Dave - To answer your question, yes, I have seen the Klondike river and I have dredged in the Alaska interior on the Fortymile river.
I'm glad you made an example out of the Klondike, it's a great opportunity for me to dispel a common myth about modern dredging.

Below is a pic of a Klondike gold dredge, It is about 150' long and 40' wide. I chose this pic because it has a good viewing angle, most bucketline dredges were actually twice this size. On the front is a continuous chain of buckets on a submersible boom (think giant chainsaw) that scoop up the bottom. The gravel is processed inside the building and dumped out the back via a conveyor up to an additional 150' long. They literally moved every bit of gravel in the entire valley and left miles of tailing piles in their path. I do not know of a single one still in operation in the north America. The last one shut down over 50 years ago.




This is a photo of a gold dredge exactly like mine. It has a 5" intake hose and is the largest allowed in this state and is larger than what most washington dredgers use. The dredge and all of it's associated gear will fit easily into the back of my shortbed pickup.




You are correct that "any damn fool" can see the "major riparian damage" of The huge bucketline dredges that have worked in the Klondike but certainly "any damn fool" can see the difference in the scale of the work being done by modern small scale mining dredges compared to the commercial operations of a century ago.

Back in those pioneer days logging practice was clearcut and burn and no replant. Fishing was sometimes done with poisons or dynamite. Times have changed and all industries have modernized their practices and machines, mining is no exception.