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The
Reversing Falls of
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Reversing Falls/Rapids
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The spectacle
of the Reversing Falls or technically more correct the Reversing
Rapids takes place just before the St. John River enters the Bay
of Fundy at Saint John,
New Brunswick. The Reversing Falls are caused when the river has
to pass through a narrow gorge and by the huge rise and fall of the
tides in the Bay of Fundy. |
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The natural
south-facing opening of the Bay of Fundy is like a funnel for the
incoming water. The tidewater is the same as in the Atlantic Ocean
when it enters the Bay, but the further up the Bay it travels the
more it gets squeezed by the narrowing sides and shallowing bottom
forcing the water higher up on the shores. On top of that the outgoing
tides collides with the incoming tide and combines to make the incoming
tide even higher. This combination of wave forces is called resonance. |
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The St. John River is the longest river in Atlantic Canada with a length of 450 miles (724km). The tides in the Bay of Fundy are amongst the highest in the world. At Saint John, NB the difference between high tide and low tide is 30 feet (10m), however further East at the end of the Bay the difference can be as high as 54 feet (18m). The tides rise and fall once about every 12 and a half hours. |
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Cause of the Extreme High Tides |
The tides
in the Bay of Fundy are the result of tidal action originating in
the South Indian Ocean flowing around the Cape of Good Hope (South
Africa) and then northward to the Bay of Fundy. The distance of the
Moon from the Earth has also a big influence at this latitude. |
Highest Tides in the World |
When
the tide is low the St. John River (the longest river in Atlantic
Canada) 450 miles (724km) flows into the Bay of Fundy. Between Fallsview
Park and the Irving Pulp Mill the river thunders through a narrow
gorge. An underwater ledge, 36 feet (12m) below the surface, causes
the water in the river to tumble downward into a 175-200 feet (58-66m)
deep pool, below the mill and under the bridge. The water then boils
in a series of rapids and whirlpools. |
Reversing Falls/Rapids |
At low
tide, the water in the Bay of Fundy is 14 feet lower than the natural
level of the St. John River. At that time the flow of the river is
downstream over the rapids into the Bay of Fundy. When the tide changes
the water level in the Bay of Fundy is gradually rising until slack
tide which is 3 hours after low tide. That is the point when the water
level of the Bay of Fundy is even with the natural level of the St.
John River. For 20 minutes the water is absolutely still, no rapids
and only at that time can boats safely navigate through the Falls.
Over the next 3 hours as the water level in the Bay of Fundy keeps
on rising higher than the St. John River's water level, the water
in the river now flows upstream over the rapids. The force of the
high tide pushes the river water upstream that it can be felt in Fredericton
80 miles (120km) away. |
Speedboat Ride through the Reversing Falls |
Nowadays, the adventurous can take a ride through the rapids on a speedboat and depending on the tides it is a leisurely ride or the adventure of a life time through white waters. |
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