Do flood channels change where gold travels? (image included)

[Ragnor]

I have been working on this problem in my head. I'm about to go to work on it on the ground. I'm just wondering what people with practical experience have found regarding this scenario. In the image shown we can see the area in question and the stream bed approximately as it is today.

The orange line indicates the river channel during epic floods.
The blue line indicates the flood channel proper.
The green line represents a dike formation. (exposed bedrock)
The broken yellow line is the text book gold line (theoretical paystreak)
highlighted in red a massive hole on a contact zone (estimated depth 30' below water level)
The brushy area between the blue line and the yellow line is a large alluvial deposit formed in 1996 from a massive flood.



My question is this. During extremely high water, when the river flows through the flood channel. Should that cause a large dropout point for gold blown out of the deep hole to settle at the upper mouth of the flood channel?

Basically can people with practical experience suggest the most likely dropout point and does the drop out point change when the river suddenly becomes twice as wide during big floods.

I am trying to decide if I should trench the flood channel to bedrock and take samples. Is that a reasonable expectation? That gold will concentrate around the head of the alluvial pile and into the inside corner of the flood channel on bedrock? It looks good to me on paper, but it's going to be a little time consuming digging those trenches.

 

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[DizzyDigger]

My question is this. During extremely high water, when the river flows through the flood channel. Should that cause a large dropout point for gold blown out of the deep hole to settle at the upper mouth of the flood channel?

Possibly...I would sample (down to about 10") from the bottom of the hole to the upper mouth.

Basically can people with practical experience suggest the most likely dropout point and does the drop out point change when the river suddenly becomes twice as wide during big floods.
I am trying to decide if I should trench the flood channel to bedrock and take samples. Is that a reasonable expectation? That gold will concentrate around the head of the alluvial pile and into the inside corner of the flood channel on bedrock? It looks good to me on paper, but it's going to be a little time consuming digging those trenches.

I wouldn't try to trench to bedrock...could be 80' down in that area.

Definitely check the inside corners!

Sent you PM.

 

[63bkpkr]

Massive floods will do massive dirt moving IF there is dirt or gravel to move and IF there is a limited amount of solid rock walls along the water flow path. If there is a solid rock wall to contain the massive flood then it has to stay within that boundary however if there is a cut through the solid rock then a portion of the flood will go through it. It all depends on the how solid the containment walls are along the path of the flood. One could expect to locate gold on high benches along the path of the flood. An interesting problem I've thought about before - yours sounds like a heck of a lot of work so be careful of your body!............63bkpkr

 

[Hoser John]

The only problem with massive floods,especially the 96 dredge stealer, is that it didn't last long enough to reconstitute the paystreaks that take MUCH time to form. You end up with a debris blast that scours the bedrock ,mixes it all up with tree stumps,massive boulders and ungodly amount of debris ripped from the hillsides. Our great Sacramento river up here that produced fantastic gold for dozens and dozens of years is now a ungodly mess with 15-30' of overburden intermixed with over 20 miles of train tracks, and wood cross supports to create massive islands,especially below Dunsmuir. Look for landslides that came into the flow as the spot to go to start. John

 

[Jeff95531]

From watching Docs videos, I get this (maybe right maybe not but is as I remember) he says the bottom gets calmer as the river rises. Soo, I'd be finding a way to at least sample the bottom of the hole (dredge, anchor, 30' pole/hose) and then follow the yellow brick road.

 

[KevinInColorado]

Only one way to know...dig a hole! In Clear Creek in north metro Denver, there's a layer about 18" down full of good gold and pitch black rocks (dyed by the organic material mixed into that layer). It's from a major flood 20ish years ago, has the best gold of all the reachable layers of material, and is not aligned with the current goldmine of the waterway. Floods are tricky!

(Sorry, I know that's not really helpful but as you can see from the posts above, there's a whole range of possibilities)

 

[kcm]

I was just about to say that water moves faster on the surface. This is the general rule, but a few things can break that rule for a brief time by forcing large amounts of water down deeper quickly. You'll often see the telltale sign of a whirlpool. In the ocean, this would be called an undertow, I think.

