Longyearbyen, Svalbard - Vulnerability and risk management of an arctic settlement under changing climate - a challenge to authorities and experts

Abstract

Longyearbyen, the administrative centre of the Svalbard archipelago, is facing most types of natural hazards under a changing Arctic climate. The catastrophic avalanche in December 2015 led NGI to review our professional work during 30 years of research and consulting in the community. Hazard zonation in Longyearbyen has been a tool in area planning, not for hazard assessment of developed areas, and mainly done during the early 1990s based on current knowledge and methods. The procedures for avalanche warning in Longyearbyen reflect that avalanche release is primarily a consequence of drifting snow, embedded surface snow and collapse of cornices. The first indication in meteorological data of a change in climate was a heavy rainfall midwinter 1995/96, years before global warming of the Arctic was documented. Field research in the 1990s documented that runout in terms of α-angle is longer in cold regions than in other areas. NGI has advised the local administration to revise the old hazard zones taking changing climate and up-dated knowledge and methods into account. The worst-case scenario in Longyearbyen will be a change towards present-day Norwegian Coastal climate with corresponding large avalanches, as well as increasing depth of the active layer and ditto potential for larger and more frequent debris flows and rockslides. Authorities and experts are facing challenging and difficult decisions concerning hazard zoning in a changing climate, design of mitigative measures, removal of exposed houses and extensive costs.