NHK has learned that about 40 percent of Shinkansen bullet train depots in Japan are located in areas that are vulnerable to flooding.
NHK examined hazard maps and other information provided by local governments for 18 rail yards used for Shinkansen trains.
JR East's depot in Nagano City, northwest of Tokyo, was not included in the survey. It was flooded last weekend when Typhoon Hagibis caused the Chikuma River to overflow. Ten bullet trains, or 120 cars, were inundated.
The city's hazard map shows the depot is in an area where floodwaters could exceed a height of 10 meters.
NHK found that seven of the 18 Shinkansen depots in other parts of Japan are also located in areas that are vulnerable to flooding.
JR Tokai has two -- one in Osaka and the other in Shizuoka Prefecture. JR Kyushu and JR West have one each in areas where floodwaters can exceed one meter.
JR Hokkaido has a depot in an area where floodwaters could reach a height of just under three meters.
Two rail yards owned by JR East and JR Tokai are in areas where floodwaters could reach heights of less than 50 centimeters.
NHK also found that three other depots are partially located in flood-prone areas.
Kogakuin University Professor Ryo Takagi is an expert on electric train systems. He says most of the important equipment for Shinkansen trains is only 20 centimeters above the tracks and it can be easily damaged if flooding occurs.
He says bullet train operators should raise the ground level of their depots as soon as possible.