Abstract
Abstract. Rock glaciers are creep phenomena of mountain permafrost. Typically, these landforms look like lava flows from a bird’s eye view. Active rock glaciers move downslope with flow velocities in the range of few centimeters to several meters per year. Thus, large masses of rock and ice can be gradually transported down-valley. In this paper we present a comparative study analyzing surface change for Tschadinhorn rock glacier, a relatively fast moving rock glacier located in the Hohe Tauern Range of the Austrian Alps. Aerial photographs (1954–2017) of both metric (conventional) and non-metric (UAV-based) aerial surveys were compared to derive multi-annual to annual flow vector fields and surface height change. For each time interval given we computed a single representative value for flow velocity and, if applicable, also for area-wide surface height change, i.e. volume change. The velocity graph obtained represents the temporal evolution of the kinematics of the rock glacier with good discrimination. Volume change was difficult to quantify since temporal changes were rather small and close to insignificance. The precision and accuracy of the results obtained were numerically quantified. Our study showed that for the Tschadinhorn rock glacier UAV-based aerial surveys can substitute conventional aerial surveys as carried out by national mapping agencies, such as the Austrian Federal Office of Metrology and Surveying (BEV). Thus, UAV-based aerial surveys can help to bridge the data gap between regular aerial surveys. The high accuracy of the UAV-derived results would even allow intra-annual change detection of flow velocity.
Highlights
1.1 Rock glacier monitoringRock glaciers are creep phenomena of mountain permafrost and can be found in all high mountain areas of the Earth (Barsch, 1996)
In this paper we use aerial photographs taken from both manned aircraft and unmanned aerial vehicles (UAVs) in order to retrieve multi-annual to annual kinematic data of the fast moving Tschadinhorn rock glacier
The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XLII-1, 2018 ISPRS TC I Mid-term Symposium “Innovative Sensing – From Sensors to Methods and Applications”, 10–12 October 2018, Karlsruhe, Germany scheduled BEV survey. All of these data were processed to provide the basis of the intended monitoring of Tschadinhorn rock glacier using both multi-temporal high resolution digital orthophotos (DOPs) and digital terrain models (DTMs)
Summary
Rock glaciers are creep phenomena of mountain permafrost and can be found in all high mountain areas of the Earth (Barsch, 1996). Rock glaciers are composed of rock debris and ice and are common geomorphological landforms of the periglacial environment. Rock glaciers move downslope by force of gravity as a result of the plastic deformation of their interstitial ice and other internal processes, such as sliding along distinct shear horizons. They become deformed over time, acting as prominent mass transport systems in alpine environments. Flow/creep velocities of rock glaciers are in the order of a few centimeters to several meters per year and movement rates may change from year to year. It is believed that medium to longterm acceleration/deceleration of rock glacier movement is caused by climate change, i.e. atmospheric warming/cooling. A clear answer can only be given by a thorough surface mass balance analysis as used in glaciology, which includes all kinds of mass flow to/from the catchment area where the rock glacier is located
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