The Denver City Council has approved sweeping proposals aimed at helping to transform downtown’s Arapahoe Square from an area dominated by parking lots into the city’s next dense, walkable neighborhood.

City planning officials envision that development eventually could bring thousands of new housing units to the area, if developer interest holds.

Zoning changes approved Monday night divide a 21-block area sandwiched between 20th Street and Park Avenue into two newly created zone districts that allow 12-plus stories closer to Park and 20-plus stories closer to 20th Street, the boundary with the Central Business District. Those unusually defined height boundaries are intentionally elastic: Developers can build even higher — up to 20 or 30 stories, respectively — if they meet criteria such as concealing parking garages from the street or designing slimmer towers atop shorter bases, called “point towers.”

Those new zone districts between 20th and Park stretch from properties fronting Lawrence Street to those fronting Welton Street, in Five Points. Broadway cuts through the rezoned area diagonally.

The height flexibility will allow taller buildings for some projects than would have been permitted by the current zoning, which pre-dated Denver’s 2010 rezoning of most of the rest of the city.

The council approved two paired zoning proposals 8-1 on Monday.

Those new maximum heights spurred a little controversy among some residents of surrounding neighborhoods, especially when coupled with no requirement for developers in the new zones to provide parking. But the rezoning process for such a large area, which is well-served by transit, has been relatively smooth in the context of Denver’s contentious development boom.

District 9 Councilman Albus Brooks, who represents most of downtown, said the zoning changes carry out the vision of the 2011 Northeast Downtown Neighborhoods Plan, which was led by his predecessor, the late Carla Madison.

On the council, the lack of any restrictions or incentives in the Arapahoe Square plans to encourage affordable housing construction gave some members pause. Paul Kashmann cited the issue in voting no — despite, he said, liking other aspects of the zoning changes. Rafael Espinoza abstained from voting, also citing misgivings.

Other members and city staff said that choice on affordable housing was made in part because Mayor Michael Hancock’s administration and the council are drafting proposals geared toward raising at least $150 million over 10 years for housing subsidies. Those likely will include a property tax increase and a new impact fee that, if enacted, would apply to future development projects in Arapahoe Square, along with the rest of the city.

The Arapahoe Square zoning text amendment approved by the council created the new high-rise zoning districts and called for creation of a design advisory board to review proposed projects, akin to the board that reviews designs in Cherry Creek North. That and the companion rezoning proposal were the subject of a public hearing before the council voted.

Denver planning officials developed the measures with a community task force that also worked to establish design guidelines, including setback requirements for higher floors.

Some high-rise residential projects have gone up in recent years in Arapahoe Square, including the Colorado Coalition for the Homeless’ Renaissance Stout Street Lofts. But surface parking lots still cover much of the area, along with small industrial and office buildings.

The area also is home to a clustering of social services nonprofits that include the Denver Rescue Mission — a source of tension with the development-rich Ballpark neighborhood nearby.

In recent months, the city has been flooded by letters and e-mails, with some passionately in support of the plans to allow more density while many others have zeroed in on aspects they oppose.

Residents of Curtis Park northeast of Park Avenue pushed back against an initial proposal for higher density to extend into their neighborhood as a transition zone. Until it can hold a wider community discussion, the city has held off on rezoning proposals that would allow buildings up to five stories there, except for properties along Park. Monday’s rezoning included mixed-use rezonings for some other areas adjacent to the new Arapahoe Square zone districts, including allowing a maximum eight stories along Larimer Street.

At the southeast end of the new “20 story-plus” zone district, some residents expressed concern that the maximum 30-story towers allowed there potentially could cast shadows on the small adjacent Clements Historic District.

Brooks and downtown advocates have supported the zoning changes vigorously, arguing that they will prime the “blank slate” of Arapahoe Square for meaningful development in coming years.

The Denver Planning Board previously approved the proposals 6-0.