Effects of Development and Impervious Surfaces on Watersheds

Last updated: 9/2/10

This list includes resources for understanding how urban development and imperious surface cover effect watersheds.

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Review Articles
General / Multiple Effects
Toxicity and Pesticides
Nutrients and Chloride
Habitat Characteristics
Thermal Impacts
Direct Channel Impacts
Aquatic Habitat Integrity
Benthic Macroinvertebrates

Review articles   (return to top of page)

Allan, J.D. 2004. Landscapes and riverscapes: The influence of land use on stream ecosystems. Annual Review of Ecology, Evolution and Systematics 35: 257-84.

Abstract: Local habitat and biological diversity of streams and rivers are strongly influenced by landform and land use within the surrounding valley at multiple scales. However, empirical associations between land use and stream response only varyingly succeed in implicating pathways of influence. This is the case for a number of reasons, including (a) covariation of anthropogenic and natural gradients in the landscape; (b) the existence of multiple, scale-dependent mechanisms; (c) nonlinear responses; and (d) the difficulties of separating present-day from historical influences. Further research is needed that examines responses to land use under different management strategies and that employs response variables that have greater diagnostic value than many of the aggregated measures in current use.

Access: Available online.

Barnes, K. B., J. M. Morgan III, and M. C. Roberge. 2002. Impervious surfaces and the quality of natural and built environments. Baltimore, Md. : Department of Geography and Environmental Planning, Towson University. 28 p.

Abstract: The growth and spread of impervious surfaces within urbanizing watersheds pose significant threats to the quality of natural and built environments. These threats include increased stormwater runoff, reduced water quality, higher maximum summer temperatures, degraded and destroyed aquatic and terrestrial habitats, and the diminished aesthetic appeal of streams and landscapes. This paper provides a basic introduction to impervious surfaces and an overview of the environmental effects of increased watershed imperviousness, with particular consideration given to the watershed of the Chesapeake Bay.

Access: Available online

Beach, D.  2002.  Coastal sprawl: the effects of urban design on aquatic ecosystems in the United States.  Pew Oceans Commission, Arlington, Virginia. 33 p.

Summary: Includes discussion of effects of imperviousness on habitat, water temperature, pollutants, and aquatic life (p. 9-11).

Access: Available online.  Also available at the DNR Library

Cappiella, K., and K. Brown.  2001.  Impervious cover and land use in the Chesapeake Bay watershed.  Center for Watershed Protection, Ellicott City, MD. 51 p.

Summary: Includes “Literature review of the impervious cover/stream quality relationship” (Appendix A, p. 33-42).

Access: Available at the DNR Library

Center for Watershed Protection. 2003. Impacts of impervious cover on aquatic systems. Center for Watershed Protection, Ellicott City, MD.  141 p.

Summary: Reviews more than 225 research studies that have explored the impact of impervious cover and other indicators of urbanization on aquatic systems.  Comprehensively reviews the available scientific data on how urbanization influences hydrologic, physical, water quality, and biological indicators of aquatic health as of late 2002.

Access: Available in the DNR Library.

FitzHugh, T. 2001. Watershed characteristics and aquatic ecological integrity: A literature review. TNC Freshwater Initiative. 12 p.

Summary: This document summarizes the findings of currently available research on the relationship between watershed characteristics and aquatic Indicators of Biotic Integrity (IBIs). It covers the results of empirical research, the practical implications for TNC s work, and future research needs. The section on practical implications primarily discusses the thresholds and indicators that have been developed to analyze the impact of watershed impervious area on IBIs. Future research needs include the development of better indicators and thresholds for the impacts of agriculture, dams, and point sources; and the role of habitat type in determining which indicators are relevant. An appendix is included with brief summaries of the key findings in the articles reviewed.

Access: Available online.

Johnson, M.P. 2001. Environmental impacts of urban sprawl: a survey of the literature and proposed research agenda. Environment and Planning A 33: 717-735.

Abstract: 'Urban sprawl' has recently become a subject of popular debate and policy initiatives from governmental bodies and nonprofit organizations. However, there is little agreement on many aspects of this phenomenon: its definition, its impacts - both nonmonetary and monetary - economic and policy models that predict the presence of sprawl, and decision-support models that could assist policymakers in evaluating alternative development schemes that may have characteristics of sprawl. In particular, there is relatively little research on urban sprawl that focuses specifically on measurement and modeling of environmental impacts. The purpose of this paper is twofold: to survey the literature on urban sprawl, with a focus on environmental aspects and to identify a research agenda that might result in a greater number of anaytical tools for academics and practitioners to characterize, monetize, model, and make planning decisions about sprawl.

            Access: Available online.

Schueler, T.R. and H.K. Holland. 1994. The importance of imperviousness. Watershed Protection Techniques 1(3): 100-111. (Also published in The Practice of Watershed Protection)

Summary: Includes “Review of key findings of urban stream studies examining the relationship of urbanization on stream quality” (Table 2, p. 105), showing that “stream degradation occurs at relatively low levels of imperviousness (10-20%)”

Access: Available in the DNR library’s journals collection.

General / Multiple Effects   (return to top of page)

Arnold, C. L., and C. J. Gibbons.  1996.  Impervious surface coverage: the emergence of a key environmental indicator. Journal of the American Planning Association 62:243-258.

Abstract: Planners concerned with water resource protection in urbanizing areas must deal with the adverse impacts of polluted runoff. Impervious surface coverage is a quantifiable land-use indicator that correlates closely with these impacts. Once the role and distribution of impervious coverage are understood, a wide range of strategies to reduce impervious surfaces and their impacts on water resources can be applied to community planning, site-level planning and design, and land use regulation. These strategies complement many current trends in planning, zoning, and landscape design that go beyond water pollution concerns to address the quality of life in a community.

Access: DNR employees should contact the library to request via interlibrary loan.

Brown, L.R. Cuffney, T.F., Coles, J.F., Fitzpatrick, Faith, McMahon, Gerard, Steuer, J.J., Bell, A.H., and May, J.T. 2009. Urban streams across the USA: lessons learned from studies in 9 metropolitan areas. J. N. Am. Benthol. Soc. 28(4):1051–1069. 

Abstract: Studies of the effects of urbanization on stream ecosystems have usually focused on single metropolitan areas. Synthesis of the results of such studies have been useful in developing general conceptual models of the effects of urbanization, but the strength of such generalizations is enhanced by applying consistent study designs and methods to multiple metropolitan areas across large geographic scales. We summarized the results from studies of the effects of urbanization on stream ecosystems in 9 metropolitan areas across the US (Boston, Massachusetts; Raleigh, North Carolina; Atlanta, Georgia; Birmingham, Alabama; Milwaukee-Green Bay, Wisconsin; Denver, Colorado; Dallas-Fort Worth, Texas; Salt Lake City, Utah; and Portland, Oregon). These studies were conducted as part of the US Geological Survey's National Water-Quality Assessment Program and were based on a common study design and used standard sample-collection and processing methods to facilitate comparisons among study areas. All studies included evaluations of hydrology, physical habitat, water quality, and biota (algae, macroinvertebrates, fish). Four major conclusions emerged from the studies. First, responses of hydrologic, physical-habitat, water-quality, and biotic variables to urbanization varied among metropolitan areas, except that insecticide inputs consistently increased with urbanization. Second, prior land use, primarily forest and agriculture, appeared to be the most important determinant of the response of biota to urbanization in the areas we studied. Third, little evidence was found for resistance to the effects of urbanization by macroinvertebrate assemblages, even at low levels of urbanization. Fourth, benthic macroinvertebrates have important advantages for assessing the effects of urbanization on stream ecosystems relative to algae and fishes. Overall, our results demonstrate regional differences in the effects of urbanization on stream biota and suggest additional studies to elucidate the causes of these underlying differences.

Access: Available online through the DNR Library's subscription.

Coles, J.F., Cuffney, T. F., McMahon, G., and Beaulieu, K.M. 2004. The effects of urbanization on the biological, physical, and chemical characteristics of coastal New England streams. U.S. Geological Survey, Professional Paper 1695, 47 p. 

Abstract: 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.

Access: Available online.

Gregory, M.B., and Calhoun, D.L. 2007. Physical, Chemical, and Biological Responses of Streams to Increasing Watershed Urbanization in the Piedmont Ecoregion of Georgia and Alabama, 2003. U.S. Geological Survey Scientific Investigations Report 2006-5101-B.

Abstract: As part of the U.S. Geological Survey National Water-Quality Assessment Program’s effort to assess the physical, chemical, and biological responses of streams to urbanization, 30 wadable streams were sampled near Atlanta, Ga., during 2002–2003. Watersheds were selected to minimize natural factors such as geology, altitude, and climate while representing a range of urban development. A multimetric urban intensity index was calculated using watershed land use, land cover, infrastructure, and socioeconomic variables that are highly correlated with population density. The index was used to select sites along a gradient from low to high urban intensity. Response variables measured include stream hydrology and water temperature, instream habitat, field properties (pH, conductivity, dissolved oxygen, turbidity), nutrients, pesticides, suspended sediment, sulfate, chloride, Escherichia coli (E. coli) concentrations, and characterization of algal, invertebrate and fish communities. In addition, semipermeablemembrane devices (SPMDs)—passive samplers that concentrate hydrophobic organic contaminants such as polycyclicaromatic hydrocarbons (PAHs)—were used to evaluate water-quality conditions during the 4 weeks prior to biological sampling. Changes in physical, chemical, and biological conditions were evaluated using both nonparametric correlation analysis and nonmetric multidimensional scaling (MDS) ordinations and associated comparisons of dataset similarity matrices.

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Holland, A. F., D. M. Sanger, C. P. Gawle, S. B. Lerberg, M. S. Santiago, G. H. M. Riekerk, L. E. Zimmerman, and G. I. Scott. 2004.  Linkages between tidal creek ecosystems and the landscape and demographic attributes of their watersheds.  Journal of Experimental Marine Biology and Ecology 298:151-178.

Abstract: Twenty-three headwater tidal creeks draining watersheds representative of forested, suburban, urban, and industrial land cover were sampled along the South Carolina coast from 1994 to 2002 to: (1) evaluate the degree to which impervious land cover is an integrative watershed-scale indicator of stress; (2) synthesize and integrate the available data on linkages between land cover and tidal creek environmental quality into a conceptual model of the responses of tidal creeks to human development; and (3) use the model to develop recommendations for conserving and restoring tidal creek ecosystems. The following parameters were evaluated: human population density, land use, impervious cover, creek physical characteristics, water quality, sediment chemical contamination and grain size characteristics, benthic chlorophyll a levels, porewater ammonia concentration, fecal coliform concentration, and macrobenthic and nekton population and community characteristics. The conceptual model was developed and used to identify the linkages among watershed-scale stressors, physical and chemical exposures, and biological responses of tidal creeks to human development at the watershed scale. This model provides a visual representation of the manner in which human population growth is linked to changes in the physiochemical environment and ultimately the nursery habitat function of tidal creeks and the safety of seafood harvested from headwater tidal creeks. The ultimate stressor on the tidal creek ecosystem is the human population density in the watershed and associated increases in the amount of impervious land cover. Measurable adverse changes in the physical and chemical environment were observed when the impervious cover exceeded 10–20% including altered hydrography, changes in salinity variance, altered sediment characteristics, increased chemical contaminants, and increased fecal coliform loadings. Living resources responded when impervious cover exceeded 20–30%. The impacts on the living resources included reduced abundance of stress-sensitive macrobenthic taxa, reduced abundance of commercially and recreationally important shrimp, and altered food webs. Headwater tidal creeks appear to provide early warning of ensuing harm to larger tidal creeks, tidal rivers and estuaries, and the amount of impervious cover in a watershed appears to be an integrative measure of the adverse human alterations of the landscape. Through education and community involvement, a conservation ethic may be fostered that encourages the permanent protection of lands for the services they provide.

