Niagara Falls diversion project in 1969

In June 1969, the U.S. Army Corps of Engineers carried out a rare engineering project by redirecting the flow of the American Falls at Niagara Falls, drying them out for five months to study the geological stability of the cliff.

Purpose of the diversion

The operation aimed to investigate why parts of the cliff were collapsing. Engineers wanted to understand the cause of the instability, which had been a growing concern for years.

Engineering method used

A 28,000-ton rock barrier was built by the Albert Elia Construction Company to channel the entire flow of water to the Canadian Horseshoe Falls, which already handled about 90 percent of the river’s flow.

Results of the dry period

The American Falls remained dry from June to November 1969, exposing a large pile of collapsed rock blocks at the base of the waterfall. This allowed engineers to examine the area in detail.

Findings and decisions

Engineers conducted core sampling, dye tracing, and strain sensor measurements. They discovered that the pile of rocks provided natural support to the cliff, and removing it would have risked further collapses. As a result, the plan to clean up the cliff was abandoned in the 1970s.

Impact on the falls

The project reduced the cliff line by about 15 percent, creating new viewpoints for visitors. In recent years, the New York State Park Office has considered a second drying of the falls to replace two historic bridges, but the project is still in the planning stage due to funding challenges.