A forecast calling for more rain today has emergency workers and residents of O'ahu bracing for worst-case scenarios.

"With a combination of last week's rains and (yesterday's rain), we could end up with a sizable disaster situation," said John Cummings, plans and operations officer for the O'ahu Civil Defense Agency. "It might not be a lot of major damage, but if it is spread out over the entire island, it could be significant."

The city's emergency operations center, located in the basement of the city Municipal Building, was up and running again yesterday and into the night. Cummings said disaster assessment from the previous rains, which prompted Gov. Linda Lingle to sign a disaster declaration, is still being conducted.

Evening rainfall was light across the state as of 10:30 last night, but isolated thunderstorms remained a possibility, the National Weather Service said.

A flash flood watch was issued for all islands until 6 p.m. today, with rain expected to continue through the weekend, possibly tapering off tomorrow afternoon or late tomorrow night.

Part of the problem facing the island is that it is still heavily saturated in several areas, particularly on the Windward Coast, where 111 homes were damaged, crops were destroyed and sewage overflowed into the streams and beach water last week.

Residents barely had time to bail out their houses before having to dig trenches, fill sandbags and move valuables to higher surfaces yesterday.

Sixteen people were staying at a Red Cross emergency shelter at the old gym on the Brigham Young University-Hawai'i campus last night, Cummings said.

At Otake Camp in Waialua, police and Civil Defense volunteers told residents to be prepared to evacuate today because the Lake Wilson dam topped its flood threshold. Cummings said the water level was going down last night.

Anthony Nery, an Otake Camp resident, said he was ready to evacuate if necessary.

"I'll just load the dogs up in my truck," said Nery, 31, as he checked on his pregnant hunting dog, Nala. "I can just leave them in the truck until the water goes back down."

Nery and his family already had several puddles of water in their yard from yesterday's early-morning rains. Some of the water came close to covering his dog kennels.

To prepare for the worst, the Nerys moved valuables and furniture from the bottom floor of the house to the second floor.

Bill Balfour, head of the O'ahu Civil Defense Agency, was surveying Otake Camp in the rain yesterday. "It was like a river out there," he said.

If the lake overflowed the dam, it could flood the camp, Balfour said. "The way the lake was rising, there was a concern," he said. "We worry about Otake Camp."

Clifford Hirayasu, deputy coordinator with O'ahu Civil Defense, was monitoring water levels at several streams that feed into Lake Wilson.

Hirayasu also responded to some reports of flooding and possible blockage at drainage ditches and under bridges.

The only severe flooding was found at a home on Hale'iwa Beach Road near the Hale'iwa Fire Station, he said.

In Central O'ahu, authorities were monitoring Waiawa Stream, near the Kamehameha Highway/Farrington Highway and H-1/H-2 junction.

Honolulu firefighters responded to three weather-related calls yesterday. Two were water evacuations and one was a call from two women who could not cross the Jackass Ginger trail over Nu'uanu Stream. The women were escorted out of the area about noon yesterday.

"I don't know what they were doing up there on a day like today," said Honolulu fire Capt. Kenison Tejada.

The state Department of Health advised residents to stay out of streams, brown murky coastal water, and standing waters that are contaminated by storm water. Warning signs also remain posted at affected beaches and streams.

Also yesterday, the state Department of Land and Natural Resources closed two state parks, Kahana Valley State Park and Malaekahana State Recreation Area.

The Neighbor Islands also got their share of rain.

The heaviest rainfall on the Big Island was in Glenwood, where slightly more than 10 inches fell in the 24 hours ending at 2 p.m. yesterday. However, Civil Defense officials had no reports of flood damage.

The 35 students attending the tiny private Mauna Loa School in Hilo were sent home after a leaking roof in one of the school's two classrooms prompted principal Allen Lipps to cancel classes.

Swollen streams caused road closures on the Big Island, the most significant being the Hawai'i Belt Road at Kawa Flats in Ka'u, between Punalu'u and Na'alehu.

Police restricted traffic to one lane for much of yesterday, and closed the road entirely from 10:20 a.m. to about 1:25 p.m. because of flooding, said Lanny Nakano, assistant administrator for civil defense.

Ka'u High and Pahala Elementary schools both released their students early at about 1:15 p.m. to make sure they could get home while the highway was open.

The National Weather Service reported nearly 7 inches of rain at Kapapala Ranch in normally dry Ka'u.

Nakano said emergency shelters were opened at the Pahala Community Center and Na'alehu Community Center, but planned to close the shelters later in the day because no one was using them.

Also closed yesterday were Kamehameha Avenue in downtown Hilo and Pohaku Drive in Hawaiian Paradise Park in Puna.

The rain gauge at Waiakea Uka above Hilo recorded 8.65 inches in the 24 hours ending at 5 p.m. yesterday. Hilo airport got 4.2 inches.

Rain also fell on Kaua'i and Ni'ihau for most of yesterday. The only report of significant flooding resulted in the closing in mid-afternoon of Kuhio Highway at the Hanalei Bridge.

Reach Peter Boylan at pboylan@honoluluadvertiser.com, Loren Moreno at lmoreno@honoluluadvertiser.com and Kevin Dayton at kdayton@honoluluadvertiser.com.