Rugged and isolated, the Rubicon River Valley on the border of El Dorado and Placer counties was for many years an idyll of old growth trees and icy swimming holes. Then the King fire roared through last month, turning a 20-mile stretch of the canyon into a vast dead zone of ashen earth and smoldering stumps.

Experts now worry that the devastation and the extreme temperatures of the fire, which scorched much of the soil and reduced its ability to hold together and absorb runoff, could lead to floods and mudslides when winter storms arrive. The same conditions affect parts of the south fork of the American River near Pollock Pines, where an arsonist allegedly started the 98,000-acre King fire on Sept. 13.

Members of the U.S. Forest Service’s Burned Area Emergency Response team, or BAER, swooped in last week, as the fire was finally contained, to assess the immediate dangers remaining in its aftermath. Members include botanists, hydrologists and geologists. Their job is to deal with such immediate threats as falling trees and crumbling roads.

BAER coordinator Eric Nicita said possible mudslides are a major concern, because when the top layer of soil cooks, it looses the fungi, bacteria and other organic material that hold it together and allow it to absorb water. In these conditions, rain runs through soil and tears it down instead of percolating into the earth.

“The only thing the water can do is roll downslope,” said Nicita, a soil scientist with the Forest Service. “All of a sudden, your flow is increasing incredibly.”