The Effects of Urbanization on the Biological, Physical, and Chemical Characteristics of Coastal New England Streams

By James F. Coles, Thomas F. Cuffney, Gerard McMahon, and Karen M. Beaulieu

U.S. Geological Survey Professional Paper 1695


This report is available in PDF


During August 2000, responses of biological communities (invertebrates, fish, and algae), physical habitat, and water chemistry to urban intensity were compared among 30 streams within 80 miles of Boston, Massachusetts. Sites chosen for sampling represented a gradient of the intensity of urban development (urban intensity) among drainage basins that had minimal natural variability. In this study, spatial differences were used as surrogates for temporal changes to represent the effects of urbanization over time. The degree of urban intensity for each drainage basin was characterized with a standardized urban index (0-100, lowest to highest) derived from land cover, infrastructure, and socioeconomic variables. Multivariate and multimetric analyses were used to compare urban index values with biological, physical, and chemical data to determine how the data indicated responses to urbanization. Multivariate ordinations were derived for the invertebrate-, fish-, and algae-community data by use of correspondence analysis, and ordinations were derived for the chemical and physical data by use of principal-component analysis. Site scores from each of the ordinations were plotted in relation to the urban index to test for a response. In all cases, the primary axis scores showed the strongest response to the urban index, indicating that urbanization was a primary factor affecting the data ordination.

For the multimetric analyses, each of the biological data sets was used to calculate a series of community metrics. For the sets of chemical and physical data, the individual variables and various combinations of individual variables were used as measured and derived metrics, respectively. Metrics that were generally most responsive to the urban index for each data set included: EPT (Ephemeroptera, Plecoptera, Trichoptera) taxa for invertebrates; cyprinid taxa for fish; diatom taxa for algae; bicarbonate, conductivity, and nitrogen for chemistry; and water depth and temperature for physical habitat. The slopes of the responses generally were higher between the urban index values of 0 to 35, indicating that the greatest change in aquatic health may occur between low and moderate levels of urban intensity. Additionally, many of the responses showed that at urban index values greater than 35, there was a threshold effect where the response variable no longer changed with respect to urban intensity. Recognizing and understanding this type of response is important in management and monitoring programs that rely on decisive interpretations of variable responses. Any biological, physical, or chemical variable that is used to characterize stream health over a gradient of disturbance would not be a reliable indicator when a level of disturbance is reached where the variable does not respond in a predictable manner.


Table of Contents



Study Design, Sample Collection, and Data Analysis

Study Design

Basin Characterization

Land-Cover Classification

Derivation of the Urban Index

Site Selection

Sample Collection

Biological Samples

Water Samples

Physical Characteristics

Data Analysis

Resolution of Taxa Ambiguities

Multivariate Analysis

Multimetric Analysis

Description of the Responses

Responses of Biological, Physical, and Chemical Characteristics to Urban Intensity

Land-Cover Changes

Biological, Physical, and Chemical Ordinations and Urban Intensity

Relations between Biological, Physical, and Chemical Ordinations

Form of Ordination Responses and Thresholds

Multimetric Analyses

Invertebrate Metrics

Fish Metrics

Algae Metrics

Habitat Metrics

Water-Chemistry Metrics

Basin Variables Used in Deriving the Urban Index

Relations among Landscape Changes, the Urban Index, and Biological, Physical, and Chemical Characteristics

Landscape Indicators of Urbanization

Biological Responses to Urban Intensity Physical and Chemical Responses to Urban Intensity

Attributes of the Multivariate Analyses

Implications for Water-Resource Monitoring and Management

Summary and Conclusions


References Cited


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For technical questions regarding this report, contact:


James Coles,

phone: 617-918-1331

EPA New England

1 Congress St. Suite 1100,


Boston MA 02114


or visit the New England Coastal Basins Study Unit NAWQA Web site at


To order a paper copy of this report, contact:


USGS Information Services

Box 25286 Denver Federal Center

Denver, CO 80225-0046

Tel: 1-888-ASK-USGS; Fax 303-202-4693



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