Once a power source vital to the region's economic growth, and once even a haven for yachts, Darby Creek remains a thoroughfare with some of the region's lushest pastoral vistas.

But it also is one of the country's most flood-prone streams, a significant drain on the National Flood Insurance Program, and a national lesson in what can go wrong along a developed waterway. Worse for the thousands who live along its 26-mile course, from the border of Chester and Delaware Counties to the Delaware River, the Darby appears to be just a major rainstorm away from spilling over its banks yet again.

The creek is so choked with wooded debris that another major flood is "a certainty," said Jeff Featherstone, director of Temple University's Center for Sustainable Communities.

"There's a new one," Edward Silberstein, a local developer whose property abuts the creek, said as he gestured toward a fallen maple spanning the creek near a ball field in Hoffman Park, in Lansdowne.

It was one of several massive trees he spotted in the water last week between Lansdowne and tiny Colwyn. Scores of others were poised to fall in along the severely eroded banks. Though downed trees can provide habitat for wildlife, they also can lead to logjams that exacerbate flooding and erosion in a narrow-banked stream such as the Darby.

Silberstein, who dreams of running a tubing operation along the creek (yes, he is serious), wondered aloud who might be responsible for removing such debris.

"Nobody, but everybody," said State Sen. Edwin Erickson, a Republican who represents Delaware County. In short — with the notable exception of Philadelphia — stream-clearing in the region is a free-for-all, and that is particularly unfortunate for Darby Creek.

It runs through a maze of privately and publicly owned land in 30 municipalities — one of the nation's most densely populated corridors.

"The Darby encapsulates about every problem attendant in stream management," Featherstone said.

Officially, according to the Pennsylvania Department of Environmental Resources, it is property owners' duty to remove tree — even if the debris wandered from upstream. However, DEP spokesman Kevin Sunday said, the law is rarely enforced. Likewise, New Jersey essentially leaves removal to individual initiative, said Bob Considine, Sunday's counterpart in the Garden State.

Erickson has introduced a bill to create regional authorities with the power to raise taxes to pay for stream maintenance. Such "special districts" are common elsewhere around the country, Featherstone said. "The Mid-Atlantic region," he added, "is really unique in that it doesn't have them."

Philadelphia, he said, is an exception in that the Water Department has an aggressive stream-management program. In 2003, the department created a Waterways Restoration Team to remove trash and natural debris, spokeswoman Joanne Dahme said.

"Philadelphia is the best case study in the United States for storm-water management," Featherstone said.

The city does have an advantage over many of its suburban neighbors, Dahme said, in that most of its stream mileage — for example, that of the Pennypack and Wissahickon Creeks — drains Fairmount Park land.

By contrast, Darby Creek has had an adversarial relationship with civilization for more than 300 years. After Welsh Quakers settled in the area in the 17th century, the creek became a source of power for lumber, grist, and textile mills, according to a Darby Creek Valley Association history.

With industrialization in the 19th century came an explosion of residential development in the watershed, further enhanced by the extensions of rail and trolley lines. Much of the building, however, predated zoning, land-management, and flood-control restrictions. The creek became a repository for contaminated runoff, illegal dumping, and other detritus of development.

Flooding has been a constant, and Darby and Colwyn have been particularly hard-hit. Since its creation in 1970s, the National Flood Insurance Program has paid out close to $9 million in losses to those two tiny boroughs.

"The fundamental problem is development upstream," said John Furth, a creek association board member.

Although it is impossible to quantify, runoff from upstream development has been a factor in downstream flooding, experts agree.

The creek has claimed a huge chunk of Darby's tax base and bitten off a whole neighborhood. After Hurricane Floyd's record rains in 1999, the government bought 37 houses along Chestnut Street, making the neighborhood off-limits to development.

"Darby and Colwyn are at the bottom of the bowl," said John Haigis, a borough resident and creek association activist. He helped organize a recent cleanup of the stream, and of the 1904 trolley bridge, which he hopes will someday be illuminated.

During the cleanup, Haigis had to contend with a tree that had attached itself to the bridge. Only with immense effort and Silberstein's equipment were they able to nudge it to the side.

Darby, desperately short of revenue, is in no position to get into the tree-removal business, Mayor Helen Thomas said.

"Removing those trees is very, very expensive," she said. "That's way more than we can afford."

Erickson's bill to use tax money for stream cleanup is in the Senate Environmental Committee. Given the antitax climate, he does not expect smooth sailing.

Still, Erickson said, "there's got to be a better way."

Contact Anthony R. Wood at 610-761-8423 or twood@phillynews.com.