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By analyzing wave patterns created during Hurricane Hector (Category 3, August 7-11, 2018) and Hurricane Lane (Category 5, August 20-27, 2018) along the coral reef-lined south coast of Moloka’i, researchers found that while strong waves did create strong currents across the reefs, their impact was largely confined to the outer reef crest, with minimal wave energy reaching the shore. These findings underscore the importance of coral reefs in coastal resilience, particularly as climate change drives rising sea levels and more intense storms.

Measuring Hurricane Waves on a Hawaiian Reef

To better understand how waves interact with coral reef structures, USGS and University of Western Australia scientists conducted the second largest hydrodynamic field experiment ever on a coral reef in 2018 along a 1,200-meter-wide reef transect off the south coast of Moloka‘i. They collected real-world data on waves, currents, and water levels while also using high-resolution numerical models to simulate how hurricane-generated waves moved across the reef.

Their results showed a clear pattern: 

• Weaker currents during Hurricane Lane: Despite wave heights up to 1.9 meters (6.2 feet), currents remained slow—typically less than 0.15 meters per second (m/s). 

• Stronger currents during Hurricane Hector: With larger waves up to 2.5 meters (8.2 feet), currents increased to approximately 0.3 m/s. 

• Wave energy loss across the reef: Although waves were powerful near the reef crest, they dissipated quickly. By the time they reached the shallow reef flat, wave heights were less than 0.5 meters (1.6 feet), significantly reducing their impact on the shore. 

Coral Reefs as Coastal Buffers

The study adds to the growing body of evidence showing that fringing coral reefs act as critical buffers against storm waves, absorbing and dissipating energy before it reaches land. However, this protection depends on the health of the reef structure.

With accelerating sea-level rise and intensifying storms, the ability of coral reefs to continue providing this natural defense may be at risk. Degraded reefs could allow more wave energy to pass through, increasing flooding, erosion, and damage to coastal communities.

The Need for Reef Conservation

As sea levels rise, researchers stress the need for further studies on how changing ocean conditions will affect wave transmission across reefs. Protecting and restoring coral reefs will be crucial in preserving their ability to shield coastlines from future storms.

This research highlights the vital role of coral reef ecosystems—not just as biodiversity hotspots, but as natural coastal defenses that may become even more important in a changing world.