The jagged shoreline of this old port city stretches past a kaleidoscopic array of grimy coal piers, gleaming office buildings, abandoned wharves, renovated townhouses, markets, dumps, parks and factories, spanning the ups and downs of a battered economy.

At one edge sprawls the massive Sparrows Point steel and shipbuilding plant, now gripped by severe recession. Thousands of workers at the Bethlehem Steel Corp. complex have been laid off. Steel mills are churning out less than half the plates, sheets, rods and wire they could produce. Orders from shipping lines and oil-rig companies are scarce. No upturn is in sight.

Across the harbor, a more promising industrial landscape is taking shape. A $1.1 billion power plant is being erected by the Baltimore Gas and Electric Co. Land is being cleared by a company subsidiary for a 281-acre industrial park. Local officials predict millions of dollars in new tax revenues. "This is really going to become 'Electric Point,' " boasts Jeffrey H. Koenig, economic development chief for Anne Arundel, the county south of Baltimore.

These two scenes of boom and slump are signs of the economic crosscurrents pummeling the waterfront area, the region's industrial backbone. The harbor front extends from the northern end of Anne Arundel County through southern reaches of Baltimore City to Sparrows Point at the southeastern edge of Baltimore County, a suburban enclave surrounding most of the city.

"What makes the city tick is what goes on along this waterfront," says Mark Wasserman, a city development coordinator. A "reawakening" is under way, he contends. "It's not all bleak."

The harbor's economic shifts are closely watched by government and industry officials seeking to stem declines and bring about a revival. The port ranks among the five biggest in the United States. The Bethlehem Steel complex is the region's largest nongovernment employer. The waterfront area includes a newly expanded General Motors Corp. plant, currently beset by layoffs. Baltimore's inner harbor, a blend of tourist sites and office buildings, has been widely praised as a landmark in urban redevelopment.

"There's a mixture of trends," says Morton Hoffman, a Baltimore-based economic consultant. "The Bethlehem Steel mill and shipyards are having significant problems. This has ripple effects on employment. . . . Other aspects of port development are improving, but they probably would not equal the negative impact on employment at Bethlehem."

At least 15,000 workers have been laid off in the waterfront area's steel, automobile and shipbuilding industries alone, says Henry Koellein Jr., president of the Metropolitan Baltimore Council of AFL-CIO Unions.

So concerned are Baltimore County officials about severe unemployment among steel, auto and shipyard workers that they have launched a retraining effort. In some southeastern sections of the county, unemployment rates have approached 20 percent, officials say. The government-financed training project, scheduled to start April 1, is aimed at preparing 1,000 dislocated blue-collar workers a year for jobs in data processing, word processing and other expanding fields.

David Carroll, a coastal resources planner for Baltimore City, says he sees three trends that may, nevertheless, signal a turnabout. In manufacturing industries, he says, "We're beginning to arrest a downward turn." Despite recent declines, he adds, the port's business now is "holding pretty steady." And he says prospects are brighter for construction and renovation of homes, commercial buildings and recreational facilities in the waterfront area.

At the depressed Bethlehem Steel complex, the statistics remain grim. More than 4,500 steel workers have been laid off since last fall. The work force at the Sparrows Point shipyards has been pared to only about a third of its normal 3,000-member strength. In addition, the company marked the end of 1982 by shutting down its third major Baltimore plant, a ship repair yard overlooking the city's inner harbor. In past years, the yard had employed 1,400 workers and handled 300 or more ships annually. Today, the black and gray metal gates are locked. A handwritten sign posted on the employment office says, "Applications are not being accepted." On a recent afternoon, the yard was as silent as a cemetery.

Nevertheless, officials point to a few encouraging signs. The mills have undergone sizable renovation, including completion last April of a $160 million, computerized coke oven, and the company forecasts an eventual upturn in steel demand.

A buyer may soon be found for the shutdown ship repair yard, city officials say. Moreover, the Navy recently awarded three shipbuilding projects, totaling around $375 million, to Bethlehem--enough, the company says, to bring employment at the Sparrows Point yards to 1,900 workers by midsummer. ne new Sparrows Point venture is also cited by county officials. Atlantic Cement Co. Inc., a Newmont Mining Corp. subsidiary, recently opened a $90 million plant to buy hot slag from Bethlehem Steel and convert it to a roadbuilding material known as slag cement. The plant's work force may eventually rise to about 100 employes, a spokesman said.

At Baltimore's port, export and import cargo fell by about 5 percent from 1981, to around 34 million tons last year. Employment dropped by an estimated 1 million work hours.

"Considering the state of the world economy and what's been happening in other ports, we felt that was a good performance," says Maryland port administrator W. Gregory Halpin. "We held our own rather well."

