‘King tides’ set to continue rise as weekend approaches
Large summer south swell is expected to build today and hold through Memorial Day
With reports of the ocean washing over Honoapiilani Highway in Ukumehame on Wednesday and Thursday, the National Weather Service is warning of possible coastal flooding in Maui County due to record-level spring “king tides.”
Weather and state officials advised residents in low-lying areas and boaters to take precautions.
A large summer south swell is expected to build today and continue through the Memorial Day weekend before steadily easing next week, the weather service said Thursday.
Impacts could include beach flooding and standing water on roadways and in low-lying coastal areas, the weather service said.
The king tides are being generated by the arrival of a large south swell of 6 to 10 feet converging with high tides, the weather service said. Higher than normal sea-level around the islands is another factor.
The combination of these conditions will result in higher than normal beach run-up, flooding and erosion, weather and state officials said.
Peak ocean heights are expected at 5:02 p.m. today and 5:49 p.m. Saturday in Lahaina and 5:36 p.m. today and 6:23 p.m. Saturday in Kihei. Other high tide periods over the weekend are Sunday, 6:38 p.m. in Lahaina and 7:12 p.m. in Kihei, and Monday, 7:31 p.m. in Lahaina and 8:05 p.m. in Kihei.
All beaches affected by waves and erosion in the past are “especially vulnerable” said Tara Owens, coastal processes and hazards specialist for the University of Hawaii Sea Grant College Program. These include Kahana and Honokowai/North Kaanapali beaches in West Maui, the beach along Halama Street in Kihei and Wailea and Makena beaches, she said.
A high-surf advisory has been posted for south-facing shores of Maui County from 6 a.m. today to 6 a.m. Sunday. The weather service expects surf to build to 6 to 10 feet by this afternoon and to continue through Saturday. It is expected to diminish to 5 to 8 feet Saturday night.
The weather service is warning of strong breaking waves and rip currents.
County and state officials reported no problems related to the king tides Thursday afternoon, though motorists reported the ocean washing over Honoapiilani Highway in the Ukumehame seawall area.
Department of Transportation spokesman Tim Sakahara said Thursday afternoon that state crews were preparing for the king tides as they would for possible heavy rains. This means checking and clearing storm drains, which could back up during high tide events, and coordinating with county departments.
Another convergence of high surf, tides and sea level is expected in July.
Owens, who is a liaison to the county Planning Department, said that there have been higher sea levels around the islands since April 2016. UH scientists believe this is related to the large El Nino event in 2015 that brought large waves that washed over highways and eroded West Maui shorelines.
El Nino events usually create a temporary sea-level rise around the Hawaiian Islands but “for some reason, we’re still experiencing those elevated sea levels as an impact of that event,” Owens said.
Hawaii Sea Grant is asking residents to help document high water levels and related impacts by submitting photos online at hawaiisealevel.org.
The state Department of Land and Natural Resources has urged landowners in low-lying shoreline areas and near waterways to consider sandbagging to protect properties, and moving electronics, vehicles and other valuables from basements and yards to higher ground.
DLNR’s Division of Boating and Ocean Recreation warned of possible increased currents around harbors this weekend, particularly on south and west shores. Boaters are encouraged to monitor their vessels to ensure mooring lines don’t get too tight and to beware of overwash around boat ramps at high tides. Canoe clubs have been advised to secure or move canoes on the beach.
DLNR boating officials are not anticipating any impacts from the king tides to state boating facilities because the tides are not expected to wash over piers.
Kim Peyton, an estuaries and coastal habitat research scientist in the Division of Aquatic Resources, explained that high tides hold back stream flow and at low tides, the wall of ocean water recedes and streams flood out to sea.
King tides create a bigger wall of ocean water, meaning these tides hold back more water in streams and can cause streams to flood their banks, even without rain. Shoreline fishponds could be damaged, as well, Peyton said
“Local current patterns in streams and bays may change temporarily as the sharp shoulders of the king tides raise and lower water levels,” Peyton said.
The higher tides also could have an impact on shoreline ecosystems, Peyton said. King tides flooding could toss juvenile fish onto roads, parking lots and other land surfaces to die, and the deafening underwater noise caused by waves smashing up against these hard surfaces can degrade habitat quality for the juvenile fish.
King tides are coming a little early to affect turtle nesting along Maui shorelines, said marine biologist Skippy Hau of the Maui Division of Aquatic Resources. Nesting season begins in June.
However, the king tides later in the summer could threaten young turtles as they emerge from their nests.
“Timing is critical,” Hau said.
* Lee Imada can be reached at firstname.lastname@example.org.