The Landslide Blog is written by Dave Petley, who is widely recognized as a world leader in the study and management of landslides.
Late last week, the prosecutor investigating the 23 September 2023 landslide at Stenungsund in Sweden held a press conference to provide an update on his investigations into the accident. Loyal readers will remember that this was a large failure that destroyed a section of a major highway, the E6 motorway between Gothenburg and Oslo, as well as a fuel station and various other buildings. Anton Larsson tweeted some excellent images of the landslide:-
At the time of the landslide, I speculated that the underlying cause of the failure could have been the dumping of material high on the slope.
“An initial working hypothesis would be that the mass of material deposited on what has become the headscarp of the landslide has destabilised the slope, triggering failure. The weather conditions at the time were rainy, and there has been heavy rainfall in recent days, but this has not been exceptional.”
Last week, the lead prosecutor, Daniel Veivo Pettersson, provided valuable new information about the causes of the landslide. There are some English language reports about his observations, which highlight that “the landslide had been triggered by a nearby construction site where too much excavated material had been piled up, putting excessive strain on the ground below.”
Swedish language reports provide more detail. The excavated material was being used to construct a business park, which had been approved. However, much more material was emplaced than had been agreed. Daniel Veivo Pettersson indicated that the additional mass might have been about 170,000 tons. The source of this material was a different construction in the Stenungsund area – he suggested that the individuals concerned may have been paid to dump this waste at the site that failed.
Technically, this explanation is logical. The additional mass would have loaded the head of the landslide, triggering failure.
The news reports indicate that three individuals are facing criminal charges of “gross public dangerous devastation, gross causing bodily harm and unauthorized environmental activities”. All three deny the charges against them.
Clearly this case will proceed to trial, but this could take the remainder of thus year.