High-resolution three-dimensional imaging and analysis of rock falls in Yosemite Valley, California

Abstract

We present quantitative analyses of recent large rock falls in Yosemite Valley, California, using integrated high-resolution imaging techniques. Rock falls commonly occur from the glacially sculpted granitic walls of Yosemite Valley, modifying this iconic landscape but also posing signifi cant potential hazards and risks. Two large rock falls occurred from the cliff beneath Glacier Point in eastern Yosemite Valley on 7 and 8 October 2008, causing minor injuries and damaging structures in a developed area. We used a combination of gigapixel photography, airborne laser scanning (ALS) data, and ground-based terrestrial laser scanning (TLS) data to characterize the rock-fall detachment surface and adjacent cliff area, quantify the rock-fall volume, evaluate the geologic structure that contributed to failure, and assess the likely failure mode. We merged the ALS and TLS data to resolve the complex, vertical to overhanging topography of the Glacier Point area in three dimensions, and integrated these data with gigapixel photographs to fully image the cliff face in high resolution. Three-dimensional analysis of repeat TLS data reveals that the cumulative failure consisted of a near-planar rock slab with a maximum length of 69.0 m, a mean thickness of 2.1 m, a detachment surface area of 2750 m 2 , and a volume of 5663 ± 36 m 3. Failure occurred along a surfaceparallel , vertically oriented sheeting joint in a clear example of granitic exfoliation. Stress concentration at crack tips likely propagated fractures through the partially attached slab, leading to failure. Our results demonstrate the utility of high-resolution imaging techniques for quantifying far-range (>1 km) rock falls occurring from the largely inaccessible, vertical rock faces of Yosemite Valley, and for providing highly accurate and precise data needed for rock-fall hazard assessment.

Remote Sensing for Landslide Investigations: An Overview of Recent Achievements and Perspectives

“…Laser scanning integrated with UAV platforms proved to be helpful in rockslide detection [128]. RS techniques such as ALS, TLS and high-resolution photogrammetry were coupled with traditional field surveys to do a better quantitative characterization of rock fall source areas and to better understand the variables and the processes involved [129].…”

“…In fact, increase of fragmental rock fall activity might be a precursory signal of major events (see, e.g., [228]), while decrease might be a sign of stabilization [229]. In Stock et al [129], this task was achieved by integrating 3D data coming from TLS surveys and high-resolution images captured from terrestrial cameras. Results from [217,222] showed that TLS could be applied to detect millimetre scale displacements prior to a rock fall event.…”

“…The analysis of erosion phenomena deserves a separate mention, which may contribute to the creation of debris flow in rivers and hence they may result in sediment supply being involved in subsequent landslides [226] or debris flows [291]. Estimation of eroded volumes is not straightforward: in the literature, there are some empirical formulae aimed at furnishing the magnitude of the sediment supply, but the best approach is to quantify it by means of laser scanning and photogrammetry [121,122,129,204,235].…”

Significance of rockfall magnitude and carbonate dissolution for rock slope erosion and geomorphic work on Alpine limestone cliffs (Reintal, German Alps)

“…The ubiquitous small-scale rockfall deposits can often not be assigned to a certain fall event and, thus, volume estimations require direct measurements, which are time-consuming and labour-intensive. A number of recent LiDAR (LIght Detection and Ranging) inventories provide unprecedented magnitude-frequency relations ranging from debris falls to block falls (Rosser et al, 2005;Abellan et al, 2011;Lim et al, 2011;Young et al, 2011) or detailed data on the disintegration of single large block falls and cliff falls (Oppikofer et al, 2008;Stock et al, 2011). While many scientists expected that LiDAR could overcome the magnitude-frequency data deficiency for smaller magnitudes, LiDAR is often incapable of quantifying small-scale rockfall activity with particles smaller than 5-7 cm (Rabatel et al, 2008;Lim et al, 2010) which may contribute a major share to mass wasting in many mountain environments (Krautblatter and Moser, 2009).…”

Common problems encountered in 3D mapping of geological contacts using high-resolution terrain and image data

“…Current challenges in geological mapping consist in collecting more consistent 3D data, but also in harmonizing geological information to build better geological models. New remote sensing techniques such as LiDAR [e.g., Lim et al, 2010;Jaboyedoff et al, 2012;Abellán et al, 2014], Photogrammetry [e.g., Sturzenegger and Stead, 2009;Firpo et al, 2011;Curtaz et al, 2014] and gigapixel photography [Stock et al, 2011;Lato et al, 2012;Kromer et al, 2014] have significantly improved the representation of three-dimensional surfaces during the last decade, especially for steep and inaccessible rock cliffs, allowing the development of high-resolution 2D geological maps [Putnam et al, 2014]. These techniques have also been used for the characterization of petroleum reservoir analogues and fracture systems at outcrop level [Olariu et al, 2008;Rotevatn, 2009;De Souza et al, 2013;Hodgetts, 2013;Penasa et al, 2014], texturing of high-resolution panoramas on digital outcrop models [Buckley et al, 2008[Buckley et al, , 2010Minisini et al, 2014] and 3D geological/mineralogical mapping [Sima et al, 2012;Kurz et al, 2013;Murphy et al, 2013].…”