Debris flows, debris floods and flash floods are among the most dangerous natural hazards that threaten people and infrastructures in mountainous areas. Very similar phenomena occur in volcanic environments, where the Indonesian term lahar is often used, instead of debris flow or mud flow, to name the equivalent phenomena occurring along volcanic slopes. The quantification of transported sediment by these flow processes, along with their frequency and features (duration, velocity, depth, etc.) is of paramount importance for hazard assessment, land-use planning and the design of mitigation measures, including early warning systems.

Documentation and monitoring of these phenomena requires the adoption of a variety of methods and the difficulties in detecting the initiation and the propagation of these processes have progressively prompted research into a wide variety of monitoring technologies. Nowadays, the combination of distributed sensor networks and remote sensing techniques represents a unique opportunity to gather direct observations. A growing number of scientists with diverse backgrounds are dealing with the monitoring of processes ranging from intense sediment transport to large lahars and debris flows. However, there is a need of improving quality and quantity of both documentation procedures and instrumental observations that would provide knowledge for more accurate maps and models.

Scientists and technicians working in the fields of hazard mapping, modeling, risk management, monitoring and warning of fast flow-like landslides are invited to present their recent advancements in research and the feedback that they received from practitioners and decision makers.