Photo: SGI/Linda Blied
Landslide risks in the Norsälven River Valley
The landslide risk assessment along the Norsälven River Valley has resulted in a comprehensive overview of the risk of landslides in the current and future climate, for communities as well as undeveloped land and for areas with vital community infrastructure.
A high landslide risk level exists, i.e. where the probability of landslide is substantial and where the consequence of a landslide would be significant for the existing community and infrastructure, along two percent of the classified landslide risk area along the Norsälven River Valley. The areas are in the southern parts at Edsvalla, Höglunda/Trossnäs, Norsbron and Vålberg in Karlstad municipality. Affected major roads and rail infrastructure are located at Edsvalla, Skårebol, Väsby and Hannäs.
A medium-high landslide risk level is common closest to the riverbanks along a greater part of the water course (13 per cent of the classified landslide risk area) where the probability of landslide is substantial, but there are no existing settlements or vital community infrastructure. A heavy landslide in these areas could cause secondary consequences such as flooding of settlements and infrastructure upstream and downstream, which have not been taken into account in this analysis.
The majority of the study area has a low risk level (85 per cent of the classified landslide risk area).
Sensitivity to the effects of climate in the event of future climate change is deemed to be the greatest in southern and central part of the area as well as along a limited part in the north.
Measures to reduce the risk of landslides
Identified areas with a high landslide risk level should be further investigated for a decision on possible measures. Measures can be implemented to reduce the probability and/or impact of the risk of landslides along the river. Probability reducing measures are usually physical in the form of excavations, press embankments and erosion protection. Impact reducing measures can be, for example, to move the buildings and facilities. Along the Norsälven River Valley there are several examples where, as a measure, properties have been purchased.
Development of simplified methodologies - A pilot project
Norsälven is the first watercourse that SGI surveyed after the Göta älv River Valley investigation (GAU), and investigation has served as a pilot project for the development of a simplified methodology for landslide risk mapping. Development of the methodology has been carried out to lower investigation costs and simplify the interpretation of the maps, and thereby increase the usability of the results. The methodology for risk mapping that has been developed is applicable for landslide risk mapping along other water courses. Both the methodology for probability classification and impact classification can be used individually, the methodology for impact classification can also be used to map other natural events.
More results
The final report SGI Publication 18 "Landslide risks in a changing climate - The Nors River valley. Part 1 - Map report and summary of results". (PDF, 14.87 MB)
There is a map viewing service where data layers with probability, impact and risk of landslide maps along the river are shown as well as additional location-bound information. Maps and menus are in Swedish.
There are also PDF maps in A3 format to print: