The “giant’s staircase”

The “giant’s staircase”

It’s hard to gauge the dimensions of this enormous spillway. Its nickname, the “giant’s staircase,” is not for nothing: each of its 10 “steps” is 122 m (400 ft.) wide, 150 m (492 ft.) deep and 10 m (33 ft.) high—the same height as a three-storey building. The total length of the spillway chute from deck to riverbed is 1.5 km—nearly a mile!

According to engineers, the spillway can discharge 16,280 cubic metres (4.3 million gallons) a second when the reservoir is full, five times the mean discharge of the Robert-Bourassa power plant. But this is exceptional—an event that is only likely to occur once every 10,000 years.
Photo: Jean-Pierre Huard