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Wilderness Tripping - BWCA & Beyond New Topic Printer Friendly Version

  re: tides
  Posted by: alexsidles on Mar-13-13 6:26 PM (EST)
 

A comprehensive, user-friendly, easy-to-use, and free resource that shows the directions of the tidal currents does not exist. There are tons of free tide tables out there, as I'm sure you're aware, but very few free places that tell you the direction of the water's movement.

There do exist a handful of current vector resources that are free, but they are incomplete in their coverage and not always very easy to use:

For SE Alaska (scroll down the list to the Alaskan stations):
http://www.co-ops.nos.noaa.gov/cdata/

For Washington and BC (select "other current stations," and the flow vector will appear below the table):
http://www.dairiki.org/tides/monthly.php/

The above two resources will show you current vectors at flood and ebb tide, but as you can see, they aren't very user-friendly and are certainly not comprehensive in their coverage.

One non-free option would be actual nautical charts. These do show current directions, but they are extremely expensive, even in electronic form. I assume a man home-rigging his canoe doesn't have the money to throw around on these, so we'll disregard them as an option.

A non-free but cheap option would be the iphone app AyeTides for about $8. This is user-friendly and more comprehensive than the websites I referenced above, but it would require bringing an iphone with you on your trip, which you may not want to do. I can't vouch for its Canadian coverage.

Here's an AyeTides screenshot showing the information you want:
http://sailing.about.com/od/equipmentgear/ss/Best-Tide-App-For-Iphone_3.htm

What I did on my Inside Passage trip was to just use tide tables (which are easily and freely available everywhere, unlike current tables), and then examined the local geography to try to guess which way the water would move. On flood tides, the water tries to move away from the nearest patch of open ocean, and on ebb tides, it tries to move toward the nearest patch of ocean ocean. The current's direction changes accordingly. This system of predicting the water's direction of movement worked fairly well for me, but I would still guess the movement direction wrong about 20% of the time, especially in areas with many twisty little channels. Just comes with the territory.

For my tide tables, I downloaded the following dataset into my handheld Garmin GPS:
http://www8.garmin.com/support/download_details.jsp?product=010-00191-00

The above dataset has only very spotty coverage for BC tides, but excellent coverage for Washington and Alaska. On the Canadian portion of the trip, I just did my best to learn local currents through observation. The tables are still worth getting, though.

For free Canadian tide (but not current) tables in greater detail than the Garmin download, you might check out the following:
http://www.waterlevels.gc.ca/eng/data/predictions/2013

Does all this seem needlessly complicated and overwhelming? Below are two online discussions that help shed some light on why all this stuff is so complicated!

http://www.macsailing.net/fbb/showtopic.php?tid/375/tp/0/all/1/

and

http://www.ayetides.com/Other/tidevcurrent.html

Hope you figure it all out! I would just go ahead on the trip and not worry too much about the currents - you will learn to anticipate them through observation as the trip goes on. Even the best nautical charts' current tables wouldn't give you complete coverage everywhere. A certain amount of interpolation and guesswork is part of the fun.

Alex

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