The Monocacy River takes its own sweet time leaving Pennsylvania, wiggling south into Maryland along the east-west border of Frederick and Carroll counties, then branching off to cut Frederick County almost in two.

It also marks the divide on perhaps the most contentious issue on the political landscape in these parts: whether preservation can be compatible with property rights.

For the past year, environmentalists and slow-growth advocates, led by a Frederick planner, have been pushing for zoning laws that would prohibit new development within about 500 feet of the Monocacy, which is the Potomac River's largest tributary and a major source of drinking water for the city of Frederick.

With Washington's exurbs spreading farther and faster, environmentalists argue that action is necessary to protect the river's scenic landscape and the quality of its water, which eventually flows into the Chesapeake Bay. For one thing, the easily eroded soil along its banks makes the river particularly vulnerable to development-related damage.

"Now is the time to look at these things, before they go too far," said Elizabeth Prongas, chairman of the New Forest Society in Rocky Ridge. "They don't understand that that kind of threat is in the offing."

But landowners along the river and property rights advocates see things differently. They argue that landowners should receive fair market value for strips of their property along the river, which would become off-limits to development. They say that creating such a buffer by legislative fiat would be an unconstitutional taking of their property.

"We're not against natural sanctuaries," said Walter T. Mills, president of Defenders of Citizens Rights Inc. "What we are against is people's rights being trampled because the government bureaucracy thinks it's a good idea but is not coming with a checkbook."

Defenders of Citizens Rights, which claims about 1,000 members, raised similar concerns in fighting a proposal to give scenic byway designation to U.S. 15, which runs north from Frederick to Gettysburg, Pa., along the base of the Catoctin Mountains. The Frederick Board of County Commissioners voted last week to seek the national designation for the road.

But environmentalists say more is at stake with the Monocacy River, and a key to protecting any river is keeping houses and industry away from its edge.

The Shawnee Indians called the winding river "Monnockkesey," which means "river with many bends," according to a fact sheet published by the Alliance for the Chesapeake Bay. Formed at the confluence of Marsh and Rock creeks in Adams County, Pa., the river flows about 58 miles before emptying into the Potomac near Dickerson. In April 1974, it was designated one of Maryland's scenic rivers.

Nearly two thirds of the river's journey from the Mason-Dixon Line to the Potomac unfolds in farmland. But pressures from suburban growth are increasing. From 1990 to 2000, the population density in the Monocacy River watershed increased 28 percent, to about 270 people per square mile, according to the Chesapeake Bay Program. The same organization estimates that the population density will grow by 17 percent by 2010.

The idea of creating buffers along the Monocacy River stalled last year, but proponents are quietly working to revive it. Among its principal champions is Timothy Goodfellow, chief planner in Frederick County's Planning Department.

"See, there's the river," Goodfellow said during a recent tour, indicating a rain-soaked valley where the river twists like a rung-out strip of green cloth.

Nearby stood several tract houses, their play sets and SUVs arranged around a cul-de-sac in the River Meadow development just outside Frederick. At least three of the new, $500,000 houses would not have been built so close to the river if Goodfellow and several preservationists had had their way. A few miles upstream, where the packed townhouses of the Dearbought development line the bank, as many as 16 houses would not be there if a 500-foot buffer had been in place.

"I think this resource has to be protected and revered -- and I don't think it is, when you see this stuff encroaching on the river," Goodfellow said. "Sure, these people have a coveted river view, but at what cost? What price?"

Two years ago, Goodfellow became Frederick County's liaison to the Monocacy Scenic River Citizens' Advisory Board, a group formed in 1978 to act as stewards for the river and provide guidance for local governing bodies. His job was to build consensus for creating a buffer zone, which became part of the county's formal plans in 1998. Besides protecting the riverbanks, the buffer might prevent people from crowding the bluffs along the river with houses, he believed.

Initially, planners encouraged the idea of an unyielding 500-foot boundary from the center of the river. To address concerns of the scenic river board and landowners, the idea was changed to a variable buffer of up to 500 feet from the center of the river.

Tom Devilbiss, a Carroll County member of the Monocacy Scenic River Citizens' Advisory Board who also works for the county government's planning office, said the group initially embraced the concept. But after a raucous public hearing drew about 160 people, many of whom were irate property owners, the board switched positions.

"It sounds like a good idea. But you've got to come up with some form of compensation for the landowners along the river," said Patricia Baumgardner, another Carroll County member of the board.

This year, however, preservationists want the proposed buffer laws enacted without the scenic river board's recommendation, as part of a broader review of Frederick County's zoning code that already is underway. It likely will be an uphill fight, however, because makeup of the Board of County Commissioners shifted to a more pro-growth stance in the last election.

"Ask the average Joe. Sure, he thinks it's a great idea: 'Let's save the Monocacy,' " said Barry Lucey, 60, of Creagerstown. "Farmers and landowners who own property along the river were just incensed at giving up that property."

Lucey, a retired dairy farmer, said he also had the least to lose if such a law passed. Several years ago, after his wife died, Lucey placed some 400 acres into a conservation easement that blocks future development. But as former chairman of the Monocacy Scenic River Citizens' Advisory Board and a friend of many fellow landowners along the river, he felt it was his duty to look out for their interests.

"Every farmer is a potential developer at the end of his life," Lucey said. "It's his nest egg."

Paul Allen, 58, a retired bus driver whose Frederick County farm is about two miles from the Pennsylvania line, said he has long mused about building a new house on the bluffs overlooking the Monocacy River. He worries that a government-decreed ban on development in the zone would be the first step toward snatching away his property without paying for it.

"Now that I own it, I have a right to put a house on top of it or on the bluff or anything else if I want to, because it's my property," said Allen, who is vice chairman of the Monocacy River advisory group.

Allen said he also worries that hikers, kayakers and others might interpret a buffer as an invitation to come and go as they please. If the public wants to preserve the property, the public should purchase it, Allen said.

James Gilford of Frederick also said many landowners fail to appreciate how preservation can help their pocketbooks.

"In a very real sense, rather than detract from the value of the land, it tends to protect the value of the land and even enhance it," said Gilford, a former Environmental Protection Agency official and biology professor. "Once someone begins talking about taking property, they stop looking at what they have. They start talking about all the horribles."

Some houses in the River Meadow subdivision overlooking the Monocacy River sit within the proposed 500-foot no-development buffer. "Sure, these people have a coveted river view, but at what cost? What price?" asks Timothy Goodfellow, Frederick County's chief planner.