Engineers shut off Niagara Falls in 1969 because the cliff was falling apart

In 1969, Niagara Falls suddenly went silent. Not from a drought: engineers shut off the American Falls because the cliff was falling apart. Giant slabs kept crashing off the edge, the pile below was swallowing the waterfall, and the water hid which rocks were safe to touch. So dump trucks poured 28,000 tons of rock into the river, building a 600-foot temporary dam that pushed the flow toward the Canadian side. Three days later the falls were dry. Crews drilled the rock, traced cracks with dye and pinned loose sections with steel bolts. Then the map showed the ugly rubble was propping the cliff up. So the rocks stayed, and the dam came out. Sources: • DVIDS (USACE Buffalo District) — https://www.dvidshub.net/news/326866/buffalo-district-recalls-dewatering-american-falls • Wikipedia — https://en.wikipedia.org/wiki/American_Falls