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54% of dead, missing in July's heavy rains were indoors; many didn't understand warnings

Houses are swept away by floodwaters and mud from a local river in the Mabicho district of Kurashiki, Okayama Prefecture, on July 9, 2018. (Mainichi)

SHIZUOKA -- Over 50 percent of the 231 people who were killed or went missing in the July torrential rain disaster in western Japan were indoors at the time, according to a disaster expert's analysis of government survey data, records and other sources.

Motoyuki Ushiyama, a professor of disaster information studies at the Center for Integrated Research and Education of Natural Hazards at Shizuoka University, released his analysis of the Fire and Disaster Management Agency records and other materials on Aug. 3.

At the announcement, Ushiyama revealed that an online agency survey showed that while 80 percent of residents in areas covered by "emergency heavy rain warnings" were aware of the warnings through television and other sources, over half did not understand what they meant.

According to Ushiyama, of the 231 who died or are missing, 125 (54 percent) were victims of mudslides, while 82 (36 percent) were victims of flooding. Of the people caught in mudslides, 74 percent were in their homes or otherwise indoors, as were 38 percent of the flood victims; the total percentage of people who had been indoors when they died or went missing was 54 percent. Just 25 percent were outdoors when disaster struck. The circumstances of 21 percent of victims remain unknown.

The ratio of those killed by wind or flood damage between 1999 and 2017 who were indoors at the time was 49 percent. The figure for the July rains is expected to rise above 54 percent.

Furthermore, over 80 percent of those who died or went missing because of mudslides were in areas considered at risk of mudslides. Sixty percent of people who suffered damage from flooding did so in areas considered possible flooding areas. This underscored the importance of informing the public of hazard maps and actually putting them to use. It also emerged that 23 people died while in the process of evacuating.

According to an online survey conducted in July on a total of 557 people in the three prefectures of Okayama, Hiroshima and Fukuoka, where emergency heavy rain warnings were issued earlier that month, 85 percent of respondents knew about the warnings, but only 47 percent correctly understood that they meant grave danger was imminent.

"(The analysis) has allowed us to understand that there is as yet no widespread public comprehension of emergency warnings," Ushiyama said.

(Japanese original by Tomohiro Ikeda, Science and Environment News Department)

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