Analysis of the hazard caused by ice avalanches from the hanging glacier on the Eiger west face

Abstract

The Eiger hanging glacier is located in the west face of the Eiger in the Bernese Alps (Switzerland). Large ice avalanches, especially if they trigger secondary snow avalanches, endanger parts of the Jungfrau ski area and the Jungfraujoch railway. The latter leads to the Jungfraujoch, one of the top tourist destinations in Europe. The formation of a crevasse immediately behind the front of the hanging glacier was detected in autumn 2015, indicating an impending icefall with a maximum ice volume of 80,000m3. Consequently, a hazard analysis was performed for four different scenarios with varying ice volumes and snow conditions. The analysis showed that a 100m high rocky ridge situated in the main flow direction of the avalanches plays a crucial role due to its braking and deflecting effect. Closure plans were prepared for the four scenarios investigated. The railway station is especially endangered in the extreme scenario assuming an ice volume of 80,000m3 and unstable snow conditions. We therefore recommended to trigger avalanches below the hanging glacier artificially after snowfall events and to install an early warning and alarm system to minimize the closure times for the railway and ski area.