Oahu residents in towns north of Honolulu faced evacuation orders Friday as flash flooding from severe rains inundated streets, damaged homes and prompted rescue operations, including for people stranded on the North Shore and at a youth retreat. The alerts were driven in part by warnings that the 120-year-old Wahiawa dam could be at risk of imminent failure, with officials telling people to leave areas downstream of the structure.
Officials said emergency sirens were heard along Oahu’s North Shore, where muddy floodwaters swallowed vehicles and swept into neighborhoods known for surfing. Honolulu officials told residents Friday morning to leave the area downstream of Wahiawa dam, which they described as vulnerable, citing the possibility of imminent dam failure.
Gov. Josh Green said more than 230 people were rescued as heavy rains pummeled Oahu and triggered the worst flooding the island has seen in 20 years. Green said no deaths were reported and that no one was unaccounted for, and he said about 10 people were taken to a hospital with hypothermia after being exposed to cold flood conditions. “There’s no question that the damage done thus far has been catastrophic,” Honolulu Mayor Rick Blangiardi said in the afternoon, as officials worked to assess the extent of destruction.
Blangiardi said officials had not yet been able to fully assess how many homes were damaged, adding that dozens—if not hundreds—had been affected. He said officials felt confident in the stability of the dams across the island but that it was hard to predict how much rain would come and what it might do, even as authorities continued to monitor the situation closely.
Rescue crews searched by air and by water for people who had been stranded, but the effort was complicated, Green said, by people flying personal drones to capture images of the flooding. In a statement about the emergency, Green also described the day as “very touch-and-go,” as more rain was expected through the weekend, following a storm last week that had dumped heavy rain across the state and led to catastrophic flooding.
The state’s monitoring focused on the dam’s changing water levels. Officials said water at the Wahiawa dam went from 79 feet to 84 feet in less than 24 hours, leaving it about six feet shy of what it can handle. They said water levels were receding at the time authorities made the warning, but that the levels could rise again if additional rain fell, affecting whether the dam could safely hold incoming water.
Evacuation orders extended beyond people living downstream of the dam. Honolulu said more than 5,500 people were under evacuation orders, including residents in shelters affected by flooding. One shelter at Waialua High and Intermediate School was evacuated because of rising water, a Honolulu spokesperson said, adding that officials needed to bus residents and their pets to another evacuation center—though by midday, 54 people still remained in the shelter.
The flooding also disrupted a youth program, officials said, with the National Guard and the Honolulu Fire Department airlifting 72 children and adults from a retreat on Oahu’s west coast. City and camp officials said the group had been attending a spring break youth camp at Our Lady of Kea’au. Camp officials said the camp’s entrance road was cut off by floodwaters, and the mayor said authorities did not want to leave the group at the retreat even though it was on high ground.
Officials said heavy rainfall contributed to the hazard, with Honolulu and national weather data indicating that parts of Oahu had received 8 to 12 inches (20 to 30 cm) of rain overnight and that the island’s highest peak, Kaala, received nearly 16 inches (40 cm) in the past day. State and federal forecasts pointed to the influence of winter storm systems known as “Kona lows,” which bring moisture-laden air to Hawaii, and some experts said the intensity and frequency of heavy rains in Hawaii have increased as global warming has progressed.
The risk around the Wahiawa dam has been an ongoing concern for years, according to the reporting. The earthen dam was built in 1906 to boost sugar production for the Waialua Agricultural Company, which later became part of Dole Food Company, and it was reconstructed after a collapse in 1921. The state said it had sent Dole four notices of deficiency since 2009, and five years ago it fined Dole $20,000 for failing to address safety deficiencies on time, while later efforts included a proposed donation of the dam and related systems to the state in exchange for repairs to bring the spillway up to safety standards.
Dole disputed the idea that the dam was damaged, stating in an emailed response that it “continues to operate as designed with no indications of damage.” Meanwhile, state officials said the dam has “high hazard potential,” and that a failure would “result in probable loss of human life,” while the state prepared next steps for acquisition of the dam’s spillway and related infrastructure as the flooding unfolded.