Hikers should stick to flat trails until it's clear where recent rains have softened mountainsides, Juneau's emergency program manager said Wednesday.
"We really don't know what is stable and what is not," Michael Patterson said.
At least one popular walk is closed until repairs can be made next spring.
A 100-foot chunk on the Salmon Creek Trail washed out, leaving no ledge for cars or hikers to pass. The damaged portion of the trail is a service road for a dam operated by Alaska Electric Light and Power Co.
The company will hire a contractor to repair the road and an engineering firm is looking at short- and long-term solutions, said Gayle Wood, spokeswoman for the utility.
For the time being, workers will reach the dam via helicopter, Wood said.
A "no trespassing" sign is posted at the trail entrance. In the middle of the missing road is an exposed penstock, or the pipe that conveys water from the dam above to a power station located near Egan Drive.
The damaged area may continue to erode, Patterson said.
The trail, starting near Bartlett Regional Hospital, is one of the more popular routes in Juneau for its wide and smooth surfaces. The damaged portion is about 200 feet above the creek, Patterson said.
Patterson and the group Trail Mix are getting reports of minor damage on various trails, but nothing as serious as Salmon Creek. James King, director of Trail Mix, said parts of the Perseverance Trail near Basin Road downtown have eroded.
Where trails were clear of debris, the sections are now holding larger rocks that may have slid from above, King said. The newly surfaced Herbert Glacier Trail was not damaged from the storms.
With rainfall frozen inside the trails, the ice acts as glue to hold many of them together. The hikes may appear to be stable, but as ice melts, pressure on the ground from hikers can trigger mud and rock slides, Patterson said.
Trails with steep inclines such as those on Mount Roberts and Thunder Mountain are not as safe as flat ones, such as the path by Juneau International Airport, Patterson said.
Record rainfalls in Juneau during the past two weeks loosened mud and rocks that fell on city streets and landed between homes. City and state cleanup efforts continue.