Early Warning Systems for Landslides: Challenges and New Monitoring Technologies

This paper discusses the practical issues related to design and implementation of early warning systems for landslides, the challenges for the future, and possible solutions to the common problems encountered. The problems related to setting the thresholds for warning and in using forecasting methods and expert judgment are discussed in detail. The main challenge in choosing the threshold values for an early warning system is to balance the conflicting requirements of capturing the critical events with a sufficient margin of reliability while avoiding false alarms. New monitoring and characterization technologies that could be implemented as part of early warning systems for different types of landslides are discussed. The integrated use of innovative instruments, thresholds, public education campaigns and other important aspects are exemplified by two very different case studies: the Åknes rockslide in western Norway and the landslip warning system for Hong Kong City.