31 May 2023
Accelerating movement at Brienz/Brinzauls
The rate of movement of the large rockslope at Brienz/Brinzauls in Switzerland is continuing to accelerate, but it remains difficult to know exactly what will happen and when. There is now a Youtube live stream of the slope, which should be visible below, via Blick TV | Municipality Albula/Alvra:-
Regular rockfall activity is occurring on the slope – indeed yesterday there was a large detachment, which was caught on the webcam.
Last week, local government released a briefing to the local residents about the landslide, which has been posted online. It’s in German but Google Translate is helpful. Particularly interesting are graphs of the landslide movement history. First is a graph of the movement of the landslide back to 2019, with the y-axis scale being in centimetres per year:-
The marked acceleration in the landslide that occurred during 2020 is clear, as is the recent acceleration of portions of the landslide.
The presentation also includes ground-based radar data that captures the portion of the slope that is now mobile – in this case the colour scale is in mm per day:-
As the image shows, it is not the whole of the landslide that is moving, but a portion in the centre of the slope that is termed “The Island” by the local geologists. The presentation includes recent data for the movement of this portion of the slope:-
The monitoring team note that the acceleration of the slope over the previous two weeks had been linear, which makes extrapolation of likely future patterns quite difficult, with a range of scenarios being possible. One possibility is that the slope fails in a series of rockfalls, whilst another is a full failure of the mobile mass (which could even destabilise more of the slope). In the meantime, the area around the slope remains cordoned off, although there are reports of people trying to access the cycling routes.
The best case scenario at Brienz/Brinzauls is that the slope fails in a series of smaller events in the coming days, removing the weak mass from the slope without destroying the village. At this point it is difficult to forecast how likely this is to play out. We watch with great interest.