Experience the Re
versing Rapids
The Reversing Rapids are created by the collision of the
Bay of Fundy’s monstrous tides and the mighty St. John
River. The Bay of Fundy tides are a result of tidal action
originating in the Southern Indian Ocean sweeping
around the Cape of Good Hope and then northward into
the Bay of Fundy. They are also affected by the distance of
the moon from the earth at this longitude. In Saint John,
the Bay of Fundy tides rise 8.5 metres (28.5 feet) and
completes a high-tide/low-tide cycle just about every 12.5
hours. To best appreciate the Reversing Rapids, try to view
them at least twice – near low tide and near high tide. A
good water-level vantage point from which to view them
is Fallsview Park.
St. John River
high-tide watermark
Bay of Fundy
The St. John River emptying into
the Bay of Fundy at low tide.
Low tide
When the Bay of Fundy’s tides are low, the full flow of the
724.2 kilometres (450 miles) long St. John River thunders
through a narrow gorge between Fallsview Park and
the Irving Pulp Mill. An underwater ledge, 11 metres
(36 feet) below the surface causes the water in the river
to tumble downward into a 53.3 - 61 metre (175-200
foot) deep pool, causing a series of rapids and whirlpools.
At this point the tidal waters are 4.4 metres (14.5 feet)
lower than the river level.
Slack tide
As the Bay’s tides begin to rise, they slow the
course of the river and finally stop the river’s flow
completely. This
short period of
The Bay of Fundy tides stopping the
flow of the St. John River at slack tide.
complete calm is
called slack tide
and lasts about
20 minutes. It is
only at this time
that boats are
able to navigate
the Rapids.
Shortly after
this slack tide,
the Bay’s tides
become higher than
the river level.
High tide
As the Bay’s tides
continue to rise,
their powerful
force gradually
reverses the flow
of the
river and the
rapids begin to
form again,
reaching
their peak
at high tide.
The effect of this reversal
is felt upstream as far as Fredericton,
more than 128.7 kilometres (80 miles) inland. At
this point the tidal waters are actually 4.4 metres (14.5
feet) higher than the river. After high tide the Bay’s
tides begin to fall and the up-stream flow of the river
gradually lowers until the tides fall to the level of the
river – resulting in another slack tide.
The Bay of Fundy reversing the flow
of the St. John River at high tide.
Enjoy harbour sightseeing tours, take part
in a zipline adventure or dine overlooking
this amazing phenomenon!
Expect only to be
delighted.
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