TOKYO - A disaster prevention experiment has shown how quickly a rain-soaked slope can collapse once visible cracks appear, highlighting the need for people in landslide-prone areas to evacuate before conditions become critical as the risk of disasters remains elevated through early next week.
The National Research Institute for Earth Science and Disaster Resilience conducted an experiment reproducing a landslide caused by prolonged rainfall.
Researchers created a soil slope measuring 9 meters wide and 7 meters long and continuously subjected it to rainfall of up to 100 millimeters per hour.
A large crack appeared in the slope about three hours after the experiment began. Just 10 minutes later, the entire slope collapsed.
Motoyuki Ushiyama, a professor at Shizuoka University's Center for Integrated Research and Education of Natural Hazards, said there is no single rainfall threshold that can determine when a landslide will occur because ground conditions vary from one area to another.
He said there is a significant possibility of landslides occurring through early next week and stressed the importance of preparing and evacuating before visible signs of danger emerge rather than waiting for abnormalities to appear.
People are being urged to check local hazard maps in advance and determine whether their homes and evacuation routes are in areas vulnerable to landslides or debris flows.
If a landslide or debris flow appears imminent, Ushiyama advised people to avoid valley bottoms and low-lying areas where debris is likely to travel and, where possible, move uphill in a direction perpendicular to the expected flow.
The same principle should be considered when deciding in advance where to evacuate.
Under Japan's five-level disaster warning system, people who may require additional time to evacuate, including older residents and families with infants, should begin evacuating when a red Level 3 warning is issued.
When a purple Level 4 warning is issued, everyone in a dangerous area should evacuate.
A black Level 5 emergency warning indicates that a disaster is highly likely to have already occurred, and people should immediately take whatever action is necessary to protect their lives.
Residents are also being urged to closely monitor the latest disaster information, including the Japan Meteorological Agency's Kikikuru real-time hazard maps.
Source: FNN
