Partially built Sunnyside flood barrier expected to be completed by spring 2026

A sheet metal wall running along Memorial Drive in central Calgary has already drawn questions from residents in the area.

Will it permanently block their view of the river? Is it some kind of public art project?

In both cases, the answer is no. The roughly 2.4-kilometre wall is part of the city's flood-mitigation effort, and is designed to keep rising water of the Bow River safely away from buildings in the Hillhurst and Sunnyside neighbourhoods.

Construction began on the project last year, as a response to flooding that hit the area in June 2013. Project manager Amy Stansky said a low-lying neighbourhood like Sunnyside can flood when the Bow River's flow rate is as low as 600 cubic metres per second. During the 2013 flood, the river was flowing at a rate nearly three times as fast.

"A lot of the area that is next to the river valleys can be more susceptible to overland flooding and groundwater seepage, and Sunnyside is one of those spots," said Stansky.

"We really want to protect Sunnyside from what we saw happening in 2013."

In some areas where the metal could impede groundwater too heavily, the city is using concrete instead, which takes up more space during construction, but will be similarly narrow as the rest of the barrier when it's built.

Stansky said the barrier, which was estimated by the city to cost $50 million last year, was chosen partly because its narrow size is less disruptive than other flood-mitigation options like an earth berm. While roughly 200 trees were cut down for the Sunnyside barrier, a berm would have required losing between 700 and 900 trees, Stansky said.

"We were able to save a lot of these big mature trees and preserve the park-like feel of this area," Stansky said.

Work is still needed to drive the wall even further into the ground, which will result in a final product that doesn't impede residents' views of the river as much. When it's completed, the wall's average height is planned to be 1.2 metres, reaching up to three metres at its tallest by the Prince's Island pedestrian bridge.

During the barrier's construction, the city is also improving seating areas, widening the pathway for cyclists and pedestrians, and turning the barrier into bench seating in some areas, Stansky said.

The project is expected to be completed next year, with a functional flood barrier in place by the spring.