How do dams influence the travel of gold?

[OwenT]

Does gold hang up behind dams? Can it get over some types? If there's a dam does all the gold below it eventually get flushed out of the river? Can gold get over some types of dams?

Here's a pic of a diversion dam on a river near me, the creek coming into it is where I think a lot of the gold comes from. I'm wondering how this has influenced the rest of the river. Note: I do find gold below the dam.

 

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[russau]

If the water is at flood stage , I would think it would . BUT at normal flow I don't think bigger gold could. Some fine gold is in constant movement in high turbidity and probly would get over the dam. IMHO

 

[jcazgoldchaser]

I remember watching a show about building a new dam. They said the issue with sediment wasn't with buildup at the dam, it's upstream where the river encounters the reservoir. It's at that point that the water slows down having encountered the stationary body of water.

 

[Oddjob]

My brother in law was telling me that he always looks for small dams in in streams or narrow rivers. He travels around the world shooting for gold and the only time I have ever seen him want to run a sluice was at one of our prospecting sites in the Carpathian Mountains.

This was 3 years ago and my family and I, and some guys I work with and their families went over for our annual trip for some fun shared prospecting. My brother in law tagged along because he wanted to go shooting for nuggets; he had seen some of the nugget we got dredging and he figured since it is 3 days far off the beaten path and we had never seen signs of recent activity from people that there would be good gold.

We got on site and set up camp and then he took off for a few hour. He came back all excited telling us about some little 6 foot tall dam that he figured had to of been from the late 1800's. We all thought he was mad but figured that one of us should at least give it a shot because that is what he does for a living and we only do it as a hobby. So he took off with a couple guys on some four wheelers with trailers packed down.

6 days later they came back with 219 grams of fines, 77 grams of chunky and 133 grams of nuggets. They said that they put in a small dent but only really hit about 10% of the dam.

So that is what we have worked the following 2 years on our annual trip; we have 6 dredges going and have gotten about 75% of it done just within the first 4 feet of the dam down to bedrock.

The trouble we have every year when we return is that there must be some major flood every spring because half of the work we have done is washed back in with new gravels.

Last year we had a 7th dredge running on the down side of the dam and they where doing really well too, but mainly all fine stuff, but still a good amount.

One year we might actually get that area cleaned out all the way if we can get in something bigger than some 4 inch dredges with 6.5 HP pumps. But it is already a 3 day push over some very messed up terrain with four wheelers and trailers, our biggest slow down is that we all have young kids and are pretty much limited as to how hard and fast we can push our selves over that terrain, but I am sure that has saved us more ways than one too.

 

[Aufisher]

I found some of my larger pickers just downstream from a dam so who knows!

 

[arizau]

If the dam is still doing it's job and not completely filled in with flood material, silt, etc. it is unlikely that any gold will go over the spillways. If there are floodgates below the top of the dam and the area up to that level is silted in then there is a chance that some gold may escape via that route when the floodgates are opened. Sometimes flood gates are opened to reduce the level of silt, etc. that has settled behind a dam.

 

[OwenT]

Awesome story Oddjob, thanks for sharing.

So if no gold is coming down in floods, is all the gold below being flushed out of the river or does it hang around in roughly the same area for a long time and the amount of time the dam has been there is irrelevant?

 

[MadMarshall]

http://www.wou.edu/las/physci/taylor/g407/kondolf_97.pdf

 

[Oddjob]

Awesome story Oddjob, thanks for sharing.

So if no gold is coming down in floods, is all the gold below being flushed out of the river or does it hang around in roughly the same area for a long time and the amount of time the dam has been there is irrelevant?

Dude I am no expert at all; my brother in law pointed us in that direction. It is nothing more than little creek dam about 6 foot tall, 40 feet wide and no gates. He showed us that we needed to be hunting on the upstream side of it and said that only fines would be found on the down stream side of it. After the haul they pulled out of there we all decided he knew this better than us.

The ground in that area is full of gold, but we were dredging streams far down from that.

To be very honest with you, I was sort hoping that one of the experts on here could answer your question better than my little claim could. Heck its the Carpathians, nothing is normal there and I would like to just as much as you would.

Arizau makes some good points, would not help me because I would not go near a dam that would require gates.

I am sure others will chime in soon enough and then you will have a pretty good combined effort to assist you; and I will learn something to just in case I find another little dam in the real world.

 

[OwenT]

So what I got from skimming that paper was that dams can keep things from being replaced downstream as they are flushed out, but they can also keep the water flow downstream from being as strong so not as much material would be moving along the river either. It talked about gravel replacement where they actual throw gravel in below the dams every year to replace it, wow.

 

[OwenT]

I wonder how close they'd let you get a dredge to dam?

 

[Au dave]

Thanks all for this thread, over my last few trips the gold has been getting sparse and a little exploration up from my new spot I have discovered a natural dam in the creek, this could be the reason....food for thought

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