In April 2018, a landslide occurred on a hill behind houses in Nakatsu City, Oita Prefecture. The landslide moved sediment over a width of more than 100 meters, completely destroying four houses and killing six people. Landslide hazard areas are found throughout Japan, and the total number of landslide hazard areas is approximately 680,000. Why do landslides occur? Experts believe they are often triggered by heavy rainfall. In this episode, we'll look at the mechanism behind landslides and the latest research on reducing their damage.
Reporter: Lemi Duncan
Dr. Hirotaka OCHIAI specializes in landslides and says that there is a common cause behind them.
A 3D map of the underground by applying an electric current. It shows that a lot of groundwater is accumulating (green and blue areas) in addition to the red areas where landslides are occurring.
Dr. OCHIAI's landslide experiment. Heavy rainfall caused this artificial landslide.