Musings about Tides and Currents

The puzzling movement of large logs on a king tide.

We turn off Sutil Channel into Quadra Island’s Drew Harbour,. The place is empty and we have our choice of anchorage. After studying the chart, observing the surface currents, surveying the contours of the land, and predicting the winds through the trees, we drop anchor on a bump off Rebecca Spit. We find it the perfect anchorage. This is later confirmed by a couple of sailors who had watched us spin peacefully throughout the gale-force winds which battered their similarly sized-boat tied up nearby at the Heriot Bay Public Wharf.

Rebecca Spit 1

As the king tide peaks and carried the beach logs off Rebecca Spit, we can see across Sutil Channel to Cortes Island and Desolation Sound beyond.

In the late afternoon we stand on deck. Through a break in the trees on the spit can look across the white capped channel to Cortes Island and the mountains of Desolation Sound beyond. As the sun sets, the winds stop, the tide peaks, and the salt logs lining the lovely curve of the spit, creep into the water. Over a hundred of them, large and small, float throughout Drew Harbour, glistening a rich brown in the setting sun. Then as the tide peaks, they all return to our curve of the spit. The whole show lasts about 90 minutes.

RebeccaSpit 2

Soon the logs from Rebecca Spit float throughout Drew Harbour.

With the same tide height predicted for the next evening, albeit it an hour later, I persuade Jack to stay up and watch the curious journey of the logs. But this time, it doesn’t happen! There’s some modest log movement off a more southern part of the spit, but yesterday’s logs merely floated briefly before falling back into place.

My Otis Redding frame of mind.

When you’re in an Otis Redding frame of mind “watching the tide roll in” and then “roll away again,” you realize a lot is going on. The interplay of tide, current, depths, heights, and wind is a wondrous mystery.

Isolated logs may be encountered anywhere when you’re underway. They may bounce up on steep waves on when the wind is against current in Johnstone’s Strait. They may float calmly, transporting a dozen gulls or a long bald eagle. We have seen a harbor seal using one to haul out while moving on.

The rule is if you see one log you do an intense search for others. This is why we say some logs are solitary. But when you see others, you know there are more.

I used to think that logs escaped log booms or slid off barges – which they do, of course – but most of them probably move around under their own steam, or rather, under the power of Nature. They fall in the forest, sometimes over streams. They may be the remains of an cannery that has been decaying since salmon runs nearly collapsed at mid-century. They may simply be among the salt logs which group and regroup along the shores in the spring tide zone. They be the new growth trees a foot and a half or two in diameter or huge old growth trees. There’s a picture of an old growth log in Tidal Passages that shows the Beyers family in front of a fresh log from Von Donop Inlet that is 17 feet in diameter!

Three years ago coming south from Alaska, I remember tucking into the Broughtons, among the most pristine waters of the coast. Just before Echo Bay our passage was littered with logs of all shapes and sizes. We motored slowly, weaving in an out of them. Fortunately the thick morning fog had burned off and they were starkly visible in the noon sun, which must have coincided with a king tide. I need to check the data on that.

Lots of data!

Back in Port Townsend a bunch of scientists, along with my friend Dave who specializes in marine weather, are studying the way King Tides hit Port Townsend shores. As part of a broad Washington SeaGrant study to predict the impact of the month’s highest tides on sea level rise, they’re feeding data into broad SeaGrant study. They use some simple sophisticated equipment and also rely on ordinary citizens who monitor the same tides with their cameras. What a wealth of new information there is in photographs stamped with time and GPS coordinates! Maybe we’ll figure this out.

Although flows of water may be riddled with riddles, there is a lot of data. It’s been accumulating since Newton. As I understand it, repeated 18 year series of observations now make it easy to pinpoint the two daily ebbs and flows that characterize our area. Our Ports and Passes manual for 2017 Tides and Currents for Washington Inside Waters, British Columbia and Southeast Alaska is 622 pages long. It’s based on research by the Canadian Hydrographic Service, which cooperates with NOAA (and registers the “negative tides” of the US as the commonsensical “zero tides” of Canada.)

Tides and currents are of course very different. Tides are measured vertically although water flows horizontally. As for currents, let’s not go there now. If you want to see the types of questions they throw up for a mariner, just keyword search the blog for “currents”.

What about non-watery currents and tides?

Thought tides and conceptual currents figure in the way we consider and talk about other realities. Is there any order there?

It seems to me that tides are broad movements. Take gold rushes. There were so many of them along the coasts of the Americas! A gold rush is something that takes root in the minds of many to draw physical tides of people from many locations into a single quest.  The past couple of years have brought to European shores tides of refugees, people embedded with compelling notions of freedom or survival.

As in Nature, non-watery tides certainly interact with currents. But currents are sharper, less superficial than tides. They cut vertically. They help explain some of the fault lines in a society. Are the evolving notions of working class and middle class currents in conflict? What about the knife edged current of contemporary “bathroom bills” that slices through the rising tide of human rights victories for LGBLT folks?

 

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