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2014年8月22日 (金)

広島土砂災害 生かされなかった過去の教訓

The Yomiuri Shimbun
Failure to learn from past disasters contributed to landslide tragedy
広島土砂災害 生かされなかった過去の教訓

A massive volume of dirt and sediment swept down valleys and engulfed many homes.

Before dawn on Wednesday, torrential rain that pounded parts of Hiroshima city triggered debris flows and cliff collapses in more than 10 locations. About 40 people have been confirmed dead, and several others remain missing. It is a harrowing disaster.

Prime Minister Shinzo Abe, who had been on summer vacation, quickly returned to the Prime Minister’s Office and ordered more Self-Defense Forces personnel to the affected areas to conduct search and rescue operations for victims of the tragedy.

A firefighter engaged in a rescue mission at the scene also died when he became buried under the mud. We hope the police, firefighters and the SDF take care to avoid being caught in secondary disasters while doing everything in their power to search for the missing people.

According to the Japan Meteorological Agency, Asa-Kita Ward in Hiroshima city was inundated by more than 200 millimeters of rain in the three hours to 4:30 a.m. Wednesday. This is 1.5 times the amount of rainfall the area gets for the whole of August in a normal year. This huge amount of rainwater swept away dirt and trees, and then poured into residential areas at the foot of hills in the ward.

Experts have pointed to the fragile geological features peculiar to Hiroshima as one reason why the damage was so extensive. The ground on which many homes were built is a kind of compacted granite scree known in Japanese as “masado.”

About 32,000 locations in Hiroshima Prefecture are designated as being at risk from landslides. That is the highest figure for any other prefecture in Japan by a significant margin. Hiroshima, more than any prefecture, needed to routinely prepare for such a disaster.

Warnings too late

In June 1999, a similar disaster, including cliff collapses, in Hiroshima city killed 20 people. This prompted the enactment of the Sediment Disasters Prevention Law in 2001.

Under this law, prefectural governments must examine areas vulnerable to landslides and other sediment disasters, and designate areas at risk as “special caution” or “caution” zones. Municipal governments are obligated to compile hazard maps showing areas at risk. The development of residential areas is restricted in special caution zones.

However, many of the areas affected by Wednesday’s landslides had not been categorized as requiring caution. There have been claims that the designation of zones at risk could not keep up with the workload due to a personnel shortage. It is regrettable that the law did not function as expected.

The Hiroshima city government issued evacuation orders and advisories to residents at 4:15 a.m. Wednesday and later. By this stage, the mudslides had apparently already occurred. The city government has acknowledged the delay in issuing the evacuation warnings was the result of “mistakes in analysis of the rainfall.”

Be that as it may, even if evacuation orders and advisories had been issued properly, evacuating in the dark as pounding rain falls also has its dangers.

It is important that all municipalities, not just Hiroshima, consider how they can safely evacuate residents during disasters that occur in the middle of the night and in the hours before dawn.

These heavy downpours were caused by warm, moist air from the south that flowed into a stationary front over the Sea of Japan. This weather pressure pattern will reportedly continue for a while. Vigilance against further disasters must be maintained, especially in western Japan.

(From The Yomiuri Shimbun, Aug. 21, 2014)


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