Heavy rainfall events have become more frequent over the last 50 years on the Big Island of Hawaii.

Researchers at the University of Hawaii Manoa found that a rare storm with daily precipitation of nearly 12 inches, occurring once every 20 years by 1960, has become a rather common storm event on the Big Island of Hawaii -- returning every 3 to 5 years by 2009.

While heavy rainfall events have become more frequent over the last 50 years on the easternmost island in Hawai'i, the opposite behavior is observed for Oahu and Maui to the west. There, rainfall extremes have become less frequent in the last five decades. This study, therefore, also reveals a regional -- that is, east to west -- difference in how precipitation patterns are responding to a changing climate.

"In the past, the frequency of heavy rainfall events was assumed to be fairly constant. However, because climate is changing, the assumption of stable precipitation climatology is questionable and needs to be reconsidered," researcher Ying Chu said in a statement. "Changes in the frequency of heavy rain events have repercussions on ecological systems, property, transportation, flood hazards, and engineering design - including sewage systems, reservoirs and buildings."

For the study, researchers analyzed extreme precipitation events and the frequency with which they occur on here islands in Hawaii -- Oahu, Maui and Hawaii Island. The number of rain gauges used was limited - the researchers used information from 24 weather stations on the three islands.

For future work, Chu said he hopes analyzing data from additional stations will provide a more detailed assessment of changing rain patterns across the Hawaiian Islands.

The findings are detailed in the International Journal of Climatology.