Sea-level rise has increased frequency of extreme coastal flooding worldwide

Peer-Reviewed Publication

Tulane University

News Release 10-Jun-2026

Human-caused sea-level rise has significantly increased the frequency of extreme coastal flooding worldwide, according to a new study led by a Tulane University researcher.

The research, published in the journal Nature Climate Change, found that coastal flooding events expected only once every 100 years are now, on average, about 12 times more likely to occur.

Climate change has made those events about four times more likely since 1900, said the study’s lead author Sönke Dangendorf, the David and Jane Flowerree Associate Professor in River-Coastal Science and Engineering at Tulane University School of Science and Engineering.

Dangendorf and an international team analyzed long-term tide gauge records alongside climate model simulations to separate the influence of human activity, natural forces and local land movement.

“Extreme sea levels occur when high tides, storm surge and rising baseline sea levels combine. As sea levels rise, smaller storms can produce flooding that previously required more severe conditions,” Dangendorf said. “At nearly half of the 130 sites analyzed in the study, a flood expected once every 100 years in 1900 now occurs at least once per decade.

In some locations, the increase is greater. At Sandy Hook, New Jersey, a 1-in-100-year event became about a 1-in-16-year event by 2005. In Wellington, New Zealand, a similar event became roughly a twice-per-year occurrence.

Local conditions can influence the magnitude of change. For example, in Manila, land subsidence linked to groundwater use has increased the frequency of extreme flooding more than 300-fold. However, across most sites, the study found that human-driven climate change is the primary factor increasing flood frequency. 

Natural forces contributed more to sea-level changes earlier in the 20th century, but the influence of human-caused warming has grown since the 1960s and now accounts for the largest share of rising sea levels and associated flood risk, Dangendorf said. 

The findings have implications for coastal infrastructure and flood planning, as historical estimates of flood frequency may no longer reflect current conditions.