In the summer of 1742, two typhoons swept across Japan in quick succession, bringing torrents of heavy rain and flooding major rivers. Records from a young monk who witnessed the floods describe a muddy wave destroying levees and sweeping through villages. As levees and rivers collapsed, floodwaters rose in Edo, Japan’s largest city and political capital, abating only days later, and resulting in fatalities of a reported 6,000 in the city.
While floods were not an uncommon occurrence in Japan, the Great Kanto Flood of 1742 was the worst flood in the country’s early modern era, and the first flood disaster in its largest urban area. It highlighted the river engineering changes that had facilitated the growth of Edo, but also increased the city’s vulnerability to floods.