ROCKY ROAD Some residents are angry about plans to make streets in Brooklyn’s Dumbo and Vinegar Hill neighborhoods easier to walk and ride on by replacing cobblestones.CreditTodd Heisler/The New York Times

They have survived in Brooklyn’s northwestern corner for over a century — handmade and rounded, their shades weathered to a medley of noble grays — rattling the frames of carriages and Chryslers, buses and bicycles beside the waterfront.

But amid efforts to make the rickety streets of Dumbo and Vinegar Hill more accessible and bike-friendly, the city has delivered a disquieting message to residents who say they were drawn to the neighborhoods for their historic feel: Many of the old cobblestones on their streets have to go.

Some of the original Belgian blocks have already been replaced with more uniform stones, including ones cut with machines and lasers, startling preservationists. In a compromise that has not eased all minds, the city’s Department of Transportation has offered to install new cobbles that are aged artificially, like a pair of stonewashed jeans, to appear more worn.

“It is far worse than I could have imagined,” said Andrew S. Dolkart, director of the historic preservation program at Columbia University, decrying the “phony urbanism” of the replacement stones. “It is appalling that the D.O.T. would destroy real historic material and replace it with a completely ersatz program.”

Plans in the neighborhood, which include expanding a pedestrian plaza beneath the Manhattan Bridge and a bike route through the area as part of the Brooklyn Waterfront Greenway project, have inspired fevered community meetings and two petitions. In past protests against bike lanes, residents and businesses have defended their parking spots and traffic flow. Here, the locals have become well versed in the tones, textures and vulnerabilities of their cobbles, insisting that no substitutes could match their folksy charms.

And across a patch of the borough that remains proudly, often willfully, disconnected from the rest, the stones have become synonymous with a New York seen as steadily slipping away in a hail of Duane Reades and $18 cocktails.

“Somebody cut those things — thousands of people,” said Doreen Gallo, the executive director of the Dumbo Neighborhood Alliance, a residents’ group. “And we’re careless.”

The Transportation Department has pledged to save as many of the old cobblestones as possible. Some have been retained, but turned 90 degrees to create makeshift bike lanes, pointing in the direction of traffic flow — a visually striking intervention that the city “just made up,” Ms. Gallo mused, to promote cycling.

But many of the stones must be replaced, the Transportation Department said, in part because, according to the Americans with Disabilities Act, stones on a crosswalk or sidewalk must vary in height by no more than a quarter of an inch — far less a discrepancy than is found along the typical stretch of Belgian block.

Mindful of some community members’ disdain for the machine-cut cobbles that already exist on Washington Street, the department has promised an exhaustive search for the perfect replica stone. (Technically, cobblestones are rounded and irregular, but New Yorkers generally describe Belgian blocks as cobblestones.)

The administration estimated that across the city’s 6,300 miles of roadway, about 15 miles of cobblestone remained uncovered by asphalt. Andy Wiley-Schwartz, the Transportation Department’s assistant commissioner for public space, said that officials had conducted a citywide study in neighborhoods that retain their historic stones, including TriBeCa, SoHo and the meatpacking district.

“There you see a much more uniform color and size of stone,” he said. “In Dumbo, there are a variety of colors and a variety of sizes.”

SMOOTHER SAILING At the corner of Washington and Front Streets in Brooklyn, some of the machine-cut replacement cobblestones have been put in place. CreditTodd Heisler/The New York Times

In areas of Dumbo and Vinegar Hill where historic stone must be replaced, the city has proposed using only colors that are already found in Dumbo — tans and beiges, browns and grays. Edges would be rounded “so they don’t have the machine look,” Mr. Wiley-Schwartz said. “They actually tumble them,” he continued. “It imitates the effect of having trucks and coaches and other things rumble over your corners for years and years.”

Janette Sadik-Khan, the transportation commissioner, said in a statement the project would “restore the street’s historical elegance while removing stumbling blocks for the thousands of people walking and biking in the neighborhood daily.”

Officials noted that the plans came in response to a street rehabilitation request from the Dumbo Improvement District. The department also plans to construct “granite cobble mock-ups” in the neighborhood for public review before a final blueprint reaches the local community board and the Landmarks Preservation Commission.

While some residents appeared receptive to the department’s presentation at a recent neighborhood meeting, others have expressed fear that, even with meticulous attention to detail, the streets cannot possibly retain an authentic ethos.

The concern is particularly acute in Vinegar Hill, a quiet stretch of no more than a handful of blocks, tucked against the water to Dumbo’s east.

“Tourists won’t come to NY just to see the new 7-Elevens and the latest asphalt,” one critic, Gina Bevilacqua, wrote on an online petition opposing “the use of machine-made or machine-altered cobblestones of any kind” in the area.

Nicholas Evans-Cato, 40, an artist who has kept a studio in the neighborhood since 1995, said the consternation was rooted in a rich history of neighborhood upheaval. Mr. Evans-Cato was among those who fought to secure Vinegar Hill’s landmark status in 1997, years after residents failed to prevent the demolition of a 19th-century church on Front Street.

More recently, some residents have condemned the interruptions wrought by filming for the HBO series “Boardwalk Empire,” complaining of noise, lost parking spaces, and a preponderance of porta-potties.

“There’s only so much chipping away at Vinegar Hill that it can sustain,” said Brook Stanton, 44, a resident for seven years. “Is there anything preventing a Taco Bell from popping up?”

Mr. Evans-Cato praised the city’s “sensitivity to the palette of the street” in its latest proposal, but said “historic districts shouldn’t be testing grounds for new forms of paving technology.”

For others, the concern may not be aesthetics but, counter-intuitively, the potential for improved navigability. The area is included as part of the Brooklyn Waterfront Greenway, a planned 14-mile route for cyclists and pedestrians. “One of the positives was the inaccessibility of the area,” said Jerome Krase, a professor emeritus of sociology at Brooklyn College. “A lot of the attraction to the place was the sense that it wasn’t going to be changing, that it was going to be too difficult to change. Who wants to drive there?”

To city officials, the argument is a nonstarter. On both legal and civic grounds, Mr. Wiley-Schwartz said, “you can’t design it to be inaccessible.” Besides, some supporters suggested, it is not as if the cobblestones have been there forever.

“Years ago, there was just gravel and stone,” said Laura Roumanos, 32, the executive producer at a gallery in Dumbo. “And when the cobblestones were introduced, people were complaining.”