Wednesday, October 20

This stands out as possible explanations for the landslide.

This is how it looks now that the landslide took place on December 30, 2020. The photo of the drone was taken on Monday, September 27, 2021, that is, two days before the presentation of the expert committee report on the landslide clay fast ground in Gjerdrum.

Various theories are presented as possible causes of the landslide at Gjerdrum. The report, which arrives at 12 noon Wednesday, will address the theories.

  • Heavy rains in the fall in advance.
  • Stream of water prone to erosion.
  • The construction activity of the municipality of Gjerdrum considered risky.

These were some of the many factors that stood out after the catastrophic landslide in Gjerdrum on the night of December 30, 2020.

Last week, Aftenposten wrote that the expert committee that investigated the landslide found a cause. A cause they trust and found this spring.

When the committee presents its report on Wednesday, it will address several of the theories that were presented in the Norwegian media this spring, and comment on them.

Here’s what happened, some of the theories and facts about the Nystulia construction site in Gjerdrum:

The landslide

  • At 04.01 on December 30, 2020, the police phone began to ring. Then it rang again. And again. Such was the catastrophic night in Gjerdrum.
  • 31 housing units in the Nystulia residential area were swallowed up by the rapid clay landslide. Ten people lost their lives.
  • Some houses moved 400 meters. The landslide area was more than 200,000 square meters. It was almost 1 kilometer long. Several minor landslides followed.

Aftenposten met with the people affected by the avalanche, after the blue lights went out. Here are their stories.

These images of the landslide shook a small local community and the rest of the country.

Causal theories and history

Objections: On January 7, Aftenposten wrote that both NVE and the county governor in 2012 had strong objections to the zoning plan for the adjacent field. Nystulia was started in 2003. The first houses were completed in 2008.

Streams: Aftenposten also wrote that several streams in the landslide area could carry away masses of soil. In 2009, the municipality of Gjerdrum warned that this could lead to landslides. Consulting firm Asplan Viak wrote in March 2009 that surface water from much of the center in Gjerdrum, Ask, ended at Brådalsbekken and Tistilbekken. According to Viak, both streams were highly vulnerable to erosion.

VG also drew attention to the currents.

In Romerikes Blad and TV 2, hydrologist Steinar Myrabø, with time from Jernbaneverket and Naturvernforbundet, said that in 2008 he had strongly warned against the development of Nystulia. He had personally discovered erosion in a stream below the residential area.

Several, like Dagbladet, were interested in a golf course built in 2010.

Even more were concerned about the weather.

When the landslide occurred in Gjerdrum, it was decided that all changes to the terrain, all construction activities, all changes in streams and drainage roads that could have caused erosion should be investigated. It was recommended to go back between 10 and 15 years in time.

Precipitation: Two days before the landslide, NVE had warned of a landslide and flood hazard in eastern Norway. The heavy rains had caused high groundwater levels and what is called “saturation” in the soil.

However, researcher Inger-Lise Solberg from the Norwegian Geological Survey (NGU), who later became part of the expert committee, claimed that the rainfall was not a direct cause of the landslide being triggered.

Self-control: On January 8, Aftenposten wrote that the contractors themselves put a stamp of approval on their own work when the construction site was established. Today that is not the law. The municipality of Gjerdrum also did not carry out a random sampling in Nystulia.

Distance: On January 13, Aftenposten wrote that the landslide could very well have started far from the buildings in Ask. Geotechnical consultants Dagfinn Moe and Inger-Lise Solberg described the landslide as an “area landslide,” a “retrogressive projectile landslide” that devours backward and rips large masses with it.

VG also wrote that it was probably a landslide.

Runway: VG also wrote that the municipality was unaware of the excavation, completion and improvement of a trail to the Gjerdrum golf course in the landslide area in November 2020. Not until the landslide had passed.

Landslide Risk: NRK wrote that NVE no longer controls all zoning plans. This can lead to risky developments without sufficient security against floods and landslides.

Security vulnerability: On May 31, NRK also wrote that the protection of a natural area a stone’s throw from the Nystulia residential area could have prevented the tragedy in Gjerdrum. The source was Gustav Grimstad, professor of geotechnics at NTNU.

On Wednesday at 12 o’clock the answer will arrive at the Gjerdrum culture house.

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