The residential land in the Omagari area of Kitahiroshima City collapsed 28 houses along the river by the 2018 Hokkaido Iburi Eastern Earthquake. In addition, the stricken area suffered heavy rain by Typhoon 21 the day before the earthquake. The cause of the damage is thought to be an increase in groundwater level in the valley-filled embankment in addition to the earthquake. Therefore, in this paper, the cause of residential land damage was estimated by slip stability analysis, and the effect of groundwater reduction method was clarified.
