National Geographic : 2013 Nov
Sewage/ rainfall mix Rainfall Sewage Gowanus Canal Watershed Watershed area Sewer-shed area AREA ENLARGED SECONDSTREETBONDSTREET GOWANUS CANAL STATENISLANDBROOKLYNMANHATTAN THE BRONX QUEENS NewYork 1 2 3 4 5 0mi 6 0km 6 CurBSide Capture Bioswales—additional 20-by-5 -foot green spaces set into sidewalks—help soak up rainwater. The curb dips twice: at the top of the swale, so that water can flow in, and again at the bottom, so that overflow is diverted and soil isn’t flooded. retention CapaCity Each segment of the sponge park is projected to process 1,850 gallons of water for every one-inch rainfall; 90 percent of the New York City area’s rainstorms are about an inch. A similar setup in Queens absorbed 38,000 gallons of water during Hurricane Sandy. JASoN TREAT, NGM STAFF. GRAPHIC: THoMAS PoRoSToCkY SouRCES: SuSANNAH DRAkE, DlANDSTuDIo; NEW YoRk CITY DEPARTMENT oF ENvIRoNMENTAl PRoTECTIoN how the Sponge park workS 1 Gravity pulls rain runoff from the sloped street into the sponge park. 2 Water is absorbed and filtered by a gravel basin under the sidewalk. 3 Excess flows to plant pits, where it is stored in air pockets in sandy soil and later gets absorbed by plants or drains into groundwater. 4 Any unabsorbed water is funneled to the sand filter under a pedestrian path. 5 Excess water flows directly into the canal.