HAU'ULA — The first major storm of the rainy season spared most residents but an unresolved problem from a flood last year has a Hau'ula home hanging over a washed out embankment and tilting toward disaster.

Rumbling in Kaipapa'u Stream in Hau'ula woke Shon Ka'ana'ana at 3:30 a.m. yesterday as a flash flood rushed from the Ko'olau Range to the ocean. He heard the sound of boulders and rocks and knew instinctively what he had to do: get out.

In the course of two hours, the stream water undercut 40 to 50 feet from the embankment next to his home, leaving part of its concrete slab foundation hanging over the stream.

"If it rains tonight, guarantee going fall," Ka'ana'ana said.

The National Weather Service posted a flash flood watch for all islands west of the Big Island.

State Civil Defense said there were no reports of weather-related damage. The city Department of Emergency Management said that other than high streams in Waikäne and Punalu'u, the Ka'ana'ana embankment problem was the only serious situation reported.

The department is researching the problem to determine who is responsible for the stream, said Melvin Kaku, department director.

Today's forecast calls for a likelihood of thunderstorms and showers in the windward and mountain areas, according to the National Weather Service Honolulu office.

While some sections of O'ahu received no rain yesterday, parts of the Windward side were drenched. A government rain gauge in Waikäne Valley recorded 5 inches of rain from 5 p.m. Thursday to 5 a.m. yesterday.

It was enough rain to cause flooding in Hau'ula, on Pokiwai Street and Pokiwai Place, said Terri Maneha, a Pokiwai Place resident. A 25-foot-wide drainage canal overflowed, causing water to flood her property and rise more than a foot above the bottom of her washing machine and water heater.

"We're not as bad as Dec. 11 last year (when the water was waist high) but bad enough to be irritating and cause damage to homes in this area that are built flat on the ground," Maneha said.

By 6 a.m. yesterday, the water had peaked and only began to recede when other neighbors opened a channel to the ocean under a bridge on Kamehameha Highway that was packed with sand, she said.

Pokiwai Street resident Robin Nelson said someone has diverted water into the drainage canal, contributing to its flooding. Nelson said government officials have promised to fix the problem.

Dangerous surf yesterday prompted the city to close Makapu'u Beach to swimmers and surfers.

Bryan Cheplic of the city Emergency Services Department said waves were 8 to 12 feet and arriving at an unusual northeast angle — the result of a wraparound effect driven by a large north-northwest swell — and that strong trade winds were creating choppy, stormy conditions.