Summer tides make shoreline erosion likely on South Shore of O‘ahu

At Waikīkī in summertime, big waves charge the air with negative ions and salt spray, long blue walls breaking into white lei of foam out to the horizon. Summer also brings the year’s highest tides, which can interrupt an ill-timed beach stroll, towel nap or picnic with a sudden soaking. Worse, those who walk out onto jetties or sea walls can get washed off and hurt on the rocks and reef below.

This summer will see 36 days with peak high tides above 2.2 feet in June, July and August, according to National Oceanic and Atmospheric Administration (NOAA) predictions. When combined with big waves, these high tides will make shoreline inundations and erosion likely, said Dolan Eversole, a geologist and coastal processes specialist for the UH Sea Grant College Program, who serves as technical adviser to the Waikīkī Beach Special Improvement District Association (WBSIDA).

“These (will be) our seasonal high tides we get every summer, nothing really exceptional or unusual,” Eversole said.

However, he added, another factor might contribute to more severe beach inundation and erosion this summer, when “a regional anomaly (in the seas around Hawai‘i) will make the high tides 2–4 inches higher than what’s on the NOAA (charts).”

Even 2–4 inches can pose problems, said Charles “Chip” Fletcher, professor of Earth Sciences, SOEST’s Associate Dean for Academic Affairs, and vice chairman of the Honolulu Climate Change Commission (HCCC). “This water level Dolan identified is something to worry about: Erosion may be worse this summer than expected, particularly on southern shores,” Fletcher said. “All this variability is superimposed on a long-term rise of sea water levels because of global warming,” he added.

Read more about it in the Honolulu Star-Advertiser (subscription required), The Garden Island, and the U.S. News & World Report.