Rapids, Whirlpools and Tlevak Narrows

This year our north-south transit of Dent Rapids, Gillard Passage, and Yuculta Rapids in one go on a difficult spring low slack was perfect. Taking a whole bunch of things into consideration, Jack worked out a strategy that put Aurora in the middle of each rapids exactly as the tide turned. What’s more we entered the series with the ebb and exited with the flood. It doesn’t get better than this.

When to take the rapids is something that mariners have to work out for themselves after studying tide and current tables and talking to people. Cruising guides such as Waggoners can only offer so much help. After forty years of cruising the Inside Passage, Bob Hale in his one page essay “Running the Rapids” (p. 241) stresses that every rapids has its own personality, characteristics and moods. He lists the four variables that mariners have to assess to find the “window of opportunity” during which they can safely transit.

First, while it’s always desirable to pass rapids at slack, you have to account for differences between high water slacks vs low water slacks.  Second, every fortnight at full and new moons there are spring tides with extreme highs and lows; these are balanced on other weeks of the month by neap tides. Third, rapids are affected by the size and shape of the bodies of water on either side of the narrows.   Fourth, you need to factor in the direction you’re traveling and the speed of your boat.

In time we have learned to visualize these things so that Hale’s conclusions make sense:

  • The window is narrowest at lower low water slack. Spring tides mean waters rise very high and fall very low.
  • The window at high water slack is wider on neap tides than on spring tides. With so much water moving the calm waters between flow and ebb don’t last very long.
  • At high water slack, the window is narrower on the rise from lower low water slack. It’s wider between the high waters of the subsequent tide cycle.

But then we encountered the Tlevak Narrows. This very short span of water just south of Craig, Alaska separates Prnce of Wales Island from Dall’s Island. The Douglass cruising guide had led us to believe they were tricky but had little to offer in the way of guidelines, except one. There’s a red buoy at the north entrance, which is visible from the south entrance as well. The currents through the Narrows are so strong that this buoy regularly disappears under the surface of the water!  The corollary is that you transit only when it’s dead vertical.

So, knowing the value of local knowledge for such challenges, we started asking around “What time is slack at Tlevak Narrows?” The more we asked – the Harbor Master, commercial fishermen, cruisers – the wider the range of answers and opinions we got.  After two days of this we knew every boat Craig Habor that wanted to transit south when we did . Our cumulative experience seemed to indicate that slack would be around 1 pm, that the window was very short, maybe five minutes, and that we should arrive by noon to keep an eye on the red buoy.

The famous buoy #4

It was a beautiful day and while we were underway, Jack decided to check AyeTides on his iPad and, low and behold, slack at Tlevak was listed for 10:45! We radioed the other boats with the news and said we were pressing on ahead. When we arrived the buoy was straight up. No more ripples on one side than on the other. No sooner were we fifty yards beyond it in the middle of the Narrows than we saw ripples indicating the waters were ebbing out to the North, creating problems for the boats behind us. Within five minutes we were exiting the narrow southern end, sharing the space with northbound traffic. On port was a brand new blue 100-ft fishing tender from Seattle. On starboard, a humpback whale!

Behind us our friends in smaller sailboats struggled. It took Scott with his outboarded Daniel Howard a full twenty minutes to make the transit. A Canadian single hander in a slightly bigger sailboat spent an hour searching for back eddies so he could push through.

Looking back on Tlevak

It all ended well and helped us see rapids in new ways. In order to be helpful, local knowledge needs to be experienced and appropriate to similarly powered boats. Tide and current tables do not lie and now they’re available even for out of the way places; $4.99 for the AyeTides app was the best investment of the year.

And now when I think about narrows, I envision the topography of the underwater walls and floor. Bottoms can range from 10 to 500 feet deep. I understand how every minute of the life of a rapids may be different from every other one in any monthly cycle of a tidal pattern. It’s sobering.


1 Response to “Rapids, Whirlpools and Tlevak Narrows”

  1. 1 Linda Sails August 1, 2012 at 7:42 am

    I can see a new writing job for you in the future.. the Baggywrinkles transiting guide for passagemaking between Seattle and Ketchikan… I’ll be ready to buy it.. heck I could even make a down payment on the book.

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