Tides and Currents

[Zaxscd]

Hi,
I have a question about tides and currents section, hopefully this is right place to post it.

For example today:
clover point tides:
low tide = 9.26
high tide = 15.27

trial island currents:
max ebb 10.15
slack ~13.45
max flood 15.48

This shows the ebb *increasing* while the tide is rising? It doesn't make sense. Normally max ebb would be in the middle region of an ebb tide, slack would be just after a low/high tide.

Am I missing something here?

[more force 4]

I think there's some oceanographers here to explain better, but as I understand it, it is because the tide is a wave - it doesn't actually have to 'pile up' the water to rise - though it does anyway, kind of like water in a long tray when you alternately lift the ends, but there is a lag.

[nanmoo]

Here is a good 'simple' explanation. MF4 is on the right track.

http://co-ops.nos.noaa.gov/faq2.html#12

[JL]

The geography of the area creates the opportunity for many back eddies etc. which accounts for the discrepancy between tidal heights & current direction ... Imagine placing bricks in a tub of water & then pulling the plug , the water will take the path of least resistance NOT flow uniformly to the drain. Look for a copy of the 'current atlas' , It was created using data buoys to measure current direction/rate in real time . http://www.nauticalmind.com/Current-Atl ... 66392.html

[rocdoc]

Check out this model animation of tidal currents. You can see how complicated the tidal currents can get around the Victoria shoreline.
http://www.pac.dfo-mpo.gc.ca/sci/juande ... mation.htm

[rocdoc]

Just ran the model. You definitely don't want to be east of Trial Island on an ebbing current.

[jim mckenzie]

How about when you see the tide obviously flowing out but the water on the beach is still rising (coming in). I saw this one day and was very confused until a diver friend told me that the surface water can be flowing in one direction while deeper water is flowing in the opposite direction. He told me that when diving one can use this to transport oneself in a direction at one depth then return by going to another depth where the water is flowing the other way.
Back eddies can be sometimes be helpful in getting you back to shore when all is lost. In some cases, rather than paddle deperately, it may be best to sit and wait for the back eddy to return you to where you started.
All this technology is wonderful but I don't think anything beats just standing on shore for a minute to assess the situation before you head out .

[AC]

Currents may tell you which way the water is going weather it is flooding
or ebbing, All of the water always moves in different directions
kind of like giant whirl pools " made from underwater obstacles .
and uneven land masses
Time differences with high and low waters at Victoria are approximate
and may very by as much as 1 hour.

[Zaxscd]

Look for a copy of the 'current atlas' , It was created using data buoys to measure current direction/rate in real time . http://www.nauticalmind.com/Current-Atl ... 66392.html

Actually I have this book. It's a bit too generalised for my purposes though.

I understand that tides and currents behave in mysterious ways, I'm more observing that the current tables listed dont seem to be accurate or, if they are accurate, dont seem to be useful for predicting shoreline currents.

Today I paddled from ogden point to oak bay marina from 10am to 11am and there seemed to be no current in the passage between trial island and the mainland, it looked like slack to me.

Also I'm pretty sure the currents around victoria used to follow the "standing wave" model as shown in nanmoos link but know it seems to be more "progressive wave", though even the progressive wave doesn't have the ebb or flood still increasing after low or high tide.

But this is just my 2c. If I can dig out my current atlas I will try to double check the predictions.

[Zaxscd]

Check out this model animation of tidal currents. You can see how complicated the tidal currents can get around the Victoria shoreline.
http://www.pac.dfo-mpo.gc.ca/sci/juande ... mation.htm

That is a fantastic link. Thanks so much. I just wish they used PDT instead of UTC.

[JL]

local time is on the right (red)... Select req'd time & click on update. http://www.pac.dfo-mpo.gc.ca/sci/juande ... =03&vel=03