Liverpool -- from seamy seaport to garden spot and industrial jewel?

Once the river teemed with ferries, pleasure craft, and massive ocean liners, many of them steaming in from New York and other United States ports. Troop ships landed GIs during World War II.

The waterfront skyline was world famous. The port was one of the world's largest. The giant Adelphi Hotel, with its high ceilings, walk-in dressing rooms , paneled suites, and basement swimming pool, glittered with well-to-do travelers transferring from the London train and the liners, or going the other way.

But now the signs of stagnation are all too obvious. The once-proud city of Liverpool needs help -- badly, just as many others do in the north and west of England, as well as in Wales, Northern Ireland, and Scotland. All suffer from decades of decline and neglect and people leaving for suburbia.

At long last help is on the way. But the challenges remain formidable.

The waters of the Mersey River, for instance, are heavily polluted. Huge docks stand derelict, their piles deep in silt. Shipping has fled so fast to ports closer to Europe that Liverpool's population has dropped 200,000 people in two decades (to just over half a million). The port handled a mere 13 million tons of cargo last year, slumping to 10th place in Britain.

The Adelphi is less than half full in summer, and British Rail, which owns it , is eager to sell it off. ''But who will pay a million pounds for a hotel in a city like this?'' employees ask gloomily.

Unemployment, standing at 20 percent, is well above the national average. Bleak, inner-city Toxteth earned a grim, worldwide reputation last year for rioting, and almost one person in two there is unemployed.

Racial tension, small by US standards, is growing. Tony Excell from Toxteth, aged 17, speaks angrily about discrimination:

''No blacks in the post office, people patronizing us, police harassing us for no reason. You in America, you had a civil war and the civil rights revolution of the 1960s for black people's rights. We have to have the same here. No blacks are in big jobs here. Me and my friends, we're fed up.''

The city council squabbles endlessly with the Merseyside County Council. With no single party able to win a majority, strong local leadership is lacking.

What are the answers? So far it has come from outside -- in the form of new laws, more money, and fresh thinking from the Conservative government in London. Since the Toxteth rioting a year ago, the Cabinet minister in charge of urban affairs, Michael Heseltine, has paid regular visits to the Merseyside area. London is working with local and county authorities, trying to speed them along and provide leadership.

Even before then, the Thatcher government had picked up some inner-city ideas from the previous Labour government, some of them borrowing from the US model cities and urban development grants.

Liverpool never had a solid basis of manufacturing on which to fall back. It had the port and a strong commercial center but lacked the nonshipping industry that nearby Manchester possessed. A London effort to send in large car plants and other factories has failed. Decisions to move away were taken by boards of directors in London, who had little involvement with local affairs.

Basil Bean sits in a waterfront building, armed with a range of planning and executive powers from Parliament, in charge of reclaiming and regenerating 865 acres of historic docks and derelict land.

Last year his quasi-governmental Merseyside Development Corporation spent (STR)17.5 million ($29.7 million). This year it will spend (STR)27 million, pumping out silt, filling in some docks and renovating others, repairing dock gates, organizing new roads.

''The idea is to inject public funds, to show industry that the area can be transformed into attractive waterfront property, and to attract private capital, which in turn will create jobs,'' Mr. Bean said in an interview.

He overflows with enthusiasm and statistics: In one six-week period, silt 35 feet deep was pumped from one dock and will be used as fill to reclaim the adjacent Riverside area in the largest urban project of its kind in the country.

On the area is being created a 250-acre site for the first International Garden Festival ever held in Britain (April-October 1984). The hope is that 3 million people will attend in a blaze of world publicity.

Mr. Bean and the director of the festival, Sir John Grugeon, see much of Liverpool's future in leisure activities and tourism.

The city has been astonishingly lax in promoting itself as the home of the Beatles, for instance. Some plans are now in hand to create a Beatles trail for overseas tourists. A group from Japan has already booked a tour for next year.

Sir John hopes the garden festival, won by Britain against Chicago among other cities, will permanently improve the site and boost the Toxteth area, which is right next door.

But both men realize only too well that another major riot in Toxteth could drive exhibitors, and tourists, away, just as last year's riots did. The Adelphi Hotel alone lost more than 1,000 bookings last year because of the rioting.

To damp down tensions in Toxteth, the director of the Merseyside Task Force set up by the Thatcher government in October last year can point to some progress.

Sitting at a table surrounded by reports and action plans, Eric Sorensen freely admits that visible progress of the kind blacks and whites alike can see and evaluate has been slow so far.

Trees have been planted along Toxteth's Princes Avenue, and some landscaping done. Blacks like Tony Excell scoff and call it tokenism.

Pleading for time (''give us until Christmas''), Mr. Sorenson ticks off a list of plans about to bear fruit.

They include (STR)20 million earmarked for better housing, efforts to boost the quality of management in council (public) housing estates, (STR)71/2 million over three years for Princes Boulevard housing, matching government funds of (STR)1 million for sport and recreation projects that have generated another (STR)1 million locally so far, and six specific plans to provide jobs and train young people.

Cutting through complex local and city government planning procedures and conflicting pressure groups is difficult. Local permission and action to set up plans for Toxteth have been slow in coming.

But a start has been made -- and Mr. Heseltine is applying urban grants and other schemes to try to refurbish inner-city slums and beautify derelict land as the Johnson administration did in the US in the 1960s.