In recent years, volcanic disasters have occurred repeatedly in Japan. In response, domestic efforts are underway to consider measures for dealing with large-scale eruptions. The Journal of Disaster Research has published several special issues that focus on volcanic disasters, featuring research outcomes related to the observation and investigation of volcanoes and disaster prevention measures.

This special issue features papers that reflect the recent trends in volcanic disaster research. Topics include observational and analytical studies of volcanic ejecta, damage assessments based on volcanic ejecta, research on debris flows triggered by rainfall following ash and tephra deposition, and studies on aviation safety and evacuation planning for residents in the event of a large-scale eruption.

Iguchi and Ishii proposed a forecasting system for ashfall amounts before eruptions around the Sakurajima Volcano by utilizing the statistical properties of ground deformation parameters associated with numerous eruptions. Kumaoka et al. proposed an airport alert system to address volcanic ash risks from large-scale eruptions at Sakurajima and analyzed the capacity of airports to accommodate evacuating aircraft. Shimizu et al. used 10 years of light detection and ranging observation data from Sakurajima to propose a threshold for distinguishing between clouds and volcanic ash. Otsuka et al. investigated small-scale spatial variations in ashfall in urban areas through numerical simulations, highlighting that wind disturbances caused by buildings significantly impact ashfall distribution, depending on the particle size. Nakada et al. demonstrated the utility of a method that automatically generates ashfall distribution contour maps and estimates the ash volume based on ashfall survey results from multiple domestic eruptions. Shimano et al. conducted colorimetric measurements on volcanic ash samples collected daily at Sakurajima and performed principal component analysis, showing that color measurement is a rapid and quantitative method suitable for monitoring volcanic activity. Takebayashi investigated river basins in the southwestern part of Sakurajima, where debris flows occur frequently, and clarified the relationships between permeability differences, gully formation rates, and sediment yield. Tsutsumi et al. examined the generation process of snowmelt-type volcanic mudflows through laboratory experiments. They revealed that when snow and gravel were mixed well, snowmelt accelerated, providing valuable insights into disaster prevention measures against such mudflows. Sugo et al. introduced a collaborative disaster preparedness effort between experts and residents in anticipation of a future large-scale eruption at Sakurajima that may cause heavy pumice and ashfalls in urban areas. They reported behavioral changes in both individual preparedness actions and communication-related activities involving others within the framework of this collaborative effort.

We hope that the results of advanced research presented in this special issue will be utilized to prevent and mitigate volcanic disasters.