TOKYO -- In October 2019, Typhoon Hagibis made landfall on the Japanese coast near Tokyo, with winds of over 195 kph and waves as high as three-story buildings. The largest typhoon to hit Japan since records began, it slashed through towns and inundated low-lying coastal areas.
Facing the prospect of massive floods, authorities were able to fall back on a recently created defense mechanism: a system of artificial caverns dug into the rock and clay underneath Saitama Prefecture, north of Tokyo. By gulping down 12.18 million cu. meters of water -- about 4,800 Olympic swimming pools worth -- it saved Greater Tokyo from an estimated 26.4 billion yen ($201 million) of damage.
