Large cities are experimenting with innovative ways to manage stormwater runoff as they confront the high costs and limitations of providing adequate flood protection through traditional stormwater infrastructure in growing urban centers, especially in low lying areas.

Conventional stormwater management in urban areas generally relies on a dedicated system of conduits and temporary retention facilities to store runoff and later transfer it to a nearby body of water. As cities grow rapidly, so do the costs of these systems while also reaching the limits of their ability to handle increasing runoff.

In response, scientists, engineers, and urban planners around the world are exploring small-scale, low-cost, and decentralized ways to manage rainfall close to where it falls. Examples of sustainable ways to meet the growing challenges of urban flood prevention and related impacts include:

  • Low impact development (LID) methods for stormwater management, first introduced in Prince George’s County, Maryland, and later embraced and promoted by the United States Environmental Protection Agency
  • Sustainable Drainage Systems (SuDS) developed in the United Kingdom
  • The concept of “sponge cities,” which applies LID methods on a large scale and was originally developed and implemented in China

Examples of these methods are bioretention areas, pervious pavements, green roofs, water harvesting, vegetative swales, and other landscape features. These methods emphasize maximized water retention and infiltration, enabling the cities to essentially act as sponges. The largest-scale application of these methods is in China, where the government has spent billions of dollars over the last few years in an effort to create 30 “sponge cities.”

In the attachment below, Bechtel Fellow and Senior Principal Hydraulics and Hydrology Engineer Angelos Findikakis discusses sustainable urban stormwater management, the challenges of developing “sponge cities,” and how international collaboration is helping to advance the promise of these strategies.