Heavy Rains in Hawai’i Can Cause Catastrophic Damage to Property

by HOM Editor

Heavy rains can happen throughout the year, putting property at risk. Cresting streams and rivers, backed-up storm drains, and saturated ground can all cause serious damage when there is an excessive amount of rainfall.

In some instances, heavy rainfall can also lead to flash floods, a rapid flooding of low-lying areas in less than 6 hours. Flash floods are known to roll boulders, tear out trees, and destroy buildings and bridges.

Manoa flood

Flood waters pushed several vehicles into the trees immediately downstream from the Woodlawn Drive Bridge. Source: National Weather Service.

The Manoa Flood

In October 2004, a severe thunderstorm moved onshore from the east-northeast over the Koolau Mountains and into Manoa Valley, causing a flash flood in the early evening hours. The intense rainfall caused Manoa Stream to quickly overflow its banks in several areas.

The worst flooding occurred when a debris-clogged bridge diverted flood waters out of the normal stream channel and sent a flood wave through a residential area and into the University of Hawai’i at Manoa campus.


The worst flooding occurred when a debris-clogged bridge diverted flood waters out of the normal stream channel and sent a flood wave through a residential area and into the University of Hawai’i at Manoa campus.


Flood waters poured into the basement of Hamilton Library and damaged or destroyed archives containing irreplaceable documents. Several instructional facilities and laboratories with critical experiments also sustained significant damage.

Luckily, there were no deaths or reported injuries. But, the total damage reached an estimated $85 million, most of which occurred on the University campus. About 120 homes also sustained varying degrees of damage.

Are You Prepared for a Flood?

Residents and business owners need to prepare for flood conditions. Before the threat of flooding becomes imminent, residents and business owners should:

  • Purchase a flood insurance policy if they do not already have one.
  • Review their current insurance policy, become familiar with what is covered, and ensure the limits are adequate for their building and personal belongings.
  • Make an emergency kit, plan evacuation routes, and keep important papers in a safe, waterproof place.
  • Itemize and take pictures of possessions.
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Source: National Weather Service, Hawai’i Flood Information and Floodsmart.gov’s Flood Risk – Heavy Rain Fact Sheet.