One Love Church volunteer Beau O'Brien of Honolulu hugs Sharmaine Arial after helping move heavy, water damaged appliances and furniture out of her Kukea Loop home Sunday in Waialua, Hawaii. (Kevin Fujii/Civil Beat via AP)

HONOLULU (AP) — The worst flooding to hit Hawaii in two decades swept homes off their foundations, floated cars out of driveways and left floors, walls and counters covered in thick, reddish volcanic mud.

Crews continued to assess the destruction Monday, but authorities said hundreds of homes had been damaged, along with some schools and a hospital.

No deaths have been reported, but more than 230 people had to be rescued. Rain continued to the southeastern part of the state and a section of the Big Island was under a flash flood warning.Gov. Josh Green said the cost of the storm could top $1 billion, including damage to airports, schools, roads, homes and a Maui hospital in Kula. He called it the state’s most serious since flooding since 2004, when floods in Manoa inundated homes and a University of Hawaii library.

On Oahu’s North Shore, famed for big wave surfing, the waters rose quickly after midnight Friday as heavy rains fell on soil already saturated by downpours from a winter storm a week earlier. Raging waters lifted homes and cars. The storm prompted evaluation orders for 5,500 people north of Honolulu — though they were later lifted — and more than 230 people were rescued from the rising waters.

Some residents fled on surfboards as water reached waist or chest high.

Farms around the state reported more than $9.4 million worth of damage as of Monday, according to a survey conducted by Agriculture Stewardship Hawaii, the Hawaii Farm Bureau and other organizations. Oahu farmers reported more than $2.7 million in crop damage.

Officials blamed some of the devastation on the sheer amount of rain that fell in a short amount of time.

Parts of Oahu received 8 to 12 inches, the National Weather Service said. That was on top of another recent storm that had dumped vast amounts days earlier. Kaala, the island’s highest peak, got nearly 16 inches late last week, on top of 26.6 inches between March 10 and 16.

Winter storm systems known as “Kona lows,” which feature southerly or southwesterly winds that bring in moisture-laden air, have been responsible for the deluges in the past two weeks. The intensity and frequency of heavy rains in Hawaii have increased amid human-caused global warming, experts say.

The worst of the storms appeared to be over by Sunday afternoon.

As the waters rose Friday, officials warned that the 120-year-old Wahiawa dam, north of Honolulu, was “at risk of imminent failure.” The dam has long been vulnerable, but worries eased as the water subsided.

The earthen structure was built in 1906 to increase sugar production for the Waialua Agricultural Co., which eventually became a subsidiary of Dole Food Co. It was reconstructed following a collapse in 1921.