On a muggy day in late August, George Jackman, an aquatic ecologist who works on habitat restoration, stood at the edge of Quassaick Creek in upstate New York.
The Quassaick, which flows through the small city of Newburgh, New York, and spills into the Hudson River, was unusually shallow after a summer with little rain. “It looks bucolic now,” Jackman said. “But it can be a raging torrent.”