Access: DNR employees should contact the library to request via interlibrary loan.

May, C. R., Horner, J., Karr, B., Mar, B. W., and E. Welch. 1997. Effects of Urbanization on Small Streams in the Puget Sound Lowland Ecoregion. Watershed Protection Techniques 2(4): 483-494.

Key finding: Physical and biological stream indicators declined most rapidly during the initial phase of the urbanization process as the percentage of total impervious area exceeded the 5-10% range (Washington). 2

Access: DNR employees should contact the library to request via interlibrary loan.

Pearce, J.B. 1991. Collective effects of development on the marine environment. Oceanologica Acta 11:287-298.

Abstract: This paper identifies issues associated with effects of industrialization and urbanization on the marine environment. Emphasis is given to the collective effects of development and impacts on living marine resources. Issues of concern include inorganic and organic contaminants, nutrient enrichment and eutrophication, physical degradation of habitat, and non-point sources of stresses. Conclusions are based on case studies and include solutions as these are being practiced.

Access: DNR employees should contact the library to request via interlibrary loan.

Wheeler, A. P., P. L. Angermeier, and A. E. Rosenberger.  2005.  Impacts of new highways and subsequent landscape urbanization on stream habitat and biota.  Reviews in Fisheries Science 13:141-164. 

Abstract: New highways are pervasive, pernicious threats to stream ecosystems because of their short- and long-term physical, chemical, and biological impacts. Unfortunately, standard environmental impact statements (EISs) and environmental assessments (EAs) focus narrowly on the initial direct impacts of construction and ignore other long-term indirect impacts. More thorough consideration of highway impacts, and, ultimately, better land use decisions may be facilitated by conceptualizing highway development in three stages: initial highway construction, highway presence, and eventual landscape urbanization. Highway construction is characterized by localized physical disturbances, which generally subside through time. In contrast, highway presence and landscape urbanization are characterized by physical and chemical impacts that are temporally persistent. Although the impacts of highway presence and landscape urbanization are of similar natures, the impacts are of a greater magnitude and more widespread in the urbanization phase. Our review reveals that the landscape urbanization stage is clearly the greatest threat to stream habitat and biota, as stream ecosystems are sensitive to even low levels (< 10%) of watershed urban development. Although highway construction is ongoing, pervasive, and has severe biological consequences, we found few published investigations of its impacts on streams. Researchers know little about the occurrence, loading rates, and biotic responses to specific contaminants in highway runoff. Also needed is a detailed understanding of how highway crossings, especially culverts, affect fish populations via constraints on movement and how highway networks alter natural regimes (e.g., streamflow, temperature). Urbanization research topics that may yield especially useful results include a) the relative importance and biological effects of specific components of urban development—e.g., commercial or residential; b) the scenarios under which impacts are reversible; and c) the efficacy of mitigation measures—e.g., stormwater retention or treatment and forested buffers.

Access: Available online.

Hydrology   (return to top of page)

Hollis, F. 1975. The effects of urbanization on floods of different recurrence intervals. Water Resources Research, 11:431-435.

Key finding: Increased bankfull discharge. Bankfull discharge increased two to five times after urbanization.2

Abstract: Studies have shown that the urbanization of a catchment can drastically change the flood characteristics of a river. Published results are synthesized to show the general relationship between the increase in flood flows following urbanization and both the percentage of the basin paved and the flood recurrence interval. In general, (1) floods with a return period of a year or longer are not affected by a 5% paving of their catchment, (2) small floods may be increased by 10 times by urbanization, (3) floods with a return period of 100 yr may be doubled in size by a 30% paving of the basin, and (4) the effect of urbanization declines, in relative terms, as flood recurrence intervals increase.

Access: DNR employees should contact the library to request via interlibrary loan.

Konrad, C. P., and D. B. Booth.  2005.  Hydrologic changes in urban streams and their ecological significance. Pages 157-177 in L. R. Brown, R. H. Gray, R. H. Hughes, and M. R. Meador, editors.  Effects of urbanization on stream ecosystems.  American Fisheries Society Symposium 47, Bethesda, Maryland.

Abstract: Urban development modifies the production and delivery of runoff to streams and the resulting rate, volume, and timing of streamflow. Given that streamflow demonstrably influences the structure and composition of lotic communities, we have identified four hydrologic changes resulting from urban development that are potentially significant to stream ecosystems: increased frequency of high flows, redistribution of water from base flow to storm flow, increased daily variation in streamflow, and reduction in low flow. Previous investigations of streamflow patterns and biological assemblages provide a scale of ecological significance for each type of streamflow pattern. The scales establish the magnitude of changes in streamflow patterns that could be expected to produce biological responses in streams. Long-term streamflow records from eight streams in urbanizing areas of the United States and five additional reference streams, where land use has been relatively stable, were analyzed to assess if streamflow patterns were modified by urban development to an extent that a biological response could be expected and whether climate patterns could account for equivalent hydrologic variation in the reference streams. Changes in each type of streamflow pattern were evident in some but not all of the urban streams and were nearly absent in the reference streams. Given these results, hydrologic changes are likely significant to urban stream ecosystems, but the significance depends on the stream’s physiographic context and spatial and temporal patterns of urban development. In urban streams with substantially altered hydrology, short-term goals for urban stream rehabilitation may be limited because of the difficulty and expense of restoring hydrologic processes in an urban landscape. The ecological benefits of improving physical habitat and water quality may be tempered by persistent effects of altered streamflow. In the end, the hydrologic effects of urban development must be addressed for restoration of urban streams.

Access: Available in the DNR Library.  Also available online.

Leopold, L. 1994. A view of the river. Harvard University Press, Cambridge, MA. 

Key finding: Increased bankfull discharge. Bankfull frequency increased two to seven times after urbanization.2

Access: Available at the DNR Library.

Sauer, V. 1983. Flood characteristics of urban watersheds in the United States. US Geological Survey Water Supply Paper 2207. 

Key finding: Increased flood peaks. 50% imperviousness of a watershed can result in a doubling of the 100-year event.2

Abstract: A nationwide study of flood magnitude and frequency in urban areas was made for the purpose of reviewing available literature, compiling an urban flood data base, and developing methods of estimating urban floodflow characteristics in ungaged areas. The literature review contains synopses of 128 recent publications related to urban floodflow. A data base of 269 gaged basins in 56 cities and 31 states, including Hawaii, contains a wide variety of topographic and climatic characteristics, land-use variables, indices of urbanization, and flood-frequency estimates.

Access: Available online.

Schueler, T. 1987. Controlling urban runoff: A practical manual for planning and designing urban best management practices. Metropolitan Washington Council of Governments. Washington, D.C., 272 pp. 

Key finding: Increased runoff volume. Parking lot produces 15 times more runoff than a meadow.2

Access: Available at the DNR Library.

Simmons, D., and R. Reynolds. 1982. Effects of urbanization on baseflow of selected south-shore streams, Long Island, NY. Water Resources Bulletin. 18(5): 797-805.

Key finding: Decreased baseflow. Two Long Island streams went dry as a result of urbanization.2

Abstract: Hydrograph analysis of six streams on the south shore of Long Island indicates that eastward urbanization during the last three decades has significantly reduced base flow to streams. Before urbanization, roughly 95 percent of total annual stream flow on Long Island was base flow. In urbanized southwestern Nassau County, storm water sewerage, increased impervious surface area, and sanitary sewerage have reduced base flow to 20 percent of total stream flow. In an adjacent urbanized but unsewered area in southeastern Nassau County, base flow has decreased to 84 percent of total annual stream flow. In contrast, base flow in two streams in rural areas has remained virtually constant, averaging roughly 95 percent of total annual flow throughout the 1955-70 study period. Double-mass curve analysis of base flow as a percentage of total annual stream flow indicates that (1) changes in stream flow characteristics began in the early 1960's in the sewered area and in the late 1960's in the later urbanized, unsewered area, and (2) a new equilibrium has been established between the streams in the sewered area and the new hydrologic characteristics of their urbanized drainage basins.

Access: DNR employees should contact the library to request via interlibrary loan.

McMahon, Gerard, Bales, J.D., Coles J.F., Giddings, E.M.P., and Zappia, Humbert. 2003. Use of stage data to characterize hydrologic conditions in an urbanizing environment. Journal of the American Water Resources Association 39(6): 1529-1546. 

Abstract: This paper presents the results of a study on the use of continuous stage data to describe the relation between urban development and three aspects of hydrologic condition that are thought to influence stream ecosystems—overall stage variability, stream flashiness, and the duration of extreme-stage conditions. This relation is examined using data from more than 70 watersheds in three contrasting environmental settings—the humid Northeast (the metropolitan Boston, Massachusetts, area); the very humid Southeast (the metropolitan Birmingham, Alabama, area); and the semiarid West (the metropolitan Salt Lake City, Utah, area). Results from the Birmingham and Boston studies provide evidence linking increased urbanization with stream flashiness. Fragmentation of developed land cover patches appears to ameliorate the effects of urbanization on overall variability and flashiness. There was less success in relating urbanization and streamflow conditions in the Salt Lake City study. A related investigation of six North Carolina sites with long term discharge and stage data indicated that hydrologic condition metrics developed using continuous stage data are comparable to flow based metrics, particularly for stream flashiness measures.

Access: Available online.

Steuer, J.J., Bales, J.D., and Giddings, E.M.P. 2009.  Relationship of stream ecological conditions to simulated hydraulic metrics across a gradient of basin urbanization, J. N. Am. Benthol. Soc., 28(4):955–976. 

Abstract: The relationships among urbanization, stream hydraulics, and aquatic biology were investigated across a gradient of urbanization in 30 small basins in eastern Wisconsin, USA. Simulation of hydraulic metrics with 1-dimensional unsteady flow models was an effective means for mechanistically coupling the effects of urbanization with stream ecological conditions (i.e., algae, invertebrates, and fish). Urbanization, characterized by household, road, and urban land density, was positively correlated with the lowest shear stress for 2 adjacent transects in a reach for the low-flow summer (p < 0.001) and autumn (p < 0.01) periods. Urbanization also was positively correlated with Reynolds number and % exposed stream bed during months with moderate to low flows. Our study demonstrated the value of temporally and spatially explicit hydraulic models for providing mechanistic insight into the relationships between hydraulic variables and biological responses. For example, the positive correlation between filter-feeding invertebrate richness and minimum 2-transect shear stress observed in our study is consistent with a higher concentration of water-column particulates available for filtration. The strength of correlations between hydraulic and biological metrics is related to the time period (annual, seasonal, or monthly) considered. The hydraulic modeling approach, whether based on hourly or daily flow data, allowed documentation of the effects of a spatially variable response within a reach, and the results suggest that stream response to urbanization varies with hydraulic habitat type.

