Officials of the Tokyo Metropolitan Government are planning to install shutters and gates at subway station entrances to keep flood water from flowing into tunnels.

Tokyo officials fear torrential rain could cause heavy flood damages to urban areas, as powerful storms have been more frequent in recent years in Japan.

They estimate that more than 60 kilometers of subway tunnels could be submerged in the worst case scenario. That's about 60 percent of all subway lines operated by the Tokyo government.

Officials now plan to install shutters and gates at 65 subway entrances by mid-2040s. They also plan to take steps to prevent water from entering through ventilation equipment.

Officials say those measures will help reduce the area of flooded subway tunnels by two-thirds.

Some construction work has already begun. The total cost is estimated at about 220 million dollars.