Bonaro -
Not sure that the paper that you generously provided the link to makes your case of limited impacts to stream habitat, water quality and biota from dredging. I admit that I only quickly read the paper (to lazy to go through it in great detail.

However it is clear that the paper was looking at fishless streams (or at least did not consider direct impacts on fish resources. It should be obvious by now that most of many of our concerns are fish based. Further the authors were unable to tease out what the chronic effects from mining/dredging. Did returning to "original" conditions mean historic conditions pre-mining or what had become the new "norm"?

It is clear that while a year or so after the dredging activities things looked more or least "norm" there also short term and localized impacts. The importance of those impacts likely would vary depending on the specifics of the particular situation. A couple things that jumped out to me if there were co-existing fish populations was the release of heavy metals at the site (and downstream for some distance). Those heavy metals are lethal to fish eggs and young fry are surprising low concentration. Of further concern was the concentration of some of those metals in the insects. Not only what those metals might do to the potential biomass of insects but how those metals may be further concentrated in the fish communities that may exist in the same system.

The authors did say that there were reductions in the biomass of periphyton (the foundation of the food chain) that in at least one case lasted into the following year. In the discussion of invertebrates the point was made that species richness and density remain more or less the same however the question of the biomass of those invertebrates was left unanswered.

Sorry cherry picking papers and data does not necessarily make your case.

Curt