Human-induced sea-level rise has significantly increased the frequency of coastal flooding in Wellington, New Zealand’s capital, according to new research. Events once considered rare, such as “1-in-100-year” floods, are now occurring approximately twice a year in the region.

The study, published recently in a scientific journal, highlights that globally, extreme coastal water levels have become about four times more common since 1900. At many locations, events that previously had a 1-percent chance of occurring annually have become at least ten times more likely by 2005.

This increased flood risk in Wellington coincides with the recent lifting of a local state of emergency, declared earlier this week due to large swell warnings affecting the city’s south coast and the southern Wairarapa region.

Scientists attribute the rise in flooding frequency primarily to human-driven climate change, which has elevated global mean sea levels by roughly 20 centimeters over the last century. The higher baseline in sea level enables tides and storm surges to surpass flooding thresholds more easily. Scott Stephens, chief scientist at Earth Sciences New Zealand, emphasized that these elevated water levels heighten the chances of extreme coastal flooding.

Rob Bell, a research associate at the University of Waikato, explained that Wellington’s small tidal range and limited variability in storm tides mean even modest sea-level increases can lead to a rapid rise in flood occurrences in the area.

The researchers warn that if sea levels continue to rise, coastal flood risks will escalate further, particularly endangering low-lying coastal communities. The findings underscore the urgent need for revised flood management strategies and adaptive measures to mitigate future impacts.