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Waterfalls

The status of the major waterfalls of the world is based not only on the height of the fall, but also on the volume of water flow. For this reason, Della Falls, the highest in Canada, is not regarded, in world literature, as a major waterfall. Niagara Falls, on the other hand, is acknowledged as one of the world's greatest cataracts because of the estimated mean annual flow of 6000 cubic metres per second.

The height of a waterfall is often subject to various interpretations. In most cases a waterfall starts with a series of rapids, then goes over a vertical or nearly vertical drop, and ends with a cataract over the debris at the bottom of the vertical drop. The heights given in the table below are those of the highest vertical or nearly vertical drop.

Reversing Falls are phenomena resulting from tidal action. At low tide, the inland waters empty into the sea over a rocky shelf in a waterfall. As the tide rises above the falls, the seawater forces its way against the river flow. The resulting turbulence, in the form of whirlpools, eddies and rapids, makes the falls appear to have actually reversed. Canada's three reversing falls are:

• Saint John River, Bay of Fundy, New Brunswick
• Wager Bay, Ford Lake, Nunavut
• Barrier Inlet, Hudson Strait, Nunavut