Experts Reevaluate Disaster Prevention Measures After Record-Breaking Typhoon Hagibis

Typhoon Hagibis (Typhoon #19) roared through Eastern Japan over this past weekend, leaving at least 75 people dead and around 200 known injured. Over 16,000 homes were submerged in the storm. As of this posting, ten are still missing and thousands of homes remain without power. 

Japan’s Meteorological Agency declared the storm had delivered “once in 50 years” rainfall levels, causing many rivers to overflow their banks and extensive flooding.

In the wake of the storm, disaster prevention experts called for a rethink on how to prepare for such increasingly abnormal weather. They noted that, although special alerts were issued and the public duly warned about the severity of the approaching colossal storm, preparations to prevent flooding had proved inadequate.

The experts agreed that dealing with such freak natural disasters is inherently difficult, but emphasized the need for a thorough review of the nation’s flood control countermeasures in order to prepare for the “future.”

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Flood Control in Nagano

On Sunday, October 13, the Ministry of Land, Infrastructure, Transport and Tourism announced that at least 90 levees and dikes had failed across the country and 142 rivers had caused flooding damage. After dikes on the Chikuma River in Nagano City were breached, residential areas were inundated and a number of residents stranded.

Not only is the Chikuma River winding, with many curves, there are also major differences in elevation along its course. On numerous occasions in the past it had wrought fearsome destruction.

This time, upstream mountainous areas recorded record-breaking torrential rainfall.

Chuo University Civil and Environmental Engineering Department Professor Tadashi Yamada said that huge typhoons like Hagibis invite orographic rainfall, localized torrential downpours near mountains, which invite widespread damage. “The width of the dikes [in such areas] are narrow, and the steep gradient strengthens the force of the water, resulting in the water overflowing the dykes,” Yamada explained.

Niigata University Associate Professor Hiroyasu Yasuda, an expert on river engineering with the Research Institute for Natural Hazards and Disaster Recovery, observed: “What we saw was that extreme amounts of rainfall far surpassing forecasts occurred simultaneously in multiple locations, resulting in flooding in various areas.”

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When Flood Control Measures Work

In certain districts, the flood control policies of the national government and regional authorities appear to have had the desired effect.

Although the record rainfall caused the Tama River in the Tokyo area to overflow, the dikes held firm. Professor Yamada explained, “The dykes proved strong, and there was no major damage.”

The new Yanba Dam in Gunma Prefecture was affected by the construction freeze imposed when the Democratic Party of Japan was in power. The dam just started “initial impoundment” (test flooding) in October to confirm safety before going into full-scale operation. However, before it could begin actual operations, rainfall from Hagibis filled it nearly to the capacity level it was designed for.

Yet, there was no confirmed damage in the basin where it is located. Those involved with the project concluded, “All of the rainfall was stored, so we can say that the dam proved its effectiveness.”

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Cost-Benefits of Flood Control Infrastructure

Nevertheless, dams, dikes, and other “hard” infrastructure are very expensive. Having learned from the devastating torrential rains that struck Western Japan in 2018, the national government not only took “hard” measures such as strengthening river dikes, but also “soft” measures such as promoting evacuations of hard-hit areas.

The “hard” side are proving especially cost-effective. Even so, the disaster of this once-in-50-years storm inevitably resulted in flood damage over a wide area.

Associate Professor Yasuda warned: “Facilities capacity is inadequate to deal with climate change, which has become a fact of life. We need to finish the construction projects currently in the planning stage, revise our presumed levels of rainfall and flooding, and review our responses accordingly.”

Time to Change How We Think About Weather Events

With disasters intensifying, a change of consciousness is called for.

Professor Toshitaka Katada, an expert on disaster social engineering with the Graduate School of the University of Tokyo, offered the following sobering analysis:

Just like with the torrential rainfall in Western Japan last year, the way in which the rain continued to fall all at once in torrents over a broad area differed from the past. So, community planning and urban structures based on earlier suppositions are proving inadequate to deal with intensifying natural disasters. In this case, the overflowing of rivers in the Nagano area caused major damage, but with typhoons it is not unusual for rain clouds to spread over a large area even before landfall for the storm itself, bringing with them heavy rains.

Although society is adjusting to beforehand responses, such as suspensions of train service, for certain things citizens have to directly encounter the disaster damage before fully realizing what’s happening. What the central government and other administrative authorities can do is limited. Vague anxiety will not save your life. It is important to visualize the real face of a disaster damage that might occur, and adjust your behavior accordingly.

Everyone in Japan needs to change his or her consciousness and bear in mind, “In the final analysis, I have to protect myself.”

(Click here to read the article in Japanese.)

Author: The Sankei Shimbun