At the foot of Second Street in Brooklyn, hard by the Gowanus Canal, is a tiny green space with a very big job.

Aptly called Sponge Park, the 2,100-square-foot plot will, when it opens next spring, intercept thousands of gallons of storm water, along with pollutants like heavy metals and dog waste, before they can enter the canal. The park’s absorbent qualities come from flood-tolerant plantings like asters, Rosa rugosa and sedge grass, as well as a network of sand beds and soils designed to hold water.

“I didn’t want to go into a community and tell them that I’m putting a wetland in their backyard,” said Susannah C. Drake, a landscape architect and founding principal of DLANDstudio, which designed Sponge Park. “That wouldn’t fly. But everyone understands what a sponge does, even if they don’t understand green infrastructure or phytoremediation.”

The park is part of a larger effort in New York City and urban areas across the country to prevent polluted storm water from flowing directly into rivers or overloading sewage treatment plants. With combined storm-sewer systems like New York’s, in which one set of pipes handles both sewage and storm water, even moderate rainfall can overwhelm treatment plants, causing raw sewage to spew into waterways.