Access: Available online through the DNR Library's subscriptions.

Taylor, B.L. 1993. The influences of wetland and watershed morphological characteristics and relationships to wetland vegetation communities. Master’s Thesis, Department of Civil Engineering, University of Washington, Seattle, Washington.

Key finding: Mean annual water fluctuation was inversely correlated to plant and amphibian density in urban wetlands. Sharp declines noted over 10% imperviousness (Seattle). 1

Access: DNR employees should contact the library to request via interlibrary loan.

Geomorphology   (return to top of page)

Allen P. and R. Narramore. 1985. Bedrock controls on stream channel enlargement with urbanization, North Central Texas. Water Resources Bulletin. 21(6): 1037-1048.

Key finding: Channels increase in size. Enlargement ratios in two urban TX streams ranged from 1.7 to 2.4. 2

Abstract: Loss due to channel erosion in the Dallas, Texas, area is estimated to approach one-half million dollars in the last several years. Hydrogeomorphic analysis of natural and urban chalk and shale watersheds was performed in the central Texas area on watersheds ranging in size from 0.5 to 10 square miles in an effort to more adequately predict channel enlargement due to urbanization. Chalk watersheds were found to have greater drainage density, greater channel slope, lower sinuosity, and greater discharge per unit area than similar sized shale watersheds under natural conditions. With subsequent urbanization of the watersheds, chalk channel enlargement was from 12 to 67 percent greater than shale channel enlargement for similar sized watersheds. Greater enlargement in chalk channels is attributed to greater channel velocities and unit tractive force. Vegetation seems to play a significant role in influencing channel adjustments to the new flow regimes brought on by urbanization. Channel response to urbanization is documented and specific nonstructural guidelines are proposed which could reduce structural loss along urban stream channels.

Access: DNR employees should contact the library to request via interlibrary loan.

Dartiguenave, C. M., ECLille, I., and D. R. Maidment. 1997. Water quality master planning for Austin. CRWR Online Report 97-6. 

Key finding: Increased transport of sediment. Bank erosion accounted for up to 75% of the sediment transport in Austin, TX study. 2

Abstract: The goal of this research is the creation of a non-point source pollution water quality model using a Geographic Information System. The area chosen for the study is the City of Austin, which partly overlays the recharge zone of the Edwards Aquifer. A model based on raster data that takes into account the presence of the recharge zone was created both in ArcView and in Arc/Info for mean annual flows and pollutant loadings. The model is able to perform the following tasks: 1) compute current pollutant loadings for TSS, BOD, COD, TOC, DP, TP, NH3, TKN, NO3, TN, Cu, Pb and Zn, 2) compute future loadings for the year 2040 for the same constituents, 3) model the effect of located and regional Best Management Practices. The model was designed so that it could deal with different sets of input parameters and locations.

Access: Available online.

Hammer, T. 1972. Stream channel enlargement due to urbanization. Water Resources Research 8(6): 1530-1540.

Key finding: Channels increase in size. Enlargement ratios ranged from 0.7 to 3.8 in urban watersheds in PA. 2

Abstract: Stream channel enlargement occurs in response to the change in streamflow regimen accompanying urbanization. This empirical study relates the imputed increase in channel crosssectional area to detailed land use data and other information for 78 small watersheds near Philadelphia. Important differences between the effects of various types of impervious land use are observed: large channel enlargement effects are found for sewered streets and area of major impervious parcels such as parking lots, and much smaller effects are observed for unsewered streets and impervious area involving detached houses. Relatively low channel enlargement effects are attributed to all types of impervious development less than 4 years old and also to street and house area more than 30 years old. The influence of impervious development on channel size is found to be significantly related to topographic characteristics of the watershed, to the location of impervious development within the watershed, and to manmade drainage alterations. Although the relative importance of these interactive factors proves difficult to establish, the most critical determinant of the amount of channel enlargement resulting from a given level of urbanization appears to be basin slope.

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MacRae, C., and M. DeAndrea, 1999. Assessing the impact of urbanization on channel morphology. 2nd International Conference on Natural Channel Systems. Niagara Falls, OT.

Key finding: Channels increase in size. Ultimate channel enlargement correlated with ultimate impervious cover.2

Summary: This research developed a methodology for placing a stream in its proper historical context in terms of channel enlargement. The MacRae and DeAndrea method utilizes historical and current data on stream crosssections and land use. Historic cross-sections are obtained from many sources including prior geomorphological research, engineering surveys or floodplain modeling. Current and historic impervious cover estimates are derived from low altitude aerial photographs taken at different intervals through the urbanization process. Using a basic hydraulic model, these data are used to characterize the pre-development and current cross-sections, and predict the ultimate cross-sections. An ultimate enlargement curve for 60 channel reaches of alluvial streams in Texas, Maryland and Vermont is presented in Figure A.2 of "Impervious cover and land use the the Chesapeake Bay watershed". 2

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Trimble, S. 1997. Contribution of stream channel erosion to sediment yield from an urbanizing watershed. Science 278: 1442-1444.

Key finding: Increased transport of sediment. Bank erosion accounted for over 66% of the sediment transport in a CA study. 2

Abstract: Stream channel erosion has long been suspected as the major contributor to long-term sediment yield from urbanizing watersheds. For San Diego Creek in southern California, measurements from 1983 to 1993 showed that stream channel erosion furnished 105 megagrams per year of sediment, or about two-thirds of the total sediment yield. Thus, because channel erosion can be a major source of sediment yield from urbanizing areas, channel stabilization should be a priority in managing sediment yield.

Access: Available online.

Walling, D., and J. Woodward. 1995. Tracing sources of suspended sediment in river basins: A case study of the River Culm, Devon, UK. Marine and Freshwater Research 46: 324-336.

Key finding: Increased transport of sediment. Bank erosion in agricultural regions only accounts for 5 to 20% of sediment load. 2

Abstract: Information on the source of the suspended sediment transported by a river is becoming an increasingly important requirement in sediment investigations. Such information is difficult to assemble by means of traditional monitoring strategies, but the 'fingerprinting' technique offers considerable potential. The use of composite 'fingerprints' in combination with a multivariate mixing model can provide a basis for determining the relative importance of both individual areas of a catchment and specific source types. The results of applying this approach to the 276-km² basin of the River Culm in Devon, UK are presented. A suite of nine fingerprint properties was employed as a composite fingerprint, and this permitted the relative contributions of seven source types to be established. These source types represented material derived from the surface af cultivated and pasture areas on each of the three main rock types and material eroded from channel banks. By collecting samples of suspended sediment at different times during individual floods, it was possible to document changes in the relative contributions of the various sources during each flood in response to runoff source and travel times. Although the multivariate fingerprint approach has a number of limitations, it also has considerable potential as a means of tracing sources of suspended sediment within a large drainage basin.

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Toxicity and Pesticides   (return to top of page)

Bryant , W.L., Jr., and Goodbred, S.L. 2008. The response of hydrophobic organics and potential toxicity in streams to urbanization of watersheds in six metropolitan areas of the United States. Environmental Monitoring and Assessment 157(1-4): 419-447.

Abstract: Semipermeable membrane devices (SPMDs) were deployed in streams along a gradient of urban land-use intensity in and around six metropolitan areas: Atlanta, Georgia; Raleigh–Durham, North Carolina; and Denver–Fort Collins, Colorado, in 2003; and Dallas–Fort Worth, Texas; Milwaukee–Green Bay, Wisconsin; and Portland, Oregon, in 2004 to examine relations between percent urban land cover in watersheds and the occurrence, concentrations, and potential toxicity of hydrophobic compounds. Of the 142 endpoints measured in SPMD dialysates, 30 were significantly (alpha = 0.05) related to the percent of urban land cover in the watersheds in at least one metropolitan area. These 30 endpoints included the aggregated measures of the total number of compounds detected and relative toxicity (Microtox® and P450RGS assays), in addition to the concentrations of 27 individual hydrophobic compounds. The number of compounds detected, P450RGS assay values, and the concentrations of pyrogenic polycyclic aromatic hydrocarbons (PAHs) were significantly related to percent urban land cover in all six metropolitan areas. Pentachloroanisole, the most frequently detected compound, was significantly related to urban land cover in all metropolitan areas except Dallas–Fort Worth. Petrogenic PAHs and dibenzofurans were positively related to percent urban land cover in Atlanta, Raleigh–Durham, Denver, and Milwaukee–Green Bay. Results for other endpoints were much more variable. The number of endpoints significantly related to urban land cover ranged from 6 in Portland to 21 Raleigh–Durham. Based on differences in the number and suite of endpoints related to urban intensity, these results provide evidence of differences in factors governing source strength, transport, and/or fate of hydrophobic compounds in the six metropolitan areas studied. The most consistent and significant results were that bioavailable, aryl hydrocarbon receptor agonists increase in streams as basins become urbanized. Potential toxicity mediated by this metabolic pathway is indicated as an important factor in the response of aquatic biota to urbanization.

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Sprague, L.A. and Nowell, L.H. 2008. Comparison of pesticide concentrations in streams at low flow in six metropolitan areas of the United States. Environmental Toxicology and Chemistry 27(2): 288-298.

Abstract: To examine the effect of urban development on pesticide concentrations in streams under low-flow conditions, water samples were collected at stream sites along an urban land use gradient in six environmentally heterogeneous metropolitan areas of the United States. In all six metropolitan areas, total insecticide concentrations generally increased significantly as urban land cover in the basin increased, regardless of whether the background land cover in the basins was agricultural, forested, or shrub land. In contrast, the response of total herbicide concentrations to urbanization varied with the environmental setting. In the three metropolitan areas with predominantly forested background land cover (Raleigh-Durham, NC, USA; Atlanta, GA, USA; Portland, OR, USA), total herbicide concentrations increased significantly with increasing urban land cover. In contrast, total herbicide concentrations were not significantly related to urban land cover in the three remaining metropolitan areas, where total herbicide concentrations appeared to be strongly influenced by agricultural as well as urban sources (Milwaukee-Green Bay, WI, USA; Dallas-Fort Worth, TX, USA), or by factors not measured in the present study, such as water management (Denver, CO, USA). Pesticide concentrations rarely exceeded benchmarks for protection of aquatic life, although these low-flow concentrations are likely to be lower than at other times, such as during peak pesticide-use periods, storm events, or irrigation discharge. Normalization of pesticide concentrations by the pesticide toxicity index -- an index of relative potential toxicity -- for fish and cladocerans indicated that the pesticides detected at the highest concentrations (herbicides in five of the six metropolitan areas) were not necessarily the pesticides with the greatest potential to adversely affect aquatic life (typically insecticides such as carbaryl, chlorpyrifos, diazinon, and fipronil).

