A rare tidal bore and a unique opportunity for a few lucky surfers

Cook Inlet, Alaska is where it all happened, and what luck it was for the few who were there to ride it…

Image is courtesy of ©Scott Dickerson and protected by copyright laws

Tidal bores are relatively uncommon – there are only about 60 places that they happen around the world. It is a phenomena where the leading edge of the incoming tide forms a wave (or waves) of water that travel up a river or narrow bay against the direction of the river or bay’s current and, as such, is a true tidal wave and not a tsunami. It can be just one wave or a whole series of waves.

There are two main features to a tidal bore:

  • The intense turbulence of the water
  • The low rumbling noise which is of such low intensity that it can be heard many miles away. This low-frequency sound is a characteristic feature of the advancing wave in which the air bubbles entrapped in the large-scale eddies are acoustically active and play the dominant role in the rumble sound.

So why this geography lesson?

Because on Thursday, 13th January, this fairly rare phenomenon occurred at the Turnagain Arm in the Cook Inlet near Girdwood, Alaska – a place where  an outstanding tidal bore happens when conditions are right.

Turnagain Arm has the second largest tidal swing in the world and is the only one that occurs in the dramatic surroundings of the far north.  The difference between low and high can be as much as 35 feet. The in-coming wave is like a wall of water anything up to 10-feet high which can reach speeds of 10 to 15 miles per hour.  At times, the wall is jumping with fish, including salmon. Thursday’s conditions provided a 5-mile ride lasting 45 minutes.

It has the added advantage of being amazingly accessible – you can see it by road along its entire 40- to 50-mile length.

courtesy of ©Scott Dickerson

As you can imagine, surfers try to predict when this phenomenon might happen.  Although ordinary surfboards are used, it is difficult to get them to perform to their best because of the turbulence of the water – the turbulence and the fluctuations. However, with the larger standup board, where a paddle is used for propulsion, surfers have been able to maximize the Turnagain tidal bore experience.

Scott Dickerson of SurfAlaska.net has kindly allowed me to use the following video of Thursday’s bore tide which he filmed from a motorised paraglider:

The first question to spring to my mind when seeing this was… can you kitesurf this wave? Tapped the question into Google and hey presto, 2 guys tried it out in 2008 – possibly the first time a bore tide had been kitesurfed!

Kite Boarding Bore Tides


Troy Henkels, worldwide adventurer, and his friend Mark (?) blasted through the 6′ wave from upstream fighting the two currents all the way. Having gone through the wave they did their best to get back into it, but the wind direction and currents prevented them from overtaking it. It’s a challenge waiting to be mastered… and if anyone has successfully done it since 2008 I would love to know! Thank you.

I asked Scott Dickerson if he knew of any more recent events, but he said that although it had been tried “I think the most challenging factor is that the wind is often going against the bore wave so it’s difficult for the kitesurfer to stay on it without doing a lot of tacking back and forth. But even then it can be hard to keep up with the wave and it moves through a lot of different wind environments.”

So the opinion from those in the know is that “SUP seems to be the king of the Turnagain Arm boretide for now.”

Having said tidal bores are a relatively rare phenomenon, they actually occur on Turnagain Arm every day, but they are fairly unspectacular. You have to wait for the 5-day window that surrounds the new and full moons. Then you must get the times for the two Anchorage low tides occurring each day. From this you will be able to work out that the bore tide should reach Bird Point 2 hrs and 30 minutes after Anchorage/Fire Island low tide. If the wind is blowing down the arm (the way it always blows—just look at how the trees grow), add another 10-15 minutes. It takes over five hours for the bore to travel from the mouth of Turnagain Arm to the end of it. Extreme low tides promise the largest bores because of the amount of water rushing back into the inlet and obviously the March and September equinox will have especially strong bore tides – particularly the Autumn one.

WARNING: If you happen to be in or near Anchorage when the tidal bore happens and fancy going out there to view it, don’t walk out onto the mud flats—people have died by getting stuck in the glacial silt and being drowned by the incoming tide! You have been warned…

I highly recommend you follow the link to Scott Dickerson’s site (SurfAlaska.net). His photographs are truly spectacular, but please note that they are protected by copyright laws.


One Response to “A rare tidal bore and a unique opportunity for a few lucky surfers”

  1. garrett
    2011 | 20 January at 17:36 #

    could be fun to kayak

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