Rockslide dams in Møre og Romsdal County, Norway

Abstract

Eleven rockslide dams exist in Møre og Romsdal county in Norway. Geological evidences indicate that more of such dams existed during the Holocene. Eight of those dams formed in prehistoric times, while two rockslide dams formed in historical time. One of the rockslide dams failed partially at the beginning of the Holocene eroding 45,000 m3 from the dam, however the remaining dam is stable and it is used for hydropower generation. Present hazard of rockslide dams is represented by the Mannen unstable rockslope. This site has a volume of 15-25 × 106 m3 and is moving up to >4.5 cm/year on measurement points. A failure of the slope would dam the Rauma valley and few farms would be flooded upriver. However, due to the large discharge of the river the dam would only prevail a short time and dam failure is likely to cause inundation downstream. Here we present a probability analysis for this scenario. © Springer-Verlag Berlin Heidelberg 2013.