A Study on Criteria of Warning and Evacuation for Large-scale Sediment Disasters Considering the Relationships with Sediment Movement and Damage

Yuna SUZUKI, Shin-ichiro HAYASHI, Shin?ya KATSURA, Mio KASAI, Nobutomo OSANAI and Tomomi MARUTANI

In Japan, Sediment Disaster Warning Information pertaining to a debris flow and slope failures due to rainfall is provided to residents based on the criteria of rainfall between the occurrence and non-occurrence of such sediment disasters. Early warning information system for large-scale sediment disasters has not yet been established, and the criteria that must be met to trigger warning have not yet been established. In this study, to estimate suitable criteria of warning and evacuation for large-scale sediment disasters in Japan, we examined and clarified the relationships among sediment movement, damage, and return period of rainfall causing large-scale sediment disasters by conducting a statistical analysis of 22 previous large-scale sediment disasters. We found that 1) large-scale sediment disasters may occur during rainfall events with a 30 to 50 year return period, and 2) longer rainfall return periods, as recorded in long-term rainfall indices (more than 24 hours), may indicate imminent large-scale sediment movement and demand attention as indicators of large-scale sediment disasters.

2018/1 387-393