Newly married couples 50 years ago may have been disappointed if their honeymoon plans included Niagara Falls.

That's because water stopped flowing over the American Falls to allow geological surveys to take place.

Shutting off water allowed geologists to examine the American Falls in detail. Source: U.S. Army Corps of EngineersA cofferdam at the east end of Goat Island just upstream of the American Falls was completed in June 1969. The temporary dam then diverted water from the American Falls to the Horseshoe Falls on the Canadian side of the Niagara River, which flows between New York State and Ontario.

Shutting off the flow allowed geologists to examine the stability of the fall's face. A large amount of talus (a slope formed by rock debris) had built up under the falls as a result of rockfalls, especially during events in 1931 and 1954.

Water at the falls flows over a more resistant layer of Lockport dolomite, about 80 feet thick. Beneath that lies a softer layer of about 60 feet of Rochester shale. As the shale is undermined and joints open in the dolomite, pressure builds, the shale falls apart and the cap is undermined.

Workers install a cofferdam upstream of the Falls. Source: U.S. Army Corps of EngineersTo conduct the research, a partnership was formed among the American Falls International Board, the U.S. Army Corps of Engineers, the New York State Parks, the New York Power Authority and several Canadian offices.

As part of the work, 48 core borings were taken. In addition, face mapping, topographic, stratigraphic and structural studies were completed; terrestrial photogrammetry to map rock fractures and joints was performed; and piezometers to measure water pressure in rock joints were installed. In addition, instruments to measure horizontal movement in the adjacent rock mass were put in place.

During the project, sprinklers kept the Rochester shale layers wet so they didn’t crumble. Talus at the base of the falls was mapped but ultimately left in place. The cofferdam was removed in late November 1969, and the American Falls returned to its previous state.

Today, the outflow from Lake Erie through the Niagara River to Lake Ontario and the St. Lawrence River is largely unregulated. However, water in the upper Niagara River, just upstream of the Falls, can be diverted to hydropower plants.

Through the years, Niagara Falls has been the punchline of many jokes, including this comedy routine by the Three Stooges.