Sept. 1 — the day the Great Kanto Earthquake hit 95 years ago and killed more than 100,000 people, mainly in Tokyo and Kanagawa Prefecture — is Disaster Prevention Day. A year before this day was designated as such in 1960, the Ise Bay Typhoon that hit central Japan left more than 5,000 casualties. The powerful earthquake that hit northern Osaka Prefecture this June reminded us that temblors can hit this quake-prone country anytime, anywhere. The downpours that hit broad areas of western Japan in July, which left more than 200 people dead or missing, came as yet another warning against the more frequent and expanding damage from extreme weather conditions linked to climate change. We must learn from these disasters and constantly update our preparedness against major disasters.
In the western Japan downpours, widespread areas from Kyushu to Kansai were hit by torrential downpours and suffered massive landslides and floods. But while the total precipitation reached record levels in many locations, most of the damage from mudslides took place at sites where such dangers had been identified.
In the Mabicho district of Kurashiki, Okayama Prefecture, a major portion of the town was flooded — up to 5 meters deep — after rivers surrounding the district breached their embankments, leaving more than 50 residents drowned. But the area and extent of the flooding were roughly the same as had been warned in a hazard map created by the city.
The risks of such disasters had been known and warned about. But despite the early warnings of torrential rains that could cause such disasters, that did not prompt many of the residents to evacuate to safety in time. Evacuation orders or advisories were issued by local governments to 8.6 million people in western Japan, but less than 1 percent are believed to have taken refuge at evacuation shelters. Government authorities need to find out why their calls did not induce the residents to evacuate. Residents, for their part, need to learn about the potential risks in their neighborhood in case of disaster and be prepared to take action to protect themselves.
The maximum daily rainfall in Kurashiki during the July downpours reportedly hit a “once-in-a-century” level. But the frequency of torrential rains in Japan is rising. According to the Meteorological Agency, the number of times an “intense” hourly rainfall of 80 milliliters or more happened in a year rose by 60 percent in the most recent decade compared with the 10 years to 1985. What we have considered “extreme weather” is becoming less and less unusual.
The kind of extended downpours that hit western Japan could cause much more extensive damage if they hit more densely populated areas of the country. Last month, five wards in Tokyo’s eastern area — Koto, Sumida, Edogawa, Adachi and Katsushika, which lie along the Arakawa and Edo rivers and many of whose residents live below sea level — released a hazard map in case of large-scale flooding and plans to evacuate local residents.
In the worst-case scenario — both the Arakawa and Edo rivers breaching their embankment after total rainfall hits 500 to 600 milliliters over three days — an extensive area that is home to some 2.5 million people, or 90 percent of the population of the five wards combined, would be flooded. The map shows that the area could be flooded more than 5 meters deep, and an area that has some 1 million residents could remain inundated for more than two weeks.
In case such massive rainfall is feared due to the approach of a powerful typhoon, local authorities will call out to residents 72 hours in advance to voluntarily evacuate. Twenty-four hours before the disaster is predicted to hit, the five wards will begin joint operations to evacuate residents to safe areas in western parts of the capital as well as to neighboring prefectures.
That sounds easier said than done, particularly in the limited time before an imminent disaster. There will be a variety of challenges that need to be sorted out, including how to secure the transportation means to quickly and safely move such massive numbers of residents as well as the places that can accommodate so many people. National as well as prefectural governments will need to take the lead in such an unprecedented operation.
The government simulating the damage in case of major disasters and creating plans for people’s evacuation alone will not save lives. Each one of us must be fully aware of disasters risk and learn what action we need to take when they hit.