One key factor, Halpin says, is the port's top ranking in U.S. exports to the Mideast, where trade has remained strong. The port has been mired, however, in a prolonged court and political battle over plans to dredge the main channel by another 8 feet to a 50-foot depth--enough to handle bigger vessels used in coal and grain exports and iron ore imports. Although environmental disputes have subsided, the $312 million project has been held up by the Reagan administration's refusal to finance it with federal funds, as Maryland hoped.

In the Canton area near the eastern end of Baltimore City's waterfront, the port's resilience is much in evidence. A foundation is being laid for a new state-run marine terminal, which will be built on more than 100 acres of muck dredged from the harbor. The dredging stems from construction of a tunnel to carry Interstate 95 around historic Fort McHenry. The $120 million terminal, officials say, will have swift access to I-95, a key asset for shippers.

Nearby on the Canton waterfront, Consolidation Coal Sales Co., a Conoco Inc. subsidiary, is spending more than $100 million to build a loading pier, planned initially to handle up to 10 million tons a year of coal mined in Pennsylvania, West Virginia and Ohio. Meanwhile, another coal pier with the same capacity was recently completed by an Occidental Petroleum Corp. subsidiary at Curtis Bay on the harbor's western edge. It will handle shipments from Island Creek Coal Co., a separate Occidental subsidiary, and from other mining companies.

Not all coal terminals have panned out. In Anne Arundel County's Marley Neck area, Pittston Co. and four other mining firms had planned a major facility on 500 acres of CSX Corp.-owned land, expected to cost up to $400 million and handle as much as 30 million tons a year. Four partners dropped out, however. Late last year, Pittston announced it had abandoned the project, saying no other company would agree to split the cost. County officials express confidence, nonetheless, that the site will lure another venture quickly.

A few blocks north of the Canton docks stands the General Motors assembly plant, also buffeted by economic countercurrents. Employment dropped last year to about 2,400 workers--1,000 fewer than in 1981 and far below the 6,500 level of 1978. The plant turned out 107,898 autos last year, a steep decline from the 150,868 cars and trucks produced in 1981 and the 468,343 of three years earlier.

Nonetheless, officials say, a turnabout was signaled last fall when GM announced it was resuming a $270 million expansion, aimed at outfitting the plant with computers, robots and laser equipment. The modernization, initially undertaken in 1980, had been suspended nine months later, setting off rumors that the facility might close. But since September's announcement, speculation has centered on whether the plant will soon add a new production line of minivans, an upbeat report the company declines to confirm.

Several new industrial parks are under way, including a 170-acre development on the former site of Fort Holabird, a largely demolished military installation situated beside the GM plant. The city-owned project, which includes a foreign trade zone for duty-free imports, is expected to bring $40 million in corporate investments and provide 2,500 jobs. Officials view its proximity to the port's large Dundalk Marine Terminal as a selling point.

The industrial center planned in Anne Arundel County by the Baltimore Gas and Electric subsidiary, Resource & Property Management Inc., has been billed as an "energy park." Fly ash, normally a utility waste byproduct, is already being trucked from a nearby coal-fired power station for use as a ground fill.

Eventually, company officials say, the project will use steam and hot water piped from the partly constructed Brandon Shores generating plant as a low-cost energy source for heating and air conditioning.

While the inner harbor's redevelopment has gained special prominence, Baltimore officials say they are now pushing for a substantial rehabilitation of other waterfront neighborhoods, including Fells Point, which lies to the east of the inner harbor, and the Middle Branch section farther to the west. Recent declines in interest rates have helped spur these plans, officials say.

At the tip of Fells Point, a huge, abandoned tobacco warehouse overlooking the harbor is being promoted by city officials as a site for a new residential or commercial complex with a marina. A vacant Fells Point vinegar bottling factory is a candidate for conversion into an inn, perhaps with a rooftop restaurant. A waterfront promenade is expected to link Fells Point with the inner harbor.

Farther east, workmen are already erecting a harborside cluster of 40 brick townhouses overlooking the water where 80 boat slips are to be built. Lou Grasnick, a lumber-business owner who is the developer of the $19 million project, says it eventually will include a mid-rise condominium complex and what he describes as "the only yacht club" in the city. "Fells Point is as hot as a firecracker," Grasnick says.

In the large Middle Branch area, the city is designing new parks, bike paths, fishing piers, a renovated boat basin and an enlarged industrial center, expected to generate 600 new jobs.

"Despite the recession that has been knocking the hell out of the heavier industry, there have been some favorable moves," says David Hash, senior vice president of the Baltimore Economic Development Corp., a nonprofit firm that advises the city government. "The city has clearly turned itself back toward the harbor."