When the National Conference on Rockslides is held in Tromsø from 29 to 31 August 2017, NGI will contribute with expertise, insight and lectures. In recent years, NGI has assisted the NVE (Norwegian Water Resources and Energy Directorate) with, for example, mapping and risk assessment of mountain slopes in Åkerneset and Joasetbergi in Sogn og Fjordane county, Opstadhornet in Møre og Romsdal county, as well as Nordnesfjellet by Lyngenfjord in Troms county.
This year's National Conference on Rockslides will commence with a round trip and guided tour of the Lyngen area, where Nordnes is one of several rockslide-prone Mountains. Approximately 6,000 inhabitants are at risk if a major rockslide hits the Lyngen area.
“We have used advanced calculation models to test how various factors could affect each other. The tests show that the wave height is dependent on the volume and thickness of the leading edge of the rockslide, the velocity when the rockslide hits the water, as well as how far out the rockslide extends before it stops. Damage will also depend on the presence of settlements and infrastructure and largely on how alerts, emergency response and evacuation are organised”, explains Carl B. Harbitz, Head of Risk, landslide geotechnics and climate impact at NGI.
"We have used advanced calculation models to test how various rockslide factors interact. Tests indicate that wave height is dependent on the volume and thickness of the wave front, the rockslide velocity upon impacting water and the reach of the rockslide before stopping. Potential damage will depend on exposed settlements and infrastructure and, not least, the effectiveness of warning, preparedness and evacuation measures", explains Carl B. Harbitz, Head of Risk, Slope Stability and Climate at NGI.
Sharing critical knowledge
NGI has some of the world’s leading experts on flood waves in fjords. They have calculated that a rockslide in Lyngen could create a surface expansion in the fjord outside populated areas of up to 25 metres. A flood wave could impact most of the low-lying parts of municipalities; Storfjord, Lyngen, Kåfjord and possibly Nordreisa. Lyngseidet is the most exposed, and is located directly across the fjord from Nordnes.
“The magnitude of such a potential natural disaster depends on a number of factors;” says Harbitz, who also contributed as an expert consultant in the making of the film Bølgen (The Wave).
The National Conference on Rockslides is organised by the County Governor of Troms together with the Police, the County Governor of Møre og Romsdal, the NVE and the Troms county municipalities of Kåfjord, Lyngen, Nordreisa and Storfjord.
Under the heading Status of rockslide work, Carl Harbitz from NGI together with Einar Anda from the NVE, will talk about inundation heights and the consequences for building applications and evacuation. Harbitz will demonstrate how NGI models flood waves following rockslides. He will address the most important challenges in this work, as well as the practical use of the results that have emerged based on the extensive efforts that has been carried out over many years amongst NGI’s experts in the field of risks and flood waves.
- A rockslide Is the collapse of large volumes of rock, from 100,000 to several million cubic metres. Historically, there are two to three major rockslide accidents every century in Norway. Most well known are the incidents at Loen in Sogn og Fjordane in 1905 and 1936 and at Tafjorden in Møre og Romsdal in 1934.
- In Troms County, the mountain slopes of Jettan, Indre Nordnes and Gámmanjunni 3 in Kåfjord municipality are continuously monitored by radar. There are also 117 unstable mountains in the county that are monitored by satellite.
- The NVE has national responsibility for monitoring rockslides in Norway. Seven unstable mountain slopes are monitored on a 24-hour basis by the NVE as they could develop rockslides.
- NGI is currently working on a framework to better quantify the uncertainty in modelling and analysis.
- Read more about NGI's expertise in flood waves (Norwegian only): https://www.ngi.no/nor/Tjenester/Fagekspertise-A-AA/Flodboelger
- Read the article: "Faren for ras kan komme til å øke" in the newspaper Aftenposten from 2015 (Norwegian only): https://www.aftenposten.no/meninger/kronikk/i/o8bg/Kronikk-Ingen-vet-med-sikkerhet-om-Akerneset-er-det-farligste-fjellet-eller-om-vi-har-en-annen-skjult-versting--Carl-B-Harbitz_-Lars-Andresen
- Watch an older video from the NGI archive of a numerical modelling/simulation of the Aaknes-Hellesylt tsunami: https://www.youtube.com/watch?v=1XabLfL5VLk