Photo/IllutrationKansai International Airport is flooded in a storm surge on Sept. 4, 2018. (Asahi Shimbun file photo)

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Almost one year after a historic storm surge caused by a powerful typhoon inundated Kansai International Airport, many parts of Japan remain vulnerable to a similar disaster.

The central government is asking 19 prefectural governments that face possible storm surges to publicize areas most vulnerable to flooding, but only Tokyo and four others have done so.

In Tokyo, it is forecast that more than 2 million residents could be forced to evacuate if rivers in the capital overflow at the same time.

In western Japan, local authorities appear to be moving slowly to draw up measures aimed to mitigate the impact of flooding despite the central government urging that emergency plans be put in place.


Typhoon No. 21, the strongest to hit Japan in 25 years, swirled through the Kansai Region about a year ago.

It unleashed a storm surge on Sept. 4 that flooded Kansai Airport, which sits on an artificial island in the Osaka Bay, and other coastal areas along the bay.

Eri Koyama, who runs a cafe in Ashiya, Hyogo Prefecture, experienced the horrors of flooding resulting from the storm surge.

Apart from Kansai Airport, many of the man-made islands in the bay were inundated, including Minami-Ashiyahama of Ashiya, where she runs a cafe near the sea. The tides hit record highs at seven sites along the bay, according to local governments.

In Minami-Ashiyahama, a storm surge flooded about 27 hectares of land, with 17 structures above floor level and 230 buildings below floor level.

Koyama, 38, said that Typhoon No. 21 differed from past typhoons in the extent of the storm surge it caused.

At around 1:40 p.m. on Sept. 4, right before the typhoon made landfall in Kobe again, the street before her coffee shop looked like a river, with water spilling over from a parking lot near the sea.

While she and her neighbors talked via a free app over whether they should evacuate, water levels kept rising to where it became impossible to distinguish between the boundary of the sea and a sea wall. Seawater even washed to the front of her shop.

Unable to evacuate, Koyama and her husband, Yutaka, 37, fled to the second floor of the shop, which they used as an office.

They reinforced the entrance and windows of the shop with magazines and towels to prevent water from leaking in. But water slowly seeped onto the floor.

“I was so nervous about how high the water would inundate (their shop),” she said.

Koyama was terrified when she heard the sound of drifting containers in the sea apparently smashing into a sea wall.

“Our house would be destroyed if containers hit it,” she recalled thinking at the time.

About 30 minutes later, the water subsided. However, the high tide that day was supposed to come around 5 p.m.

The couple decided to flee in their car. But they abandoned the evacuation attempt after driving only several hundred meters. The car’s engine appeared to have caught fire.

“It is too late to evacuate after the rain and winds became stronger,” Koyama recalled. “We should have evacuated in the morning, considering that a car submerged in water cannot be driven.”

Japan is no stranger to the devastation caused by a storm surge in which huge waves are created due to a typhoon or an extremely low pressure system and the sea level rises.

More than 5,000 people were killed in the storm surge caused by the Isewan (Ise Bay) Typhoon in September 1959. Most of the damage was reported in Aichi and Mie prefectures, which surround Ise Bay.


The 19 prefectures that are most in danger of storm surges are located in the vicinity of Tokyo Bay, Ise Bay, Osaka Bay, Seto Inland Sea and the seas of Ariake and Yatsushiro, both of which are in western Kyushu.

The central government is asking them to release information on their areas most prone to flooding by March 2021.

Release of information on high-risk areas is expected to make it possible for local residents to prepare for a disaster and devise evacuation plans.

Of the 19, only Tokyo, Chiba, Kanagawa, Hyogo and Fukuoka prefectures have published such information.

A storm surge and flooding could cause extensive chaos in the Tokyo metropolitan area.

In the event of simultaneous flooding of the Arakawa and Edogawa rivers, up to 2.55 million residents in Koto, Edogawa, Sumida, Katsushika and Adachi wards in eastern Tokyo that are located near the rivers and Tokyo Bay would have to evacuate.

In Edogawa Ward, where 70 percent of the land is below sea level, almost all the ward is predicted to be flooded for about one or two weeks after large-scale flooding takes place.

In May, many Edogawa residents expressed alarm when ward authorities distributed hazard maps to all 340,000 households warning of the danger of remaining in the ward when flooding is highly likely.

Local authorities say the two most important things for residents in the event of flooding is to evacuate early and secure a safe venue to go to.

Edogawa officials plan to issue an evacuation advisory via a community wireless system for residents three days before a disaster could hit the ward.

In June, local officials called on residents to discuss with their friends and relatives outside Edogawa Ward in advance where they can evacuate to in the event of major flooding.

(This article was compiled from reports by Tatsuya Chikusa and Ryunosuke Kanayama.)