How does a rivers gold get replenished with a Dam in place upstream?

[StrandedSailor]

Newbie question, but how does the bear River or any river’s gold get replenished with a dam only a couple miles or so up stream? I understand that gold eroding off of the banks downstream the dam would wash down to become placer gold but seems like a lot of gold for that that small of distance.

Thanks in advance!

 

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[N-Lionberger]

It doesn't. Any gold up stream will be caught by the dam. Any gold washing in below the dam is being washed down from feeders and high benches.

 

[StrandedSailor]

That’s what I was thinking. Thanks.

 

[N-Lionberger]

The areas upstream of dams are interesting to poke around in, the dam backs up water and creates a massive low pressure zone where the river runs into that, in areas where the dams create lakes at the height of summer/fall a lot of these spots are high and dry.

 

[StrandedSailor]

The areas upstream of dams are interesting to poke around in, the dam backs up water and creates a massive low pressure zone where the river runs into that, in areas where the dams create lakes at the height of summer/fall a lot of these spots are high and dry.

I never thought about that, thanks for the knowledge!

 

[OreCart]

I have wondered about that too, but differently in that the dams were Beaver Dams and not man=made dams.

Where I found my lode gold, at its base is a wet area in a ravine. No defined moving water or anything, just wet. But then a few hundred feet away a stream forms; wide enough to step across, but is starting to have banks, flowing water, etc. Then almost immediately that water flows into a swamp because beavers put a dam in it's lower part.

I found placer gold in the outflowing stream, so I assume, before the beavers put in their dam, water flowed through the swamp area and gold was deposited.

But what the heck can you do? I would think with all that vegetation growing, then dying, annually; there is no way you could dig that muck up, but it must be burying a lot of gold?

I am thinking my only hope is, digging on both sides of the swamp, going up each hillside and seeing if during exceptionally high water in the past, gold was deposited in the banks. This would be doubtful because it would be more likely running in the fast water in the center of the swamp, but there is 5 feet of muck there now (not to mention environmental laws).

 

[Bejay]

No doubt gold is captured above dams where the water flow is reduced. That demarcation line can be a very rewarding spot. However below a dam there can be gold that was captured prior to a dam being placed and the "spill over" the dam can cause such turbulence that the gold can be "plucked" from its resting place and re-distributed below the dam. In other words unless all the gold had been removed prior to the dam the "below dam" riverbed/streambed can "reassemble the placer deposits".


Bejay

 

[KevinInColorado]

This is a classic newbie question. However the dam has only been there for decades while the gold has been migrating for many millennia. The works of man are trivial and temporary in the great arc of natural history.