Scene — From the March 2016 issue

The Hidden Rivers of Brooklyn

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Back in the Vechte’s drainage, Diegel showed curious passersby, with the help of his map, where the blue ponds and streams of the green Gowanus once lay. Remarkably, not a single person we encountered on a five-hour walk didn’t know what a combined-sewer overflow was. Some even knew about the two-pronged approach that the city’s Department of Environmental Protection had taken to fixing the watershed’s problems: “gray” infrastructure, which includes storage tanks, pumps, and pipes, and “green” infrastructure, which is low-tech, mimics natural systems, consumes far less energy than gray infrastructure, and costs less per gallon to build and maintain.

New York City’s commitment to green infrastructure in the Gowanus is most visible in the ninety or so enlarged tree pits, called bioswales, that collect rain and runoff. Plants in the bioswales sequester or break down the pollutants typically found in storm water — oil and grease, heavy metals, pathogens from dog droppings — and return water to the air through evapotranspiration. Whatever the plants can’t absorb is filtered through eight feet of soil and gravel back into the earth.

Photograph of Vechte’s Brook by Miska Draskoczy

Photograph of Vechte’s Brook by Miska Draskoczy

“If you take green infrastructure to scale, you’ll achieve a critical mass of storm-water capture,” said Adrian Benepe, the former commissioner of the New York City parks department and a current vice president of the Trust for Public Land. According to the D.E.P., even a 5 percent reduction in the volume of water processed at wastewater-treatment plants would cut the city’s carbon emissions by 15,661 metric tons — the equivalent of taking 3,297 cars off the road. “Distributing thousands of water-absorbing structures around the city, rather than building a few centralized tanks, is just as effective, far cheaper, and more resilient to climate change,” said Tom Ballestero, a civil engineer who directs the University of New Hampshire’s Stormwater Center.

Over the next several years, the D.E.P. plans to create some 5,000 bioswales throughout the city. It also plans to install permeable paving, which allows rain to seep into the earth; replace concrete traffic islands with landscaped planters; and retrofit public parks and schoolyards with porous pavers, synthetic turf, and rain gardens, which are similar to bioswales. All together, the city expects its green-infrastructure initiative to reduce combined-sewer overflows by roughly 3.8 billion gallons a year.

Other cities have taken similar steps. Los Angeles is managing its periodic deluges with permeable pavement and rain gardens that allow water to seep into the city’s depleted aquifer, instead of sluicing it out to sea. The city is also replacing eleven miles of concrete in the L.A. River with green terraces and wetlands. Flood-plagued communities along the Missouri and Mississippi Rivers are restoring natural floodplains rather than hardscaping them with levees. Philadelphia is planting enough bioswales, grassy roofs, and wetlands, at a cost of $800 million over twenty-five years, to make permeable a total of fifteen square miles.

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’s most recent book is Bottlemania: Big Business, Local Springs, and the Battle over America’s Drinking Water (Bloomsbury).

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