Gerard McMahon - Academia.edu (original) (raw)

Papers by Gerard McMahon

Research paper thumbnail of Water-quality in the Albemarle-Pamlico drainage basin

Research paper thumbnail of Using Video to Communicate Scientific Findings -- Habitat Connections in Urban Streams

The U.S Geological Survey (USGS) National Water-Quality Assessment Program (NAWQA) provides infor... more The U.S Geological Survey (USGS) National Water-Quality Assessment Program (NAWQA) provides information about (1) water-quality conditions and how those conditions vary locally, regionally, and nationally, (2) water-quality trends, and (3) factors that affect those conditions. As part of the NAWQA Program, the Effects of Urbanization on Stream Ecosystems (EUSE) study examined the vulnerability and resilience of streams to urbanization. Completion of the EUSE study has resulted in over 20 scientific publications. Video podcasts are being used in addition to these publications to communicate the relevance of these scientific findings to more general audiences such as resource managers, educational groups, public officials, and the general public. An example of one of the podcasts is a film examining effects of urbanization on stream habitat. "Habitat Connections in Urban Streams" explores how urbanization changes some of the physical features that provide in-stream habitat a...

Research paper thumbnail of Responding to sea level rise and extreme events through climate change adaptation strategies: A case study using the network of Atlantic National Wildlife Refuges

Background/Question/Methods Coastal ecosystems and the services they provide to humans are especi... more Background/Question/Methods Coastal ecosystems and the services they provide to humans are especially vulnerable to climate-related impacts from sea level rise, coastal erosion, and extreme weather events such as hurricanes, as well as concomitant influences from human activities including land-use change, hardened shorelines, coastal barriers, habitat fragmentation, invasive species and other stressors. National Wildlife Refuges (NWRs) have responsibility for managing many coastal ecosystems, including the fragile habitats, migratory species and listed plant and animal taxa that may be dependent on these areas for all or part of their life cycles. The challenges inherent in these responsibilities became increasingly evident after Hurricane Sandy. The DOI Climate Science Centers (CSCs) are federal-University partnerships created to provide scientific information, tools and techniques that managers and others can use to anticipate, monitor and adapt to climate change. Results/Conclus...

Research paper thumbnail of Application of Multilevel Modeling in Study the Effects of Urbanization in Stream Ecosystems

The US Geological Survey conducted a study on the effect of urbanization on stream ecosystems (EU... more The US Geological Survey conducted a study on the effect of urbanization on stream ecosystems (EUSE) in nine different metropolitan areas of the country, using a gradient approach. The aim of the study was to understand the relation among distal (e.g., watershed and riparian scale) and proximal (stream segment and reach above the sampling point) stressors on stream biota (fish,

Research paper thumbnail of Multinomial regression for analyzing macroinvertebrate assemblage composition data

Research paper thumbnail of Effects of Urbanization on the Condition of Streams in the Piedmont of North Carolina: Responses of Benthic Macroinvertebrate Assemblages

The effects of urbanization on the physical, chemical, and biological characteristics of streams ... more The effects of urbanization on the physical, chemical, and biological characteristics of streams in the North Carolina Piedmont were investigated as part of the U.S. Geological Survey's National Water-Quality Assessment (NAWQA) Program. Over 1,200 candidate basins (2-3rd order streams) were identified using a 30-m digital elevation model. A multimetric urban intensity index (UII) derived from population, infrastructure, land use, land

Research paper thumbnail of Responses of Benthic Macroinvertebrates to Urbanization in Nine Metropolitan Areas of the Conterminous United States

The effects of urbanization on benthic macroinvertebrates were investigated in nine metropolitan ... more The effects of urbanization on benthic macroinvertebrates were investigated in nine metropolitan areas (Boston, MA; Raleigh, NC; Atlanta, GA; Birmingham, AL; Milwaukee-Green Bay, WI; Denver, CO; Dallas-Fort Worth, TX; Salt Lake City, UT; and Portland, OR) as a part of the U.S. Geological Survey National Water Quality Assessment Program. Several invertebrate metrics showed strong, linear responses to urbanization when forest

Research paper thumbnail of Judging a Brook by Its Cover: The Relation between Ecological Condition of a Stream and Urban Land Cover in New England

Northeastern Naturalist, 2010

The US Geological Survey conducted an urban land-use study in the New England Coastal Basins (NEC... more 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 reppresented a gradient of urban intensity. Among various biological, chemical, and physical factors surveyed at each site, benthic invertebrate assemblages were sampled from stream riffl es 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 specifi c point-source stressors.

Research paper thumbnail of Effects of Urban Development on Water-Quality in the Piedmont of North Carolina--The NAWQA Urban Land-Use Gradient Study

AGU Fall Meeting …, 2004

A study of urban basins located in the Piedmont of North Carolina is underway as part of the US G... more A study of urban basins located in the Piedmont of North Carolina is underway as part of the US Geological Survey National Water-Quality Assessment (NAWQA) to determine the relation between level of urban development and water quality. Data were collected ...

