Mayor Don Iveson is not surprised Yellowhead underpasses flooded during Wednesday night's storm.

Firefighters rescued six people out of three vehicles stuck in underpasses after a flash flood, which also caused a sinkhole in the area.

"Most of the pumps and drainage systems in some of those overpass areas, they can handle a one-in-10-year event," Iveson said. "I don’t know what last night was but it was much more serious than that. It's normal for this to happen."

Underpasses on Whitemud Drive flooded in 2016.

The mayor predicts rainfall will get more intense due to climate change, and the city will continue looking at improving its infrastructure to be prepared.

"We looked at underpasses a few years ago," Iveson said. "Some of them, we may be able to alleviate flooding like this; others it may be prohibitively expensive."

EPCOR said it takes half a metre of water to cause problems for most vehicles.

Westbound traffic on the Yellowhead will be rerouted until the roads are fixed.