2022 Volume 59 Issue 5 Pages 205-217
This study analyzes the influence of surface water and groundwater flows on a landslide in Takumi area, Tomioka City, Gunma Prefecture induced by Typhoon Hagibis on 12 October 2019. Firstly, a surface infiltration model and surface runoff simulation module were integrated into a water table prediction model developed previously. Then the hydrological integration process was validated on a tilted impermeable V-catchment system and trialed on a Plexiglas sandbox system. Finally, the extended model was used to describe the infiltration and exfiltration process, surface water flow as well as groundwater level distribution for a study area in Takumi Village during the Typhoon. According to simulation results, both surface water and groundwater flows have gathered on the landslide sites where the slopes are concave. Surface water and groundwater have interacted with each other to form flows over time and cause the groundwater level in the study area to rise. At the time of the landslide, the groundwater level had reached the slope surface in most of the cells at the collapsed sites. As a result, the safety factor for slopes decreased significantly and landslides occurred. Therefore, both surface water and groundwater flows were thought to be the landslide triggers.
