When Niagara Falls Ran Dry

The Horseshoe Falls have never again been silenced by the wind and ice, and an ice boom installed in Lake Erie in 1964 will ensure that they never do. The flow of water over the American Falls, however, was cut off once again, from June 12 to November 25, 1969. On this occasion, the American Falls were dried artificially to permit geological studies of the face of the Falls. A 600-foot cofferdam was constructed of 27,800 tons of rock and earth to prevent water from flowing towards the American Falls. Once the face of the Falls was exposed, loose stones were sandblasted away, and a sprinkler system was installed to water the shale layer which would deteriorate unless kept moist.

Over the next six months, geologists studied the rock formations of the cataract to determine what action could be taken to stop the erosion of the falls and prevent rock slides. A walkway was constructed on the riverbed to accommodate tourists, who were predicted to increase by about one million people while the American Falls were dry. At 10:05 am on November 25, 1969, the first scoop of earth and rock was removed from the cofferdam. The first gush of water came through at 11:05 am, and by mid-afternoon, the water was once again flowing over the American Falls with its usual force.

Although the Horseshoe Falls have never frozen over, the American Falls have done so several times, as they receive only a tenth of the water in the Niagara River, and are much shallower than the Horseshoe Falls at their crest. In 1909 and 1936, the flow of water over the American Falls ceased completely, and it has also slowed to a trickle on a number of occasions during severely cold winters.