New fence above Multnomah Falls Lodge designed to catch falling boulders
CASCADE LOCKS, Ore. – Workers installed a fence on the cliff above Multnomah Falls Lodge to protect visitors from falling debris in the wake of the Eagle Creek Fire.
The wildfire that swept through the Columbia River Gorge burned away vegetation that could slow down or even stop falling rocks. It also loosened rock and debris when flames destroyed moss and soil holding rocks in place.
A group of U.S. Forest Service specialists known as the Burned Area Emergency Response (BAER) team started looking at potential rockfall hazards in the Eagle Creek burn area five months ago when the fire was still just 50 percent contained.
"And when they came in to assess hazards and how to mitigate it," said U.S. Forest Service spokesperson Rachel Pawlitz, "one of the things they did was ran a computer simulation model to see what some of the geologic processes in the gorge are and how they work."
The team used computer software developed by the Colorado Geological Survey to simulate what boulders of various sizes would do when they tumble from the now-barren cliff face above Multnomah Falls Lodge.
"When they modeled thousands of rocks, they designed it to catch 98 percent of the rocks that came down," said Pawlitz.
The U.S. Forest Service said the new 8-foot fence can stop boulders, and is strong enough to stop the force of a full-size pickup going 35-mph.
“By running the simulation model, they looked at the size and the angularity of the rocks and they looked at the surrounding topography to see how far would they go, how much energy would they have and how high would they bounce,” said Pawlitz.
The lodge is back open to the public after being forced to close by the fire. The Multnomah Falls lower viewing area is still closed.
Crews plan to replace another rockfall fence higher up on the cliff near Multnomah Falls before reopening the falls viewing area.
"So that we can safely get the public back up to Benson Bridge and to the upper viewing platform," said Ryan Cole, an engineering geologist with the Mount Hood National Forest.