When you look at the mighty Horseshoe Falls, it's difficult to imagine any force strong enough to stop this gigantic rush of water - yet it is on record that Mother Nature did stop the flow, back in 1848.
In March of that year, local inhabitants, accustomed to the sound of the river, were greeted by a strange, eerie silence. Niagara had stopped! For thirty long, silent hours, the river dried up and those who were brave enough walked or rode horses over the rock floor of the channel. Then, with a roar that shook the foundations of the earth, a solid wall of water, cresting to a great height, curled down the channel and crashed over the brink of the precipice. Niagara was back in business to the immense relief of everyone.
News traveled slowly in those days but the explanation finally came. High winds set the ice fields of Lake Erie in motion and millions of tons of ice became lodged at the source of the river, blocking the channel completely until finally a shift in the forces of nature released it and the pent up weight of water broke through.
Lake Erie is the major producer of ice that flows down the Niagara River and is capable of producing 16,093 square kilometers (10,000 square miles) of ice.
The ice is blown down the river and over the Falls, where it becomes caught as the river narrows near the Canadian Maid of the Mist Landing; some of the ice is pushed back upriver, which can build up to form an ice jam. Ice jams can be very erosive; ice grinds on the river bed, moves large boulders and alters the shoreline. When wind stops forcing water out of Lake Erie into the river, the water level drops leaving the ice jam aloft like a bridge.
The Ice Bridge
The phenomenon of the ice bridge is a familiar occurence each winter. Usually in January, a mild spell followed by a strong southwest wind breaks up the ice on Lake Erie and sends it down the Niagara River and over the Falls. The wet ice forced up out of the water below the Falls freezes into a huge mass, growing into a structure of considerable size and strength, not unlike a glacier. As shown in this photo of photographers on the ice in the 1890s, visitors to the Falls would often venture out on the ice bridge - vendors would even set up stalls to sell refreshments. Since a tragic event in 1912, when the ice suddenly broke up and two tourists were killed, going out on the ice bridge has been strictly prohibited.
The Ice Boom
Ice jams along the river would often seriously hamper power diversions and damage shoreline installations. Since 1964, these problems have been reduced with the installation of an Ice Boom across the mouth of the river. With the approval of the International Joint Commission, the Power Entities created a floating timber boom 2.7 km (1.7 mi) long, spanning the inlet to the Niagara River approximately 300 m (1,000 ft) southwest of the water intake crib for the City of Buffalo, across to the Town of Fort Erie.
The boom has 22 spans, each with a series of 11 floating steel pontoons, anchored to the river bed at 122 m (400 ft) intervals by a 6.4 cm (2.5 in) diameter cable. Each pontoon is 9 m (29.5 ft) long, 41 cm (16 in) high and 56 cm wide.