Mapping of landslide risks in a changing climate – development of simplified methodology

Abstract

The Swedish Geotechnical Institute (SGI) is assigned by the Swedish government to perform risk assessment for landslides in soft soil along priority watercourses as one part of the national climate adaptation funding. From the previously developed landslide risk mapping methodology applied for the Göta River Valley emerged a need for a less extensive methodology that could be implemented at significantly lower cost. Hence, the aim is to develop a sufficiently simplified methodology that could provide a basis for planners in municipalities and county administrative boards in their work with prioritization and preparation of adaptation measures. A criterion was also that such a methodology should ease the interpretation of the landslide risk maps, thereby increasing the societal relevance and usability of the results. The Norsälven River valley was used as a pilot area. The landslide risk analysis along the Norsälven River valley has resulted in a comprehensive overview of the landslide risk in the present and future climate, for built-up as well as undeveloped land and areas with vital infrastructure. The main implications of the climate change for the Norsälven River valley concerns the effect of increased erosion on the slope stability caused by increased water flow. The simplified methodology for landslide risk mapping that has been developed is applicable for landslide risk mapping along other river valleys. However, some modifications will be necessary due to site specific conditions.