If nuclear war is imminent and the president orders Washington evacuated, most of Alexandria's 100,000 residents are supposed to paste ID cards on their windshields, pack wills and credit cards, leave their pets, guns and booze behind and head for the hills.

About 40,000 of them are to pull onto four-lane Duke Street and head west. About 19,000 of them will begin a six-hour drive, much of it over narrow, mountain roads, to Webster Springs, W. Va., (population less than 1,000) where they are expected to stay for at least a week, even if no attack comes.

This scenario from Alexandria's recently published 154-page "crisis relocation" plan, one of hundreds of such plans being drafted nationwide, comes as a surprise to Webster Springs. "Did you say 19,000 people?" says Mayor R.J. Jorishie. "I haven't heard a word about it. I don't know how we'd handle it, frankly. We've only got two grocery stores here, no civil defense shelters. Did you say 19,000? The government would have to come in here and do a hell of a job for us to be able to handle 19,000."

He's not the only person finding it difficult to be civil about civil defense. Alexandria's plan, the prototype of plans for all major municipalities in the Washington area, has not found many fans among Alexandria officials.

"I think it's asinine," says Alexandria City Councilman James Moran. "It's like Alice in Wonderland."

"It's ridiculous and misleading to the citizens in the worst way," says Councilman Donald Casey. "In a nuclear war, anyone who lives in this area is going to die. To say or believe anything else is absolutely criminal."

"I'm very disturbed by it," says City Manager Douglas Harman, who is also the city's civil defense director. " . . . The danger is that anyone might actually believe this thing could work. I'm very upset about it."

Officials in at least 14 states, including Cambridge, Mass., and Boulder, Colo., have rejected the plans for their communities. In Alexandria, where the plan is set to be discussed by the City Council Tuesday night, Harman is telling city employes they should waste no time working on it.

Rep. Les Aspin (D-Wis.) has called the plans "extremely dangerous nonsense" that could help trigger the nuclear war it was designed to cope with. The plans, he said, are products of " . . . a bunch of Pentagon officials trying to make work for themselves."

And Massachusetts Institute of Technology physician Eric Chivian, who teaches a class on the effects of nuclear war at Harvard University, says the complications of moving entire city populations to areas are nothing compared to the problems of housing them in fallout shelters once they get there.

The author of Alexandria's plan, James Surratt, a nuclear civil protection planner in the state office of Emergency and Energy Services with a 1982 budget of $213,000, defends it. "The plan is based on a number of bland assumptions," he says. "That we'll have adequate warning time, that people will do their jobs, that people won't panic, that people will work resolutely to save themselves."

The Defense Department has been selling a $4.2 billion, seven-year civil defense package to Congress this spring, arguing that the evacuation of U.S. cities would save 70 to 80 percent of the American population in an all-out nuclear war. Civil defense officials concede that evacuation plans are sketchy, but that they are the first step in a plan to construct a network of stocked fallout shelters in rural areas and an army of trained shelter managers.

Yet, critics of Alexandria's plan cite numerous problems:

Gridlock: The plan anticipates the evacuation of at least 80,000 Alexandrians. More than half of them are supposed to leave town on usually clogged Duke Street (Rte. 236). With Maryland, the District and the rest of Northern Virginia also fleeing across the Potomac, the civil defense planners expect 5 million area residents to be evacuating on Virginia roads.

"What if 5 percent of the cars get out on the road and run out of gas?" asks Harman. "You'll have people racing out of town without bothering to look at their gas tanks. Who's going to man the gas pumps? Who has authority over city roads? Me or the Army or the state police?"

Panic: The estimated 17,000 Alexandrians who don't own autos are supposed to go to local schools, where they board buses that are supposed to shuttle them to the University of Virginia in Charlottesville. "If I was driving a bus down to Charlottesville in the middle of a nuclear emergency, I don't know that I'd come back," says Charles Rule, Alexandria's fire chief.

The Stay-Behinds: Local police, firemen and municipal workers are expected to stay behind, direct traffic, prevent looting, transport hospital patients and look after the 20,000 residents expected to refuse to evacuate or be unable to leave, such as the seriously ill. "I have serious doubts whether police, fire and municipal workers, guys worried about their families, will stay when it comes down to a question of being dry-roasted or flash-fried," says Rule.

Post-Attack Picture: "I'm unable to talk about post-attack," says George Urquhart, one of the authors of the plan. "These plans assume that no attack will take place. That's where our planning stops. We have nothing to do with rebuilding cities, or agriculture. Hopefully, that will be developed down the road."

Surratt describes the reaction to Alexandria's plan--"skepticism bordering on hostility"--as fairly typical of localities. But he defends nuclear evacuation planning as "better than doing nothing at all."

A spokesman at the regional office of the Federal Emergency Preparedness Agency in Philadelphia, which is coordinating evacuation planning for this area, says that while there may be problems with evacuation plans, the American people will pull together as they have always done in a crisis. "In any disaster people's better qualities come out," he says.

"We're all operating under certain assumptions," Surratt said. "Ours is that people will do their jobs, not panic, and work resolutely to save themselves. They critics assume that everyone will panic and that workers will bug out. Obviously, the truth is somewhere in between."

Chivian and other critics, however, say that even if evacuation goes smoothly, if a war were to occur and people were required to stay in crowded shelters for days, weeks or months, their chances of survival would still be slim. "The sanitation problems in shelters would be unbearable," says Chivian, because it is difficult to filter out radiation and even those in shelters could get mild radiation sickness, characterized by vomiting and diarrhea.

U.S. fallout shelter blueprints allow for 20 square feet of space per person, roughly the size of a single bed, Chivian says. "People will be in darkness, unless the shelters have independent power sources," he says. "Communications will likely be cut off." Air will be stale, humid and hot, he says, particularly if heat producing light sources are used.

"Kids will be crying," Chivian says. "For adults, cut off from the outside world, possibly with family members missing and unaccounted for, the psychological stress will be enormous."

The underlying worry of critics of relocation plans is that they increase the likelihood of nuclear war, that one superpower's evacuation might be interpreted by the other as preparation for a first strike. "My fear is that all of this is a cheap and easy way of dealing with a very dangerous psychological problem," says Harman, "that it's part of a game in an international war of nerves that just might get out of control."

Those who support the evacuation plan, however, say that despite its problems the plans could save millions of lives. "I'm with everyone who says, 'Let's try to eliminate nuclear war,' " says state evacuation planner Urquhart. "But you can't do that overnight. Until we do, what else do we have to fall back on? No plan is like giving away the fan before you get the air conditioning."