And while the global population grew by 18.6% from 2000 to 2015, the population in these areas outpaced that growth, increasing by 34.1% over the same period. That means between 58 million and 86 million more people were exposed to flooding in those places over the course of 15 years. "It's not particularly surprising that floods would increase," says Beth Tellman, cofounder of the flood-mapping startup Cloud to Street and the lead author of the study. "But what was striking to me was that people were moving into places where we've observed flooding in the past." The researchers looked at over 3,000 events in the Dartmouth Flood Observatory database, which logs floods reported in media coverage.