Abstract
The Totsu-Kawa Hazard that occurred in August 1889 was triggered by heavy rainfall in Nara Prefecture, Kii peninsula, central Japan, and claimed the lives of 1492 persons (in Nara and Wakayama Prefecture). Many landslides occurred in mountain slopes and the landslide debris dammed up mountain valleys to form many large landslide dams. After few hours to 30 days, the landslide dams then collapsed, and the big flood rushed down along the Totsu-Kawa valley into the Shingu City. The Arida-Kawa Hazard that occurred in September 1953 was triggered by heavy rainfall in Wakayama Prefecture, Kii peninsula, and claimed the lives of 1046 persons. Many landslides dams were formed and collapsed, and the big flood rushed down along the Arida-Kawa valley. We studied the process of formation and collapse of many landslide dams.
