Beach erosion likely due to abnormally high tides

Unusually high tides may be largely responsible for recent episodes of severe erosion at Sunset Beach and Waikiki Beach, a coastal scientist said Wednesday.

Tides 3 to 6 inches higher than normal were recorded in Honolulu Harbor and at other National Oceanic and Atmospheric Administration gauges across the state over the past month, said Dolan Eversole, NOAA Sea Grant Coastal Storms Program coordinator.

"A couple of inches of water can make all the difference," said Eversole, a coastal geologist.

He said the abnormally high tides are probably the result of regional "mesoscale eddy" effects — massive warm-water bulges that pass through the Hawaiian Islands in duration of weeks to months.

A similar warm-water eddy was identified by a University of Hawaii study as a major factor in severe erosion that mysteriously plagued the Kaanapali Alii Resort in West Maui in 2003.

"It was pretty dramatic," Eversole recalled, adding that sandbags were brought in to protect the hotel. "But just like this time, there were no giant swell events that you could put your finger on that caused the sand to disappear."

Eversole said Sea Grant agents across Hawaii are reporting few other recent abnormal erosion problem areas, which indicates that while higher water levels may not be the sole cause, they can exacerbate an existing erosion hot spot.

"It’s not a trigger but a catalyst that can make a problem beach unravel fast," he said.

Meanwhile, city and state officials agreed Wednesday to move sand from in front of the Honolulu Police Department Waikiki Substation to build up the severely eroded stretch at Kuhio Beach.

City crews, working under the direction of state Department of Land and Natural Resources beach experts, will mobilize equipment this evening during low tide to remove debris and transfer at least enough sand to cover an exposed concrete foundation, officials said.

"It will be a temporary fix," said Jesse Broder Van Dyke, spokesman for Hono­lulu Mayor Kirk Caldwell. "The next swell could erode the sand. But right now it doesn’t look like it should for our tourists."

Kalakaua Avenue will be closed for 20 minutes between 11 a.m. and noon today while heavy equipment is moved next to the beach. Also, the makai lane of Kalakaua will be closed between 7:30 p.m. and 3:30 a.m. Friday.

A long-term solution is now under study, said DLNR spokeswoman Deborah Ward.

She noted that scientists also will be looking at the question of whether the removal of a couple of small groins during the 2012 Kuhio Beach sand replenishment project may have contributed to the recent erosion.

But that could take a few more seasons of data to figure out, Ward said.

At Sunset Beach, homeowners are talking with engineering firms about some kind of large-scale measure to slow the erosion threatening about 10 homes sitting dangerously close to a newly carved 20-foot beach cliff, officials said.