The densely populated urban areas of Osaka and Nagoya as well as the western Kyushu region surrounding the Ariake Sea are at risk from rising sea levels resulting from higher oceanic temperatures.
According to research released Saturday, the region could face flooding because dikes and banks may collapse in typhoon-linked high tides and seismic tidal waves.
The pace of rise in the sea level has been relatively slow but could gain momentum if global warming accelerates, according to Shinichi Iwasaki, a researcher at the National Institute for Earth Science and Disaster Prevention.