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Nutrients and Chloride   (return to top of page)

Morgan, R. P., K. M. Kline, and S. F. Cushman.  2007.  Relationships among nutrients, chloride and biological indices in urban Maryland streams.  Urban Ecosystems 10:153-166.

Abstract: Using a spatially extensive urban database constructed from the Maryland Biological Stream Survey (MBSS), we describe the relationships of nutrients in small-order streams to eight defined categories of percent catchment urbanization, correlations between chloride and conductivity in urban streams, and relationships between nutrients and chloride with two Maryland-specific indices of biotic integrity for benthic macroinvertebrates and fish assemblages. Stream nutrients become elevated with increasing percent catchment urbanization, followed by increases in all four measured nitrogen species and total phosphorus at catchment urbanization levels greater than 10%. There was a strong collinear relationship (r 2=0.90) between chloride and conductivity (trimeans) across all eight urbanization classes, where Cl (mg/L)=−0.397+0.188*conductivity (μS/cm). Critical values for all water quality parameters with the two Maryland biological indices were derived using quantile regression, with significant regressions developed for 11 of 16 water quality parameters and the two biotic indices. For nitrate (NO3-N), the critical thresholds between fair and poor stream quality for the two Maryland biological indices were 0.83 mg/L (benthic macroinvertebrate assemblages) and 0.86 mg/L (fish assemblages). Increasing stream nutrient and chloride levels, associated with widespread catchment urbanization intensity, now affect many small streams in Maryland, with implications for decreasing water quality in major tributaries and the Chesapeake Bay.

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Salinity   (return to top of page)

Kaushal, S. S., P. M. Groffman, G. E. Likens, K. T. Belt, W. P. Stack, V. B. Kelly, L. E. Band, and G. T. Fisher.  2005.  Increased salinization of fresh water in the northeastern United States. Proceedings of the National Academy of Sciences 102:13517-13520. 

Abstract: Chloride concentrations are increasing at a rate that threatens the availability of fresh water in the northeastern United States. Increases in roadways and deicer use are now salinizing fresh waters, degrading habitat for aquatic organisms, and impacting large supplies of drinking water for humans throughout the region. We observed chloride concentrations of up to 25% of the concentration of seawater in streams of Maryland, New York, and New Hampshire during winters, and chloride concentrations remaining up to 100 times greater than unimpacted forest streams during summers. Mean annual chloride concentration increased as a function of impervious surface and exceeded tolerance for freshwater life in suburban and urban watersheds. Our analysis shows that if salinity were to continue to increase at its present rate due to changes in impervious surface coverage and current management practices, many surface waters in the northeastern United States would not be potable for human consumption and would become toxic to freshwater life within the next century.

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Bacteria   (return to top of page)

Mallin, M. A., K. E. Williams, E. C. Esham, and R. P. Lowe.  2000.  Effect of human development on bacteriological water quality in coastal watersheds. Ecological Applications 10:1047-1056. 

Abstract: Human development along the land–seawater interface is considered to have significant environmental consequences. Development can also pose an increased human health risk. In a rapidly developing coastal region we investigated this phenomenon throughout a series of five estuarine watersheds, each of which differed in both the amount and type of anthropogenic development. Over a four-year period we analyzed the abundance and distribution of the enteric pathogen indicator microbes, fecal coliform bacteria and Escherichia coli. We also examined how these indicator microbes were related to physical and chemical water quality parameters and to demographic and land use factors throughout this system of coastal creeks. Within all creeks, there was a spatial pattern of decreasing enteric bacteria away from upstream areas, and both fecal coliform and E. coli abundance were inversely correlated with salinity. Turbidity was positively correlated with enteric bacterial abundance. Enteric bacterial abundance was strongly correlated with nitrate and weakly correlated with orthophosphate concentrations. Neither fecal coliforms nor E. coli displayed consistent temporal abundance patterns. Regardless of salinity, average estuarine fecal coliform abundance differed greatly among the five systems. An analysis of demographic and land use factors demonstrated that fecal coliform abundance was significantly correlated with watershed population, and even more strongly correlated with the percentage of developed land within the watershed. However, the most important anthropogenic factor associated with fecal coliform abundance was percentage watershed-impervious surface coverage, which consists of roofs, roads, driveways, sidewalks, and parking lots. These surfaces serve to concentrate and convey storm-water-borne pollutants to downstream receiving waters. Linear regression analysis indicated that percentage watershed-impervious surface area alone could explain 95% of the variability in average estuarine fecal coliform abundance. Thus, in urbanizing coastal areas waterborne health risks can likely be reduced by environmentally sound land use planning and development that minimizes the use of impervious surface area, while maximizing the passive water treatment function of natural and constructed wetlands, grassy swales, and other “green” areas. The watershed approach used in our study demonstrates that the land–water interface is not restricted to obvious shoreline areas, but is influenced by and connected with landscape factors throughout the watershed.

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Habitat Characteristics   (return to top of page)

Booth, D. B., Montgomery, D.R., and J. Bethel. 1996. Large woody debris in the urban streams of the Pacific Northwest. Pp.In: Effects of Watershed Development and Management on Aquatic Ecosystems. Roesner, L.A. (ed.), Proceedings of ASCE/Engineering Foundation Conference. August, 1996. Snowbird, UT. 

Key finding: There is a decrease in the quantity of large woody debris found in urban streams at around 10% impervious cover (Washington). 2

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Booth, D. 1991. Urbanization and the natural drainage system—impacts, solutions, and prognoses. Northwest Environmental Journal 7(1):93–118. 

Key finding: Channel stability and fish habitat quality declined rapidly after 10% imperviousness (Seattle). 1

Abstract: Drainage systems consist of all of the elements of the landscape through which or over which water travels. These elements include the soil and the vegetation that grows on it, the geologic materials underlying that soil, the stream channels that carry water on the surface, and the zones where water is held in the soil and moves beneath the surface. Also included are any constructed elements, including pipes and culverts, cleared and compacted land surfaces, and pavement and other impervious surfaces that are not able to absorb water at all. A landscape can be divided into individual drainage basins, each of which contains all the elements of a drainage system that contribute water to one particular stream channel.

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Horner, R.R., Booth, D. B., Azous, A., and C. W. May.1996. Watershed determinants of ecosystem functioning. In: Effects of Watershed Development and Management on Aquatic Ecosystems. Roesner, L.A. (ed.), Proceedings of ASCE/Engineering Foundation Conference. August, 1996. Snowbird, UT.

Key finding: Embeddedness. Interstitial spaces between substrate fill with increasing watershed imperviousness. 2  

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Richey, J.S. 1982. Effects of urbanization on a lowland stream in urban Washington. PhD Dissertation. University of Washington.

Key finding: Changes in stream features. Altered pool/riffle sequence with urbanization. 2

Abstract: The effects of nonpoint source pollution due to urbanization and stormwater runoff on the structure and function of an urban stream in western Washington, Kelsey Creek, were investigated in comparison to a nearby, control stream, Bear Creek. The results of the study indicated that changes in stream hydrology and geomorphology were the critical agents in causing alterations in the ecological structure of the stream. Important changes in the hydrologic regime included increased peak flows, decreased minimum flows and an acceleration in hydrograph rise and fall. Constriction of the channel resulted in a substantial reduction in stream surface area, the space available for biotic activity. The number and size of debris dams, which provide storage sites and protected habitat, were greatly diminished. Higher stream power resulted in increased fluvial transport, channel erosion and bed instability.

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Scott, J., Steward, C., and Q. Stober. 1986. Effects of urban development on fish population  dynamics in Kelsey Creek, Washington. Transactions of the American Fisheries Society. 115:555-567.

Key finding: Changes in stream features. Loss of habitat diversity. 2

Abstract: A 30-month study of the comparative dynamics of the fish populations inhabiting Kelsey Creek, located in the City of Bellevue, Washington, and a nearby pristine control stream suggest that urban development has resulted in a restructuring of the fish community. Environmental perturbations, including habitat alteration, increased nutrient loading, and degradation of the intragravel environment appeared to have a greater impact on coho salmon Oncorhynchus kisutch and nonsalmonid fish species than on cutthroat trout Salmo clarki. Although the total biomass (g/m2) of fish in each stream was similar, its composition differed markedly. Ages 0 and I cutthroat trout were the majority of the fish community inhabiting Kelsey Creek, whereas the control stream supported a diverse assemblage of salmonids of various ages and numerous nonsalmonids. The rapid growth and greater biomass of salmonids in Kelsey Creek (a 2-year mean of 3.51 g/m2 versus 2.03 g/m2 in the control stream) resulted in a total annual net production of these species of 1.6 to 3.3 times that of the control stream (a 2-year mean of 7.6 g/m2 versus 3.5 g/m2 in the control stream). Marking and outmigrant studies indicated that environmental disruptions in the urban stream do not result in the displacement of the salmonid inhabitants.

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Spence, B., Lomnicky, G., Hughes, R., and R. Novitzki. 1996. An ecosystem approach to salmonid conservation. TR-401-96-6057. ManTech Environmental Research Services Corporation, Corvallis, OR.

Key finding: Large woody debris. Important for habitat diversity and anadramous fish. 2

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Short, T.M., Giddings, E.M.P., Zappia, H., Coles, J.F. 2005. Urbanization effects on habitat characteristics of streams in Boston, Massachusetts, Birmingham, Alabama, and Salt Lake City, Utah. In Brown, L.R., Gray, R.H., Hughes, R.M., and Meador, M.R., eds., Effects of urbanization on stream ecosystems. American Fisheries Society, Symposium 47, Bethesda, Maryland, p. 317-332. 

Abstract: Relations between stream habitat and urban land-use intensity were examined in 90 stream reaches located in or near the metropolitan areas of Salt Lake City, Utah (SLC); Birmingham, Alabama (BIR); and Boston, Massachusetts (BOS). Urban intensity was based on a multi-metric index (urban intensity index or UII) that included measures of land cover, socioeconomic organization, and urban infrastructure. Twenty-eight physical variables describing channel morphology, hydraulic properties, and streambed conditions were examined. None of the habitat variables was significantly correlated with urbanization intensity in all three study areas. Urbanization effects on stream habitat were less apparent for streams in SLC and BIR, owing to the strong influence of basin slope (SLC) and drought conditions (BIR) on local flow regimes. Streamflow in the BOS study area was not unduly influenced by similar conditions of climate and physiography, and habitat conditions in these streams were more responsive to urbanization. Urbanization in BOS contributed to higher discharge, channel deepening, and increased loading of fine-grained particles to stream channels. The modifying influence of basin slope and climate on hydrology of streams in SLC and BIR limited our ability to effectively compare habitat responses among different urban settings and identify common responses that might be of interest to restoration or water management programs. Successful application of land-use models such as the UII to compare urbanization effects on stream habitat in different environmental settings must account for inherent differences in natural and anthropogenic factors affecting stream hydrology and geomorphology. The challenge to future management of urban development is to further quantify these differences by building upon existing models, and ultimately develop a broader understanding of urbanization effects on aquatic ecosystems.

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Thermal Impacts   (return to top of page)

Galli, J. 1991. Thermal impacts associated with urbanization and stormwater management best management practices. Metropolitan Washington Council of Governments, Maryland Department of Environment, Washington, D.C.

