Dec 05, 2018

Sand Mattress Successfully Combats Beach Erosion

The sand mattress, installed one year ago, have been protecting Honolulu’s Waikiki Beach from erosion

Sand mattress successfully combats erosion in Hawaii
Sand mattress successfully combats erosion in Hawaii

A $3,000 sand mattress installed along Waikiki beach in Honolulu, Hawaii, has proved successful at preventing beach erosion. One year after installing the 100-by-12 ft sand-filled mattress to stabilize the shoreline, researchers with the University of Hawaii’s Sea Grant College Program have found the tool effective at preventing erosion with the exception of a summer storm.

“It has been a big success. This erosion mattress has done exactly what was intended,” said Dolan Eversole, the Waikiki Beach management coordinator for the University of Hawaii’s Sea Grant College Program. “It doesn’t magically solve the erosion, but it simply keeps the dirt fill in place.”

According to Hawaii News Now, a storm in late August triggered a south swell that coincided with the king tides, resulting in minor erosion along the beach.

“Wave overtopped the entirety of that area of Waikiki Beach by the hula mound, and there was some slumping as water went behind the mattress and sucked out some of the sand,” said Matthew Gonser, the coastal and water program manager for the city’s Office of Climate Change, Sustainability and Resiliency.

To combat the challenge, the city added sandbags as a temporary solution, which now are covered by sand due to the shift in seasons. The sandbags combined with the sand-filled mattress have successfully combated erosion at a low-cost to the city. The Waikiki Beach Special Improvement District Assn. donated $3,000 to the city for the cost of the mattress and the product vendors worked on the project for free while the rest of the labor was completed by city staff.

“Almost certainly, the shoreline would have moved landward,” said Eversole. “How far landward, it’s hard to say, but I would estimate between 10 and 20 ft more landward.”