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[clarki]

This morning, the flood tide peaked in the lower Fraser at 9 AM. At 10 AM, as I was leaving, the tide was definitely ebbing as evidenced by the water levels dropping, yet there was still flotsam floating upstream...

Thinking there might be 2 layers of water, yet I can't wrap my head around why the top layer would still be pushing up river?

[Rodney]

This happens during almost every peak tide when I fish around Queensborough.

Can't really explain it, I failed hydrology back in University....

[milo]

I'm just speculating here:

There's two layers of water - fresh and salt. As the tide ebbs, salt water is lighter and stays on the surface flowing upstream until the effect of the receding tide and with it the rush of fresh water going downstream fully neutralizes the upstream flow of saltwater.

Feel free to destroy my theory.

[Rodney]

I'm just speculating here:

There's two layers of water - fresh and salt. As the tide ebbs, salt water is lighter and stays on the surface flowing upstream until the effect of the receding tide and with it the rush of fresh water going downstream fully neutralizes the upstream flow of saltwater.

Feel free to destroy my theory.

Actually, saltwater is more dense than freshwater.

[milo]

Actually, saltwater is more dense than freshwater.

So much for my theory. 

[clarki]

I understand that there is a tidal "plug" of saltwater that pushes up as far as the Port Mann. If I recall, this plug sits below a layer of freshwater.

But I think you might on to something, Milo. I wonder if the intertia of the upriver flowing, top freshwater layer isn't easly overcome. The analogy of stopping a train comes to mind. Perhaps it takes longer, after the tide changes ,for the receeding salt water to began to "drag" the top layer downstream.

Rodney: Although I was fishing in the Queesnsborough area, this is the first time in 6 or 7 pink seasons that I have noticed this. I guess my powers of observation are rivalled only your knowledge of hydrology.

[Jeff_]

I would definitely say there are several layers of water with different densities at any given time in the Fraser due to saltwater intrusion (This article says up to 16km.) Though I can't really explain the upstream with any certainty, I would also guess inertia has something to do with it. The water might be receding but the "main" body of water that was moving upstream hasn't caught up with the tide. Thats my guess.   

[RalphH]

So much for my theory. 

your theory is right you just reversed the layers. The lower tongue of salt or brackish water can reach at least to Port Mann at certain times of the year and on certain tides.

Other than that layering or stratifying of water doesn't generally happen in rivers and streams.

[KingOfEastVan]

Water will take the path of least resistance and not all channels drain equally, backflow does occur.

[FreshyPT]

Wiki, not the best source but read and probe for more information at the library ... if you have not forgotten where your local library is localed 

http://en.wikipedia.org/wiki/Estuarine_water_circulation

[Whopperman]

I'm sure the government has something to do with this..

Those bastards!!!!! Now they're breaking the laws of water physics.

[chronic_topdawg]

I'm sure the government has something to do with this..

Those bastards!!!!! Now they're breaking the laws of water physics.

 

[Ian Forbes]

Blame it on the big oil companies and their pipe line. 

[islanddude]

This phenomena occurs in the Johnstone Straits also. The middle of the channel will be ebbing but along the shore it will be flooding. Go figure.

[sugartooth]

Perhaps the wind is blowing this flotsom upstream??