National | Regional voices: Chubu

Sixty years after deadly Ise Bay typhoon, experts say Chubu disaster prevention needs an update

Chunichi Shimbun

The Ise Bay typhoon, a killer storm that swept through the Chubu region on Sept. 26, 1959, claiming more than 5,000 lives, became an opportunity for the nation to make great progress in disaster prevention efforts, including the construction of seawalls and river levees, as well as the enactment of the Disaster Countermeasures Basic Act.

But 60 years after the disaster, experts are calling for new measures and preparation amid increasing possibilities of unprecedented disasters triggered by, for instance, global warming and urbanization that could cause damage unimaginable back then.

Aging seawalls

Seawalls and river levees built in the region following the Ise Bay typhoon are regularly inspected and are repaired when cracks are found, but it’s been more than 50 years since they were constructed.

Due to the aging of the seawalls, the dikes may collapse, says Takashi Yasuda, head of Aichi University of Technology in Gamagori, Aichi Prefecture, and a specialist in coastal meteorological engineering.

“There is a possibility that it may break at places where water has penetrated into the soil that supports the concrete structure and made it weak,” Yasuda said. “We can’t predict where the breaks might happen” because it is difficult to identify such points.

Takashi Tashiro, designated professor of water disaster prevention studies at Nagoya University, pointed out that many small- and medium-sized rivers are not sufficiently prepared to prevent disasters.

“I believe about half of the rivers that need disaster prevention measures are not well prepared,” Tashiro said.

Ironically, embanking riversides can cause greater damage in areas below sea level.

“If water overflows a 4-meter-high embankment into an area 2 meters below sea level, the water would flow down 6 meters, bigger than would be expected without an embankment, and could result in greater damage,” he said.

The skyscraper effect

Yasuda said urbanization, namely the increase of high-rise buildings, is another factor that could worsen damage from typhoons and heavy rain.

“Unimaginably strong winds could hit urban areas (because of skyscrapers),” he said.

If wind blows into narrow spaces between high buildings, it accelerates in what is called the Venturi effect.

“At crossings in urban areas, vehicles could be blown away and crash into buildings and people,” Yasuda said.

Compared with the time of the Ise Bay typhoon, the rapid development of residential areas is also said to be raising the risk of disasters.

While rice paddies functioned as reservoirs in the past, providing a place that can hold water overflow from rivers, residential areas don’t have the capacity to hold the water.

Paved streets also don’t hold water like soil, increasing the possibility of damage.

“Subways are also a concern,” Yasuda said. “If Nagoya’s underground shopping district is submerged, the damage would be devastating.”

Heavy goods

At the time of the Ise Bay typhoon, lumber stocked at Nagoya port was washed away, causing great damage when it slammed into houses and buildings.

Today, numerous freight containers and vehicles fill the port waiting to be exported.

“They could flood in, just like lumber did,” Tashiro of Nagoya University said.

Along with industrial development, the coastal area of the Tokai region is filled with large-scale petrochemical complexes. There are also various other factories in inland districts, posing the risk of chemical and oil spills — like the one that occurred in Omachi, Saga Prefecture, following torrential rain in August.

“Piling up four or five containers is out of the question,” said Aichi University of Technology’s Yasuda. “Measures such as building windbreak fences (around dangerous objects) must be taken.”

Limits to prevention

Toshitaka Katada, project professor at the University of Tokyo’s Graduate School of Interdisciplinary Information Studies and a specialist in disaster-related social engineering, said the dangerous thing is to think disaster prevention measures are sufficient, considering that the term “unexpected” is often used to describe recent natural disasters.

“We must think of measures based on the premise that not all disasters can be prevented,” Katada said.

Since typhoons form over warm seawater, they usually weaken as they approach Japan. But as in the case of Typhoon Faxai, which hit Chiba Prefecture in early September, recent typhoons tend to maintain their intensity as they make landfall.

“This is because the temperature of seawater around Japan is rising due to global warming,” Yasuda explained. While Typhoon Faxai had a maximum instantaneous wind speed of 207 kilometers per hour in Chiba, there are estimates that typhoons with wind gusts of some 300 kph could hit the Chubu region before the end of this century.

Yasuda stresses the importance of community-level cooperation in dealing with natural disasters.

“Instead of relying on authorities, residents of communities should take the lead in working out their own evacuation plans,” he said.

Tashiro said people should first learn about the history of disasters in the area they live in and the current risks, then think about how they should act in various situations.

“It is dangerous to judge something is safe just by its appearance,” Tashiro said. “It is important to be aware that there are things you don’t know (about disasters).”

Children draw pictures inside a gigantic rainwater storage tunnel currently under construction in Nagoya. | CHUNICHI SHIMBUN
Children draw pictures inside a gigantic rainwater storage tunnel currently under construction in Nagoya. | CHUNICHI SHIMBUN

Storm water storage

In response to the torrential rain that hit the Tokai region in 2000 and August 2008, the Nagoya Municipal Government is currently constructing a gigantic rainwater reservoir on the east side of Nagoya Station.

The facility, being built about 50 meters underground, is a 5 km-long tunnel with a diameter of 5.75 meters running south from the city’s Nishi Ward to Nakagawa Ward. It will be able to store 104,000 cubic meters of water.

As of August, some 1.5 km of the tunnel had been excavated.

A water pumping facility is also being built in Nakagawa Ward to discharge rainwater collected from the storage tunnel and other drainage systems into the Nakagawa Canal. The 65.2-meter-deep facility will be able to drain roughly 13 cubic meters of water per second.

Through such measures, the city of Nagoya aims to more or less prevent flood damage by rainfall of up to 60 millimeters per hour and avoid houses from being submerged by rainfall of up to 97 mm per hour.

“In order to protect citizens’ lives and economic activities, we hope to improve safety against torrential rain through a variety of measures,” said an official of the city’s waterworks and sewage bureau.

Junior high school students in the town of Wanouchi, Gifu Prefecture, study during a class on becoming a bōsaishi, or disaster expert. | CHUNICHI SHIMBUN
Junior high school students in the town of Wanouchi, Gifu Prefecture, study during a class on becoming a bōsaishi, or disaster expert. | CHUNICHI SHIMBUN

Disaster prevention experts

The town of Wanouchi, Gifu Prefecture, has become the nation’s first municipality to train junior high school students to become qualified as bōsaishi, or disaster prevention experts.

In order to be certified as bōsaishi, it is necessary to take a course authorized by the Tokyo-based nonprofit group Japan Bousaisi Organization and pass an exam.

At Wanouchi Junior High School, the only junior high in the town, all second-year students take the course every year. This year, 90 students have been attending lectures offered by prefectural officials, university professors and fire officials since June to learn about natural disasters and disaster prevention measures, including how to read a hazard map.

On Sept. 20, bōsaishi Junichi Takagi explained to the students that people certified as bōsaishi basically work as volunteers rather than working under administrative bodies.

Ryusei Matsubara, 14, who attended the lecture, said: “Things we learned are difficult, but are all necessary to protect ourselves.”

“I learned CPR, so if I see someone collapsed, I want to help the person,” said Ritsuki Ichiryu, 13.

This section features topics and issues from the Chubu region covered by the Chunichi Shimbun. The original article was published on Sept. 26.

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