Avalanche Laboratory Nordkette/Innsbruck – On the technical design of the Arzler Alm avalanche test site

The south-facing Arzler Alm avalanche path above Innsbruck, Tyrol, has a release area at approximately 2300 m a.s.l. on the Nordkette range and a runout zone reaching the immediate vicinity of an Innsbruck city district at about 650 m a.s.l. Following several very large avalanche events during the last century, extensive mitigation measures were constructed, including multiple breaking mounds and a catching dam, designed to withstand avalanche volumes of up to 1 million cubic meters. An exceptional snowstorm during the winter of 2018/19 triggered a large avalanche that caused substantial forest damage and highlighted the continued necessity of these protection structures.

During recent renovation works, a comprehensive measurement system was installed in the uppermost breaking mound. This structure is 5 m high, wedge-shaped, and approximately 10 m wide. Force measurements on a structure of this scale provide a rare opportunity to improve current engineering standards by describing avalanche-obstacle interactions. The measurement system consists of multiple 0.25 m² pressure plates installed on the mountain-facing sides of the breaking mound and record data at 10 kHz. These sensors capture both frontal impact forces and shear forces generated during flow deflection along the lateral flanks. To place local force measurements into the context of entire avalanche events and to quantify avalanche occurrence frequency, a state-of-the-art avalanche radar observes the full avalanche track continuously. The setup is complemented by video cameras from multiple viewing angles and allows future expansion with additional instrumentation, such as seismic sensors, fiber-optic sensing systems, and optical velocity measurements.

The test site has been operational since early 2026. We primarily present the technical design, site layout, and instrumentation and in case discuss data collected from avalanches during the current winter season. However, as the experiments rely entirely on natural avalanche activity and the statistical recurrence interval for avalanches reaching the mitigation structures is approximately one event per season, the availability of force measurements cannot be guaranteed for every year.

The Arzler Alm Avalanche Test Site is part of the Avalanche Laboratory Nordkette (Innsbruck, Austria), where recording of forces in snow fences, observations of glide snow activity and measurements with in-flow sensors in artificially released avalanches are performed. It complements other existing full-scale European avalanche research facilities such as Vallée de la Sionne (Valais, Switzerland) and Ryggfonn (western Norway). The year-round accessibility enables detailed manual field campaigns, including investigations of avalanche deposits, snow compaction in front of breaking mounds, and volumetric and entrainment processes. The south facing, large altitude range combined with significant new snow amounts during northwesterly snowstorms promotes avalanches that may transition from cold, dry flow regimes at release to warm, wet conditions in the deposition zone, making this new site particularly valuable for the large variety of avalanche release types, flow regimes and their evolution.