The Planning Board unveiled its rezoning petition for the Concord-Alewife section of Cambridge at a public hearing Tuesday, a rezoning city officials said is intended to guide development in a densely populated area and get people out of their cars.

Residents say the improvements will invite too much additional traffic, while not taking into consideration the possibility of flooding and contamination to the Alewife reservoir.

The plan covers an area that includes Danehy Park, Alewife Station, Alewife Brook Reservation, Blair Pond, Rafferty Park, Concord Avenue and the northern section of Fresh Pond.

The proposal would create four zoning districts with lower floor area ratios and lower height limits for buildings and six districts that would — by special permit — allow the opposite. The plan would also increase open space requirements for development and encourage future development to include proper drainage, according to the city’s proposal.

Infrastructure improvements would include widening and redesign of the roadways to improve circulation within the Quadrangle, a bicycle and pedestrian bridge and better stormwater management in area that would serve as a park.

Most of the opposition to the plan centered around concern over whether there was sufficient flood planning and attention to traffic issues, Cambridge planning and zoning director Lester Barber said.

Several residents denounced the proposal, primarily because of Flooding fears.

Each property owner is bound by city requirements to provide for proper drainage, Barber said yesterday, but residents said that in an area that is subject to Flooding to begin with, the plan did not take into account the full impact of future development.

The plan takes into account flooding from serious storms, but not one of the magnitude of Hurricane Katrina, which devastated New Orleans and other areas, resident Michael Nakagowa said.

The water supply and electrical substations are especially vulnerable, he said, referring to the Fresh Pond reservoir and water treatment plant.

Even now, he said, sewers in the area have backed up, and areas in which sanitary and storm sewers combine could end up causing pollution in the event of a massive storm.

The backwater would run over into Alewife Brook, he said.

Resident Carolyn Mieth, a former member of the city planning board, said the plan “has so many flaws it should be dropped and a whole new process done, just like the citywide rezoning.”

“There is so much wrong with it,” she added. “But it is quite clear the planning board has no intention of listening to people.”

Her biggest concern, she said, is not what is in the plan, but what is not in the plan, pointing to the section on “transfer of development rights.”

She said she fears an orgy of development might occur if the rezoning is approved by the City Council, and “they don’t have any plan to deal with the regional traffic,” she said.