Abstract
Sakurajima is an active volcano on which even a small amount of rainfall can cause a debris flow due to the remobilization of accumulated volcanic ejecta on its slopes. The Japanese national government has constructed sabo facilities in the area because of frequent debris-flow disasters in the past and has conducted various types of debris-flow monitoring programs. Various types of sensors, such as wire, optical, vibration, and acoustic instruments, have been installed to detect debris flows, while camcorders and mud sampling systems have been installed to track the debris-flow process. Observations using these monitoring instruments have enabled clarification of debris-flow characteristics. Even so, more data on debris-flow discharge are required to improve the accuracy of debris-flow monitoring and to determine when and how debris flows occur.
