It's one thing to live in a remote valley in the Applachian mountains where big floods have become so common that a heavy rain keeps people awake with fear.

But when people from the federal government say in effect, that the valley isn't worth saving, those are just about fighting words.

A year and one week from the day when the last major flood rushed down the Tug Fork of the Big Sandy River, dividing West Virginia and Kentucky, upwards of 1,000 people form the valley came marching on Congress yesterday.

They came by chartered train and bus, by plane and by private car, to pour out their demand - they want the Tug Fork tamed - to an array of congressional and executive branch officials, from the White House on down.

Lafe Ward, a West Virginia state senator from Williamson, which was devastated by the 1977 flood, summed up the feeling in a speech that got him a standing cheer:

"We don't come as beggars . . . We are talking about survival, the survival of an area that feeds more than 10 percent of our national energy [coal] production.

"They Army Corps of Engineers says it only does what Congress wants. Our representatives say they only do what the Corps remmends. It appears the Congress recommends. It appears the Congress and the Engineers should get their act together. Our people want to know how you can spend billion on overseas relief without a benefit-cost ratio."

What the delegation got during a four-hour session in a Senate office building was a lot os sympathy, but much more of the litany of government: the benefits don't justlfy the costs.

If being well-connected politically mean anything, the Tug River people should be in clover. One of their senators, Robert C. Byrd, is the majority leader. Another, Jennings Randolph, chairs the Environment and Public Works Committee, which authorizes dam projects.

From the Kentucky side,Sen. Walter (Dee) Huddleston sits with Byrd on APpropriations, which turns loose the money. And their congressman, Rep. Carl Perkins, is a part of the House leadership.

But these connection haven't got them that far. Their biggest problem comes from the hilly terrain that causes more building on the flood-plain and a Corps of Engineers cost-benefit ratio that makes large-scale flood protection a dubious investment.

Last year's flooding caused millions of dollars of damage in the region, cost the government millions more in relief aid, ruined or damaged 6,000 homes and intensified the residents' frustration.

With that background, the Tug Valley residents argued yesterday that their case is special: they must have federal flood protection help, whether the cost-benefit ratio justifies it or not.

The engineers, however, estimate that a big dam on the Tug Fork might cost $700 million. Less extensive local protection would cost less, but this work it hard to justify, the corps says.

Byrd, Randolph, Huddleston and the other legislators are trying to push through a bill that would let the corps do whatever is needed - no matter the cost-benefit ratio - to provide protection. But it's stuck in a legislative tangle.

The Applachian legislators said they thought they might get it unstucks, but after that, who knows? Such a departure from the traditional cost formula might invite a presidential veto.

White House aides listened yesterday, but didn't offer great hope. "The people have made quite a case for the uniqueness of their problem," said Dan Tate, a presidential assistant. "But I don't know what the president woulddo.