Countermeasure for Sediment Disaster

Improvement in Sediment Disaster Control Facilities

In areas with risk of sediment disaster, including those in the Izu and Ogasawara islands and hilly and mountainous areas of the Tama area, the Bureau is constructing sabo dams, crib walls, lava diversion channels and other infrastructure to make the areas better prepared for natural disasters such as landslides and debris flows due to heavy rains, and lava flows from volcanic eruptions.

  • Construction of the Omiyasawa Lava Diversion Channel (Nomashi district, Oshima Town)
  • Construction of crib walls to protect houses against landslides (Hatsuzawa district, Hachioji City)

Promotion of Sediment Disaster Prevention Measures on Oshima Island

In 2013, Typhoon No. 26 (Typhoon Wipha) wrought havoc on Oshima Island, with a record 24-hour rainfall of 824 mm causing severe damages. Slope failures occurred in many areas, and debris flows ran across different watersheds. Following the disaster, the TMG established a panel to discuss measures to respond to the sediment disaster on Oshima Island, whose members include outside experts. The panel looked into how the disaster unfolded, and studied facility improvement for landslide mitigation and other matters. Currently, recovery efforts, including the work to raise the height of a sediment retaining facility, are underway, based on the outcome of the discussion at the panel.

Regions designated as areas of sediment disaster Alert (As of April 1st. 2011)
mage of raising the height of a sediment retaining facility to enhance its capacity
(Okanazawa River)

Designation of Sediment Disaster Alert Areas

The TMG is in the process of designating sediment disaster alert areas, in accordance with the Sediment Disasters Prevention Act*, for such purposes as raising public awareness of the risk, facilitating preparation for possible evacuations, and restricting land development in hazard areas.
*Act on Sediment Disaster Countermeasures for Sediment Disaster Prone Areas

Regions designated as areas of sediment disaster Alert (As of April 1st. 2011)
Progress in the Designation of Landslide Hazard Areas, etc. (as of January 1, 2014)

Announcement of Sediment Disaster

The TMG and the Japan Meteorological Agency jointly issue sediment disaster warnings, which are conveyed to the public by the media, when a heavy rain warning signal an increased risk of sediment disasters would require evacuation.

Information Transmission Routes for Sediment disaster Warnings
How to communicate a landslide warning to residents.


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