Forest Service public affairs officer Frank Carrol says the fire created "hydrophobic" soil conditions in which water runs off without being absorbed. The volume of water overwhelmed stream channels, he says, and eroded and collapsed their banks.
The storm closed numerous logging roads and created a log dam that rerouted the Boise River over the top of Forest Service road 268, which accesses the small community of Atlanta.
Steve Yundt of Idaho Fish and Game believes the fish populations in at least a portion of the Boise and Crooked rivers were "wiped out."
Yundt says the washouts were not influenced by the logging and road construction in the area, but he warned that further logging activities will increase the probability of future landslides.
Some environmentalists believe logging played a role. "Most of the mud came from logging roads and slopes bared by previous logging," says Ron Mitchell of the Idaho Sporting Congress. "Crooked River ran clear until it hit a road washout, but everything downstream of the road was scoured by a torrent of mud."
The Boise National Forest has no immediate plans to alter the logging project.