Emergency officials in Hawaii ordered people near a dam in the northern part of Oahu to evacuate on Friday and warned that it was in danger of failing after heavy rain overnight pushed the reservoir to critically high levels.
Water in the Wahiawa Reservoir was just a few feet below the top of the dam early Friday morning, according to Gov. Josh Green of Hawaii. The dam had not failed but was at “imminent risk of failure,” the Oahu Department of Emergency Management said shortly after 9 a.m. local time.
Floodwaters have already cut off road access in the area, according to the emergency management officials and the National Weather Service, which warned that “widespread flooding of roadways and low-lying areas is ongoing.”
Emergency officials urged people in Waialua and Haleiwa to evacuate to higher ground if possible, calling the rising waters “catastrophic.”
Preliminary data from a flood sensor operated by the United States Geological Survey showed that at 8 a.m. local time, water levels in the Wahiawa Reservoir reached 85.10 feet, surpassing the previous record of 85 feet that was set in October 2005.
Mr. Green told a local a local television station that the top of the dam is 90 feet tall, and he called 88 feet “a very critical threshold.”
The governor also detailed harrowing rescue efforts for people stuck in floodwaters, including a group of 70 people who were surrounded by water at a campsite. It is currently spring break for public schools in Hawaii, the governor said, and there were many children in the group.
“I was told they are safe right now,” he said. “But they were having difficulty getting out because there was so much water around them.”
In a video posted to social media, he described flooding that had reached “up to chest level” in some areas.
The governor also said that the Coast Guard will conduct search-and-rescue operations if needed. “It’s going to be a very touch-and-go day,” Mr. Green said. He added that the National Guard has been deployed.
The flash flooding threat came as yet another system delivered heavy rain, only days after a multiday storm brought over two feet of rain to some locations across Hawaii.
While this latest storm is not expected to be as strong as the last one, the Weather Service warned that the soil in many places is already saturated and so it requires less rain to cause flooding. Streams were rising quickly on Friday as rain poured into them.
“Because the ground was so primed for this storm, we’re seeing things get bad pretty quickly,” said Stephen Parker, a meteorologist with the Weather Service office in Honolulu.
The storm arrived Thursday night and was expected to bring a chance of rain through at least Sunday.
Heavy showers and thunderstorms brought over a foot, even two feet, of rainfall to parts of northern Oahu in just the last day, the Weather Service said.
In total, the Waialua area, a residential area downstream from the Wahiawa Reservoir, has recorded about 20 inches of rain since last Friday, amid back-to-back storms. One location in the mountains nearby measured nearly 30 inches of rain, according to the Weather Service.
The recent storms are what forecasters call a Kona low. This type of seasonal storm is not uncommon during the rainy season in Hawaii, which runs from November through April, but it tends to bring more rain and move slower than typical storms. They can dump heavy rain for extended periods over the same location.
“Last night, north Oahu was in the bull’s-eye of the heavy rain,” Dennis Trotter, a meteorologist with the Weather Service, said on Friday.
Aimee Ortiz covers breaking news and other topics.
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