Engineers struggle to put streams back into the urban landscape
For generations, prudent city planning called for draining streams into culverts. Now planners see the mistake of subverting nature.
By Brian Bienkowski | Environmental Health News
When Jacob Napieralski brought some kids from Detroit to his campus at University of Michigan-Dearborn, he got to show a few something for the first time: a river. The Rouge River, which empties into the Detroit River, borders the campus in the Detroit suburb.
“I was amazed at how many kids had never seen a river before,” said Napieralski, an associate professor of geology at the University of Michigan-Dearborn. All the more ironic as Detroit’s historical landscape was crisscrossed with streams.
Those streams got buried as city planners, to make way for orderly pavement and busy city life, buried streams underground.
Detroit has buried more than 310 miles of stream channels since 1906.
As the U.S. faces billions worth of upgrades to handle wastewater, researchers point to vast swaths of river-less city acreage as a warning to future urban planners and sewerage districts.
Regions and cities most prone to overflowing sewers—such as Detroit, Chicago and others throughout the Rust Belt—long ago buried over streams and creeks that provided connections to larger waterways and did a lot of the dirty work now overwhelming wastewater plants.
Researchers say the lesson is simple—at least in principle: work with the natural environment instead of fighting it.
“Not only is there the economic value in keeping rivers, by helping control flooding, but it also provides aquatic habitats, feeding grounds for migratory birds … all of this is removed when we remove it from the system,” Napieralski said.
Decades ago as the country industrialized, pavement and buildings crept out from city centers as folks flocked to cities. In the process, streams would be buried, diverted in pipes or ditches. It’s unclear exactly how many streams have been sent underground in the U.S. But in some urban cores it’s substantial—like Baltimore, where researchers estimate 66 percent of streams have been buried.
Such changes, especially in the industrial Midwest, left cities without critical stream and river connections that perform a lot of the dirty work that wastewater treatment plants now do.
“It’s an interesting relationship. There are things we need that nature provides, but we’ve also imposed our will in cities where we need dry space” for development, said Meredith Steele, an assistant professor of landscape ecosystems at Virginia Tech.
Some places imposed their will more than others: Napieralski and a colleague recently mapped areas they dubbed “urban stream deserts”— land in cities where streams have been buried or removed. They estimated 6 percent of U.S. urban areas—more than 4400 square miles—were stream deserts.
The Great Lakes region alone accounted for 1,400 square miles of stream desert, with Chicago and Detroit comprising roughly 30 percent.
Not surprisingly, both cities have longed struggled with combined sewer overflows and other wastewater discharges to the Chicago and Detroit rivers.
Over the past 50 years, researchers estimate that urban land has quadrupled—now comprising about 59 million acres. That, along with more people and a lot of them living in cities, has helped spur an urgent $271 billion need in the U.S. to handle storm water runoff and maintain and improve its wastewater treatment systems, according to an EPA survey released in January.
The EPA estimates in the Great Lakes region more than $80 billion is needed over the next 20 years to curb sewage overflows and protect drinking water. Projections of more frequent and intense storms in the region due to a changing climate only add to the urgency.
Burying streams and channeling storm water into pipes and paved channels causes more flooding, whereas more natural stream systems can retain excess water and naturally filter it.
In addition to the flooding, researchers reported last year nitrates travel much farther in buried streams than open ones. Nitrates, which enter water via both farms and industry runoff, are necessary for plants but if they build up too much in water can result in harmful blooms of algae, which are toxic to fish.
Some cities have dug up rivers—a process called daylighting—where formerly buried rivers are uncovered and fully or partially restored. In many cases, full restoration is impossible—or simply too expensive.
But even partial restoration can bring success.
One such success: the Arcadia Creek in Kalamazoo, Michigan, which sat buried underground for more than 100 years before portions—about 1,500 feet total —were daylighted two decades ago. Long a source of flooding because the culvert containing the buried creek couldn’t handle excess runoff, businesses no longer have to purchase flood insurance, according to the nonprofit American Rivers organization.
Another stream, the Saw Mill River in Yonkers, New York, was daylighted five years ago, creating more than 13,000 square feet of new aquatic habitat and revitalizing the downtown area.
The “solution is somewhere in this gradient between the designed, technological engineered approach and complete restoration,” said Nancy Grimm, a professor and researcher at Arizona State University who studies the interaction of climate change, human activities and ecosystems.
There haven’t been a lot of daylighting projects in the U.S. because it’s not easy, said Laura Craig, director of science, economics and river restoration with American Rivers.
“If everything lines up and there’s the ability to daylight, it removes barriers for fish, improves benefits for neighborhood, and benefits areas that use combined sewers,” which often overflow into nearby waterways, Craig said.
But it’s not just a matter of busting up the concrete. Sometimes there are buildings on top of streams. And it’s complicated to decouple underground streams from the channelized system of pipes.
The daylight portion of the Arcadia Creek and Saw Mill River projects cost $7.5 million and $19 million, respectively.
Plus city space can be at a premium. “Cities that may have limited space are probably less likely to daylight,” Steele said. “You have to weigh the value of open space versus the value of having the open land.”
Stream restoration cannot just focus on the ecological, Grimm said, but has to incorporate the social and technological implications as well. “The reality is land is expensive. And the hand of people is present in cities and cannot be ignored,” she said.
Napieralski said while U.S. cities may be getting away from burying important rivers, the developing world should take note.
“Almost the entire city of Detroit is riverless, but it was filled 150 years ago,” he said.
“This is a precautionary tale for new developments: don’t go down this path.”