Case 5: Norway 1 - Landslides

The following is a preliminary assessment of how small remote communities in the region of Trøndelag in Mid-Norway will be affected by climate change – the main hazard in focus, in this case, is landslides. The assessment will be developed further as the project progresses.  

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The region of Trøndelag

Trøndelag is a region in Mid-Norway, bordering Sweden in the East and the Norwegian Sea in the West (Figure 1). Trøndelag stretches over an area of around 42 000 km2 and has more than 450 000 inhabitants. The CliCNord project will focus on several small remote communities located in different municipalities in the region. Although being remotely located, there is some central infrastructure in this area, such as the E6 road and railway connecting Southern and Northern Norway, the E14 road, and the Meråker railway connecting the city of Trondheim to Sweden, the Røros railway between Trondheim and Hamar as well as power lines connecting southern and northern Norway and connecting Mid-Norway to Sweden.

The business activities in the case areas focus on agriculture, forestry, reindeer husbandry, hydropower and wind power production, small enterprise and industry, and tourism. In addition, some of the areas serve as a recreational area for many Norwegians who have their holiday homes there.

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Figure 1 Trøndelag in Norway. Map: NordNordWest

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Photo: Johannes Hardeng

The hazard: Landslides

Norway’s national plan for the mapping of risk related to landslides (NVE, 2011) classifies landslides in Norway based on the different materials involved: bedrock, loose material, and snow (Figure 2).​

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Figure 2 Classification of landslides (NVE, 2011). English translation by authors based on NVE, 2015.

  • Bedrock landslides are grouped into rock falls, rock slides, and rock avalanches according to their volume with rockfalls being defined as small blocks up to 100m3, rockslides having volumes up to 10 000 m3, and blocks that split up on their way down the slope, and rock avalanches having volumes over 10 000 m3 (NGI, n.d).  

  • Landslides involving loose material include debris slides and debris flows which are triggered by loose material on steep slopes and river courses that are saturated by heavy rain and/or snowmelt. The third type of landslides involving loose material is the quick clay slide which happens in clay that originally was deposited below sea level. Quick clay slides can develop very quickly, be very large, and have serious consequences (NGI, n.d.).

  • Slides involving snow are classified into avalanches and slush flows. Avalanches start at steeper slopes (more than 30⁰) than slush flows and slush flows have more free water between the snow particles in the slides (NVE, 2013).

Rockslide - Photo: Johannes Hardeng

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In Norway, water is always a contributing and often triggering factor for landslides which are often caused by strong precipitation combined with high groundwater levels, snowmelt, and high temperatures (Trøan, 2017). Krøgli et al. (2018, p. 1428), for instance, refer to ”rainfall- and snowmelt-induced landslides” and describe that these kinds of landslides often happen ”in clusters, in large numbers and scattered over a large area”. Rainfall and snowmelt-induced landslides cause large damages to infrastructure, such as roads, railways, and buildings every year. In mountainous areas in Norway, landslides happen almost every day, but most of them are not registered because they do not cause any damage to humans and the built environment.

 

In Trøndelag, all three types of landslides (bedrock, loose material, and snow) have exposed several vulnerabilities. Some of the most destructive and famous quick clay slides in Norway happened in Trøndelag. The Verdal slide in 1893 was Norway’s deadliest landslide ever recorded: 116 people died, 105 farms were destroyed and about 600 livestock died (see picture below).  

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Verdalsraset. Photo: Public domain

In 1978, large parts of the village of Rissa (15 farms, 2 houses, 1 cottage, 1 hamlet house) were taken by a quick clay slide and one person died. The quick clay landslide in Rissa was filmed and the film was seen around the world (see video below).

Another example is the quick clay slide that happened during the first hours of the 1st of January 2012 at Esp, about 10 km outside the city of Trondheim. It had a volume of volume 350000 m3 (Kalsnes et al., 2016). There were no casualties, but 50 people were evacuated for several days.

Other types of landslides (rock, debris, snow) happen much more frequently than quick clay slides, however, mostly without the same severity. In 2012, for example, the popular Dovrebanen train line between Trondheim and Oslo faced disruption after a debris slide washed out the ground under the tracks. The landslide also cut off the E6 highway in the same area.

