It's a dark decade we face, if the nation's economy goes the way popular financial writer Howard J. Ruff fears.

Ruff's prediction of possible "chaos" in our cities as the result of "social anger and inflation-disrupted markets" could make you flee to the countryside -- which is one of the things he advises if you want to survive, financially intact, the "economic smashup."

"No, he insists, he's not a "profit of doom." Which is what Time magazine called him last year when the hardback version of his book, "How To Prosper During the Coming Bad Years," hit the best-seller lists and stayed there almost a year. (His book is now out in paperback -- warner, 384 pages, $2.75 -- with 1.5 million copies in print.)

Forbes classified him among the "panic prophets."

Basically, he says, "I'm optimistic. Guys that write doomsday books don't put 'prosper' in the title."

There will be "bad years generally, " he believes, "but they don't have to be bad for those who figure out what to do."

And though he sees the country "about to enter its greatest test period since the Civil War -- an inflationary spiral leading to a depression that will be remembered with a shudder for generations," he believes the nation's economy is "marvelously resilient."

"It will get terribly sick, but my guess is that nothing can really kill it."

Ruff's dominant survival theme is individual self-sufficiency, stemming in part from his Mormom upbringing and a bad business experience that changed his life. "Nineteenth-century American values broght to the 20th century," he calls it. "I think we're moving into an era where self--sufficiency is more important."

It's a theme that has brought him a large following in the past five years: 135,000 subscribers to his twice-monthly newletter Ruff Times, a nationally syndicated TV show called "Ruffhouse" and an upcoming syndicated radio commentary.

Some of Ruff's advice for the bad times he predicts:

"Sell (or trade) all big-city or suburban real estate and invest in small-town income property. Move if possible." You get a better house for the money in small towns, he says, and you'll be better off if there are food and energy shortages.

Have a half-bag of silver coins (and of gold, if possible) for each member of the family. If paper money collapses, you'll need them for necessities.

Avoid unsound debt, but borrow for income-producing investments.

Begin buying and storing such durable goods as warm clothing, tools -- even soap, toliet paper, motor oil and light bulbs -- that the government might ration or put price controls on. "Buy them on sale now and use them later when the cost more."

"Store enough food for one year." Freeze-dried or dehydrated, not canned or frozen.

Ruff has pretty much followed his own advice.

He bought a house in a small central California town, Modesto, though he soon plans to move to Provo, Utah, where several of his nine children are in college. He owns a small apartment building in nearby Turlock, Calif. He has gold and silver and recently purchased "a couple of diamonds" and "colored gems."

And he has stored and 18-month supply of food. "I fully expect that relatives wo don't believe me will need help."

To really be self-sufficient, he tells his readers they also ought to have a well on their property and their own power generator.

Does he have a well? No, but, "There's a stream."

Ruff, 49, started out to be a musician, preparing, as he now sees it, "for a career as one of the country's 2,000 best baritones." In the last '50s, he was a soloist for the Air Force Singing Sergeants here.

That gave him free hours for a part-time jobe as a stockbroker. He got hooked on business. Back home in the San Francisco area, he was jolted in 1968 by the sudden collapse of his speed-reading franchise. "I told myself I'd never let myself be vulnerable like that again."

Ruff has an optimistic word for Washington. Even if things get bad elsewhere in the country, the nation's capital probably will not suffer much.

"Government is a growth industry in good times and bad. This is the most recession-proff city in America. It's the seat of government, and government isn't going to get any smaller."