Abstract
Abstract. Tourists and hikers visiting glaciers all year round face hazards such as sudden terminus collapses, typical of such a dynamically evolving environment. In this study, we analyzed the potential of different survey techniques to analyze hazards of the Forni Glacier, an important geosite located in Stelvio Park (Italian Alps). We carried out surveys in the 2016 ablation season and compared point clouds generated from an unmanned aerial vehicle (UAV) survey, close-range photogrammetry and terrestrial laser scanning (TLS). To investigate the evolution of glacier hazards and evaluate the glacier thinning rate, we also used UAV data collected in 2014 and a digital elevation model (DEM) created from an aerial photogrammetric survey of 2007. We found that the integration between terrestrial and UAV photogrammetry is ideal for mapping hazards related to the glacier collapse, while TLS is affected by occlusions and is logistically complex in glacial terrain. Photogrammetric techniques can therefore replace TLS for glacier studies and UAV-based DEMs hold potential for becoming a standard tool in the investigation of glacier thickness changes. Based on our data sets, an increase in the size of collapses was found over the study period, and the glacier thinning rates went from 4.55 ± 0.24 m a−1 between 2007 and 2014 to 5.20 ± 1.11 m a−1 between 2014 and 2016.
Highlights
Glacier- and permafrost-related hazards can be a serious threat to humans and infrastructure in high mountain regions (Carey et al, 2014)
In relation to unmanned aerial vehicle (UAV) photogrammetry, similar point densities were found in all sample locations, especially for the standard deviations that were always in the 22–29 point m−2 range
terrestrial laser scanning (TLS) suffered from severe occlusions, which prevented acquisition of data in the central part of the sample area, while UAV photogrammetry was able to reconstruct the upper portion of the sample area but not the vertical cliff
Summary
Glacier- and permafrost-related hazards can be a serious threat to humans and infrastructure in high mountain regions (Carey et al, 2014). But still threatening for mountaineers, are the detachment of seracs (Riccardi et al, 2010) or the collapse of ice cavities (Gagliardini et al, 2011; Azzoni et al, 2017). While these processes are in part typical of glacial and periglacial environments, there is evidence that climate change is increasing the likelihood of specific hazards (Kaab et al, 2005a). Glacier and permafrost retreat, which has been reported in all sectors of the Alps (Smiraglia et al, 2015; Fischer et al, 2014; Gardent et al, 2014; Harris et al, 2009), is a major cause of slope instabilities, which can result in debris flows by debuttressing rock and debris flanks and promot-
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