An illustration of Vechte’s house, with the brook highlighted (Image: Courtesy of Eymund Diegel)

On a chilly Sunday morning, Eymund Diegel stands at the intersection of 5th Avenue and 2nd Street in Brooklyn, just a block from the park where the Old Stone House, built in 1699, now lives. There’s a blue tube full of maps slung across his shoulder. Not long before, he had been spreading those maps across the walls of a coffee shop to point out details of the Gowanus watershed, the places where the original Brooklyn and ours overlap. He checks that the traffic is clear and indicates the sewer covers in the middle of the crosswalk.

“So, if you put your ear on this sewer plate right here,” he says, “that’s Vechte’s Brook right there.”

In his free time, Diegel canvasses city streets for clues, in order to put together a very specific piece of New York’s history: where the water underneath the city now lives. Across the country, in Dubuque, Kalamazoo, Washington, D.C., San Francisco, and many other cities, municipal governments have been thinking of uncovering these streams and reincorporating them into urban landscapes.

First, though, someone has to find out what happened to the water.

A 1782 map of the area, with the waterways’ course drawn in (Image: Courtesy of Eymund Diegel)

Back in 1699, when Claes Arentson Vechte picked the spot to build his stone house, his farm was right on a brook that fed into the nearby Gowanus Creek. The body of water was chock-full of oysters then, which provided both food and a transport route to the more bustling ports of Manhattan. By the time the house was demolished in 1897, though, Brooklyn had grown to be one of the largest cities in the country. The streets around the house were gridded into city blocks, and the Gowanus Creek had been transformed into a polluted, industrial canal, lined with warehouses and rank with sewage.

Most of the house had been buried when the street grid had raised the grade of the land, and in the 1930s, when the city Parks department decided to rebuild the house, excavators had to dig it out of the ground in order to rebuild on the current surface of the city.

The brook that once flowed by it, though, had disappeared.

Diegel’s investigators measuring stream sounds late at night (Photo: Courtesy of Eymund Diegel)

In his day job, Diegel makes maps for city agencies; in his extracurricular hours, he makes maps of Gowanus’ lost watershed, so many at this point that he has thick piles of print-outs that, together, make a convincing picture of what this neighborhood once looked like and what it could resemble, in some ways, again. A native of South Africa, Diegel has lived in this neighborhood of Brooklyn since 1997, and for the past five or so years, he has dedicated early mornings, late nights, and weekends to trying to suss out the fate of the brooks and streams that once made this part of the city a marshy wetland.

This knowledge, he thinks, could help convince planners and the city government to change this place in the one with more natural features–more water, more green space–and help transform the Gowanus Creek into a thriving waterway, instead of one so polluted the federal government has declared it a Superfund site.

“As a country boy, you’re used to reading clues, of where the birds might be or the bigger frogs can be caught,” he says. “When I came here, I thought, well, this is weird. It’s all flat and gray. But it isn’t if you look more closely.” By layering observations of trees and weeds, buildings large and small, and the Gowanus Canal with maps old and new, along with other sources of data, Diegel has been working to deduce the structure of the Gowanus watershed and understand the ways in which it’s still affecting the people who live in this area. And, at this point in his research, he thinks he knows what the watershed once looked like, and how that maps onto Brooklyn today. He’s been very effective at mapping things that are off the radar of city planners.

An 1880s ward map of the area (Image: New York Public Library/Courtesy of Eymund Diegel)

Diegel’s interest in Vechte’s Brook began with an aerial photograph of the Gowanus Canal, which he had captured with an outdated digital camera, attached to a balloon, a strategy he had picked up from Public Lab, a non-profit that develops DIY tools for environmental investigators.

He had been working with the local Gowanus Canal Conservancy to measure and map the plant cover in the area. But, sitting in a neighborhood coffee shop, looking at the shot, he noticed an intriguing detail: the ice was melting exactly where it should linger longest, in the shadow of a bridge.

That was his first clue that under the paved streets of Park Slope, a whole system of streams that had once fed the Gowanus Creek still exist. Some of this active watershed had been diverted into sewers and stayed there, but some had broken free of the sewer networks to creep back into the canal. It was as if, in the decades that people had neglected the infrastructure their predecessors had built, the land had begun its own natural restoration process.

Diegel’s reconstruction of Vechte’s brook (Image: Courtesy of Eymud Diegel)

Ultimately, the point of this project is to integrate the streams hidden underneath the city surface with the world of Brooklyn today. When the city plants trees, for instance, perhaps those trees could go where there’s a natural flow of water, and they’re more likely to thrive and survive. Neighbors who are all dealing with regularly flooded basements could realize that they’re living atop the path of an old creek and could collaborate to build a drain system that will keep their buildings dry.

Understanding the true nature of a neighborhood like this one, built atop a wetland, could have larger impacts, too. A subway lines runs along 4th avenue, the unofficial dividing line between Park Slope and Gowanus, where the slope flattens into the basin of the canal. In times of heavy rain, the canal and the subway tunnels are both at risk of flooding, and even when it doesn’t rain, groundwater leaks into the subway system. Diegel likes the idea of a system of street creeks, that would imitate natural systems by channeling groundwater and runoff into the canal, and that could also help move water above the subway tunnel. It’s not enough to just study what happens in the built environment; to prepare for events like Hurricane Sandy, city planners need to peek below.