Heavy Weather over Kyushu
Humans and nature clash under changing climate
Again this week, Japan’s southwestern island of Kyushu has been devastated by floods and mudslides caused by extreme rainfall. On July 6, 2020, the Japan Meteorological Agency, JMA, issued a level 5 — its highest — heavy rain warning in Fukuoka, Nagasaki and Saga prefectures. Evacuation advisories have been issued targeting more than 1.4 million people. By July 9th, at least 62 people in Kyushu have died and another dozen or so are missing as a result of the weather disaster. The government has deployed at least 80,000 Self-Defense Forces (SDF) and coast guard personnel alongside fire fighters and police to the region for search and rescue operations.
In some areas, rainfall has reached 225 mm (9 inches) in single day. The average annual rainfall on the island is high, around 2,000 mm on average (ranging from 1,612 mm in Fukuoka in the north to 2,300 mm in Kagoshima furthest south). It is thus a relatively wet place even normally — and now it is towards the end of the rainy season, Tsuyu, when 300–400 mm is expected for the month of July — but the current figures mean that the island has seen more than half of its normal monthly precipitation fall within just one day. At this pace, half of the annual rainfall will have fallen in just one week.
The rains have brought heavy floods and overflowing rivers in the mountainous region. According to Kyodo News, 59 rivers have flowed over their banks and there have been at least 179 landslides. In some of the worst cases, entire mountain sides slip away bringing along big trees and entire forest patches to the valleys. Houses and cars are submerged in mud.
In 1993, Kyushu experienced the most devastating rainfall-caused disaster in history. That cool summer, the rainy season was exceptionally long and the peak of torrential rains took place in early-August, long after Tsuyu should have been over. Then, too, parts of Kyushu experienced rainfall of more than 1,000 mm in a week. In 2019, a veteran Asahi Shimbun correspondent who was then based in the paper’s Kagoshima office recalled the devastation, with cars piled up by the flowing water, even a twisted train. Debris flows caused large damage: there were 22 major ones, especially in the coastal areas where the mountains run directly into the sea, and where the major roads and railways are located. Some 2,500 people were trapped in cars, buses and trains, and had to be evacuated by boat.
This week, the amount of rain received in Kyushu is highly exceptional even by the Tsuyu standard — except that the same happened last year. Exactly a year ago, I was in Japan watching real-time as the tragedy unfolded, although I was safely tucked away much further north on the main island, Honshu, where the rain was much lighter. Also then, more than 1,000 mm of rain fell on Kyushu in just one week.
The year before that, too, it was the same. That time the worst hit areas were Nagasaki as well the western parts of Honshu, from Hiroshima to Kyoto, with coastal stretches on the Sea of Japan getting their share. At least 225 people were confirmed dead in the related mudslides and landslides or having their vehicles swept away by floods. In worst affected areas, the flood waters rose to 5 meters (over 16 ft). The rains finally eased during the second week of July when also the temperatures soared. More than 11,000 households were left without electricity and, thus, without air conditioning and clean water.
The year before that, in 2017, torrential rainfall and floods left 155 people dead and forced the evacuation of two million people, mostly again in Kyushu. At that time, it was the most devastating rain-related event in Japan in nearly three decades.
So what is happening? Why have these extreme weather anomalies suddenly become regular annual events? And why are they wreaking so much havoc? After all, Japan is one of the richest and most developed countries in the world, with arguably the most sophisticated disaster risk reduction system anywhere. There seem to be a number of reasons, all ultimately linked to human actions.
According to WWF, the impacts of climate change are already being felt in Japan, specifically in terms of increased frequency and intensity of heavy rains and other extreme weather events. There is growing scientific evidence to support this conclusion. Warming sea surface in areas of the East China Sea pushes the seasonal rain front and warm air northward to Japan even when the rainy season is officially over. The immediate cause of the events in the past years has been the presence of a nearly stationary non-tropical low front known as Meiyu or Baiu. According to JMA, a very moist and warm seasonal front hovering above Kyushu causes heavy rainclouds to form above the island, affecting areas in western and central Japan.
The JMA’s latest annual Climate Change Monitoring Report published in September 2019 concludes that: “On a longer time scale, a trend of increased intensity in extreme precipitation events in Japan is observed” and this trend is seen “in association with global warming.”
The impacts of flooding have been made worse by unsustainable management of the often steep hillsides enabling landslides and mudflows. Japan also has a long history of trying to control floods by channeling rivers in concrete and constructing dams, levees and others structures for water management. These often heavy-handed civil engineering works have frequently had the opposite effect to the desired one, as during high rainfall events the rivers have sought their natural courses instead of sticking to the narrow engineered channels. With climate change, the increasing events of extreme rainfall and flooding have led to such structures being overwhelmed even more often and even more dramatically.
The above factors combined with the aging demographics of Japan have proven deadly, as reported by the New York Times on July 9, 2020. The worst single tragedy in this week’s floods took place in the town of Kuma, in Kumamoto prefecture, where floodwaters inundated a nursing home. While SDF and police officers evacuated about 50 elderly people and staff using rubber boats, it appears that 14 residents may have lost their lives. Bound to wheelchairs, people were not able to escape the advancing waters to higher floors.
Japan is likely the country that is best prepared in the world to cope with natural hazards and disasters. After all, the volcanic archipelago has always been exposed to multiple hazards, from typhoons to earthquakes. Consequently, its inhabitants have developed a unique resilience towards such events. It has high building standards and it has set effective early-warning systems. There are regular disaster drills in which most people participate, and Japan has a well-educated and disciplined population that is well prepared.
Still, climate change will pose increasing challenges that will have high human, material and financial costs. Adaptation to this new normal will require much more than better engineered barriers, or even improved early-warning and evacuation systems. The best way would to avoid habitation and construction of infrastructure in areas most susceptible to weather-related hazards, such as steep slopes and valleys or exposed coasts. Unfortunately, much of Kyushu consists of mountains and coasts.
Most importantly, nature-based solutions, such as river basin management that builds the resilience of communities and people while respecting the natural environmental processes, are both more sustainable and often cheaper to implement than engineering structures. Instead of channeling rivers in concrete, it is better to let them flow naturally so that there is more space to absorb flood waters. Vegetation cover absorbs excess water better than paved surface and also protects coastal areas from storms. Trying to control natural forces is futile, especially as climate change is introducing ever more variability and unpredictability to the weather patterns. A more sustainable solution is to adapt and to adjust the way we build and live in closer harmony with nature.
Meanwhile, the rains continue in Kyushu but the weather forecast seems to provide some respite for the days to come.
.
