High-Resolution Imaging of Rock Falls in Yosemite National Park

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