Key finding: Temperature. Increase in stream temperatures five to twelve degrees Fahrenheit with urbanization (check figures) 2

Access: Available online.  Also available at the DNR Library.

Direct Channel Impacts   (return to top of page)

Dunne T., and L. Leopold. 1978. Water in environmental planning. W.H. Freeman and Company, New York, NY.

Key finding: Reduction in 1st Order Streams. Replacement by storm drains and pipes increases erosion rate downstream. 2

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Metropolitan Washington Council of Governments (MWCOG), 1992. Watershed restoration sourcebook. Department of Environmental Programs, MWCOG, Washington, DC.

Key finding: Fish blockages. Fish blockages caused by bridges and culverts. 2

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Sauer, V. 1983. Flood characteristics of urban watersheds in the United States. US Geological Survey Water Supply Paper 2207.

Key finding: Channelization and hardening of stream channels. Increased instream velocities often leading to increased erosion rates downstream. 2

Abstract: A nationwide study of flood magnitude and frequency in urban areas was made for the purpose of reviewing available literature, compiling an urban flood data base, and developing methods of estimating urban floodflow characteristics in ungaged areas. The literature review contains synopses of 128 recent publications related to urban floodflow. A data base of 269 gaged basins in 56 cities and 31 states, including Hawaii, contains a wide variety of topographic and climatic characteristics, land-use variables, indices of urbanization, and flood-frequency estimates.

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Aquatic Habitat Integrity   (return to top of page)

Black and Veatch. 1994. Longwell Branch Restoration-Feasibility Study. Vol. 1. Carroll County, MD Office of Environmental Services. 220 p.

Key finding: Fish, insect, and habitat scores were all ranked as poor in 5 subwatersheds that were greater than 30% imperviousness (Maryland). 1

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Boward, D., Kayzak, P., Stranko, S., Hurd, M., and T. Prochaska. 1999. From the mountains to the sea: The state of Maryland’s freshwater streams. EPA 903-R-99-023. Maryland Department of Natural Resources, Monitoring and Non-tidal Assessment Division, Annapolis, Maryland. 

Key finding: Several sensitive species of amphibians were not found at impervious levels greater than 3%. Only a few intolerant species were found at impervious levels greater than 25%. Brook trout were not found in watersheds with greater than 2% imperviousness (Maryland). 2

Summary: In The Mountains to the Sea: the State of Maryland’s Freshwater Streams, the Maryland Department of Natural Resources (MDDNR) provides information on the status of the biological community in the state’s streams. The relationship between land use and impervious cover is examined for fish, macroinvertebrates, amphibians and other sensitive species. Above a 15% impervious cover threshold, streams were found to have a poor or fair biological condition. Sensitive species, such as the native brook trout, were shown to disappear beyond two percent impervious cover. Other relationships between land use and stream water quality are covered in the document as well. 2

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Coles, J.F., Cuffney, T.F., McMahon, G., and Rosiu, C.J. 2010. Judging a brook by its cover - the relation between ecological condition of a stream and urban land cover in New England. Northeastern Naturalist 17(1): 29-48.

Abstract: The US Geological Survey conducted an urban land-use study in the New England Coastal Basins (NECB) area during 2001 to determine how urbanization relates to changes in the ecological condition of streams. Thirty sites were selected that differed in their level of watershed development (low to high). An urban intensity value was calculated for each site from 24 landscape variables. Together, these 30 values represented a gradient of urban intensity. Among various biological, chemical, and physical factors surveyed at each site, benthic invertebrate assemblages were sampled from stream riffles and also from multiple habitats along the length of the sampling reach. We use some of the NECB data to derive a four-variable urbanintensity index (NECB-UII), where each variable represents a distinct component of urbanization: increasing human presence, expanding infrastructure, landscape development, and riparian vegetation loss. Using the NECB-UII as a characterization of urbanization, we describe how landscape fragmentation occurs with urbanization and how changes in the invertebrate assemblages, represented by metrics of ecological condition, are related to urbanization. Metrics with a strong linear response included EPT taxa richness, percentage richness of non-insect taxa, and pollution-tolerance values. Additionally, we describe how these relations can help in estimating the expected condition of a stream for its level of urbanization, thereby establishing a baseline for evaluating possible affects from specific point-source stressors.

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Crawford, J., and D. Lenat. 1989. Effects of land use on water quality and the biota of three streams in the Piedmont Province of North Carolina. USGS. Water Resources Investigations Report 89-4007. Raleigh, NC, 67 pp.

Key finding: A comparison of three stream types found urban streams had lowest diversity and richness. Urban streams had substantially lower EPT scores (22% vs 5% as the number of all taxa, 65% vs 10% as a percent abundance) and IBI scores in the poor range (North Carolina). 2

Abstract: Three small streams in North Carolina 's northern Piedmont were studied to compare the effects of land use in their watersheds on water quality characteristics and aquatic biota. Devil 's Cradle Creek (agricultural watershed) had more than two times the sediment yield of Smith Creek (forested watershed) (0.34 tons/acre compared to 0.13 tons/acre), and Marsh Creek (urban watershed) had more than four times the yield of Smith Creek (0.59 tons/acre). Concentrations of nutrients were consistently highest in Devil 's Craddle Creek. Concentrations of total copper, iron, and lead in samples from each of the three streams at times exceeded State water quality standards as did concentrations of total zinc in samples from both Smith and Marsh Creeks. Successively lower aquatic invertebrate taxa richness was found in the forested, the agricultural, and the urban watershed streams. Invertebrate biota in Smith Creek was dominated by insects, such as Ephemeroptera, that are intolerant to stress from pollution, whereas Devil 's Cradle Creek was dominated by the more tolerant Diptera, and Marsh Creek was dominated by the most pollution-tolerant group, the Oligochaeta. Fish communities in the forested and agricultural watershed streams were characterized by more species and more individuals of each species, relative to a limited community in urban Marsh Creek. Three independent variables closely linked to land use--suspended-sediment yield, suspended-sediment load, and total lead concentrations in stream water--are inversely associated with the biological communities of the streams.

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DeVivo, J.C., Couch, C.A., and B. J. Freeman. 1997. Use of Preliminary Index of Biotic Integrity in Urban Streams around Atlanta, Georgia. Pp. 40-43 in 1997 Georgia Water Resources Conference.

Key finding: As watershed population density increased, there was a negative impact on urban fish and habitat. Urban stream IBI scores were inversely related to watershed population density, and once density exceeded four persons per acre, urban streams were consistently rated as very poor (Atlanta). 2

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Klein, R. 1979. Urbanization and stream quality impairment. American Water Resources Association. Water Resources Bulletin. 15(4): 948-963.

Key finding: Macroinvertebrate and fish diversity declines rapidly after 10% imperviousness (Maryland). 1

Abstract: A study was conducted in the Piedmont province of Maryland to determine if a relationship exists between stream quality and the extent of watershed urbanization. During the first phase of the study 27 small watersheds, having similar characteristics but varied according to land use, were investigated. Using these controlled conditions, eliminating as many interferences as possible, this first phase was intended to determine if a definite relationship did exist between the two factors. Finding that the first phase was successful the second was initiated which consisted of a comparison of biological sampling data, from other studies, with degree of watershed urbanization. The purpose of this second phase was to ascertain if the relationship between degrees of urbanization and decline in stream quality was linear as watershed area increased and in streams spread throughout the Maryland Piedmont. The principal finding of this study was that stream quality impairment is first evidenced when watershed imperviousness reaches 12%, but does not become severe until imperviousness reaches 30%.

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Masterson, J. P., and R. T. Bannerman. 1994. Impacts of stormwater runoff on urban streams in Milwaukee County, Wisconsin. National Symposium on Water Quality. American Water Resources Association.

Key finding: A study of five urban streams found that as land use shifted from rural to urban, fish and macroinvertebrate diversity decreased (Wisconsin). 2

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Schueler, T. and J. Galli. 1992. Environmental impacts of stormwater ponds. In Watershed Restoration SourceBook. Anacostia Restoration Team. Metropolitan Washington Council of Governments. Washington, DC. 242 p. 

Key finding: Fish diversity declined sharply with increasing imperviousness, loss in diversity began at 10% to 12% imperviousness. Insect diversity metrics in 24 subwatersheds shifted from good to poor over 15% imperviousness (Maryland).1

Access: Available in DNR Library.

Steedman, R.J. 1988. Modification and assessment of an index of biotic integrity to quantify stream quality in southern Ontario. Canadian Journal of Fisheries and Aquatic Sciences 45:492–501.

Key finding: Strong negative relationship between biotic integrity and increasing urban land use/riparian condition at 209 stream sites. Degradation begins at about 10% imperviousness (Ontario). 1

Abstract: A multivariate measure of stream quality, the Index of Biotic Integrity (IBI), was adapted to southern Ontario and calibrated to watershed land use on a variety of spatial scales. The fish fauna at 209 stream locations on 10 watersheds near Toronto, Ontario, was sampled with a backpack electrofisher in the summers of 1984 and 1985 to provide biological information for the IBI. Watershed urbanization, forest cover, and riparian forest were measured from 1:50,000 scale topographic maps and related to IBI estimates by linear regression.

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Wang, L., Lyons, J., Kanehl, P., and R. Gatti. 1997. Influences of watershed land use on habitat quality and biotic integrity in Wisconsin streams. Fisheries 22 (6) :6-11.

Key finding: Amount of urban land use upstream of sample sites had a strong negative relationship with biotic integrity, and there appeared to be a threshold between 10-20% urban land use where IBI scores declined dramatically. Watersheds above 20% urban land invariably had scores less than 30 (poor to very poor) (Wisconsin). 2

Abstract: We analyzed relationships between watershed land use and habitat quality, and between watershed land use and biotic integrity for 134 sites on 103 streams located throughout Wisconsin. Habitat quality and index of biotic integrity (IBI) scores were significantly positively correlated with the amount of forested land and negatively correlated with the amount of agricultural land in the entire watershed and in a 100-m-wide buffer along the stream. Correlations were generally stronger for the entire watershed than for the buffer. Relationships between forested land and habitat and biotic integrity were linear, although there were several outlying sites with lower-than-expected IBI scores. Relationships with agricultural land use were more complex, with an obvious decline in habitat quality and IBI scores apparent only when agricultural land use exceeded 50%. Even when agricultural land use exceeded 80%, some sites maintained relatively good habitat quality and biotic integrity. These “good” sites tended to have relatively high gradients and rocky substrates, and had not been channelized. High urban land use was strongly associated with poor biotic integrity and was weakly but significantly associated with poor habitat quality. There appeared to be a threshold value of urbanization between 10% and 20% beyond which IBI scores were consistently very low. Overall, watershed land uses had strong effects on habitat quality and biotic integrity in Wisconsin streams.

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Yoder, C., and R. Miltner. 2000. Using biological criteria to assess and classify urban streams and develop improved landscape indicators. In Proceedings of the National Conference on Tools for Urban Water Resource Management & Protection: Published by the US Environmental Protection Agency, Office of Research and Development, Washington, D.C. 

