|Bay of Fundy: Tidal Bore on the Salmon River near Truro, Nova Scotia|
Water moving upstream in a river bed? Yes! During some earth-reshaping cataclysm, geological eons ago? No. It’s happening as you read this, every day, twice a day at high tide, in a few places on this planet, including at the Bay of Fundy in Canada. It’s called a tidal bore.
The Bay of Fundy is home to the world's highest tides, rising and falling up to a record 53 feet (16 meters) a day. Because of the size and power of the tides, different, extraordinary phenomena occur around the bay. Among them are tidal bores.
A tidal bore happens when the leading edge of the rising tide forms a wave that moves upstream, against the current of a river. This is likely to be seen when tides push a huge volume of sea water into a funnel-shaped bay, such as the Bay of Fundy, and up a river mouth. The sea water has nowhere to go but up the river.
Weeks before traveling to the Bay of Fundy, I had researched which river mouths present good tidal bores, picked the Salmon River near the town of Truro, and googled Truro Tidal Bore Times (the bore times don’t necessarily match the high tide times). Armed with directions to auspiciously-named Tidal Bore Road, I arrived 20 minutes in advance.
tidal bore location in the Bay of Fundy
Credit: Wikipedia map with red dot added by Caroline Hatton
Before the arrival of the tidal bore, I moved into position among the tourists dutifully lined up along the shore with cameras at the ready. Very little water flowed downstream (from right to left), in only one of two channels separated by a sand bank in the middle of the wide, shallow river bed. Here's a video of what we saw:
When the tidal bore arrived from the left, I caught the first glimpse of its front edge rounding the river bend and heard the murmur of the wave despite the steady roar of the wind. Then the sea water filled the channel on the far side of the river, leaving the sand bank in the middle dry for now. The frontal wave in the far channel traveled to the right, out of sight. Next, the sea water filled the channel on the near side of the river, as seen in the video. Finally, the sea water covered the sand bank in the middle of the river bed. The whole show had lasted less than ten minutes.
After I left, the sea water should have kept flowing upstream for hours. The fish must have been confused.
Although the magnitude of the incoming wave wasn’t exactly a surfer’s dream, I found the notion of the high tide going up river, mind-blowing. Little did I know that I would witness a similar phenomenon on a massively larger scale later in my trip. But that’s for another blog post.
For more info:
The link in the above text, about rivers with good tidal bores, also provides info about tidal bore rafting. https://www.bayoffundy.com/activities/tidal-bore-rafting/
Read another blog post by Caroline Hatton, about the collapse of The Hole on Long Island in the Bay of Fundy. https://theintrepidtourist.blogspot.com/2017/11/canadas-bay-of-fundy-about-hole-that.html
Read another blog post by Caroline Hatton, about the Bay of Fundy’s Joggins Fossil Cliffs. https://theintrepidtourist.blogspot.com/2015/11/canadas-joggins-fossil-cliffs-guest.html