Labor contracts in some of the nation's basic industries -- coal, rail, postal, shipping and a good deal of construction -- come up for renewal this year, and the settlements may be expensive.

Many labor economists expect first-year wage increases in major contracts to average around 10 percent, slightly above the 9.5 percent of last year.

Labor leaders say members need such increases to get even with inflation, which was running at an annual rate of 12.6 percent in November. But pay raises of that size will also make it more difficult for the Reagan administration to bring inflation down. Because wages are such a large part of production costs, economists look to wage rates as a measure of the so-called underlying inflation rate.

The expected settlements could also affect the competitive position of U.S. firms internationally, according to Audrey Freedman, labor economist for the Conference Board, a nonprofit, New York-based economic research organization.

"In the 1980s, productivity [or output per manhour] is not increasing. Every wage boost raises production costs. Some plants and companies carrying these labor costs are failing," Freedman said. To keep those companies alive, she said, labor leaders may have to do in 1981 what some were forced to do last year -- "lead [their] members into wage concessions."

But labor leaders such as William H. Wynn, president of the United Food and Commerical Workers and a member of the Conference Board's labor outlook panel, disagree.

"No employers will live or die because of labor costs," Wynn said.

Other labor leaders say the settlements this year will be too few to affect inflation significantly; it is a relatively light bargaining year with only about 2.6 million workers covered by major contracts that are expiring. Labor leaders also say members still are losing purchasing power because prices have risen faster than wages.

"Even with the 9.5 [percent] increases in 1980, our people were trailing behind the inflation rate. And we expect them to trail anywhere from 3 percent to 4 percent" behind inflation in 1981, said Rudolph Oswald, research director for the ALFO-CIO.

Labor economists say cost of living adjustment (COLA) clauses will help raise the price of settlements negotiated this year.

According to David Schlein, an economist with the Bureau of Labor Statistics, about 42 percent of the workers under major contracts expiring this year are covered by COLA agreements.

"Major contracts [those covering 1,000 or more workers] with COLA clauses have tended to provide for a larger total wage increase" than those without such protection, with the living cost adjustment adding at least 1.1 percent in these contracts, Schlein said in a Labor Department report on upcoming bargaining activity.

In a view supported by other economists, Schlein predicts the COLA issue will play an important role in talks between representatives of the nation's nearly 600,000 postal workers and the U.S. Postal Service management on a contract up for renewal July 20.

"The postal talks . . . are anticipated to be difficult," Schlein said. "Management, under pressure to cut costs, may seek to roll back union gains won in previous rounds, particularly the 'uncapped' COLA clause" that allows postal workers' pay to keep pace with inflation, he said.

Schlein said the postal unions "almost certainly will resist such efforts," and could possibly strike. But he pointed out that strikes by federal workers are forbidden and are punishable by fines, which the unions would presumably seek to avoid.

Briefly, this is the outlook for the other five major industries bargaining this year:

Coal -- The national contract between the United Mine Workers of America and the Bituminous Coal Operations Association, affecting 139,000 workers, expires March 27. The UMW's new leaders say they expect an early contract settlement "beneficial to the union's membership" without a strike of the sort that badly hurt both sides last time, in 1978.

Railroads -- Contracts affecting nearly 500,000 workers are up for renewal March 31. No strike is expected.

Airlines -- Bargaining effecting nearly 100,000 airline employes will continue throughout the year. Airline deregulation, which already has cost some carriers' profits and jobs, is expected to temper the bargaining demands of industry unions. No strikes are expected.

Martime -- Three-year agreements covering 50,000 seamen in dry cargo and tanker operations expire in early June, according to the Schlein report. Important areas of discussion will concern wages, vacation and health benefits. No strikes are expected.

Longshore -- Contracts affecting 11,500 West Coast workers, nearly all represented by the International Longshoremen's and Warehousemen's Union, expire July 1.Negotiations are important because a strike could interrupt operations of all firms using West Coast docking facilities and "can quickly affect shipping, trucking, railroads and eventually can spread to other industries," according to the Schlein report. Job security is likely to be a major issue in the longshore talks. No strike is expected.