I'm with Jeff - concentrate on the 30' hole if you can. Wait for a time of calm waters (as it goes there) and then find a friend with diving experience and gear to go down and investigate - or maybe buy yourself a video camera and build a waterproof box to lower down while it's recording - get an idea of what's down there.

 

[Jeff95531]

Yeah but after reading M.E.G.'s thread working the bottom of the falls, I'm having second thoughts. There is likely a ton of debris on top of the bottom. Did I say that right

 

[mike(swWash)]

Maybe I missed something, does the creek go left to right or right to left?

I'd be digging the crap out of the little gravel bar myself to start with or dredge towards it from up stream.

 

[Jeff95531]

I was thinking right to left mike. Nice honey hole if able to get to the bottom of it.

 

[63bkpkr]

Along the NFAR just down river from where the Beacroft Trail touches the valley floor there is this great waterfall, not to wide, not to tall off of the water, 10'(?) (during summer when it is safe to swim it) with a pool under the falls that is 15' - 20' deep. "On the top of the bottom", lies a good sized group of good sized boulders. Historically some miner's dug a tunnel around the falls and flumed the water further down stream allowing them to, I will guess here, clear the overburden from the bottom of the bedrock. What did they find, was it worth it? It was one heck of a lot of work for the adventure!


Moving large rocks should be done by winching and that requires some heavy duty equipment and more work and help. Someone once told me to "Pick my fights wisely"! Don't know that I've really listened to that wisdom (both shoulders need surgery) though I think it has some value to it Be careful with yourself and best of luck.....................63bkpkr

 

[Ragnor]

Maybe I missed something, does the creek go left to right or right to left?

I'd be digging the crap out of the little gravel bar myself to start with or dredge towards it from up stream.

The stream flow is from right to left, It comes out of a steep bedrock canyon and flares out just behind the hole. It's the first big dropout in the system. The problem with that gravel bar is that it gets allot of material from the landslide area just below the hole. It's Qal (Quaternary alluvium) it does not appear to carry much values in that slide area. bedrock is 8-10 feet at that gravel bar.

 

[Ragnor]

In this case I do not see any way to re-route the water, even if it were legal. Well, not without a massive undertaking. Including blocking downsteam to prevent back-flow. It's just too shallow of a grade.

Someone asked is the flood channel the old channel? I did some looking and digging in there yesterday. The channels shows some very old decaying bedrock at one end. There is also a second bench about 15-20 feet above that channel. My guess is land slides occasionally divert the stream to that side of the canyon. When and how often is anyones guess. I started hitting compacted gravel @ about 3' in the channel. It did not get any gold from there. The hole went below the water table and started filling with water and sluffing so I moved up stream. My observations put bedrock at around 8'. Certainly more than a one man job if I plan to work any other areas this summer.

 

[wtetro]

Any chance gold gets to drop, it will...a deep channel will typically have slower moving water, less turbulent and with depth gives gold more opportunity to settle. I know gold travels the least path of resistance. Have you tried a lead weighted balloon? For me, if I saw that channel, and there are land slides falling into that stream, I'd at least sample the front and inside edges of the channel, especially where you have the blue line drawn. If it cuts like that, there's an eddy created and gold will take up residence there...ya ya ya, gold is where you find it, but that's where I'd start on the channel. Right where the yellow dotted line hits the channel proper, I'd hit that area first. Looks like a nice find, let us know what the results are

 

[Terry Soloman]

I would think there would be multiple drop outs. Certainly at the mouth coming out of the "steep bedrock canyon and flares out." But keeping in mind what Hoser John pointed out about flood walls moving down stream - "...You end up with a debris blast that scours the bedrock ,mixes it all up with tree stumps,massive boulders and ungodly amount of debris ripped from the hillsides. ...Look for landslides that came into the flow as the spot to go to start." Great advice. I would also hit that downstream curve like a $100.00 date, if you get my drift.

 

[johnedoe]

This may offer some insights to see how rivers move and change a bit.....
http://www.eeescience.utoledo.edu/Faculty/Krantz/Hazards/Hazards.Chap_05b.meandering_rivers.pdf