The stream has been hidden for years, buried under the streets of Southwest Baltimore's poorest neighborhoods, almost forgotten.
Only when it rains does the stream come alive, an underground current that carries with it the litter of storm drains - plastic bags, soda cans and other trash. It emerges near the Carroll Park golf course, disgorging into a rocky bed of the Gwynns Falls that holds a fetid cocktail of sewage and garbage.
Far more dangerous is the pollution that the naked eye can't see - nitrogen, zinc and lead from automobile exhaust, among other sources. The chemicals accumulate on roads and sidewalks and are washed into waterways when it rains.
In a common stream, vegetation would slow that down and microorganisms in the water would feed on the pollutants. But a buried stream - one paved over or filled in with dirt to accommodate development - has no such life forces. It is a direct chute from the city streets to the falls and then to the Patapsco River and, eventually, the Chesapeake Bay.
"These streams are just ecosystems waiting for water," said Sujay Kaushal, an ecologist with the University of Maryland's Center for Environmental Science. "What's happening to them is like emphysema. If you compromise the smallest capillaries, then the patient can't breathe."
Kaushal spends much of his time searching for buried streams in hopes of persuading state and local governments to restore some of them. To help him, he has enlisted Andrew Elmore, a landscape ecologist from the center's lab in Frostburg. Elmore uses advanced mapping techniques to locate the streams, then computer modeling to determine how many have been silted over.
Together, they have found hundreds of buried streams in the Gunpowder and Patapsco watersheds alone, and they believe that more exist in Howard, Anne Arundel, Carroll and Harford counties. Bringing streams back involves removing the concrete or dirt that covers them, remaking the stream bed and planting vegetation to keep the soil in place. So far, just a handful of streams has been restored.
The practice of burying streams began more than a century ago.
Baltimore's builders wanted to direct water away from people's homes - both to prevent flooding and because, in the days before modern sewage and storm drains, being too close to the flow was a health hazard. Because Baltimore is part of the Chesapeake Bay's drainage area, thousands of tiny guts and gullies fill with water during heavy rain. But when it's dry, they don't look like streams. So, one by one, developers filled them in.
"No one was breaking the law," said Darin Crew, restoration manager for the Herring Run Watershed Association, which has discovered buried streams around the city's northeastern neighborhoods. "It was just the old engineering - get it as quickly as possible off the street and as quickly as possible into the storm drain."
Kaushal estimates that Baltimore city and county have covered over more than 900 miles of streams. The water, however, never got the message. When it rains, the water continues to follow centuries-old flow patterns. It wants to go into the stream, whether buried or not, because that's where it always went.
Far more difficult than locating the streams has been restoring them, a process known as "daylighting." Many flow under roads or houses that realistically can't be torn down. Even where stream restoration is possible, the cost is about $200 per linear foot - a large investment for projects in obscure locations that few will see. And even when a stream can be uncovered, it needs a large floodplain in which to drain, and often part of that has been paved over, too, said Bill Stack, the city's water resources chief.
"The opportunities for daylighting are very, very slim," he said. "We're lucky if we do one a year."
Stack said the city has uncovered one stream buried in a storm drain near Stony Run in North Baltimore. Workers removed part of the drain to create a meandering channel, instead of having water go through concrete and pipes. Funding came from city motor vehicle funds as well as a small state grant, Stack said. The city expects to begin work on a similar project next summer in the Maiden Choice area, using funds from the U.S. Army Corps of Engineers.
Stack agrees with Kaushal's assessment that the buried stream in Carroll Park has contributed to an "ecological Chernobyl" and said the city is trying to improve the water quality.
The problem is not limited to the Chesapeake Bay watershed. Nationwide, developers routinely paved over streams, making ditches to direct the water away from the land, said Larry Larson, executive director of the Association of State Floodplain Managers. Only now, he said, are regulators demanding that developers take stormwater into account when planning for future growth.