Daylighting Takes Off as Cities Expose Long-Buried Rivers

There's likely an underground stream in your city, but it may soon be seeing the light.

Uncovering buried streams has had huge impacts in places as diverse as Seattle, Washington, Kalamazoo, Michigan, and even Seoul, Korea—improving local water quality, providing habitat for fish and birds, and turning neglected parking lots and roads into public parks that boost neighbors' property values and can revitalize entire cities. And city planners everywhere are starting to take note.

In Yonkers, the fourth largest city in New York State, officials are a third done with a "daylighting" project—a term for the opening up of underground streams (see "11 Rivers Forced Underground"). In addition to exposing a waterway that had long been covered, the effort has already sparked plans for a new minor-league ballpark and new housing.

"I credit the city and the people who ... figured that having a nice river in a downtown was something that was, economically, really good," said Ann-Marie Mitroff, director of river programs for Groundwork Hudson Valley, an environmental justice nonprofit.

But why are all these streams covered at all? Flash back more than a hundred years. In many urban areas around the world, small streams were just getting in the way. You couldn't build on top of them, and the rapidly growing populations in many cities were throwing all their sewage into open water.

Often, engineers found that the simplest solution was to bury the streams, routing the water into pipes and paving over the top. In Yonkers, "the Army Corps of Engineers put a parking lot on top of it, which everybody thought was progress," Mitroff said. [Editor's note: A spokesperson for the U.S. Army Corps of Engineers says there are no records of the agency covering streams in Yonkers, and said the Corps would not have had jurisdiction to do so. They pointed to local authorities as most likely responsible; National Geographic has been unable to confirm that.]

In some cities, more than 70 percent of streams have been paved over. In many cases, city residents don't even know that there are buried waterways under their feet.

Now, new research and a desire to revitalize urban cores is leading to a host of daylighting projects. Uncovering buried streams has been proposed in San Francisco, Baltimore, and Detroit, as well as in smaller urban areas nationwide.

Uncovering streams can help reduce flooding. When it rains in a "natural" watershed, soil and plants absorb the water. When it rains onto a parking lot that drains into an underground pipe, the potential for flooding is much larger.

According to a new report from advocacy nonprofit American Rivers, released July 17, urbanization increases the likelihood of floods getting worse. One study found that paving over 25 percent of a watershed could turn a formerly rare severe flood into a twice-a-decade event. When more than 65 percent of a watershed is paved over, those so-called "hundred-year-floods" could hit every year.

Watch the Money Flow

Early daylighting projects, like Arcadia Creek in Kalamazoo, focused on the economic benefits of bringing streams back to the surface. Turning a parking lot into a 3/4-mile-long (1.2-kilometer-long) strip of Arcadia Creek in downtown Kalamazoo created a park that hosts five annual festivals and generates $12 million in annual tourism dollars.

But Arcadia Creek isn't really a creek. According to a report from the Virginia Tech Water Resources Research Center, the Arcadia Creek project and similar ones do "not resemble streams per se, but rather canals with surrounding parkland ... [the streams] are very controlled water channels [with] concrete-lined basins."

In Seoul, a $384 million project daylighted three miles (five kilometers) of stream that has most of its water pumped in from a river seven miles (11 kilometers) away. Both parks have been successful in boosting the economic value of the surrounding land and bringing locals a little closer to nature.

Digging up a stream isn't cheap. In Hutchinson, a town in rural Kansas, daylighting just three city blocks of Cow Creek cost more than $4 million, including relocating four buildings out of the new floodplain. But compared to the cost of unearthing, replacing, and reburying the city's aging pipes, building a new downtown park was an easy choice.

Not all daylighting projects need to be the centerpiece of an urban revitalization project. In Washington, D.C., the District Department of the Environment (DDOE) is undertaking small daylighting projects of a few hundred feet (around a hundred meters) in upper Northwest D.C., which is more suburban than urban, despite its location within the nation's capital.

Each project will create a small amenity for immediate neighbors, but they are mostly intended to mitigate local flooding and improve water quality. "Water in a pipe is not exposed to biological processes that break down pollution," said Steve Saari, watershed protection specialist with DDOE.

A recent EPA study found that streams exposed to sunlight are up to 23 times more efficient at processing nitrogen, which left unprocessed can cause dead zones where fish cannot survive.

Return of a "Living Stream"

In Yonkers, the uncovered stream is "a living stream," Mitroff says. The first reopened part of the stream (which opened in 2012) is already filled with fish and "fairly good-size" American eels, up to 18 inches (46 centimeters) long. "It's remarkable," Mitroff said.

In D.C., only months after daylighting a tributary to Rock Creek, "we've seen a lot more birds, and a lot more unusual birds," said Saari. And, he added, "we had frogs. It was incredible."

http://news.nationalgeographic.com/news/2013/07/130730-daylighting-exposing-underground-rivers-water-urban-renewal/