High surf washing over Kamehameha Highway near Kaaawa Valley Road has washed out and closed one lane of the highway, police said.
The closure comes as the National Weather Service extended a high surf warning for north and west shores of Kauai County, Oahu and Molokai and north shores of Maui until 6 a.m. Friday.
Police issued the closure notice at about 4:39 p.m.
Police said one lane is open and traffic is being contra-flowed around the area.
The state Department of Transportation tweeted that crews were assessing the damage to the shoulder of the road from the surf at about 4:30 p.m.
Police called the city Emergency Management Department to ask for volunteers to help direct traffic around the damaged shoulder at about 5 p.m., said John Cummings, a spokesman for the department.
Forecasters expect surf of 20 to 30 feet on north shores and 15 to 20 feet on west shores to gradually lower to advisory levels overnight.
Weather service forecasters said a northwest swell can sometimes wrap around and hit Kaaawa, which is on the northeastern side of the island.
High surf could be seen coming over the road in the area Wednesday afternoon.
The surf was also coming over Kamehameha Highway near the Rock Piles surf spot near Sunset Beach on the North Shore. The Ocean Safety and Lifeguard services agency posted video of the waves on their Facebook page. But Cummings said the Emergency Management Department did not receive reports of surf over the road there today.
The Department of Transportation completed emergency repairs last year to a section of Kamehameha Highway in Kaaawa between Trout Farm Road and Keo Place because of damage to the road beacuse of wave erosion. The repaired road is north of the area that washed out today.