Niagara Falls is one of the world's great ecological wonders, dumping a rush of 3,160 tons of water over its crest every second. That's likely why more than 100,000 people showed up to see part of the waterfall suddenly run dry in 1969 — a feat that was orchestrated not by nature, but by engineers. Niagara Falls consists of three waterfalls: Horseshoe Falls (the largest), Bridal Veil Falls (the smallest), and American Falls, which today stands 190 feet tall. But major rock falls in 1931 and 1954 shortened the American Falls' drop by nearly half, threatening its structural stability. So in June 1969, the U.S. Army Corps of Engineers "dewatered" the massive cataract in an attempt to survey its sturdiness and give crews an opportunity to remove the enormous rock pile sitting below (although that plan was later abandoned due to cost concerns). Temporary cofferdams were built above the American Falls, diverting water to the other two drop-offs and effectively drying out the waterfall for months. Seeing the underlying rocky riverbed was a rare sight; onlookers hadn't seen the bare crest since March 1848, when an ice dam on the Niagara River curtailed the watery curtain. This time, scientists used the water shutoff to map the waterfall's face, collect core samples, and install water pressure monitors. Work at the site was completed in five months, and by November 1969, the U.S. Army Corps of Engineers removed its dam, unveiling a restored waterfall to a surge of visitors. |
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