NORTH SHORE, OAHU (HawaiiNewsNow) - Monday's swell, which brought wave faces up to 70 feet, was one of the strongest surf events in Hawaii in 50 years, according to the National Oceanic and Atmospheric Administration.
NOAA officials said the swell's size can be linked in part on a strong El Niño.
Meanwhile, North Shore residents are bracing for another round of massive surf and storm surge forecast to come in Thursday.
A High Surf Warning remains in effect for the north and west shores of Niihau, Kauai, Oahu and Molokai, and the north shores of Maui and the Big Island through 6 a.m. Friday. A High Surf Advisory is in effect for west shores of Maui and the Big Island and for east shores of Oahu.
Forecasters say Oahu's North Shore should expect 20- to 25-foot surf Wednesday and Thursday.
Adam Lerner, an Ocean Safety Lieutenant stationed at Chun's Reef in Haleiwa, said Monday's swell was "huge."
"I tell everybody it was extra, extra large," he said.
Lerner says Monday's swell was one of the biggest he's ever seen. The monster waves caused serious erosion at Chun's, where officials about 30 feet of beach was lost in a night. Lifeguards were able to push their tower back before it fell into the ocean.
As the surf subsided Tuesday, beachfront homeowners spend the day assessing property damage and trying to protect what they could before the next swell rolls in.
"I've surfed Waimea for many years and we're expecting the largest swell that I've ever seen forecast here in Hawai'i, so it's exciting and yet a little bit nerve-wracking," said Brian Bowman, whose Waimea Bay front yard was washed out by monster waves several times Monday.
A home on Kamehameha Highway many feared would wash away after its sea wall collapsed was sagging on Tuesday, but still standing. Structural engineers were on site to assess their options, but much of the front yard was pulled away in the large surf.
State officials say there are steps homeowners can take to protect their beachfront properties.
"If you have a sea wall and your sea wall has failed, you can contact us, or contact a respective county permitting authority to determine if an emergency permit is available to repair the sea wall," said Sam Lemmo, the administrator for the Department of Land and Natural Resources Office of Conservation and Coastal Lands.
"If you're gonna use sand bags, I'd say feel free to use them to protect their home from flooding but try not to put the small sand bags out on the beach because they'll only get washed away and they'll end up out on the reef, they'll be little protection from small sand bags," Lemmo said.
Big wave surf events are nothing new for the North Shore, but the one-two punch of back-to-back massive swells are putting some residents on edge and have highlighted some of the area's aging infrastructure.
Blake McElheny, a North Shore resident, said there are have been studies of the North Shore coastline to determine what's needed to deal with worsening erosion and rising seas.
"I think one of the things we're hoping is that the North Shore, as a resource for all of Oahu as well as millions of visitors a year, will get the attention it deserves in terms of planning and infrastructure investment so that we can continue to host people from around the world and around the island, but also keep our families safe," he said.
State officials say anyone whose property has suffered from erosion or flooding damage should call a licensed coastal engineer with experience in shoreline management and erosion control or contact DLNR directly at 587-0377.