Nearly 14 inches of rain Monday led to the overtopping of the Kaupakalua Reservoir and Dam, forcing the evacuation of some 150 downstream homes.

In addition, the Maui Fire Department responded to more than a dozen calls for help from residents trapped by rising waters, officials said, and at least a half-dozen homes appeared to be damaged or destroyed.

Hana Highway, which was inundated with muddy water, was closed much of the day from Peahi Road to Keanae. It was reopened by 7 p.m., but Kaupakalua Road remained closed and impassible in some areas.

Maui Mayor Michael Victo­rino surveyed the flooding in Haiku on Monday evening and reported that a half-dozen homes were heavily damaged or destroyed.

Earlier in the day, Victo­rino urged residents in low- lying areas to evacuate and advised others to stay home and shelter in place. He also warned motorists to turn around if they came upon high water.

“Ladies and gentlemen, this is a real flooding situation we have not seen in a long time. In fact, some of the residents have told me that this is the worst they’ve seen in over 25 years,” he said in a livestream on Facebook.

Evacuation shelters were opened at the Paia Community Center, Hana High School and the Eddie Tam Center in Makawao.

Will Ahue, National Wea­ther Service meteorologist, said a rain gauge in the Haiku area recorded 13.81 inches of rain between 7 a.m. and 3 p.m.

“That’s a lot of water in a short period of time,” Ahue said.

More storms could be on the way, he said, as a flash flood watch was scheduled to run though tonight.

It was at 1:30 p.m. Monday that the state was notified the dam’s spillway was running high with water. The state Department of Land and Natural Resources said the notification initiated a Level 2 emergency, and by 2:50 p.m. the dam was starting to overtop the embankment.

“Today we notified state and county officials that due to the unprecedented rainfall, the Kaupakalua Reservoir and Dam, owned by East Maui Irrigation, reached peak levels causing the overtopping of the dam,” said Shan Tsutsui, chief operating officer of Mahi Pono, which owns the reservoir jointly with Alexander &Baldwin.

Former Lt. Gov. Tsutsui said the dam did not fail, despite reports to the contrary. The water poured over the dam.

An earthen structure built in 1885, Kaupakalua Dam is one of the oldest on Maui, measuring 57 feet high and 400 feet long and capable of holding 68 million gallons of water.

By 3 p.m. officials had closed Makawao Avenue at the Piiholo Road intersection, Makawao Avenue close to the Kokomo Road intersection, Brewer Road, Kee Road, Kaupakalua Road just past West Kuiaha Road, and Makani Road at Old Hale­akala Highway.

All county parks were also closed.

Gordon Gillis of the American Red Cross on Maui said 18 people were at the Hana shelter, and there were six cars and their occupants at the Paia Community Center. But the shelter population could change, he said, depending on whether the county was going to let people go back into their homes. That was uncertain at 7 p.m. Monday.

“We’re grateful for the community members who have brought water and food,” Gillis said. “It’s really awesome support from the community.”

Maui Beach Hotel in Kahului offered a rate of $139 per night for anyone temporarily displaced by flooding Monday, the mayor announced at about 8 p.m.

Earlier in the day, thunderstorms battered the Valley Isle, with heavy rain beginning in Upcountry Maui at midmorning, leading to flooded roads in the Olinda- Makawao area.

In Kaupakalua, Liam Ball decided to take a drive to Makawao at 3:30 p.m., but he could get only as far as Hanzawa’s Variety Store. He headed back to his Awalau Street home, with muddy water flowing all over the road.

Ball, a real estate broker, said he was going to try again 15 minutes later, but his neighbor warned him not to go.

“He said the water was 4 feet deep — as high as the doors on his huge monster truck,” Ball said. “It was really scary.”