redwood Meadows.

But Phillips said the Springbank reservoir, combined with local upstream mitigation to protect those communities, was deemed the best option of several being considered for the Elbow by Deltares — a Dutch research group.

"This option will protect everyone involved much quicker," Phillips said.

She said the dam would more expensive and come with a "very real risk of catastrophic failure during the construction phase," in addition to more damage to an environmentally-sensitive area.

Politics

Calgary was devastated by billions of dollars in flood damage in 2013. (Jonathan Hayward/Canadian Press)

Phillips claimed her government was acting quickly with this "difficult decision" because Calgary can't wait for flood protection.

She accused the previous PC government of "dilly-dallying" on the file in the wake of the catastrophic 2013 flood, which caused billions of dollars of damage in the city and marked the costliest natural disaster in Canadian history.

Rick Fraser, the PC's environment critic, dismissed Phillips' criticism, noting it was the previous government under premier Jim Prentice that initially proposed going with the Springbank option.

"A lot of the heavy lifting was done," Fraser said. "Really, it's the work that we did."

Flood history

Powerful rains drenched regions of Alberta in June 2013, causing the worst flooding in decades. Rivers bulged and overflowed on to city streets, forcing tens of thousands of residents to evacuate their homes. The flooding caused as much as $6 billion in damage — the most costly disaster in Canadian history.

Several flood prevention and control projects have been on the drawing board since the disaster struck.

The previous Tory government had said it would go ahead with a controversial plan for an off-stream storage site, or dry reservoir, in Springbank west of Calgary that would divert flood water from the Elbow River.

In June, city council came out in support of a plan to build a flood diversion tunnel under Heritage Drive, linking the Glenmore Reservoir with the Bow River, at a cost of about $500 million.

Last month, the City of Calgary came up with a list of short-term flood resiliency projects it wants the province to help fund.

Eight projects estimated to cost $50 million are on the list, including berms for the Bonnybrook Wastewater Treatment Plant and the Calgary Zoo, and a new pumping station to prevent storm drains from backing up into the Sunnyside area north of the Bow River.