Managing Water Quantity (Research)

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

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

Participating Departments

Agricultural and Biological Engineering

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

Emerging Discoveries

Urban development reduces flash flooding chances in arid West

November 12, 2019

Urban development in the eastern U.S. results in an increase in flash flooding in nearby streams, but in the arid West, urbanization has just the opposite effect, according to a Penn State researcher, who suggests there may be lessons to be learned from the sharp contrast.