A Tale of Many Cities: Using Low-Impact Development to Reduce Urban Water Pollution

Over 80% of the U.S. population lives in urban areas, a number that is projected to increase to almost 89% by 2050 (United Nations, 2011). Increasing urbanization puts pressure on centralized stormwater systems, which are expensive to expand and focused on just one task—conveying stormwater to a treatment plant. Urban stormwater is, however, as polluted as untreated domestic wastewater and urban runoff is estimated to be responsible for 47% of the miles of impaired ocean shoreline, 22% of seriously polluted lakes, and 14% of seriously polluted rivers (U.S. Environmental Protection Agency (EPA), 2006; p. 4-23). In addition, many older cities have combined sewers that convey both sewage and stormwater; they were a significant improvement over the above-ground sewer ditches that existed before combined sewer systems were created in the mid-1800s, but many combined sewers discharge harmful waste when storms overload the system (Tibbetts, 2005). Green infrastructure projects—such as green roofs (or eco-roofs), bioswales, permeable surfaces, and rain gardens—are decentralized approaches that may generate multiple benefits such as the reduction of urban water pollution, provision of open space, reduction of air pollution, and improvements in human health. This article describes new approaches being used to control urban stormwater on public and private property, discusses insights from economic theory about optimal stormwater policy design, and provides examples of projects being implemented in several U.S. cities.