Understanding differences across U.S. urban watersheds aids in planning better stormwater management

Image credit: Stevan Earl

Image credit: Stevan Earl

Problem

How can urban and suburban areas better prepare for increased frequency and intensity of extreme rainfall events?

Flash floods caused by excessive runoff over impervious surfaces not only can damage property but could also be deadly. Responses to these intense and sudden changes in streamflow, or flashiness, depend on variations in climate and biophysical context as well as stormwater management practices.

Findings

Engineers and ecologists studied how hydrologic characteristics varied with urban development in arid environments. Urbanization in these watersheds surprisingly increased water retention and reduced flashiness.

  • They analyzed 14 years of flow records for 19 watersheds in central Arizona, both urban and nonurban and ranging in size from less than a square mile to 175 square miles.

Impact

The sharp contrast between eastern and western urbanization in the United States uncovered by this research provides significant lessons in the nuances of stormwater management for engineers and planners. This unique study documented for the first time:

  • Reduced flashiness of arid urban streams in the West, a pattern that is opposite of that typically seen in eastern cities
  • The significant role of “dry weather flows” from sources other than rain events and the influence of stormwater management efforts that were integrated into urban growth

Related Research Area: Environmental Resilience

Research Credit

Team

  • Lauren McPhillips, Stevan Earl, Nancy Grimm, Rebecca Hale

Partners

  • Global Institute of Sustainability, Arizona State University
  • Idaho State University

Competitive Funding

  • National Science Foundation/Urban Resilience to Extremes Sustainability Research Network, National Science Foundation/Central Arizona-Phoenix Long-Term Ecological Research

Federal and State Appropriations

  • USDA NIFA Hatch Multistate Project PEN04726, Accession #1020769

Published Research

Urbanization in Arid Central Arizona Watersheds Results in Decreased Stream Flashiness

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Office for Research and Graduate Education

Address

217 Agricultural Administration Building
University Park, PA 16802-2600