The extraordinary occurrence of the Reversing Falls stems from the dramatic tidal fluctuations in the Bay of Fundy, which boast the world’s highest tides. The Bay of Fundy’s natural southward-facing entrance acts like a funnel, channeling the forceful ocean tides directly into it. As the tidal water enters the bay at its widest point, it appears normal. However, the water’s behavior changes as it moves further up the bay, being constricted by the progressively narrowing sides and the continuous shallowing of the bay floor, which forces the water to rise along the shores. The outgoing low tide clashes with the incoming high tide, merging their forces to create an even higher incoming wave. This amalgamation of wave forces is known as resonance.
The tides in the Bay of Fundy are influenced by tidal movements originating in the Southern Indian Ocean, which travel around the Cape of Good Hope and subsequently northward into the Bay of Fundy. The moon’s distance from the Earth at this longitude also plays a role. In Saint John, the bay tides can reach heights of 28.5 feet. When the tide is low, the 450-mile-long St. John River empties into the bay. The river’s full flow rushes through a narrow gorge between Fallsview Park and the Pulp Mill, cascading over a submerged ledge 36 feet below the surface and plummeting into a 175-200 foot deep pool below the mill and under the bridge. The water then churns into a series of rapids and whirlpools.
As the bay tides start to rise, they decelerate the river’s flow and eventually halt it entirely. This brief period of complete stillness is known as slack tide
, during which boats can navigate the Falls safely. Shortly after slack tide, the bay tides exceed the river level, causing the river to initially flow upstream slowly. As the bay tides keep rising, the reverse flow intensifies, and rapids form, peaking at high tide. This reversal effect is noticeable as far as Fredericton, over 80 miles inland, where the tidal waters are 14.5 feet higher than the river level.
After high tide, the bay tides start to recede, and the river’s upstream flow gradually diminishes until the bay tides and river level are equal, resulting in another slack tide. The river then resumes its usual course, flowing back out of the bay. The bay tides continue to decrease below the river level, and at low tide, the rapids once again reach their peak, flowing downstream. At this point, the tidal waters are 14.5 feet lower than the river level.
The tide experiences a rise and fall approximately every 12.5 hours. To fully appreciate the Reversing Falls, it is recommended to view them at least twice in a day—near low tide and high tide. Fallsview Park offers an excellent vantage point to observe the Falls, situated not far from the Reversing Falls Information Centre. The Reversing Falls Roof Top Theatre on the observation deck features a twelve-minute film presentation that explains the Reversing Falls phenomenon and highlights various attractions in the Saint