In 1969, the Army Corps of Engineers accomplished an awesome feat: They turned off Niagara Falls. They did it to clean up the area, and check for structural integrity. Here are pictures of this bizarre episode in structural engineering history.
These pictures were taken by tourists who visited the dry falls in 1969. Environmental design blog Mammoth explains the context:
For six months in the winter and fall of 1969, Niagara's American Falls were "de-watered", as the Army Corps of Engineers conducted a geological survey of the falls' rock face, concerned that it was becoming destabilized by erosion. During the interim study period, the dried riverbed and shale was drip-irrigated, like some mineral garden in a tender establishment period, by long pipes stretched across the gap, to maintain a sufficient and stabilizing level of moisture. For a portion of that period, while workers cleaned the former river-bottom of unwanted mosses and drilled test-cores in search of instabilities, a temporary walkway was installed a mere twenty feet from the edge of the dry falls, and tourists were able to explore this otherwise inaccessible and hostile landscape.
Here is what the falls look like normally, gushing with water.
To "de-water" the falls, workers erected a 600-foot cofferdam in the Niagara River at the head of Goat Island, and diverted the water from the American Falls to the Horseshoe Falls.
Here are more photos of the dry falls.
All photos from Russ Glasson's Flickr stream, taken from scans of his family's historic snapshots.
This io9 flashback originally appeared on io9 in 2010.