Niagara Falls
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Niagara Falls is a set of massive waterfalls located on the Niagara River in eastern North America, on the border between the United States and Canada. Niagara Falls comprises three separate waterfalls: the Horseshoe Falls (sometimes called the Canadian Falls), the American Falls, and the smaller, adjacent Bridal Veil Falls. While not exceptionally high, Niagara Falls is very wide. With more than 6 million cubic feet (168,000 m²) of water falling over the crestline every minute in high flow, and almost 4 million cubic feet (110,000 m²) on average, it is the most powerful waterfall in North America. Niagara Falls is located 16 miles (26 km) away from the U.S. city of Buffalo and 43 miles (69 km) from the Canadian city of Toronto.
Some sources erroneously quote that Niagara Falls has an average flow of approximetley 5,700 cubic metres per second (340,000 m²/min) (12,000,000 ft²/min) (200,000 ft²/s) or even slightly more. This figure is derived from the average rate of flow (5,720 m²/s) (202,000 ft²/s) of the Niagara River. This volume would pass over the falls if there were no hydroelectric water diversion upstream from the falls; however, water is diverted continuously from Niagara and this figure is approximately three times the actual average flow volume over the falls.
Niagara Falls is renowned for its beauty, and is both a valuable source of hydroelectric power and a challenging project for environmental preservation. A popular tourist site for over a century, the natural wonder is shared between the twin cities of Niagara Falls, Ontario and Niagara Falls, New York.
The Falls drop about 170 feet (52 m), although the American Falls have a clear drop of only 70 feet (21 m) before reaching a jumble of fallen rocks which were deposited by a massive rock slide in 1954. The larger Horseshoe Falls are about 2,600 feet (792 m) wide, while the American Falls are 1,060 feet (323 m) wide. The volume of water approaching the Falls during peak flow season is 202,000 cubic feet per second (5,720 m²/s). During the summer months, when maximum diversion of water for hydroelectric power occurs, 100,000 ft²/s (2,832 m²/s) of water actually traverses the Falls, some 90% of which goes over the Horseshoe Falls. This volume is further halved at night, when most of the diversion to hydroelectric facilities occurs.
Preservation efforts
For the first two centuries after European settlement of the area, land on both sides of Niagara Falls was privately owned. Development and commercial ventures threatened the natural beauty of the area, and visitors sometimes had to pay entrepreneurs a fee to view the Falls through holes in a fence. Public dissatisfaction led to the Free Niagara movement, which included the artist Frederick Church, the landscape architect Frederick Law Olmsted, New York Assemblyman Thomas Vincent Welch, and the journalist Jonathan Baxter Harrison. A series of Harrison's letters to newspapers in Boston and New York (collected in the 1882 pamphlet The Condition of Niagara Falls, and the Measures Needed to Preserve Them) were particularly influential in turning public opinion in favor of preservation.
In 1885, New York state began to purchase land from developers, under the charter of the Niagara Reservation State Park. In the same year, Ontario established the Queen Victoria Niagara Falls Park for the same purpose. Both organizations have proved remarkably successful operations that have restricted development on both sides of the Falls and the Niagara River. On the Canadian side, the Niagara Parks Commission governs land usage along the entire course of the Niagara River, from Lake Erie to Lake Ontario.
Until the modern era, the Falls were receding southward owing to erosion from two to ten feet (0.6 to 3.0 m) per year. This process was slowed initially by diversion of increasing amounts of flow from the Niagara River into hydroelectric plants in both the United States and Canada. On January 2, 1929 Canada and the United States reached an agreement on an action plan to preserve the Falls. In 1950, the two countries signed the Niagara River Water Diversion Treaty, which more specifically addressed the issue of water diversion.
In addition to the effects of diversion of water to the power stations, erosion control efforts have included underwater weirs to redirect the most damaging currents, and actual mechanical strengthening of the top of the Falls. The most dramatic such work was performed in 1969. In June of that year, the Niagara River was completely diverted away from the American Falls for several months through the building of a temporary rock and earth dam (clearly visible in the photo at right), effectively shutting off the American Falls. While the Horseshoe Falls absorbed the extra flow, the U.S. Army Corps of Engineers studied the riverbed and mechanically bolted faults which would otherwise have hastened the retreat of the American Falls. A plan to remove the huge mound of talus deposited in 1954 was abandoned owing to cost, and in November 1969, the temporary dam was dynamited, restoring flow to the American Falls. Even after these undertakings, Luna Island, the small piece of land between the main waterfall and the Bridal Veil, remained off limits to the public for years owing to fears that it was unstable and could collapse into the gorge at any time.
Preservation efforts have extended beyond and above the Falls themselves. Recent construction of several tall buildings (most of them hotels) on the Canadian side has caused the airflow over the Falls to change direction. Students at the University of Guelph demonstrated, using scale models, that the air passes over the top of the new hotels, causing a breeze to roll down the south sides of the buildings and spill into the gorge below the Falls, where it feeds into a whirlpool of moisture and air. The result is that the viewing areas on the Canadian side are now often obscured by a layer of mist.[9] Another possible explanation for the mist is a rise in local ground temperatures due to global warming. In either case, solving the problem will be difficult.
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