Strategies for mitigation of risk associated with landslides Farrokh Nadim 1 & Suzanne Lacasse 2 1 Director, International Centre for Geohazards / NGI, Oslo, Norway 2 Managing Director, Norwegian Geotechnical Institute / ICG, Oslo, Norway e-mail: farrokh.nadim@ngi.no Abstract Beyond risk communication and public awareness campaigns, pro-active strategies for the mitigation of risk associated with landslides can broadly be categorised as (1) structural slope-stabilization measures to reduce the frequency and severity of the landslide hazard, and (2) non-structural measures, such as land- use planning and early warning systems, to reduce the hazard consequences, and measures to pool and transfer the risks. Identification of the optimal risk mitigation strategy involves: (1) identification of possible landslide triggering scenarios, and the associated hazard level; (2) analysis of possible consequences for the different scenarios; (3) assessment of possible measures to reduce and/or eliminate the potential consequences; (4) recommendation of specific remedial measure and if relevant reconstruction and rehabilitation plans; and (5) transfer of knowledge and communication with authorities and society. Keywords: Landslide; Risk Mitigation, Risk Management, Early Warning System 1.0 INTRODUCTION Landslides represent a major threat to human life, property and constructed facilities, infrastructure and natural environment in most mountainous and hilly regions of the world. Statistics from The Centre for Research on the Epidemiology of Disasters (CRED) show that landslides are responsible for at least 17% of all fatalities from natural hazards worldwide. The socio-economic impact of landslides is underestimated because landslides are usually not separated from other natural hazard triggers, such as extreme precipitation, earthquakes or floods. This underestimation contributes to reducing the awareness and concern of both the authorities and the general public about landslide risk. Climate change, increased susceptibility of surface soil to instability, anthropogenic activities, growing urbanisation, uncontrolled land-use and increased vulnerability of population and infrastructure as a result, all contribute to the growing landslide risk. In areas with high demographic density, protection works often cannot be built because of economic or environmental constraints, and is it not always possible to evacuate people because of societal reasons. Furthermore, according to the European Union Strategy for Soil Protection (COM232/2006), landslides are one of the main eight threats to European soils. Many coastal regions have cliffs that are susceptible to failure from sea erosion (by undercutting at the toe) and their geometry (steep slope angle), resulting in loss of agricultural land and property. This can have a devastating effect on small communities. For instance, parts of the north-east coast cliffs of England are eroding at rates of 1m / yr. Water has a major role in triggering of landslides. Figure 2 shows the relative contribution of various landslide triggering events factor in Italy. Heavy rainfall is the main trigger for mudflows, the deadliest and most destructive of all landslides. Many of the future climate scenarios predict changes of hydrological cycles, more extreme precipitation events, concentrated rain within shorter periods of time, meteorological events followed by sea storms causing coastal erosion and melting of snow and of frozen 1