Oregon is an outdoorsman's dream. The state has pristine beaches, miles of unsullied hiking trails, bountiful fishing streams and, in season, the hills are alive with the sound of hunter's rifles.

But Portland, the state's only "big" city, is a sporting dichotomy. Settled in the northwest sector of this ecological, outdoor wonderland, the only game in town for this city is an indoor one -- professional basketball.

While most of the NBA cities struggle with attendance figures, the Portland Trail Blazers play in sold-out Memorial Coliseum.

There isn't a seat or standing room space available for the final eight Blazer home games this season. The home finale April 7 against Los Angeles will be the 100th consecutive time the Blazers have drawn a capacity house for a regular season or playoff game.

Including 300 standing-room tickets that are sold, capacity at the Coliseum is 12,666.

The Trail Blazers without Bill Walton are having trouble staying above.500, but at the Paramount Theater, less than five miles from the Coliseum, an average of 1,773 fans are paying $5 each to watch closed-circuit telecasts of Blazer games.

Last season, an average of 2,706 watched the Blazer games on the theater screen.

Why is Portland drawing so well in the face of declining NBA attendance elsewhere?

"There's kind of a rule of thumb in professional sports that a championship can carry you for three years no matter what happens," said Trail Blazer General Manager Harry Glickman, involved in promoting professional sports in the city since the 1950s.

The reason for the team's success at the gate is not solely the 1976-77 championship season. In their nine-year history, the Trail Blazers have averaged 9,048 fans, but more than 12,000 the past four seasons.

"I guess you might say the absence of any other major league sport is a reason for our success," Glickman continued. "Unless you consider the (North American Soccer League) Timbers major league. I do, but they play at a different time of the year.

"We don't have hockey, football and major league baseball, the main competitors for the sports dollar."

There is very little competition even for the entertainment dollar. Rarely is there a symphony or rock concert scheduled the night of a Blazer home game. There is little professional theater.

What is unusual about the Trail Blazer success story is that the rest of Portland's sports picture isn't very bright.

Hardly any other tenants ever fill the Coliseum.The Far West Classic, which used to be one of the nation's biggest collegiate holiday basketball tournaments, is holding its last tourney in 1981.

The University of Portland, which enjoyed an 18-9 season in the West Coast Athletic Conference, averaged only 2,500 at the Coliseum.

Minor league ice hockey left town in 1974 and Class AAA baseball drew sparsely last year.