Qualitative Rockfall Hazard Assessment: A Comprehensive Review of Current Practices

Rockfall phenomena represent a major hazard in mountainous areas because they can cause severe damage to infrastructure and buildings as well as serious injuries and fatalities. Rockfalls do not pose the same level of economic risk as large-scale landslides, yet they are responsible for a similar number of accidents and fatalities. Therefore, appropriate land-use planning is necessary to protect people, buildings and facilities from rockfall hazards. Over the last two decades, several methodologies have been proposed to assess rockfall hazards, identify potentially dangerous areas (i.e., rock cliffs with failure-prone blocks) and provide guidelines for choosing and installing the most appropriate mitigation measures. This paper provides a comprehensive review of the existing rockfall hazard assessment methodologies. In particular, the review focuses on qualitative methods that allow a rapid evaluation of a rockfall hazard without costly and time-consuming numerical simulations. The most commonly adopted methodologies in Europe and North America are described and critically analyzed to highlight their differences and similarities and to identify their primary advantages, limitations and fields of application.