Engineering-Geological Analysis of a Subaerial Landslide in Taan Fiord, Alaska

Abstract

On 17 October 2015, a large-scale subaerial landslide occurred in Taan Fiord, Alaska, which released about 50 Mm3 of rock. This entered the water body and triggered a tsunami with a runup of up to 193 m. This paper aims to simulate the possible formation of a weak layer in this mountainous slope until collapse, and to analyze the possible triggering factors of this landslide event from a geotechnical engineering perspective so that a deeper understanding of this large landslide event can be gained. We analyzed different remote-sensing datasets to characterize the evolution of the coastal landslide process. Based on the acquired remote-sensing data, Digital Elevation Models were derived, on which we employed a 2D limit equilibrium method in this study to calculate the safety factor and compare the location of the associated sliding surface with the most probable actual location at which this landslide occurred. The calculation results reflect the development process of this slope collapse. In this case study, past earthquakes, rainfall before this landslide event, and glacial melting at the toe may have influenced the stability of this slope. The glacial retreat is likely to be the most significant direct triggering factor for this slope failure. This research work illustrates the applicability of multi-temporal remote sensing data of slope morphology to constrain preliminary slope stability analyses, aiming to investigate large-scale landslide processes. This interdisciplinary approach confirms the effectiveness of the combination of aerial data acquisition and traditional slope stability analyses. This case study also demonstrates the significance of a climate change for landslide hazard assessment, and that the interaction of natural hazards in terms of multi-hazards cannot be ignored.

A Sustainable Approach to Geomatic Methods in Ravine Monitoring and Associated Natural Disaster Prevention

“…International research papers on landslides and hill stability monitoring can show us new methods that we can try to integrate in the study of the erosion process. Different methods have been used in other research papers, as follows: "Owing to the complex nature and inconsistent mechanism of landslides, understanding the major triggering factors underlying their occurrences and modeling their spatial probability have been challenging tasks, mainly researched through statistical, deterministic, and heuristic approaches" [16]. "The statistical methods are usually constructed using linear correction analysis between historical landslides and predisposing factors.…”

Sensitivitätsanalyse der unterschiedlichen Einflussfaktoren auf numerische Untersuchungen von Hangrutschungen

“…Both landslides have been well documented and investigated [1,2]. The failure mechanisms and likely triggering mechanisms have been established.…”

“…The Taan Fiord landslide took place on 17 October 2015 at the Taan Fiord in Alaska [1,[3][4][5][6]. Roughly 50 million m 3 of rock was dislocated in the landslide which led to a tsunami with a height of up to 193 m [4].…”

“…The Taan Fiord is located in the St. Elias Mountains on the southeast coast of Alaska, where regular seismic activity is known to occur. The calculations are therefore always performed with a pseudostatic load of 0.3 g [1]. The geology of the landslide belongs to the Kulthieth Formation which largely consists of sediment rock (sand-and mudstone) [1,5,6].…”

“…The calculations are therefore always performed with a pseudostatic load of 0.3 g [1]. The geology of the landslide belongs to the Kulthieth Formation which largely consists of sediment rock (sand-and mudstone) [1,5,6]. There is a glacier tongue at the base of the landslide whose expansion is subject to significant fluctuation but whose volume is on average decreasing as the years go by.…”