Rock Fall Risk Study Leads to Closures at Yosemite National Park

Popular visitor lodging areas at Yosemite Valley will be closed permanently due to risk of rock falls after a report was released, according to officials today. Yosemite National Park and the U.S. Geological Survey quantitatively assessed rock fall risk in Yosemite Valley to identify hazard areas, which prompted park officials to announce that 18 sites -- canvas and wood cabins -- in Curry Village and six campsites near El Captian will be closed due to high risk.

"Rock falls are common in Yosemite Valley, California, posing substantial hazard and risk to the approximately four million people that visit Yosemite National Park each year," the report notes.

Researchers used a variety of techniques -- including laser mapping and a three-dimensional computer program that simulates rock-fall runout -- to create an analysis of cliffs and pinpoint the greatest danger of boulder crashes. While being 180 feet of the base of the cliff is the greatest danger area, there is about a 10 percent chance of rock fall farther out every 50 years.

The majority of rock falls occur during winter and spring, particularly during periods of heavy rainfall, snow melt, or subfreezing temperatures. However, large rock falls have also been documented during warmer weather.

Two rock falls caused minor injuries and significant structural damage in Curry Village in October 2008. The park permanently closed down several accommodations and employee housing units as a result of the damage and to reduce overall risk. The new closures, combined with the ones from 2008, will further reduce overall risk associated with structures in the Yosemite Valley by 95 percent, according to the National Park Service.

Since 1857, rock falls in the area have killed 15 people and injured 85.

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