Scenes of utter devastation emerged from flood-ravaged areas of West Virginia yesterday where swollen rivers have left valleys stripped bare of soil and vegatation, ripped homes off their foundations, killed tens of thousands of animals, destroyed businesses and perhaps shattered local economies for years to come, officials said.

Many towns remained without sewage or water treatment facilities, and drinking water for some state residents was being trucked in from 70 or more miles away.

The National Guard was flying grain and other livestock feed by helicopter to some counties, where more than 100,000 turkeys and chickens have already drowned or starved and were being removed with bulldozers because of the threat of disease.

State officials placed the death toll in West Virginia at 23. Local officials expected the number to climb, with at least 35 persons still missing.

Estimates of the damage were still being tallied by state and federal officials yesterday, but it could run to half a billion dollars or more. President Reagan has declared eight West Virginia counties disaster areas eligible for federal assistance.

State officials are seeking federal aid for 14 others.

In Virginia, the death toll from flooding remained at 18, and officials estimated $551 million in damage for the Roanoke-Lynchburg area alone.

Reagan yesterday declared 10 localities in that region of the state eligible for federal assistance, including Roanoke, Franklin, Alleghany, Rockbridge and Botetourt counties.

Estimates were still being compiled for the Shenandoah River valley, also hard hit by the floods, and for Richmond, where an 80-square-block area of the city was inundated by the swollen James River.

The president designated six counties in Pennsylvania as disaster areas. One person was killed in flooding there.

In the stricken areas of West Virginia, county officials were beginning the task of making long-range plans for thousands of persons whose industries and agricultural lands were devastated.

"We're looking at 700 families homeless, 39 business destroyed and 20 percent of the cropland destroyed and not restorable except as pasture," said Jim Underwood, planner for Pendleton County in the state's eastern panhandle.

"This is a major economic disaster for the county," Underwood said. "We're going to have to reorient the economic basis for the county."

Larry Kuykendall, the mayor of Moorefield on the South Branch of the Potomac, said he expects it will be three years at least before things return to normal there, where streets in the town of 2,400 continued to be littered with parts of houses and other debris.

"I'm afraid the damage to the entire county Hardy will run into the millions of dollars," Kuykendall said. "There's trailers still out in the streets covered with mud. In some streets, there are big holes with cars buried in them. One giant sinkhole opened up and a small apartment building went down. The second floor's now on the ground level.

"We have about 108 to 119 businesses with damage. We lost one whole end of the local motel. The river just picked it up and moved it around. The high school and the elementary school were both damaged. All the books are ruined, and they're down there now with backhoes moving it out."

Kuykendall said the floods destroyed most of a new $1 million municipal sewage treatment plant. Townspeople yesterday were waiting for results of tests on the local water to come back from the state capital at Charleston, and drinking water was being trucked in by tanker from Winchester, Va., 72 miles away.

In the town of Romney, which sits above the Potomac's South Branch, the water and sewage plants were submerged when the flood hit.

In nearby Green Spring, "The water simply backed up and covered the whole town," said Stephen Haines, president of the Hampshire County Commission.

"It took out virtually all of the tracks of the South Branch Valley Railroad," Haines said. "In an instant, there was like a wall of water . . . . We have some farms up here where there's virtually no topsoil at all. It's just bare rock. It stripped it all the way down."

The Red Cross yesterday was sending cleanup supplies into West Virginia from as far away as Oregon.

The relief agency ran out of trucks to transport the materials and was using a bus donated by General Electric in Pittsfield, Mass.

Officials directing the massive cleanup effort, unprecedented in West Virginia history, yesterday reflected on a disaster that struck with a fury apparently none had anticipated, even as the rivers began to rise Monday after more than a week of rain there.

Some towns were hit without warning. But even in others downstream, lives were lost because residents refused to believe the early flood predictions.

"The biggest problem I had Monday was getting people to take it seriously," said Moorefield Mayor Kuykendall. "People did not want to leave their homes. I called the local radio station and went over there to make a tape to warn people. I literally had to run in and run out because the road was already being covered with water.

"Some who are still missing were last seen on a roof of a building that went floating down the river."

Pendleton planner Underwood said, "There were people that refused to be evacuated . . . . They just couldn't believe it could get as bad as it did. Nobody could imagine the magnitude of what was going to happen."

Underwood, who also is a rescue worker there, said he and a team of specialists went out at midnight Monday to try to extricate a couple from a trailer park near Franklin.

"When we got there, the trailer park was gone," he said. "I was watching trailers go by. Propane tanks were floating by and hissing and sputtering. The whole valley was full of water, and now the valley is scorched. There's nothing out there but trash."

For Underwood and others, well-laid disaster plans became meaningless when the flood hit.

Those who were supposed to im- plement the plans were trapped by the rising waters. Then basic equipment began to give out, and whole areas suddenly were isolated from the outside world as power and telephone lines snapped.

Underwood and other disaster workers in Franklin resorted to a local ham radio operator who relayed vital information to state officials in Charleston as the flood developed.

"Our emergency service radios went out because we had no electricity to recharge the batteries," Underwood said.

Hundreds remained homeless yesterday, and the National Guard and local groups were serving thousands of meals. But many of the homeless shunned the public shelters and apparently were staying with relatives and friends.

"The economic impact on this community is just going to be tremendous, said Kuykendall.

"I don't know how many of them will rebuild. I hope they do."