Re: [Paddlewise] Translating Tides Into Currents Around Islands and Estuaries

From: Dave Kruger <dkruger_at_pacifier.com>
Date: Wed, 17 May 2000 09:30:45 -0700
Tom wrote:

> MSN/RiDem wrote: ...There is a freeware program call XTide....

> I checked out this program and it looks good for tides.  But from the little I know about currents, being a newbie, I understand that around islands and such the currents may not be so easily decerned simply from the tide table. [snip]  So now how does one figure out the currents? I've heard the currents around some of the necked down parts [in LIS] can hit 8 knots and form whirlpools.  Is it just a matter of gaining local knowledge?

Yes and no.  NOAA has current stations as well as tide stations.  If the area
you want to paddle has current stations where you need to know them, you are
set.  If not, then some variation of "local knowledge" will have to substitute.

Caveat:  even the NOAA data is sometimes off significantly, owing to
second-order effects (not handled in the current algorithm), and to variables
not included in the NOAA algorithm.  E.g., the variation in flow of a river
where it enters the estuary.  Here (Columbia River, OR/WA), what happens at the
first dam above tidewater affects currents a lot near the dam and somewhat even
a hundred miles below the dam.

Talk to other mariners and see what they do in your area.

Note:  a more complete, easier to use program is an (expensive) commercial one
sold by Nobeltec:  http://www.tides.com/

-- 
Dave Kruger
Astoria, OR
no affiliation with Nobeltec
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Received on Wed May 17 2000 - 09:28:50 PDT

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