Urban Stormwater Runoff: the Grey and the Green

Stormwater runoff, and for some cities dry-weather runoff, is the largest source of pollution in our nation’s waters. Out of necessity, and because of the Environmental Protection Agency’s (EPA) stricter enforcement of the Clean Water Act (CWA) statutes, cities are becoming leaders in the movement to better manage stormwater runoff. Some are designing and implementing green infrastructure (GI) approaches that are being watched closely as potential role models. Others are working hard to find the right balance between green and grey infrastructure to address pollution challenges and to better serve their citizens.

Aurora Swanson, an Executive Master of Natural Resources (XMNR) alumna, examined the urban runoff challenges our cities face, particularly in light of increasing population and climate pressures as part of her graduate capstone project. The report describes the characteristics of GI and conventional grey infrastructure, and discusses the urban runoff approaches of three cities – Philadelphia, Washington, D.C., and Santa Monica – all striving to manage urban runoff holistically. Although their overall approaches are different there are some common themes in reintegrating the green services that we have stripped away over the past few decades.

Local governments are seeing the need (and being required) to take a more active approach in tackling pollution problems caused by urban runoff. They must each understand their own needs, terrain, political, and budgetary realities to find the best solutions. These three cities provide useful case studies to illustrate the many options that exist to meet the needs of different communities.

For a more in-depth view of what elements compose green or grey infrastructure, and useful case studies, please read Swanson’s report Urban Stormwater Runoff: the Grey and the Green.