Sea-level rise and the associated increased flood risk threaten many coastal areas of the world. But it's been somewhat hazy where coastal adaptation is most urgent and when the figurative flood gates will open.

Now a new study by a team of international researchers shows that within 30 years, the estimated probability of flooding will be 10 times higher in more than a quarter of the nearly 500 locations studied. The increase is most rapid in central America, southern Europe, South Africa, and parts of Asia and Australia. The researchers, from Princeton University, Utrecht University, Deltares, NIOZ, among others, devised a new method to calculate when we can expect the likelihood of flooding to increase in specific areas, which informed the finding.

As the Earth continues to warm from climate change, it's difficult to know when sea levels will rise high enough to warrant upgrades in coastal protection, in part because levels of existing coastal infrastructure vary globally. The finding can help communities and policymakers estimate of how quickly they must put coastal protection measures in place. 

“Our study shows that sea-level rise is shortening the runway for delivering coastal adaptation projects,” said D.J. Rasmussen, coauthor of the study and a former postdoctoral researcher at Princeton’s Center for Policy Research on Energy and the Environment. “This is not good news given how long it has taken solutions to get implemented in the past."