2021 Volume 58 Issue 1 Pages 28-39
In recent years, an increasing number of sediment-related disasters are being caused by heavy rains in Japan. In such events, it is typically socially vulnerable people like elderly population in hilly and mountainous areas that suffer. For reducing such sufferers, it is important to establish functional early warning systems that allow enough time for the vulnerable people to evacuate, however, no soil physical approach has yet to be agreed to make such warning possible. In this study, a soil physical approach was developed to estimate in-slopes pore water pressure that triggers surface failure, using soil water index (SWI), and was adopted to a slope in Tatsuno Town located in mountainous Nagano Prefecture in Japan. We verified our approach through the exercise by estimating pore water pressure at known occurrence of surface failures that triggered debris flows in the region at the very heavy rainfall in July 2006. We also verified the approach when we applied it to occurrences of another sediment outflows that triggered traffic closures in the event. These facts demonstrated that the approach could contribute to functional warnings and evacuation decision makings, that could help socially vulnerable population in sediment disasters.
