Detailed Yosemite Rockfall Report
Yosemite Valley River
Yosemite, CA - National Park and USGS scientists, in collaboration with academic geologists, completed an internationally peer-reviewed study. The study utilized new data and technologies to map the cliffs and talus slopes, date ancient rockfalls, and perform computer simulations of potential future rockfalls.
Existing structures within the hazard line were evaluated using a numerical "risk metric" that quantifies the risk posed to human life and safety. Several high-risk structures within the hazard zone will no longer be occupied and others will be repurposed or relocated as the policy is implemented.
Structures that will be closed include some concessionaire employee housing and a few hard-sided cabins and tent cabins at Curry Village, which will no longer be available for occupancy.
Yosemite National Park Spokesperson Kari Cobb says, "Although it is not practical to eliminate all rockfall risk, these actions, combined with the closures in Curry Village implemented in 2008, will reduce the overall risk associated with structures in Yosemite Valley by 95 percent."
Rockfalls are natural processes that continue to shape Yosemite Valley. More than 900 rockfalls have been documented over the 150 years of the park's history, a few people have been killed by such geologic hazards and many others injured.
The information in the study was adopted by Yosemite National Park this month. The full report, Quantitative Rockfall Hazard and Risk Assessment for Yosemite Valley, Yosemite National Park, California, can be found at www.nps.gov/yose/naturescience/rockfall.htm.
Written by Sabrina Ambler