The river gets terrifyingly high every June, but there isn't usually too much rain. This spring has been like Seattle, it has been cold and wet with the usual seasonally high river.
Calgary, the land that urban planning forgot, is stuck on stupid when it come to these things. There is way too much development along the river and much of it is pretty high density and it is the official policy of the city to just keep cranking it up further and further. Because what goes better in a flood plain with a high water table than a high-rise with half a dozen floors of underground parking?
When the railroad came to town it followed the rough contour of the river valley and everything since was built out from there, rather than a mile in either direction at much higher elevation.