From OPB: A new study sums up what scientists now know about the environmental effects of removing dams from rivers.
It concludes that rivers and fish respond quickly after a dam is removed, and the results are mostly positive.
Before dam removal had been studied, Grant said, scientists thought it might take decades for rivers to disperse the accumulated sediment. But that was not the case in almost all the documented cases. In most cases, it was only a matter of weeks or months.