Catastrophic flooding keeps hitting Hawaii astwo back-to-back storms pummeled the islandswith rain and damaging winds.
Authorities say it's the worst flooding the state has seen in 20 years, as torrents of water wash out homes, damage roads and threaten to bust through a dam.
The threat of the dam failure in northern Oahu prompted an emergency evacuation of thousands on the morning of March 20. TheHawaii Emergency Management Agencylater clarified that the 120-year-old dam had not failed but "is at imminent risk of failure."
Evacuations were ordered for Haleʻiwa and Waialua, where an alert warned that all roads out are at risk of "imminent failure."
"LEAVE NOW," the alert said.
Gov. Josh Green said there have been no deaths or people unaccounted for during the flooding, but called it the worst the state has seen since the early 2000s. Some 200 people have been rescued from the flooding and about 10 presented at hospitals with hypothermia, he said.
"This is a major threat to our people and to our state," Green said at a news conference March 20.
The morning of March 21, the National Weather Service in Honolulu said two systems are continuing to drive rain (sometimes as heavy as 2 to 4 inches per hour), thunderstorms and an increased risk of flash flooding through the weekend. A flood watch was in place for the whole state through the afternoon of March 22.
The dam is in Central Oahu near the Schofield Barracks, off the Kamehameha Highway. Assembly areas had been established for people required to evacuate or who were unable to get home. Oahu (Honolulu County) has 13 dams, according toUSA TODAY's dam-tracking database. Of those, seven have a "high" or "significant" hazard potential classification. The Wahiawa dam is private, built in 1906 and used primarily for irrigation. It's considered in poor condition, with a high hazard potential.
Water in the Kaukonahua Stream near Wailua just northwest of the reservoir rose more than 10.5 feet on March 20, several inches higher than it had reached on March 13, according to weather service data.
On March 20, the weather service reported that a foot of water was flowing over a road one mile east of Waialua, inundating several cars and homes. "Civilians had to be rescued and transported on a bulldozer," the bulletin stated.
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Kona storms – Hawaii's winter cyclones
A series of low pressure systems have struck Hawaii in March. They're a winter phenomenon, often called kona lows or kona storms, for the Hawaiian word "kona" for leeward. The winter storms typically impact the leeward side of the islands that are usually sheltered from tradewinds and intense rains, according to Steven Businger, a professor in the meteorology department at the University of Hawaii.
On average, one to two kona storms impact Hawaii during the November-to-March season, but it's very rare for two to form within the same month, let alone within a week, AccuWeather meteorologists said.
The first round of stormsimpacted the islands from March 10 to March 16, the outlet reported. It brought local rainfall totals of over 4 feet.
Worst flooding in 20 years
The flooding in Hawaii is the worst the state has seen since the 2004 Manoa Flood, Green said. A flood on Oct. 30, 2004, was one of several flash floods amid a storm that brought heavy rain. Rain peaked at a rate of 1.29 inches in a 15-minute span and 8.71 inches in 6 hours.
Manoa Stream overflowed in several areas. The worst flooding happened when a flood wave tore through a residential area and onto the University of Hawaii at Manoa campus. Floodwaters destroyed irreplaceable documents in the basement of Hamilton Library and caused damage to several laboratories with critical experiments, according to the National Weather Service.
No deaths or injuries were reported, but damage reached about $85 million at the time. About 120 homes were damaged, and a foot bridge over Manoa Stream was destroyed.
Damage from the March 2026 flooding could total $1 billion, Green said. That includes damage to numerous homes, roads, schools, airports and a hospital on Maui, he said.
One home on Kaihulo Drive in Mokuleia near Waialua was swept onto the beach in a flash flood on the morning of March 20.
"Remnants of the house appear to be split in half, and parts of the house appear to have collapsed," according to a storm report from the weather service.
A road in Makaha Valley on Oahu was closed in both directions March 20 after part of it collapsed, sending vehicles over the edge, another storm report said.
This article originally appeared on USA TODAY:Catastrophic flooding in Hawaii as Oahu faces evacuations, dam fears