After about an hour of torrential rain, restaurant manager Takuro Suzuki feared he would drown.

Suzuki, 42, and six other staff members were trapped inside Japanese-style dining bar Osashimiya in the basement of a building near Jiyugaoka Station in Tokyo’s Meguro Ward during the downpour on Sept. 11.

“If this store gets filled up with water, it’s over for us,” Suzuki said he thought as the water level kept rising.

Heavy rainstorms have increased in frequency across the country, and scenes of landslides, flooded farmland and raging rivers are becoming more common.

But experts say the events on Sept. 11 showed that city centers also cannot afford to be complacent about extreme weather events.

And the speed at which the rainwater poured in and blocked escape routes at Suzuki’s restaurant underscored the dangers of urban underground spaces during torrential rain.

LIKE A WATERFALL

According to Suzuki, the rain started around 2 p.m. on Sept. 11 and gradually intensified. Thunder was heard, and water started to leak from the ceiling and pipes inside the restaurant.

Just before 3 p.m., rainwater rushed down the stairs into the restaurant, like a waterfall pouring in from the street, he said.

Staff members closed the glass entrance door to prevent further damage. But they found they could not push the door open again because of the constant pressure from the flowing water. Even three men could not budge the door.

Water continued to spill into the restaurant.

One staff member made an emergency call using a smartphone. The power went out, sending the restaurant into darkness.

“We may die,” Suzuki said he thought at the time.

However, a vendor familiar with the restaurant came to the site. After seeing the plight of the staff members, the vendor broke the door and helped the seven escape at 3:15 p.m.

By then, the water inside the restaurant was knee-deep.

The Japan Meteorological Agency issued a heavy rain alert for the Tokyo area that day after observing 134 millimeters of rainfall in the hour until 3:20 p.m. in the Midorigaoka district of Meguro Ward.

Urban areas, of course, are not immune to damage from rain.

In 2003, record-breaking torrential rain flooded the underground mall near JR Hakata Station in Fukuoka.

In 2013, heavy rain inundated the underground shopping area in Sakae district in Nagoya.

Despite these disasters, many people in big cities still have a false sense of security during heavy rain, experts say.

GET ABOVEGROUND

Professor Masato Sekine of Waseda University, an expert in urban disaster science, warns that large amounts of rainwater can quickly flow into underground spaces, trapping people inside.

“It is essential to recognize the risks when heavy, localized rainfall hits highly developed underground urban areas,” he said. “You should never go underground during storms, even just to take shelter from the rain. If streets are flooded, get out of the basement immediately.”

Professor Hiroaki Furumai of Chuo University’s Research and Development Initiative who is an expert in urban environmental engineering, said preparedness is crucial to keeping safe.

He recommends that people identify flood risks along commonly used routes, such as around their homes or workplaces, and plan evacuation routes in advance.

Furumai also advises people to avoid underground roads and underpasses during heavy rain and to take refuge on the second floor or higher.

“Urban areas with extensive underground spaces are full of danger,” he said. “We must not take it lightly and it is important to be prepared.”

‘IMPOSSIBLE TO PREVENT’

Although the staff members escaped the flooding at Osashimiya, the restaurant has not recovered from the damage.

On Sept. 16, five days after the storm, the refrigerator and tables inside the restaurant remained overturned.

“It happened in just a moment,” Suzuki recalled. “I had never expected something like this could happen in downtown areas. It is impossible to prevent this.”

Suzuki said he still doesn’t know when he can reopen the restaurant.

He estimates that lost sales for September alone will be 8 million yen to 9 million yen ($54,100 to $61,000).

(This article was compiled from reports by Minori Oshita and Hisaki Tamanaha.)