BOISE — The National Weather Service is warning Idaho residents using National Forest lands to be wary of possible flash flooding, as recent wildfires have scorched rain-sopping vegetation from hillsides.
A flash flood watch goes into effect at midnight Monday and continues through Tuesday on Boise National Forest areas burned by the massive Elk, Pony and Little Queens fires.
A flash flood watch is also in effect for the Payette National Forest, where the Weiser Complex Fire has burned about 40 square miles along the Snake River near Brownlee Reservoir.
Forest managers say fire-hardened soil will repel rainfall, preventing it from soaking into the earth, and heavy rain is expected in recently burned areas beginning Monday night. As a consequence, creeks and rivers could swell quickly.
“Travelers should be cautious if high water is encountered at creek crossings and avoid those areas,” said Boise National Forest spokesman David Olson. “In addition, minimizing travel on roads in burned areas is suggested until the flood watch elapses due to the risk of rocks falling onto a road.”
Forest managers are also warning of the potential for increased rock fall, as well as partially burned snag trees plummeting down charred hillsides.
Culverts have an increased chance of plugging due to the high flows and could wash out road surfaces quickly, potentially cutting people off behind land or rock slides.