The death toll on Tokyo's Izu Oshima island from the torrential rains caused by Typhoon No. 26 has risen to 18, the Tokyo metropolitan government announced Thursday morning.
The Metropolitan Police Department, the Tokyo Fire Department and the Ground Self-Defence Force increased the number of personnel in the search and rescue operations for survivors to about 650, but the operations on the island in the Izu Islands chain made little progress.
Meanwhile, the land ministry's research organ has discovered evidence of debris flows-the geological phenomena in which torrential rain washes away soil and fragmented rock like a rapid stream-in the affected area on the island.
According to the Tokyo government, the death of a 76-year-old woman was confirmed early Thursday, bringing to 18 the number of deaths on the island. Initially, 43 people were reported missing, but the metropolitan government has confirmed the safety of seven people. Among the dead, the identities of three people were confirmed, but their names were not announced. As the identities of the remaining 15 people have not yet been confirmed, there is a possibility that they are part of the 36 people now reported missing.
On Wednesday, researchers from the National Institute for Land and Infrastructure Management of the Land, Infrastructure, Transport and Tourism Ministry inspected the island from a helicopter. They confirmed evidence of landslides on several spots on the eastern side of slopes of the volcanic island, in addition to the western side of the island where the houses of the victims were located.
They also found spots where soil and rocks are piled up in the middle of the mountain. If there is another bout of rainfall on the island, the piled-up soil and rocks may start moving, which would cause debris flows again, the ministry warned.
The ministry is continuing its inspection and studying what measures should be taken.
The main characteristic of a debris flow is its rapid speed of 20 to 40 kph. Other sediment-related disasters include slope failure, in which an entire slope slowly slides down, and rockfall, in which soil and rocks fall from a very steep slope.