Geomorphology and Susceptibility to Rainfall Triggered Landslides in Gudbrandsdalen Valley, Norway

Abstract

During the last decade, several high-intensity landslide events have changed the image of the Gudbrandsdalen valley in Central Eastern Norway from a region with moderate landslide activity to being considered one of the most active landslide areas in Norway. Succeeding a localized, but intense, landslide event in the Northern part of the valley in year 2008, two larger regional events occurred in the years 2011 and 2013. Many landslides were triggered in each of these events, including flash floods and debris flows/debris slides in small and steep tributary rivers along the valley slopes, as well as translational and rotational slides on open slopes. In the first phase of the 2008 landslide event, landslides were triggered in dry weather, by ground-water flow from infiltration of snowmelt in areas far away from the landslide zone. In the 2011 and 2013 events, most landslides were triggered by intense rainfall, sometimes with daily rainfall of 30–50 mm and more. For this region, with annual rainfall as low as 300 mm, such daily rainfall values are unusual, and the landscape is sensitive to extreme rainfall. Although high susceptibility to extreme rainfall events has been clearly demonstrated through these events, the effect on landslide activity of an expected climate change towards a generally more humid regional climate needs further research. In the Centre for Research-based Innovation (CRI) “Klima 2050”, financed by the Research Council of Norway and other public, private and scientific partners in the period 2015–2022, work is underway in order to improve the understanding of landslide processes and triggering mechanisms in this environment.