The quick clay landslide in Rissa - 1978 (Norwegian)

Climate change in Trøndelag and effects on landslides

Climate change is expected to bring an increase in rainfall and extreme weather events in Norway (Government.no, 2014). This will also increase the risk of landslides. A very recent report (Hisdal et al., 2021) summarizes the expected climate changes for Nord-Trøndelag (North Trøndelag) and Sør-Trøndelag (South Trøndelag) up to the year 2100 based on downscaled climate models from the fifth IPCC Assessment Report. It is mainly based on the representative concentration pathway 8.5 scenario (the so-called RCP 8.5, which is the worst-case scenario). The average temperature is expected to increase with 4.0⁰ C in Sør-Trøndelag and with 4.5⁰ C in Nord-Trøndelag.

Yearly precipitation is expected to increase by 20% in Trøndelag with significant seasonal variations. Hence, a major increase in precipitation is expected for summer and autumn. Significantly more and stronger heavy precipitation events are expected around the year during all seasons. The amount of snow – and the snow season – will decrease significantly and there will be more melting periods during the winter (Hisdal et al., 2021).

These expected changes in climate will affect the risk of landslides. As the weather is one of the important triggering factors for landslides, it is expected that landslides caused by rainfall/flood, snow, and snowmelt will increase (Hisdal et al., 2021; Dolva & Petkovic, 2017; Krøgli et al., 2018; Aall et al., 2018). Hisdal et al. (2021) mention that most attention needs to be paid to debris slides, debris flows, and slush flows in Trøndelag in this context.

Quick clay landslides can also increase due to more frequent and larger floods as well as increased and heavy rainfall that can lead to erosions in rivers and streams which again may lead to quick clay landslides (NGU, 2015/2020). The risk is particularly high in Sør-Trøndelag which has large quick clay deposits (Hisdal et al., 2021). Evidence of prehistoric quick clay slides is usually found under the marine limit and is a natural part of the long-term landscape evolution. Today, human interference such as digging and filling related to building activities is the most common cause of quick clay slides (NGU, 2015/2020; Kalsnes et al., 2016).  In addition to debris, slush, and quick clay landslides, increased precipitation may also lead to more rockfalls and rockslides (NVE, 2020).

For Norway as a whole, it is not only expected that the number and size of landslides will increase but also that they occur in new locations (Dolva & Petkovic, 2017; Krøgli et al., 2018; Aall et al., 2018). L’Heureux et al. (2018) expect that landslides will increase during the spring and fall seasons and decrease during summer.

However, it is not possible to include all relevant aspects in these analyses. There is, for example, the possibility that an increase of the forest area and the moving of the tree line to higher altitudes due to higher temperatures may reduce the risk for landslides in certain areas. Further, it is difficult to predict whether increased precipitation will be rain or snow at higher altitudes, which have different consequences for landslides. However, studies show that precipitation and extreme weather events in Norway have increased during the last 40-50 years and also impacted the number of landslides to be expected at present (NVE, 2020).

Dangerous section of mountain road without fencing runs along a steep cliff face, you can

Vulnerability

Due to the expected effects of climate change on the severity and frequency of landslides in the case study area, the physical vulnerability will increase. Physical vulnerability refers to the “probability (or the potential) of a given physical component or element to be affected or damaged” (Meslem & Lang, 2017:2). The physical components include the built environment, such as homes, roads, bridges, hospitals, schools, and government buildings.

Landslides and avalanches are the natural hazards in Norway responsible for most losses of human life (Meld. St. 33, 2012–13). Between 1960 and 2020 around 150 people lost their lives in landslides and avalanches, more than 15 in Trøndelag (List of landslides in Norway - Wikipedia, 2021). Landslides are also responsible for damage to critical infrastructure. Yearly, around 200 landslides hit roads, and 30 hit railways in Norway (Hisdal et al., 2017). The E14 and E6 roads and the railways from Trondheim towards the East, North, and South passing through the case study areas represent important infrastructure. Although physical structures to protect critical infrastructure from landslides are common in Norway, the existing physical measures are not sufficient to address current and future landslide risks. Due to the enormous areas at risk for landslides additional physical measures and their maintenance are expensive (Krøgli et al., 2018; Aall et al., 2018). Hence, forecasting and warning systems have become increasingly important (Dolva & Petkovic, 2017; Krøgli et al., 2018).

