From Resources Coalition:
The effects of suction dredging for gold have long since been determined to be considered “de minimis” or simply stated; so minor as to merit disregard! We keep having environmental groups make claims that suction dredging destroys fish habitat, and that the only solution is to completely ban suction dredging altogether.
I have never understood how anyone could make such a statement with a straight face. It must be that they do not understand geology or even more specifically fluvial geomorphology. It may be that they just don’t like suction dredging!
Mt. St. Helens erupted on May 18, 1980 with a total force equivalent to 400 million tons of TNT, the same as 20,000 Hiroshima size atomic bombs. The natural catastrophe left behind became a living laboratory to study the geologic and life processes which were both affected in a dramatic and sudden fashion.
The North Fork of the Toutle River experienced a major lahar, the debris from the eruption traveled down the Toutle River a distance of approximately seventeen miles, and then all the way to the mighty Columbia River. It was thought that all fish were killed and the river would be sterile for generations to come.
Continue reading here: http://www.resourcescoalition.org/Toutle.html