Tidal Bore Research Society
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Here is a little information about Cook Inlet, Anchorage, and the Turnagain Arm (of Cook Inlet). Cook Inlet is a large body of water that from north to south is about 150 miles long. It's width narrows from about 50-60 miles at its mouth down to about 20-30 miles. At Anchorage, the waters of Cook Inlet split. One branch enters the Knik Arm (pronounced kanik) and the other branch enters the Turnagain Arm....
Courtesy John Markel
The Knik Arm extends north for about 25 miles and its anywhere from about 2 miles to 6-8 miles wide. This is a very shallow body of water and a lot of mud flats are visible when the tide is out. I have neither watched for or seen bores in the Knik Arm, though it does seem that, given these conditions, they might exist.

The Turnagain Arm extends east/west from Anchorage. At its mouth it is about 10 miles wide and it begins to narrow almost immediately. Over its approximately 40 mile length it narrows to almost nothing, with its mean width being about 2-3 miles.

Prior to 1964 navigation was possible within the Turnagain Arm. But on March 27th, 1964, a magnitude 9.2 earthquake raised the bottom of the Arm so that now it is too shallow for boats.

I have only seen three bore tides in the Arm, one by accident, one on Friday May 3rd, 2000, and one on Saturday May 4th, 2000.

I have learned that the bores can be seen entering the narrower part of the Arm at a place known as Beluga Point approximately one hour after Anchorage's low tide. Beluga Point is between mile markers 111 & 110, headed east, along the Seward Highway. Here a finger of water with a foamy tip appears far out in the Arm. There are high-powered telescopes at Beluga Point that make spotting this finger easy.

From Beluga Point, the tide can be followed east along the Seward Highway. There are several turn-ous along the highway, perfect for keeping track of the tide's advance.

Unfortunately, at least in my limited experience, most advance is done in very shallow water where there is little more to watch than the advancing finger of water, which, by the way, may be only one of several, though the others are farther out in the Arm and difficult to see at times.

Between mile marker 104 and 103 on the Seward Highway, headed east, there is a small turn-out. The water here is deeper, though it may change seasonally, and here is where I've seen the dynamic bore tide.

About 1-1/2 hours after Anchorage's low tide, the tide reaches this area. It forms into 8-10 parallel waves. The waves I've seen have been about two feet high and sometimes they break and tumble forward. The tide does seem to gain speed here, though this may have more to do with the fact that the tide is now only yards away rather than miles.

The water moves up the arm in a march that is absolutely amazing. People travelling the Seward Highway park to watch the event and it doesn't take long for the small turn-out to become over-crowded.

The tide really does seem to be travelling at close to 10 mph's here, if that's even possible, and it passes this point quickly.

I have gone farther into the Arm from this point along the Seward Highway but have not really seen much because of the shallowness. I know that if I followed the tide along its entire path that there would be other places where I could watch the dynamic tide, but I have not yet taken the time. At the moment I'm glad to have figured out the time factor and from here i'll try to figure out other places along the Seward Highway (which, by the way, runs along the full length of the Turnagain Arm) where the bore tide can best be viewed.

The keys here are that the tide can be seen at Beluga Point about one hour, +/-, after Anchorage's low tide. It can be seen near mile marker's 104-103 about 1-1/2 hours after Anchorage's low tides.

I reference Anchorage's low tide because that time is printed in the paper everyday and so is readily available. There are tide books available as well.

Written and contributed by Curtis Morris

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