Throughout its history, the Gowanus Canal's sewage problems have been exacerbated by the effects of stormwater. For years, heavy rains have flooded streets and caused sewage lines to overflow, contributing to the canal's contamination. Much of the Gowanus Canal area is at sea level, in a Zone A risk area for flooding. To help prevent flooding, the city is investing in various methods of stormwater management. One related improvement has been the creation of specialized curbside gardens, or bioswales, along sidewalks to absorb stormwater and reduce sewer overflows into the canal. A community-based non-profit organization, the Gowanus Canal Conservancy, is involved in stewardship of the bioswales. In 2015, the city built Sponge Park, along the canal's western bank at Second Street. The park doubles as a stormwater catchment area, absorbing pollutants before they can go into the canal.