High-Resolution Imaging of Rock Falls in Yosemite National Park

Yosemite Valley has experienced over 600 rock falls since 1850, but determining the exact source areas, volumes, and failuremechanisms for these rock falls has previously been difficult because of a lack of comprehensive imagery of the cliff faces.We obtained high-resolution imagery, acquired before and after large rock falls in Yosemite Valley, California, by combiningof gigapixel panoramic photography and terrestrial laser scanning (LiDAR). Following comprehensive baseline imageacquisition of Glacier Point in eastern Yosemite Valley, two large rock falls occurred from within the imaged area in Octoberof 2008. We used repeat gigapixel photography acquired with GigaPans to characterize the rock-fall detachment surface andadjacent cliff area in high resolution. Coupled with LiDAR analyses, these photos reveal that the rock falls consisted of a nearplanar, vertically oriented rock slab with a detachment surface area of 2,409 m2 and a volume of 5,663 m3. These data informhazard assessment for this and other rock-fall events in Yosemite. Our results demonstrate the utility of high-resolutionimaging techniques for quantifying rock falls from the large vertical rock faces of Yosemite Valley.