Prepare to take action for early evacuation due to prolonged heavy rain

Yomiuri Shimbun file photo
Japan Meteorological Agency in Minato Ward, Tokyo.

In many parts of the country, it has been raining hard for an extended period as if it were the rainy season. There is a possibility that heavy rain will continue over a widespread area for several more days, so people need to beware of landslides and flooding.

Record rainfall amounts have been observed mainly in western Japan since the rain began to fall on Aug. 11, with some areas having accumulated over 1,000 millimeters. At one point, the Japan Meteorological Agency issued special heavy rain warnings for Saga, Nagasaki, Fukuoka and Hiroshima prefectures.

The number of houses flooded in Kyushu and other areas has reached several thousands, and the number of people told to evacuate nationwide is in the millions. Mudslides and the flooding of roads continue to occur in various parts of the nation, leaving some people dead or missing. The central and local governments need to do their utmost in search and recovery efforts.

Such heavy rain usually occurs around July, when there is a stationary seasonal rain front. This year, however, a high-pressure system in the Pacific Ocean that should be over Japan is farther south, creating in the vicinity of Honshu a long front like one seen in the rainy season.

When the temperature rises by 1 C, it is said that the amount of water vapor in the atmosphere increases by 7%. Heavy rain has poured down over a wide range of areas as a result, with this atmospheric pressure pattern similar to that in the rainy season appearing amid the high heat of midsummer. Linear precipitation bands that have caused damage in various areas in recent years have also been verified.

This month, the Intergovernmental Panel on Climate Change (IPCC) of the United Nations compiled a report stating that the effects of global warming are clearly starting to appear. It is feared that torrential rains said to occur once every several tens of years will continue to occur almost annually.

This time, in addition to rivers overflowing, there have been cases of the inundation of drainage facilities, which occurs when rainwater flowing into sewage systems exceeds the drainage capacity and spews back out to the ground. As such flooding from drainage facilities can occur suddenly even in urban areas, caution is needed.

It has been raining on and off. It is difficult to determine when to evacuate, but a temporary lull in the rain does not mean that it is a reassuring situation. There is a possibility that the ground has already come loose. It is necessary to consider evacuating early to avoid doing so at nighttime.

If evacuation centers become crowded, there are also concerns about evacuees being infected with the novel coronavirus. Going to an acquaintance’s home or hotel is also an option. Even if some people live on the upper floors of a sturdy condominium building, they need to stockpile food and water. Evacuation plans should be made according to the circumstances of each household.

The risk of landslides and floods varies greatly from region to region. In recent years, it has become possible to view various kinds of information, such as the distribution of risk of disasters caused by rain that the JMA publishes on its website.

It will be important to actively gather information on weather and disasters, and be ready to judge the degree of danger on our own and act accordingly, rather than merely waiting for instructions from the central and local governments.

— The original Japanese article appeared in The Yomiuri Shimbun on Aug. 17, 2021.