Although physical vulnerability to landslides is rather high in Trøndelag due to the area’s topology, several studies assert Norway - as one of the richest countries in the world - rather low vulnerability to the direct impact of climate change due to well-functioning institutions, a highly educated population and a good economy (Aall et al., 2018). Hence, economic, social, and institutional resilience is generally high, the infrastructure is of good quality, and the competence and resources within climate change adaptation are rather high. However, how this high general resilience translates to resilience to climate change-induced landslides in particular communities and how economic and social vulnerability will develop is difficult to forecast. Aall et al. (2018) argue that although we have rather good knowledge about how climate will change and how this change will affect nature, there is a knowledge gap concerning the communities’ overall vulnerability to climate change at present and in the future.

As located in small and remote municipalities, the communities we will study in this CliCNord case are more vulnerable and less resilient than bigger more centrally located communities due to limited resources, expertise, and manpower for systematic climate change adaptation work. The integrated resilience index developed by the ClimRes project (NTNU, 2019) maps social resilience, economic resilience, institutional resilience, community competence, housing and infrastructure, and environmental resilience in all Norwegian municipalities and demonstrates how different the municipalities are when it comes to these different aspects of resilience. This underlines the importance of focusing on the complexities, diversity, and situatedness of climate change resilience and small remote communities’ ability to cope with climate change-related hazards such as landslides.  

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Emergency management

There is a clear – though complex – division of responsibility for the emergency management related to landslides and floods on the national level through the legislation and the authorities' management documents:​

  1. Through the Norwegian Water Resources and Energy Directorate (NVE) at the Ministry of Petroleum and Energy is responsible for floods and landslides. NVE engages in flood management and warning, mapping of flood and quick clay slides, and administers an emergency preparedness system.

  2. The Ministry of Local Government and Modernization is the overriding planning and building authority and has an important coordination function vis-à-vis the county governor.

  3. The Ministry of Justice and Emergency Preparedness has the general responsibility for public safety and emergency preparedness.

  4. The Ministry of Climate and the Environment has the overall responsibility for climate change adaptation (Government.no, 2017).

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In addition to the four ministries acting on the national level, the municipalities are responsible for ensuring safety against floods and landslides during new building and infrastructure development and through local emergency preparedness. Hence, the municipalities must be active, map local risk and vulnerability, and take responsibility for managing the flood and landslide risk at the local level. The mapping of areas at risk of landslides is still considered one of the most important tasks. Knowledge about these risk areas is often lacking, although it is a very effective measure of landslide prevention to include the knowledge gained from the mapping in planning and development processes (Tangeraas & Høyvik, 2020). Furthermore, municipalities should have emergency preparedness plans to deal with extreme events, such as landslides.

Åbn bøger

References

  • Aall, C., Aamaas, B., Aaheim, A., Alnes, K., Oort, Bv; Dannevig, H; Hønsi, T. (2018). Oppdatering av kunnskap om konsekvenser av klimaendringer i Norge. CICERO & Vestlandsforskning. Report 2018: 14.

  • Dolva, B.K. & Petkovic, G. (2017): Natural Hazards in a Changing Climate in Norway, In Thakur, V., L’Heureuz, J., Locat, A (Eds): Landslides in Sensitive Clays. Springer: Cham. Pg. 539-548.

  • Government.no (2014). Climate change. https://www.regjeringen.no/en/topics/climate-and-environment/climate/innsiktsartikler-klima/climate-change/id2076641/

  • Hisdal, H., Bjordal, H., Colleuille, H., Engeset, R., Helgås, G., Odberg, M.M., Sivle, A., Steinvik, K (2017).  Evaluering av snø- og jordskredvarslingen, NVE report 38. https://publikasjoner.nve.no/rapport/2017/rapport2017_38.pdf

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  • Kalsnes, B., Nadim, F., Hermanns H.O., Hygen, H.O., Petkovic, G., Dolva, B.K., Berg, H., Høgvold, D.O. (2016). Landslide risk management in Norway. In: Slope Safety Preparedness for Impact of Climate Change. CRC Press

  • Krøgli, I., Devoli, G., Colleuille, H., Boje, S., Sund, M., Engen I.K. (2018). The Norwegian forecasting and warning service for rainfall- and snowmelt-induced landslides. In: Natural Hazards and Earth System Sciences 18, 1427-1450.

  • L’Heureux, J.S., Høydal, Ø.A., Paniagua Lopez, A.P., Lacasse, S. (2018). Impact of climate change and human activity on quick clay landslide occurrence in Norway. Second JTC1 Workshops on Triggering and Propagation of Rapid Flow-like Landslides. Hong Kong 2018.

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