Key finding: For watersheds smaller than 100 mi2 a significant drop in IBI scores occurred at around 15% imperviousness (Ohio).2

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Yoder, C.O., R. Miltner, and D. White. 1999. Assessing the status of aquatic life designated uses in urban and suburban watershed. In R. Kirschner (Ed.). National Conference on Retrofit Opportunities for Water Resource Protection in Urban Environments. EPA/625/R-99/002. 

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Yoder, C. 1991. The integrated biosurvey as a tool for evaluation of aquatic life use attainment and impartment in Ohio surface waters. In Biological Criteria: Research and Regulation, Proceedings of a Symposium, 12-13 December 1990, Arlington, VA, U.S. EPA, Office of Water, Washington, DC, EPA-440/5-91-005:110. 

Key finding: 100% of 40 urban sites sampled had fair to very poor index of biotic integrity scores (Ohio). 1

Access: Available at the DNR Library.

Benthic Macroinvertebrates   (return to top of page)

Benke, A.E., Willeke, F.P., and D. Stites. 1981. Effects of urbanization on stream ecosystems.  Completion Report Project No. A-055-GA. Office of Water Research and Technology. US Dept. of Interior.

Key finding: Negative relationship between number of aquatic insect species and urbanization in 21 streams (Atlanta).1

Abstract: The effects of urbanization on 21 stream ecosystems were studied in the Atlanta area in 1-3 sq mile watersheds varying from 3-100 % green space, from 0-98% residential-commercial, and with house densities from 0-941 sq miles. The primary index of stream quality was community composition of aquatic macroinvertebrates. The streams were in a single area where physico-chemical conditions and composition of macroinvertebrates should be very similar under natural conditions. While there were widely-varying degrees of urbanization, pollution (as indicated by standard water quality measures) was not at all obvious, and differentiation of stream communities was more subtle than is often encountered in studies of gross pollution. A significant relationship was found between urbanization and number of species/families (but not with species/family diversity, indicating less utility for a diversity index). Hence, identifying macroinvertebrates to the family level is sufficient in assessing differing degrees of stress in streams. Cluster analysis distinguished three major groups of streams: clean, intermediate, and degraded. High residential land use, low levels of green space, and high house densities were associated with degraded streams. (Zielinski-MAXIMA)

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Cuffney, T.F., Brightbill, R.A., May, J.T., and Waite, IR. 2010. Responses of benthic macroinvertebrates to environmental changes associated with urbanization in nine metropolitan areas. Ecological Applications 20(5): 1384–1401.

Abstract: Responses of benthic macroinvertebrates along gradients of urban intensity were investigated in nine metropolitan areas across the United States. Invertebrate assemblages in metropolitan areas where forests or shrublands were being converted to urban land were strongly related to urban intensity. In metropolitan areas where agriculture and grazing lands were being converted to urban land, invertebrate assemblages showed much weaker or nonsignificant relations with urban intensity because sites with low urban intensity were already degraded by agriculture. Ordination scores, the number of EPT taxa, and the mean pollution-tolerance value of organisms at a site were the best indicators of changes in assemblage condition. Diversity indices, functional groups, behavior, and dominance metrics were not good indicators of urbanization. Richness metrics were better indicators of urban effects than were abundance metrics, and qualitative samples collected from multiple habitats gave similar results to those of single habitat quantitative samples (riffles or woody snags) in all metropolitan areas. Changes in urban intensity were strongly correlated with a set of landscape variables that was consistent across all metropolitan areas. In contrast, the instream environmental variables that were strongly correlated with urbanization and invertebrate responses varied among metropolitan areas. The natural environmental setting determined the biological, chemical, and physical instream conditions upon which urbanization acts and dictated the differences in responses to urbanization among metropolitan areas. Threshold analysis showed little evidence for an initial period of resistance to urbanization. Instead, assemblages were degraded at very low levels of urbanization, and response rates were either similar across the gradient or higher at low levels of urbanization. Levels of impervious cover that have been suggested as protective of streams (5–10%) were associated with significant assemblage degradation and were not protective.

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Cuffney, T.F., Zappia, H., Giddings, E.M.P., and Coles. J.F. 2005. Effects of urbanization on benthic macroinvertebrate assemblages in contrasting environmental settings: Boston, Massachusetts; Birmingham, Alabama; and Salt Lake City, Utah. In Brown, L.R., Gray, R.H., Hughes, R.M., and Meador, M.R., eds., Effects of urbanization on stream ecosystems, American Fisheries Society, Symposium 47, Bethesda, Maryland, p. 361-407. 

Abstract: Responses of invertebrate assemblages along gradients of urban intensity were examined in three metropolitan areas with contrasting climates and topography (Boston, Massachusetts; Birmingham, Alabama; Salt Lake City, Utah). Urban gradients were defined using an urban intensity index (UII) derived from basin-scale population, infrastructure, land-use, land-cover, and socioeconomic characteristics. Responses based on assemblage metrics, indices of biotic integrity (B-IBI), and ordinations were readily detected in all three urban areas and many responses could be accurately predicted simply using regional UIIs. Responses to UII were linear and did not indicate any initial resistance to urbanization. Richness metrics were better indicators of urbanization than were density metrics. Metrics that were good indicators were specific to each study except for a richness based tolerance metric (TOLr) and one B-IBI. Tolerances to urbanization were derived for 205 taxa. These tolerances differed among studies and with published tolerance values, but provided similar characterizations of site conditions. Basin-scale land-use changes were the most important variables for explaining invertebrate responses to urbanization. Some chemical and instream physical habitat variables were important in individual studies, but not among studies. Optimizing the study design to detect basin-scale effects may have reduced the ability to detect local-scale effects.

Access: Available online.

Garie, H. and A. McIntosh. 1986. Distribution of benthic macroinvertebrates in streams exposed to urban runoff. Water Resources Bulletin 22: 447-458.

Key finding: Drop in aquatic insect taxa from 13 to 4 noted in urban streams (New Jersey). 1

Abstract: A study of benthic macroinvertebrate community composition was conducted at eight sites along Shabakunk Creek, a small stream in Mercer County, New Jersey, which receives urban runoff. The relationship between changes in substrate composition and the nature of the benthic macroinvertebrate community has been examined. Organisms were collected seasonally from natural substrates in riffles. Attempts to employ artificial substrates for invertebrate collection proved unsuccessful, as the population on the samplers was not representative of that in the stream bed. Number of total benthic macroinvertebrate taxa collected declined from 13 in relatively undeveloped upstream areas to four below heavily developed areas, while population density decreased simultaneously in the same areas. Periphyton samples collected from natural substrates were analyzed for selected heavy metals. Significantly higher heavy metal concentrations are reported from substrates sampled below heavily developed areas, and changes in these values are discussed with regard to changes in benthic macroinvertebrate distribution.

Access: DNR employees should contact the library to request via interlibrary loan.

Hicks, A.L., and J.S. Larson. 1997. The impact of urban stormwater runoff on freshwater wetlands and the role of aquatic invertebrate bioassessment. The Environment Institute, University of Massachusetts. Amherst, MA.

Key finding: Significant declines in various indicators of wetland aquatic macroinvertebrate community health were observed as impervious cover increased to 8-9% (Connecticut). 2

            Access: DNR employees should contact the library to request via interlibrary loan.

Horner, R.R., Booth, D. B., Azous, A., and C. W. May. 1996. Watershed determinants of ecosystem functioning. In: Effects of Watershed Development and Management on Aquatic Ecosystems. Roesner, L.A. (ed.), Proceedings of ASCE/Engineering Foundation Conference. August, 1996. Snowbird, UT.

Key finding: Biological health of the macroinvertebrate community declined as imperviousness increased. It appears that stormwater treatment practices (STPs) are capable of mitigating some of these impacts within the 12-23% I range. Above this range, declines in biological condition continue at a similar rate to sites without STPs. Evidence suggests that if high levels of riparian forest or wetlands >30m are saved, a doubling in total impervious area could occur while still maintaining high B-IBI and fish ratio scores.  Steepest decline of biological functioning after 6% imperviousness. There was a steady decline, with approx 50% of initial biotic integrity at 45% impervious area. (Puget Sound, Washington). 2

            Access: DNR employees should contact the library to request via interlibrary loan.

Jones, R. and C. Clark. 1987. Impact of watershed urbanization on stream insect communities. Water Resources Bulletin 23(6): 1047-1055.

Key finding: Urban streams had sharply lower diversity of aquatic insects when human population density exceeded 4 persons per acre (estimated 15% to 25% impervious cover.) (Northern Virginia). 1

Abstract: The impact of urbanization on stream insect communities was determined by sampling 22 sites in northern Virginia representing a range of human population densities. Watershed development had little effect on the total insect numbers (no./sq m), but shifted the taxonomic composition markedly. Relative abundance of Diptera (mainly chironomids) increased at more highly urbanized sites, while most other insect orders including Ephemeroptera (mayflies), Coleoptera (beetles), Megaloptera (dobsonflies), and Plecoptera (stoneflies) decreased. Trichoptera (caddisflies) exhibited a variable response. Genus diversity and richness (number of genera) were significantly higher in less urbanized streams. Two genera of chironomids were positively correlated with increased urbanization, while 14 other genera (scattered through several orders) were negatively related to human population density. Principal components analysis demonstrated a gradient from more urbanized to less urbanized stations based on generic and order level biological data. Results indicate that watershed urbanization has a major impact on benthic insect communities even in the absence of point source discharges.

            Access: DNR employees should contact the library to request via interlibrary loan.

Moore, A. A., and M. A. Palmer.  2005.  Invertebrate biodiversity in agricultural and urban headwater streams: implications for conservation and management.  Ecological Applications 15:1169-1177. 

Abstract: The urbanization of agricultural lands is currently one of the dominant patterns of land use change in developed countries. In the United States and parts of Europe, this has led to the implementation of agricultural land preservation programs and riparian protection and replanting efforts along urban streams. The ecological benefits of such programs for the conservation of freshwater biodiversity have yet to be fully explored. We designed a study to investigate the patterns of stream macroinvertebrate community structure along a gradient of agriculture to urban development, and the patterns among urban streams that vary in the amount of intact riparian buffer. In 2001 and 2002, we sampled the 29 small headwater streams comprising the outlying tributaries of four watersheds just north of Washington, D.C., in Montgomery County, Maryland, USA. This region has had dramatic urban development over the last 50 years, yet significant efforts have been made to maintain riparian buffers and promote preservation of agricultural land. Macroinvertebrate richness was strongly related to land use, with agricultural streams exhibiting the highest macroinvertebrate diversity. Taxa richness was related negatively and linearly (no statistical threshold) to the amount of impervious surface cover. For the urban streams, there was a strong positive relationship between invertebrate diversity and riparian forest cover. Urban streams with high amounts of intact riparian forest exhibited biodiversity levels more comparable to less urban areas despite high amounts of impervious cover in their catchments. The agricultural headwater streams in this study were not only more diverse than the urban headwaters, but their levels of macroinvertebrate diversity were high compared to other published estimates for agricultural streams. These higher richness values may be due to widespread use of “best management practices” (BMPs), including no-till farming and the implementation of woody and herbaceous riparian buffers, which may alleviate many acute stressors caused by cultivation. These findings suggest that, if managed properly, the preservation of agricultural land from development may help conserve stream invertebrate biodiversity, and that maintenance of riparian forests even in highly urbanized watersheds may help alleviate ecological disturbances that might otherwise limit macroinvertebrate survival.

