Let the River Run

“Whether you instantaneously remove a structure or you take it down in stages turns out to be a huge determinant about the nature and mechanism of the downstream erosion,” says Gordon Grant, a geomorphologist at the U.S. Forest Service’s Pacific Northwest Research Station in Corvallis, Ore. “We sort of knew this, but we hadn’t really explored and understood it. How does a river get its teeth back into all this stored sediment?”