A study performed by the U.S. Geological survey and published in Science reveals that rivers respond quickly to dam removal. In the past forty years, more than 1000 dams have been removed from US rivers due to safety concerns, sediment buildup, and inefficiency. According to Jim O’Connor, a geologist with the U.S.G.S. and lead author of the study, “rivers quickly erode sediment accumulated in former reservoirs and redistribute it downstream, commonly returning the river to conditions similar to those prior to impoundment." Because of this, more and more dams are coming down as a means of river restoration.