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Effects of Urbanization on Stream Ecosystems

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Stream with low level of urban intensity.


Stream with moderate level of urban intensity.


Stream with high level of urban intensity.

Portland, Oregon

Portland information sheet (2 pg PDF, 2.96 Mb)

This information sheet highlights selected findings of a comprehensive assessment by the National Water-Quality Assessment Program of the U.S. Geological Survey of the effects of urban development on stream ecosystems in nine metropolitan study areas. These are a few of the findings from the study in the Portland Metropolitan Area.

Prepared for November 30, 2012 Congressional briefing

Study design:

Twenty eight sites were selected with drainage basin areas between 5 to 40 square miles (13 to 104 square kilometers) and had minimal natural variability among them. The land use gradient went primarily from agriculture to urban. Sites represented a broad range of urban intensity from low to high.

Landcover, urban intensity, and site locations

Time of study:

Site selection in 2003.
Data collection from spring 2004 to fall 2004.

General Description:

The Portland study area is located in western Oregon and parts of Washington, USA. Major cities are Portland, Eugene, and Salem, Oregon. The population the Portland-Salem Metropolitan Area has increased 26.3 percent from 1990 to 2000 and was about 2.3 million people in 2000 (U.S. Census Bureau, 2000).

The study area is in the Willamette Valley ecoregion (Omernik 1987), which is characterized as a broad, lowland valley with a mosaic of vegetation of rolling prairies, deciduous and coniferous forests, and extensive wetlands. Landforms consist of terraces and floodplains that are interlaced and surrounded by rolling hills.

Agriculture (primarily grass seed crop) is the dominant land use in the region (Uhrich and Wentz 1999). Elevation of the study area ranges from about 0 to 4,364 feet (0 to 1330 meters) above sea level (U.S. Geological Survey, 2005).

The climate is characterized by cool, wet winters and warm, dry summers with a mean annual temperature of 52 degrees Fahrenheit (11.1 degrees Celsius) and mean annual precipitation of 57 inches (145 centimeters)(Daymet, 2005). Most of the precipitation occurs between October and April.

Highest flows occur from November to March and lowest flows occur in summer and fall. Streams in this region support warm-water biological communities.

Featured Publication:

Waite, I.R., Sobieszczyk, Steven, Carpenter, K.D., Arnsberg, A.J., Johnson, H.M., Hughes, C.A., Sarantou, M.J., and Rinella, F.A., 2008, Effects of urbanization on stream ecosystems in the Willamette River basin and surrounding area, Oregon and Washington: U.S. Geological Survey Scientific Investigations Report 2006-5101-D, 62 p.

For more information about the study area —

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