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"Geohazards" are events caused by geological conditions and processes that pose severe threats to humans, property and the natural and built environment. Earthquakes, floods, landslides, volcanoes, avalanches and tsunamis (waves caused by e.g. large underwater mass movements and earthquakes) are typical examples of geohazards. Each year, natural disasters cause countless deaths and formidable damage to infrastructure and the environment. In 2004-5, more than 200 000 people lost their lives in natural disasters. Material damage was estimated at USD 300 billion. Many lives could have been saved and enormous destruction could have been avoided if the geo-profession had known more about forecasting of geo-hazards and mitigation of hazard and risk. The need to improve the ability to deal with the geo-hazards and geo-risks was accentuated by increased sliding and flooding in many regions in recent years, concern for geohazards in production and transport of oil and gas and the catastrophic Indian Ocean tsunami in December 2004.
The most common geo-related natural disasters on land are landslides caused by heavy precipitation, floods, earthquakes, erosion, and anthropogenic actions. Risk management integrates the recognition and assessment of risk with the development of appropriate strategies for its mitigation. Risk is the measure of the probability and severity of an adverse effect to life, health, property, or the environment. Mitigation and reduction of hazard and risk can be achieved by reducing (1) the frequency (probability) of an adverse event/threat occurring and/or (2) the vulnerability and/or exposure of the elements at risk. Early warning systems have gained strong interest in recent years, and there is an important role for such systems in the mitigation of hazard and risk. Examples are given in the lecture.
The selection of optimum mitigation strategies needs to be based on quantitative probabilistic hazard and risk assessment, coupled with useful knowledge on the technical feasibility, as well as costs and benefits, of risk-reduction measures. Twenty-first century solutions require approaches encompassing the technological and the societal perspectives. Experts acting alone and strictly within their own field of experience, cannot choose the optimum set of mitigation and prevention measures in many risk contexts. The technical details can conceal that decisions need to also take into account the social/political system. Such approaches will require value judgment. Conflicting interests, as well as often conflicting and uncertain evidence, characterise many landslide risk decision processes.
The lecture presents recent work on the assessment, mitigation and management of geohazards from a geotechnical perspective, but with full awareness of the need of the societal component in the analyses.
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