The Stream Doctor

December 1st, 2003

Email YOUR Questions directly to the Stream Doctor. This is your opportunity to get an experts professional opinion on anything stream related.

Q. From GCMRiff: Do you have any info or opinions on the effects of small scale gold suction dredging?

A. Yes, in both cases. First of all, I'm not sure just what you mean by "small scale gold suction dredging." This could range from one guy in a SCUBA outfit suctioning stream beds to a "small scale" commercial operation. If you could be more specific, I might give you a better response than what is below.

Any suction dredging of streams can and probably will have a deleterious effect on the ecology of a stream; the scale of the operation is what is important. At a minimum, it will probably destroy the benthic invertebrates living on and among the stones that are dislodged. Some of these may survive and drift downstream, but some will not. This is a direct physical impact. On top of that, the silt and fine sand stirred up will settle out on the stones ownstream, coating the algae and invertebrates with a layer of sediments that can wipe them out. This material can also be harmful to salmonid reproduction if the suspended sediments settle in redds and suffocate the developing embryos. Now a single diver turning over stones in pools looking for nuggets probably won't have a serious impact, but escalation from this will result in an escalation of the impacts. There is a lot of scientific information published on the impacts of dredging on stream ecology, and this would be applicable whether they were dredging for gold or gravel. All of it says essentially what I've said above; the impacts are mainly from physical disruption of the habitat and the downstream impact of the suspended sediments. In some cases, chemical impacts can also result if the dredging operation introduces chemicals into the stream or alters the natural chemical regime.

If you have a question, please feel free to contact me.
~ C. E. (Bert) Cushing, aka Streamdoctor
105 W. Cherokee Dr.
Estes Park, CO 80517
Phone: 970-577-1584

The 'Stream Doctor' is a retired professional stream ecologist and author, now living in the West and spending way too much time fly-fishing. You are invited to submit questions relating to anything stream related directly to him for use in this Q & A Feature at

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