Streams are a simple but valuable natural gift. They abate flooding and remove pollutants while adding beauty and value to the land around them. No design or construction needed. At least not much. That’s just what streams do as they glide and tumble along their natural course.

But thousands of streams no longer follow their natural course. Hijacked to carry wastewater or paved over to make way for development, they travel in underground pipes, contributing little to the quality of life above as they flow through the darkness below.

Most will remain buried forever, trapped and forgotten beneath buildings, streets and parking lots. Yet a select few are being uncovered — at least in part — through the growing practice of daylighting.

“The practice of daylighting is really in its infancy, but the idea that we can in some cases bring streams out of pipes and to the surface is really attractive to people,” says Laura Craig, an associate director at American Rivers, a nonprofit organization based in Washington, D.C. “On the East Coast, many of our cities have 70 percent or more of their streams and rivers underground.”

Returning streams to the open restores their function as green infrastructure — the concept of using natural processes to cleanse runoff, curb storm surges and perform other environmental services — and recaptures a lost public amenity. By preserving — or in this case restoring — critical natural areas, daylighting streams is a smart growth approach to creating more livable and sustainable communities.

The Saw Mill River flows 23 miles from its headwaters before emptying into the Hudson River in Yonkers, N.Y. For nearly 100 years, the last half-mile passed through an underground flume built to protect downtown Yonkers from flooding and from the mix of human and industrial pollution poisoning the river’s waters.

Today, a growing stretch of a cleaned up Saw Mill River flows in the open through the heart of Yonkers — a catalyst for ongoing downtown revitalization efforts in the city of 200,000 just north of New York City.

“It’s doing even more than what the city of Yonkers anticipated in terms of stimulating redevelopment of many old and empty industrial buildings in the historic downtown,” says Ann-Marie Mitroff, river program director for Groundwork Hudson Valley, an environmental organization that helped lead the Saw Mill River restoration.

The first section of the Saw Mill River to be set free from the flume — which remains in place to serve as an overflow channel during heavy rain — runs for two blocks through a former parking lot that is now a park. Two more sections of the $48-million daylighting project will add a pedestrian walkway, courtyard and park, bringing the total length of exposed river to about six blocks.

Daylighting the Saw Mill River adds a public amenity while new zoning that was adopted at the same time allows greater density — a one-two economic development punch generating a flurry of residential, retail and office planning and construction in downtown Yonkers.

Daylighting also improves habitat for wildlife because it restores the Saw Mill River’s bed and banks to a more natural state. The Saw Mill River is home to the American eel, a species in serious decline up and down the East Coast, so creating a healthy ecosystem and food chain was an important goal.

Cincinnati is embarked on a $276-million public works project that revolves around daylighting a long buried creek to help reduce combined sewer overflows.

Lick Run became part of the Cincinnati’s wastewater system more than 100 years ago when the creek was funneled into a pipe to carry both sewage and stormwater — a common practice in many cities. The system works well until heavy rains overwhelm the pipe and send overflows of stormwater and raw sewage into the surrounding Mill Creek watershed before the foul flood can reach a sewage treatment plant.

Daylighting a mile of Lick Run and flanking it with wetlands — which store and absorb runoff — will provide a separate channel for stormwater to flow into Mill Creek without mixing with sewage. The project will include walking trails and recreation areas, demolishing aging buildings to create a public amenity that could stimulate new development in the challenged neighborhood.

Seattle is riddled with creeks that disappear into a pipe, pop back up, then disappear into a pipe again. “Typically, it’s where somebody wanted to build something or just to get the stream out of the way,” says Miles Mayhew, strategic advisor with Seattle Public Utilities.

Over the last decade, the city has completed several daylighting projects designed to improve water quality, enhance wildlife habitat — particularly for salmon — and add green space to neighborhoods that in many cases were the biggest advocates for undertaking the work.

“A lot of it has been community driven in a lot of ways,” Mayhew says.

When a developer sought to build a mixed-use project in the parking lot of a shopping mall, citizens successfully fought to require that Thornton Creek, which ran through a pipe beneath the parking lot, be uncovered as part of the project.

“Technically, it’s a water quality channel,” Mayhew says. Instead of rushing through a pipe, stormwater winds slowly through the channel, which is planted with native plants that filter and process sediments, pollutants and nutrients such as nitrates — which can cause toxic algae blooms — before the runoff reaches Lake Washington.

The creek — or water quality channel — doubles as park space for residents of Thornton Place, the much acclaimed transit-oriented development it now flows through. “It’s a big-time amenity,” Mayhew said.

Unlike many buried streams, Trout Brook in St. Paul wasn’t interred below streets and buildings. Much of it was piped beneath a relatively open natural valley that was gradually filled to accommodate railroad tracks and associated uses starting in the 1880s.

Starved for green space, the surrounding neighborhood pushed the city to buy 42 acres of the former railroad property. The primary goal was to create a nature sanctuary and fill a missing link in a regional trail system, but the project also presented an opportunity to bring Trout Brook back to the surface in a new channel.

A new stormwater management system of filtration ponds and wetlands feeds Trout Brook. Together, they remove sediment, pollution and nutrients from runoff before the creek eventually flows back into a pipe and empties into the Mississippi River.

“The nature sanctuary in and of itself didn’t need to have a water feature, but Minnesotans are very keen about water quality (because) 50 percent of our surveyed waters are not fishable, swimmable or drinkable,” says Deborah Karasov, executive director of Great River Greening, a local environmental organization that is helping the community plant grasses and trees in the sanctuary. “The fact that Trout Brook receives so much stormwater from this highly urbanized area and treats it before it goes into the Mississippi is very important.”

Uncovering the creek also creates educational opportunities. “When you hide a stream, people are oblivious to their impact on water quality, but now people are more aware of it,” Karasov says.

Trout Brook is one of several daylighting projects completed in the Minneapolis-St. Paul area with others likely to follow. “A lot of people are appreciating the possibilities of daylighting,” Karasov says.

Brad Broberg is a Seattle-based freelance writer specializing in business and development issues. His work appears regularly in the Puget Sound Business Journal and the Seattle Daily Journal of Commerce.

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