Access: Available online.

Pedersen, E. and M. Perkins. 1986. The use of benthic invertebrate data for evaluating impacts of urban runoff. Hydrobiologia. 139: 13-22.

Key finding: Macroinvertebrate community shifted to chironomid, oligochaetes, and amphipod species tolerant of unstable conditions (Seattle). 1

Abstract: The benthic macroinvertebrate population of a stream in an urbanized watershed was compared to the benthos in a rural stream. Using buried samplers, no significant difference between streams was found in total numbers of invertebrates, indicating no long term loss of colonization potential in the urban stream. Classifying the benthos in functional family groupings (based on Cummins, 1973) showed the rural stream to have nearly twice the functional diversity of the urban stream. The benthos of the urban stream was dominated by a few groups of invertebrates which could adapt to the erosional/depositional nature of the substrate and could utilize transient, low quality food sources. The density of invertebrates was adequate to support a coho salmon and cutthroat trout population in the urban stream. Apparently, the salmonids feed on available benthos and do not select specific benthic trophic groups. An evaluation of six similarity coefficients using cluster analysis showed that only the Canberra Metric index was able to represent the raw data according to known data associations.

            Access: DNR employees should contact the library to request via interlibrary loan.

Shaver, E., J.Maxted, G. Curtis, and D. Carter. 1995. Watershed protection using an integrated approach. In Stormwater NPDES-related Monitoring Needs. Engineering Foundation. Crested Butte, Colorado. August 7–12, 1994. American Society of Civil Engineers. 

Key finding: Insect diversity at 19 stream sites dropped sharply at 8% to 15% imperviousness.  Strong relationship between insect diversity and habitat quality; majority of 53 urban streams had poor habitat (Delaware). 1

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Fish   (return to top of page)

Brown, L.R., Gregory, M.B., and May, J.T. 2009. Relation of urbanization to stream fish assemblages and species traits in nine metropolitan areas of the United States. Urban Ecosystems 12(4): 391-416.

Abstract: We examined associations of fish assemblages and fish traits with urbanization and selected environmental variables in nine major United States metropolitan areas. The strongest relations between fishes and urbanization occurred in the metropolitan areas of Atlanta, Georgia; Birmingham, Alabama; Boston, Massachusetts; and Portland, Oregon. In these areas, environmental variables with strong associations (rs0.70) with fish assemblages and fish traits tended to have strong associations with urbanization. Relations of urbanization with fish assemblages and fish traits were weaker in Denver, Colorado; Dallas-Fort Worth, Texas; Milwaukee-Green Bay, Wisconsin; and Raleigh, North Carolina. Environmental variables associated with fishes varied among the metropolitan areas. The metropolitan areas with poor relations may have had a limited range of possible response because of previous landscape disturbances. Given the complexities of urban landscapes in different metropolitan areas, our results indicate that caution is warranted when generalizing about biological responses to urbanization.

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Dreher, D.W. 1997. Watershed urbanization impacts on stream quality indicators in Northeastern Illinois. pages 129-135 In D. Murray and R. Kirshner (Eds.) Assessing the cumulative impacts of watershed development on aquatic ecosystems and water quality. Northeastern Illinois Planning Commission. Chicago, IL. 

Key finding: There is a strong correlation between population density and fish community assessments such that as population density increased, community assessment scores went from the better-good range to fair-poor (Illinois). 2

Access: DNR employees should contact the library to request via interlibrary loan.

Galli, J. 1991. Thermal impacts associated with urbanization and stormwater management best management practices. Metropolitan Washington Council of Governments, Maryland Department of Environment, Washington, D.C.

Key finding: Abundance and recruitment of brown trout declines sharply at 10% to 15% imperviousness (Maryland). 1 

Access: Available online.  Also available at the DNR Library.

Fraker, Michael E., Snodgrass, J.W., and Morgan, F. 2001. Differences in Growth and Maturation of Blacknose Dace (Rhinichthys atratulus) across an Urban-Rural Gradient. Copeia 2002(4):1122-1127.

Abstract: To investigate changes in the biology of blacknose dace (Rhinichthys atratulus) populations accompanying watershed urbanization, we sampled dace from four watersheds in the Baltimore, Maryland area, representing a gradient from urbanized to rural conditions. Dace from the most urbanized watershed grew to greater standard lengths during their first year of life when compared to dace from other watersheds but grew little during their second year. Dace from the other watersheds showed slower growth during their first year but continued to grow through age II. Approximately 90% of age I dace from the most urbanized watershed were mature at age I, whereas only 25% of age I dace from the other watersheds were mature. Dace from the most urbanized watershed also reached maturity at shorter standard lengths than dace from the other watersheds. Growth and maturation of dace from the most rural watershed were similar to those reported for dace from other regions. We conclude that watershed urbanization results in increased growth rates of young blacknose dace, and in heavily urbanized (. 90% urban land use) watersheds, decreased age and size at maturity.

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King, R.S., J.R. Beaman, D.F. Whigham, A.H. Hines, M.E. Baker, and D.E. Weller.  2004.  Watershed land use is strongly linked to PCBs in white perch in Chesapeake Bay subestuaries.  Environmental Science and Technology 38:6546-6552. 

Abstract: We related total PCBs (t-PCBs) in white perch (Morone americana), an abundant estuarine resident that supports a valuable recreational and commercial fishery in the mid-Atlantic region, to the amount and spatial arrangement of developed land in watersheds that discharge into 14 subestuaries of Chesapeake Bay. We considered the intensity of development in watersheds using four developed land-use measures (% impervious surface, % total developed land, % high-intensity residential + commercial [%high-res/comm], and % commercial) to represent potential source areas of PCBs to the subestuaries. We further evaluated the importance of source proximity by calculating three inverse-distance weighted (IDW) metrics of development, an approach that weighted developed land near the shoreline more heavily than developed land farther away. Unweighted percentages of each of the four measures of developed land explained 51−69% of the variance in t-PCBs. However, IDWs markedly improved the relationships between % developed land measures and t-PCBs. Percent commercial land, weighted by its simple inverse distance, explained 99% of the variance in t-PCBs, whereas the other three measures explained as much as 93−97%. PCBs historically produced or used in commercial and residential areas are apparently persisting in the environment at the scale of the watersheds and subestuaries examined in this study, and developed land close to the subestuary has the greatest unit effect on t-PCBs in fish. These findings provide compelling evidence for a strikingly strong linkage between watershed land use and t-PCBs in white perch, and this relationship may prove useful for identifying unsampled subestuaries with a high risk of PCB contamination.

Access: Available online.

Limburg, K.E. and R. E. Schmidt. 1990. Patterns of fish spawning in Hudson River tributaries: response to an urban gradient? Ecology 71:1238-1245. 

Key finding: Resident and anadromous fish eggs and larvae declined sharply in 16 tributary streams greater than 10% imperviousness (New York). 1

Abstract: Large rivers are not well understood with respect to ecological patterns and processes. Although some generalizations have been made, the geographic scope of large rivers presents considerable sampling difficulties for evaluation of many system-wide phenomena. Furthermore, studies of large rivers often fail to consider interactions between the lotic portion and surrounding watershed. Two features of many large river watersheds, their large geographic extent and their occupation and use by humans, should render them good candidates for the manifestation of anthropogenic, ecological gradients. One approach is to examine properties of tributary watersheds within the overall drainage basin, as a function of urbanization. We demonstrate the approach with a study conducted to evaluate the contribution of nontidal tributaries to anadromous fish spawning within a large, riverine estuary.

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Meador, M.R., Coles, J.F., and Zappia, H. 2005. Fish assemblage responses to urban intensity gradients in contrasting metropolitan areas: Birmingham, Alabama, and Boston, Massachusetts.  In Brown, L.R., Gray, R.H., Hughes, R.M., and Meador, M.R., eds., Effects of urbanization on stream ecosystems. American Fisheries Society, Symposium 47, Bethesda, Maryland, p. 409-423.

Abstract: We examined fish assemblage responses to urban intensity gradients in two contrasting metropolitan areas: Birmingham, Alabama (BIR) and Boston, Massachusetts (BOS). Urbanization was quantified by using an urban intensity index (UII) that included multiple stream buffers and basin land uses, human population density, and road density variables. We evaluated fish assemblage responses by using species richness metrics and detrended correspondence analyses (DCA). Fish species richness metrics included total fish species richness, and percentages of endemic species richness, alien species, and fluvial specialist species. Fish species richness decreased significantly with increasing urbanization in BIR (r = –0.82, P = 0.001) and BOS (r = –0.48, P = 0.008). Percentages of endemic species richness decreased significantly with increasing urbanization only in BIR (r = – 0.71, P = 0.001), whereas percentages of fluvial specialist species decreased significantly with increasing urbanization only in BOS (r = –0.56, P = 0.002). Our DCA results for BIR indicate that highly urbanized fish assemblages are composed primarily of largescale stoneroller Campostoma oligolepis, largemouth bass Micropterus salmoides, and creek chub Semotilus atromaculatus, whereas the highly urbanized fish assemblages in BOS are dominated by yellow perch Perca flavescens, bluegill Lepomis macrochirus, yellow bullhead Ameiurus natalis, largemouth bass, pumpkinseed L. gibbosus, brown bullhead A. nebulosus, and redfin pickerel Esox americanus. Differences in fish assemblage responses to urbanization between the two areas appear to be related to differences in nutrient enrichment, habitat alterations, and invasive species. Because species richness can increase or decrease with increasing urbanization, a general response model is not applicable. Instead, response models based on species’ life histories, behavior, and autecologies offer greater potential for understanding fish assemblage responses to urbanization.

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Uphoff, J., M. McGinty, B. Richardson, P. Piavis, H. Speir, and M.F. Topolski.  2005.  Interim assessment of yellow perch Perca flavescens habitat and population dynamics in Severn River, a suburbanized Chesapeake Bay sub-estuary.  Fisheries Technical Report Series, Number 46, Maryland Department of Natural Resources, Fisheries Service, Stevensville. 

