竹の川山崩れ  [in Japanese] Takenokawa Landslide  [in Japanese]

The Takenokawa landslide at Takenokawa, Itsuki Village, Kuma County, Kumamoto Prefecture, occurred 1:30 am of 29th June, 1984, after a heavy rainfall attaining 57.5 mm/h. It crushed 5 houses and killed l4 persons. This area is composed of limestone, shalstein, slate and chert of Mesozoic age. The thin Aso pyroclastic deposit, which is sometimes underlain and sometimes covered by river gravels and talus deposit is on the slope of the hard basal Mesozoic formations. The forest road running zigzag on the slope of the landslide area cuts the Aso pyroclastic deposit body three times (upper, middle and lower courses) forming Z shape. I think the disaster occurred in the weathered, water-saturated and heavy Aso pyroclastic deposit between the middle and upper course where the deposit lost its support by the slope cutting. The disaster investigation team or the Forestry Agency concluded that it occurred by high pore water pressure supplied from the basal limestones by the heavy rain and the team insists not by the road construction but the unexpected heavy rain for its cause. Here, I stress that the disaster is much related with the road construction.