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Turnagain's Bore Tides

© James Soos

Thousands of years ago, glacial movement carved out what is known today as Turnagain Arm. Extending 43 miles southeast from the head of Cook Inlet, this long body of water with a depth in excess of 1000 feet cradles the southern portion of the Anchorage Bowl, ending near Girdwood, AK. Glacial fed streams and rivers originating in the Chugach Mountains empty their waters into the Arm, and over time, this natural wonder has mostly filled with sediment, transforming what was once a deep fjord into a shallow basin with an ever-changing maze of channels beneath it’s waters.

The draining tide is a sight to see as water rushes towards Cook Inlet, revealing a silt filled gorge with a network of rivers and streams flowing through channels cut by the water’s movement. However, because of the narrow and shallow Turnagain Arm’s length, it is still draining its waters into the Inlet as a new tide begins to rush in. This, along with Cook Inlet’s large tide range of 35 foot plus, creates a phenomenon known as a Bore Tide.

Water from the extreme tidal flux in Cook Inlet floods into Turnagain Arm, overriding the outgoing water and creating an abrupt edge to the incoming tide. This forms a wall of water, resembling a wave, which travels up the Arm at 10- 15 miles per hour. Depending on the depth and width of the channels within Turnagain Arm, Bore tides can range anywhere from 6 inches to 6 feet in height.

Turnagain Arm is a rich wildlife habitat, attracting many species of birds to its shores. Of course, salmon enter the Arm during spawning season to reach their breeding grounds farther up the rivers that meet these waters at the base of the Chugach Range. Spring brings migrating Beluga Whales to Alaska, and they can be seen swimming in Turnagain throughout the summer.

Seward Highway, the only road connecting Anchorage and the Kenai Peninsula, travels along Turnagain Arm’s route, allowing easy access for people to enjoy the scenic views and recreational activities this area boasts. Yet, many are unaware of the danger posed by the thick layer of sediment, most of it around 1000 feet deep, exposed during low tide. The silt is best described as having the consistency of peanut butter. Unfortunately, this layer appears stable, coaxing some of the more adventuresome folks to walk out on its deceptive face. But, it is too late once one has realized the mistake, and many flounder in an ooze which acts much like quicksand. A few have lost their lives, being trapped in the silt when the tide began filling the Arm again, drowning the victims before they could be saved. As with all outdoor activities, caution and common sense should rule every step.