Sea-level rise driven by climate change is exposing Wellington to coastal flooding that would once have been considered exceptional, climate scientists say.

A new NIWA study finds that what used to be regarded as one-in-100-year coastal flood events are now occurring roughly twice a year along Wellington's most exposed coastlines. Lead author Dr Eleanor Wickham said human-caused sea-level rise had made coastal sea-level extremes four times more frequent since the start of the century.

"The flood we used to plan a century around is now the flood we plan a winter around," she said.

The findings are likely to feed directly into Wellington City Council's coastal adaptation plan, due for consultation later this year, and have renewed calls for managed retreat at the most exposed sections of the south coast.