Neustift in Austria: boulder vs house, the boulder won

In Neustift in Austria, a 4 metre high boulder struck a house on 2 April 2021 having detached from an adjacent slope.  This image below, from Tyrol ORF, gives an idea of the scale of the event:-

The boulder that struck a house in Neustift in Austria. Image from Tyrol ORF.

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The image below, also from Tyrol ORF, shows the track of the boulder prior to striking the house:-

The track of the boulder that struck a house in Neustift in Austria. Image from Tyrol ORF.

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Note that the boulder has crashed through two flexible rockfall barriers:-

Destroyed flexible barriers along the track of the boulder that struck a house in Neustift in Austria. Image from Tyrol ORF.

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Clearly, barriers on this scale were not designed to catch a boulder of the scale of the one that struck the house.  Fortunately there were no casualties in this event.

The boulder has a very strong tabular shape (like a very large, flattened pebble of the type that you could skim on flat water).  The track, and the orientation of the boulder in the house, suggest that the rock was rotating along its short axis, much like a wheel.  It also appears that the boulder was losing contact with the surface at times (see the second image), thus rolling and bouncing down the slope.  If a tabular boulder gets into this configuration of movement it is both stable and highly mobile, allowing the long runout across the field before striking the house.

The adjacent properties have been temporarily evacuated whilst a 3 m high berm is being built to provide short term protection. The house in Neustift that was struck by the boulder will need extensive reconstruction:-

The interior of the house struck by the boulder in Neustift in Austria. Image from Tyrol ORF.

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The simple necessity of removing the boulder is going to be a challenge given both the scale of the rock and the likelihood of significant structural damage to the corner of the property.

This is the latest of several of these events in recent years.  I’m reminded of Rocky, the famous boulder from the 2011 Christchurch earthquakes.