Rockville City Manager Larry N. Blick, who helped oversee the transition of Rockville from quiet county seat to high-rise business district, is resigning after nearly 13 years to become city manager of Colorado Springs.

Blick, 47, announced at a Rockville City Council meeting Monday that he will resign in two months. He said yesterday that he will assume his new position in October, at a salary of $79,000 a year. Blick now earns $66,000 annually.

Officials of Rockville, Maryland's second-largest city, say Blick has run a smooth operation as manager. During his tenure, much of the Montgomery County seat's turn-of-the-century downtown has been torn down and a central shopping mall and office towers built.

The Rockville Mall, in turn, the cornerstone of the city's unsuccessful urban renewal project, has been through several evolutions, changing owners and names. It is now being rebuilt into a major office-and-retail center next to a 250-room luxury hotel.

Blick was also instrumental in instituting a cost-saving plan that broke the impasse in labor negotiations over salary hikes for public workers in 1975.

He was city manager during two of the four years Rockville won a national All-American City award from the National League of Cities.

Mayor Viola D. Hovsepian said the City Council will meet next month to decide how to pick a new manager.

The Colorado Springs City Council last week had selected another candidate for the position. But that person, Tallahasse, Fla., City Manager Daniel Klaman, said that he would not be able to accept the job because of personal reasons, Watkins said.

Before he came to Rockville, Blick was assistant city manager of Boulder, Colo., for four years. He said that he is looking forward to moving back to that state with his wife, Susan, and their three children.

"It's a growing and dynamic area," Blick said.

"Growth management is an issue there. Also, the city owns its own electric and gas utility works," he said. "It will be challenging to learn those operations."