Big waves, transient beaches

HANALEI — Sand is shifting around Kauai again, and the big winter waves have come back to the North Shore.

Over the past few days on Kauai, wave height has reached 15 to 20 feet, and some of the beaches have become almost nonexistent.

“Hanalei Bay has lost almost all of its beach and the tourists are having to sit in peoples front yards,” said Terry Lilley of Hanalei.

While some of this activity could be attributed to changing ocean conditions, the changing conditions are also part of the island’s seasonal changes.

“It is the time of the year when the North Pacific, winter-storm-generated, north-northwest swells reach Kauai, with waves up to and exceeding 25 to 35 feet in height,” said Kauai geologist Chuck Blay.

Those wave systems move sand along the Napali Coast and around the Mana Coastal Plain from Polihale Beach to the beaches along the Pacific Missile Range Facility. Sand gets deposited at beaches all the way to Oomano Point (Davidson’s) in Kekaha.

“The beach at Majors Bay narrows by as much as 500 to 600 feet through the winter months of November to February,” Blay said. “The beach at MacArthur widens by 300-450 feet through the winter.”

Following the north-northwest winter swells, the sand is pushed back west and northwestward through the summer, from Kekaha to PMRF, he explained.

“These are some of the planet’s most dynamic beaches,” Blay said. “It’s a bit more complex than that, but these are the major changes that we observe through the winter season.”


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