Abstract: The Severn River, located on the Chesapeake Bay’s western shore within the rapidly developing Baltimore-Washington D.C. corridor, has been closed to yellow perch harvest since 1989 in response to largely unknown, but assumed detrimental habitat conditions. During 2001-2003, we assessed yellow perch habitat in the heavily developed Severn River watershed (17% impervious surface or IS) by combining stock assessment (larvae-adults), experimental stocking (larvae-juveniles), and water quality monitoring (temperature, salinity, dissolved oxygen). We contrasted yellow perch population and water quality characteristics in Severn River with developed reference systems (10-20% IS), relatively undeveloped reference systems (≈ 2% IS), and historic Severn River data from periods of lesser development. Hatching success of Severn River eggs was extremely low and larval relative abundance was very low during 2001-2003. Wild juveniles were not caught in summer during 2001, were present at very low levels in 2002, and were better represented during 2003. Hatchery juveniles were common after stocking during 2002-2003. Adult yellow perch did not exhibit excessive non-harvest related mortality or decreased growth. At this time, depressed egg and larval viability appear to be critical factors suppressing the resident population. Two significant habitat quality issues potentially impacting yellow perch population dynamics were described in our study of Severn River – possible salinity intrusion into the upper tidal spawning area and larval nurseries due to landscape changes, and poor summer dissolved oxygen (DO) throughout juvenile and adult habitat. Frequent violations of salinity requirements were observed for larvae (93% of measurements) and dissolved oxygen violations were common for juveniles and adults in summer (≈5% at the surface, 20-40% at mid-depth, 70-80% at the bottom). Based on our study, dissolved oxygen conditions unsuitable for yellow perch survival were common in urbanized watersheds and uncommon in less urbanized systems. Other issues, such as contaminants, exist that were not covered in the habitat variables we evaluated. If poor egg and larval viability observed in the Severn River is now normal, then the river’s population may be entirely dependent upon immigration of good Head-of-Bay yearclasses.

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Uphoff, J. H.  2008.  Identifying priority areas for protection and restoration: Chesapeake Bay striped bass spawning and larval nursery areas as a model.  Fisheries Technical Report Series Number 52, Maryland Department of Natural Resources, Fisheries Service, Stevensville. 

Access: Available online.

Weaver, L.A. 1991. Low-intensity watershed alteration effects on fish assemblage structure and function in a Virginia piedmont stream. Unpublished Masters Thesis. Virginia Commonwealth University. 77 pp.

Key finding: As watershed development increased to about 10%, fish communities simplified to more habitat and trophic generalists and fish abundance and species richness declined. IBI scores for the urbanized stream fell from the good to fair category (Virginia). 2

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Algae   (return to top of page)

Coles, J.F., Bell, A.H., Scudder, B.C., and Carpenter, K.D. 2009. The effects of urbanization and other environmental gradients on algal assemblages in nine metropolitan areas across the United States. U.S. Geological Survey Scientific Investigations Report 2009-5022, 18 p. 

Abstract: The U.S. Geological Survey conducted studies from 2000 to 2004 to determine the effects of urbanization on stream ecosystems in nine major metropolitan study areas across the United States. Biological, chemical, and physical components of streams were assessed at 28 to 30 sites in each study area. Benthic algae were sampled to compare the degree to which algal assemblages correlated to urbanization, as characterized by an urban intensity index (UII), relative to other environmental gradients that function at either the watershed or reach scales. Ordination site scores were derived from principal components analyses of the environmental data to define environmental gradients at two spatial scales: (1) watershed-scale gradients that summarized (a) landscape modifications and (b) socioeconomic factors, and (2) reach-scale gradients that characterized (a) physical habitat and (b) water chemistry. Algal response was initially quantified by site scores derived from nonmetric multi-dimensional scaling ordinations of the algal assemblage data. The site scores were then correlated with a set of algal metrics of structure and function to help select specific indicators that would best represent changes in the algal assemblages and would infer ecological condition. The selected metrics were correlated to the UII and other environmental gradients. The results indicated that diatom-taxa in the assemblages were distinctly different across the nine study areas, likely due to physiographic differences across the country, but nevertheless, some algal metrics were applicable to all areas. Overall, the study results indicated that although the UII represented various landscape changes associated with urbanization across the country, the algal response was more strongly related to more specific factors generally associated with water quality measured within the stream reach.

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Potapova, M., Coles, J. F., Giddings, E.M., and Zappia, H. 2005. A comparison of the influences of urbanization on stream benthic algal assemblages in contrasting environmental settings. In Brown, L.R., Gray, R.H., Hughes, R.M., and Meador, M.R., eds., Effects of urbanization on stream ecosystems. American Fisheries Society, Symposium 47, Bethesda, Maryland, p.333-359. 

Abstract: Patterns of stream benthic algal assemblages along urbanization gradients were investigated in three metropolitan areas—Boston (BOS), Massachusetts; Birmingham (BIR), Alabama; and Salt Lake City (SLC), Utah. An index of urban intensity derived from socioeconomic, infrastructure, and land-use characteristics was used as a measure of urbanization. Of the various attributes of the algal assemblages, species composition changed along gradients of urban intensity in a more consistent manner than biomass or diversity. In urban streams, the relative abundance of pollution tolerant species was often higher than in less affected streams. Shifts in assemblage composition were associated primarily with increased levels of conductivity, nutrients, and alterations in physical habitat. Water mineralization and nutrients were the most important determinants of assemblage composition in the BOS and SLC study areas; flow regime and grazers were key factors in the BIR study area. Species composition of algal assemblages differed significantly among geographic regions, and no particular algal taxa were found to be universal indicators of urbanization. Patterns in algal biomass and diversity along urban gradients varied among study areas, depending on local environmental conditions and habitat alteration. Biomass and diversity increased with urbanization in the BOS area, apparently because of increased nutrients, light, and flow stability in urban streams, which often are regulated by dams. Biomass and diversity decreased with urbanization in the BIR study area because of intensive fish grazing and less stable flow regime. In the SLC study area, correlations between algal biomass, diversity, and urban intensity were positive but weak. Thus, algal responses to urbanization differed considerably among the three study areas. We concluded that the wide range of responses of benthic algae to urbanization implied that tools for stream bioassessment must be region specific.

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Palmer, M. A.  2009.  Reforming watershed restoration: science in need of application and applications in need of science.  Estuaries and Coasts 32:1-17. 

Abstract: Coastal and inland waters are continuing to decline in many parts of the world despite major efforts made to restore them. This is due in part to the inadequate role that ecological science has played in shaping restoration efforts. A significant amount of fundamental ecological knowledge dealing with issues such as system dynamics, state changes, context-dependency of ecological response, and diversity is both under-used by managers and practitioners and under-developed by ecologists for use in real-world applications. Some of the science that is being ‘used’ has not been adequately tested. Thus, restoration ecology as a science and ecological restoration as a practice are in need of reform. I identify five ways in which our ecological knowledge should be influencing restoration to a far greater extent than at present including a need to: shift the focus to restoration of process and identification of the limiting factors instead of structures and single species, add ecological insurance to all projects, identify a probabilistic range of possible outcomes instead of a reference condition, expand the spatial scale of efforts, and apply hierarchical approaches to prioritization. Prominent examples of restoration methods or approaches that are commonly used despite little evidence to support their efficacy are highlighted such as the use of only structural enhancements to restore biodiversity. There are also major gaps in scientific knowledge that are of immediate need to policy makers, managers, and restoration practitioners including: predictive frameworks to guide the restoration of ecological processes, identification of social-ecological feedbacks that constrain ecosystem recovery and data to support decisions of where and how to implement restoration projects to achieve the largest gains. I encourage ecologists to respond to the demand for their scientific input so that restoration can shift from an engineering-driven process to a more sustainable enterprise that fully integrates ecological processes and social science methods.

Access: Available online 

Mitigation   (return to top of page)

Booth, D.B. 2000. Forest cover, impervious surface area, and the mitigation of urbanization impacts in King County, Washington. King County Water and Land Resources Division. Seattle, WA. 

Summary: Booth provides a review of the scientific framework for basing management decisions on the impact of urbanization on aquatic systems and the use of impervious cover as an indicator. The ability of forest cover to minimize impacts on stream stability at low levels of impervious cover is documented. Also expressed, is the concept that impervious cover, as a single land use parameter, may not be an appropriate indicator of stream health in rural watersheds with impervious cover measurements of less than 10%. 2

Access: Available online.

Environmental Resources Management (ERM). 2000. Stream condition cumulative impact models for the Potomac subregion. Prepared for the Maryland-National Park and Planning Commission, Silver Spring, MD.  

Key finding: A study of first and second order stream conditions in urbanized watersheds found that for streams rated as being in excellent or good condition watersheds had either high levels of riparian buffers (>67%) or moderate buffers (>33%) in combination with moderate storm water management (at least 33% of imperviousness treated) (Maryland). 2

Access: DNR employees should contact the library to request via interlibrary loan.

Horner, R., May, C., Livingston, E., and J. Maxted. 1999. Impervious cover, aquatic community health, and stormwater BMPs: Is there a relationship? 

Summary: This study, using watersheds in Maryland, Texas, Colorado and Washington state, evaluated the ability of structural and nonstructural management practices to mitigate and ameliorate the impacts of impervious surfaces on biological communities. It found that nonstructural techniques such as riparian buffers and upland forest retention were more effective at ameliorating the impacts of impervious surfaces than structural management practices. They did, however, conclude that the ability of these nonstructural techniques to mitigate biological impacts was limited to low levels of impervious cover and that at higher levels of impervious cover biological impacts were difficult to prevent. 2

            Access: Available online.

Jones, R.C., Via-Norton, A., and D. Morgan. 1996. Bioassessment of the BMP effectiveness in mitigating stormwater impacts on aquatic biota. In: Effects of Watershed Development and Management on Aquatic Ecosystems. Roesner, L.A. (ed.), Proceedings of ASCE/Engineering Foundation Conference. August, 1996. Snowbird, UT.

Key finding: Unable to show improvements in biological community at 8 sites downstream of stormwater treatment practices as compared to reference conditions (Virginia). 2

            Access: DNR employees should contact the library to request via interlibrary loan.

Maxted, J. and E. Shaver. 1996. The Use of Retention Basins to Mitigate Stormwater Impacts on Aquatic Life. L. In: Effects of Watershed Development and Management on Aquatic Ecosystems. Roesner, L.A. (ed.), Proceedings of Engineering Foundation Conference. August, 1996. Snowbird, UT.

Key finding: No significant difference in biological and physical metrics for 8 stormwater treatment practice (STP) sites versus 33 sites without STPs (with varying impervious area). STP s did not attenuate the impacts of urbanization once the watershed reached 20% impervious cover, and did not prevent a shift in the macroinvertebrate community from pollutant sensitive species to pollutant tolerant organisms (Delaware). 2

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National Research Council. 2009.  Urban stormwater management in the United States.  National Academies Press, Washington, D.C. 

Abstract: The rapid conversion of land to urban and suburban areas has profoundly altered how water flows during and following storm events, putting higher volumes of water and more pollutants into the nation's rivers, lakes, and estuaries. These changes have degraded water quality and habitat in virtually every urban stream system. The Clean Water Act regulatory framework for addressing sewage and industrial wastes is not well suited to the more difficult problem of stormwater discharges.  This book calls for an entirely new permitting structure that would put authority and accountability for stormwater discharges at the municipal level. A number of additional actions, such as conserving natural areas, reducing hard surface cover (e.g., roads and parking lots), and retrofitting urban areas with features that hold and treat stormwater, are recommended.

Access: Available to read online.

Endnotes:   (return to top of page)

1 Key finding summarized in: Schueler, T.R. and H.K. Holland. 1994. The importance of imperviousness. Watershed Protection Techniques 1(3): 100-111.

2 Key finding summarized in: Cappiella, K., and K. Brown.  2001.  Impervious cover and land use in the Chesapeake Bay watershed.  Center for Watershed Protection, Ellicott City, MD.


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