Abstract
Snow melt meteorological conditions and landslide clay characteristics were investigated regarding the Hachimantai Sumikawa hot spa landslide/mud flow disasters occurred at the beginning of May, 1997. Factors affecting for landslides in the snowy regions are generally attributed to snow cover depth, melting snow and heavy rainfall. The main triggers of the prsent topic under debate natural disasters were also considered to be a heavy rainfall ahead of the appearance of the disasters and a continuous snow melting phenomenon.
On the other hand, landslide clay samples were taken from the Sumikawa landslide area, and several soil tests were performed to investigate the physical and mechanical characteristics. Two types of clay were found at the Sumikawa river site along the trace of landslide, and the main clay mineral of the clay samples were analyzed as Kaolin clay by X-ray powder diffraction patterns. According to the soil tests, the softer clay is considered to be a conductive clay to the landslide because of its high water content, low residual shear strength, and high liquid limit.
