Off the coast of Osaka, Japan sits one of the most ambitious infrastructure projects in history – Kansai International Airport. This vital travel hub serving the Kansai region of Japan was built in the 1990s on a massive man-made island in Osaka Bay, the first airport ever constructed completely on an artificial island. But despite its pioneering engineering, Kansai International rests on shaky ground, with the artificial island sinking at a faster rate than anticipated.
Kansai’s island measures 2.5 miles long and 1 mile wide, constructed from rocks and sand dredged from the bottom of Osaka Bay. But engineers had not anticipated the extreme weight of the concrete runway and terminal pushing down on the soft seabed soil and bedrock. Land surveys have shown that some areas of the island have sunk over 16 feet since the airport opened in 1994, nearly double what engineers predicted. That’s enough to noticeably tilt the airport terminal and require the costly raise of bridges leading out to the island.
And experts worry the worst is yet to come, with new data showing the island could sink up to 66 feet by 2060 as sea levels rise due to climate change. That would submerge entire runways and halt airport operations, not to mention the billions spent on upkeep for the sinking structures. Already, elevated support columns have had to be built underneath subsiding retaining walls around the island’s perimeter to brace them and prevent their collapse.
Yet remarkably, aviation authorities remain adamant that the airport is safe, secure, and not in danger of shutting down for the foreseeable future. The government has proposed everything from adding more fill material to the island’s foundation to constructing taller support columns underneath structures.
But some engineers are skeptical such efforts can reverse the sinking in the long run. And locals fear that a major earthquake or typhoon could accelerate the island’s descent and cause it to breach. For now, the landmark airport beloved by tourists and business travelers alike continues to operate as normal, even as the ground disappears below it. But Kansai serves as a sobering reminder of what happens when human engineering meets natural forces, and doesn’t quite measure up.