In an unprecedented move, the state closed an 11.5-mile stretch of Kamehameha Highway along Oahu’s North Shore on Monday in anticipation of dangerously high surf.

Local traffic and city buses were still able to pass through, but otherwise both lanes were closed from 2 to 6 p.m. from Haleiwa to Turtle Bay.

“We want to make sure that everyone gets in and out of the North Shore area safely, gets home at the end of the workday or gets out to go to their work in the coming hours,” said Mayor Kirk Caldwell, who held an afternoon press conference with state officials and his emergency services director, Mark Rigg.

The closure was the largest ever in the state for a roadway without damage, said state Highways Division Deputy Director Ed Sniffen.

“We’re restricting access to people who absolutely need to be there,” namely residents and people who work in the area, Sniffen said.

Caldwell said “huge wave heights and a lot of wave action” were being reported in conjunction with an afternoon high tide.

City officials were also concerned that a house near Alligator Rock and Waimea Bay had a retaining wall washed out and was exposed to the high surf. Hawaii News Now reported that the owner abandoned the home.

Ocean Safety Division reported water rushing over the roadway near Laniakea, Chun’s Reef and Rock Piles and people crossing past areas cordoned off with yellow tape.

The city closed the following North Shore beaches: Haleiwa Beach Park, Alii Beach Park, Sunset Beach Park and Waimea Bay. Also closed was Yokohama Bay on the Leeward Coast.

The city closed Makapuu Beach Park due to debris from a roughly 15- to 18-foot-long boat that broke off its mooring at about 2:15 p.m. in Waimanalo. The boat washed into the surf zone at Makapuu, where the wrap from the swell brought 10- to 15-foot surf, Rigg said.

The boat broke in half. The bow ended up on the beach, and debris from it covered the beach.

In Kaneohe Bay a catamaran overturned, breaking its mast at about 3 p.m., leaving a person hanging onto the boat and another swimming in the water. Fire personnel rescued the swimmer about 400 yards offshore and worked to bring the boat to shore.

On the North Shore two lifeguard towers, including one at Laniakea Beach, were threatened by the surf. A tower at Chun’s Reef, perched high atop a sand berm, had to be moved back because it was going to fall forward, said Emergency Services Department spokeswoman Shayne Enright.

Lifeguards gave out 950 warnings on North Shore beaches. On the Leeward Coast they made six rescues and issued 1,000 warnings. On the east side they made 115 rescues and issued 1,250 warnings, mostly at Sandy Beach but also at Makapuu and Kailua on the Windward Coast.

At Waimea Bay, lifeguards estimated surf was averaging 50 feet, but onshore wind created choppy conditions, Enright reported.

Rigg said a wave that washed up on a North Shore beach knocked a lifeguard off an all-terrain vehicle as he rode to warn beachgoers about the dangerous surf conditions.

Surf of 30 to 40 feet battered Makaha Beach, and crews cleared sand and debris from Farrington Highway in Makaha.

Waves washed across the roadway in Kaaawa, where a section of Kamehameha Highway had washed out Feb. 11 due to erosion from high surf. Sniffen said the repaired roadway was holding up.