Funny thing is that those trails are in the mountains in Kananaskis provincial park. Even Banff and Canmore got flooded. We had a whole combination of things that caused the flooding - ground already saturated from runoff and above average rainfall, high temps in the mountains, rain on top of the snow in the mountains, and a single day with around 200mm of rainfall. One of the trails we run goes straight up a hill and back down it and even it was damaged by all the water running downhill. Naturally since water takes the path of least resistance it tends to flow down the trails a lot.
It really is amazing how powerful water can be. All the bridges in those pictures cross over creeks that normally you can jump across or wade through and never get your knees wet. Seeing what the creeks carved out during the flood it's pretty obvious they would've easily killed anyone getting too close.