Research paper thumbnail of Support of Total Maximum Daily Load Programs Using Spatially Referenced Regression Models

Journal of Water Resources Planning and Management, 2003

Research paper thumbnail of Urban streams across the USA: lessons learned from studies in 9 metropolitan areas

Journal of the North American Benthological Society, 2009

Studies of the effects of urbanization on stream ecosystems have usually focused on single metrop... more 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 (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, physicalhabitat, 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.

Research paper thumbnail of QUANTIFYING URBAN INTENSITY IN DRAINAGE BASINS FOR ASSESSING STREAM ECOLOGICAL CONDITIONS

Journal of the American Water Resources Association, 2000

RefDoc Refdoc est un service / is powered by. ...

Research paper thumbnail of NUTRIENT MASS BALANCE FOR THE ALBEMARLE-PAMLICO DRAINAGE BASIN, NORTH CAROLINA AND VIRGINIA, 1990

Journal of the American Water Resources Association, 1997

ABSTRACT: A 1990 nitrogen and phosphorus mass balance calculated for eight National Stream Qualit... more ABSTRACT: A 1990 nitrogen and phosphorus mass balance calculated for eight National Stream Quality Accounting Network (NASQAN) basins in the Albemarle-Pamlico Drainage Basin indicated the importance of agricultural nonpoint sources of nitrogen and ...

Research paper thumbnail of USE OF STAGE DATA TO CHARACTERIZE HYDROLOGIC CONDITIONS IN AN URBANIZING ENVIRONMENT

Journal of the American Water Resources Association, 2003

This paper presents the results of a study on the use of continuous stage data to describe the re... more 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. (KEY TERMS: hydrologic variability; watershed management; surface water hydrology; urban water management; stream ecology.)

Research paper thumbnail of Delineation and Evaluation of Hydrologic-Landscape Regions in the United States Using Geographic Information System Tools and Multivariate Statistical Analyses

Environmental Management, 2004

Hydrologic-landscape regions in the United States were delineated by using geographic information... more Hydrologic-landscape regions in the United States were delineated by using geographic information system (GIS) tools combined with principal components and cluster analyses. The GIS and statistical analyses were applied to land-surface form, geologic texture (permeability of the soil and bedrock), and climate variables that describe the physical and climatic setting of 43,931 small (approximately 200 km 2 ) watersheds in the United States. (The term ЉwatershedsЉ is defined in this paper as the drainage areas of tributary streams, headwater streams, and stream segments lying between two confluences.) The analyses grouped the watersheds into 20 noncontiguous regions based on similarities in land-surface form, geologic texture, and climate characteristics. The percentage of explained variance (R-squared value) in an analysis of variance was used to compare the hydrologic-landscape regions to 19 square geometric regions and the 21 U.S. Environmental Protection Agency level-II ecoregions. Hydrologic-landscape regions generally were better than ecoregions at delineating regions of distinct land-surface form and geologic texture. Hydrologic-landscape regions and ecoregions were equally effective at defining regions in terms of climate, land cover, and water-quality characteristics. For about half of the landscape, climate, and water-quality characteristics, the R-squared values of square geometric regions were as high as hydrologic-landscape regions or ecoregions.

Research paper thumbnail of Effect of Environmental Setting on Sediment, Nitrogen, and Phosphorus Concentrations in Albemarle-Pamlico Drainage Basin, North Carolina and Virginia, USA

Environmental Management, 1998

/ Environmental settings were defined, through an overlay process, as areas of coincidence betwee... more / Environmental settings were defined, through an overlay process, as areas of coincidence between categories of three mapped variables\Mland use, surficial geology, and soil drainage characteristics. Expert judgment was used in selecting factors thought to influence sediment and nutrient concentrations in the Albemarle-Pamlico drainage area. This study's findings support the hypothesis that environmental settings defined using these three variables can explain variations in the concentration of certain sediment and nutrient constituents. This finding underscores the importance of developing watershed management plans that account for differences associated with the mosaic of natural and anthropogenic factors that define a basin's environmental setting. At least in the case of sediment and nutrients in the Albemarle-Pamlico region, a watershed management plan that focuses only on anthropogenic factors, such as point-source discharges, and does not account for natural characteristics of a watershed and the influences of these characteristics on water quality, may lead to water-quality goals that are over- or underprotective of key environmental features and to a misallocation of the resources available for environmental protection.KEY WORDS: Environmental setting; Water quality; Watershed management; Nutrients; Sediment

Research paper thumbnail of Toward a Scientifically Rigorous Basis for Developing Mapped Ecological Regions

Environmental Management, 2004

Despite the wide use of ecological regions in conservation and resource-management evaluations an... more Despite the wide use of ecological regions in conservation and resource-management evaluations and assessments, a commonly accepted theoretical basis for ecological regionalization does not exist. This fact, along with the paucity of focus on ecological regionalization by professional associations, journals, and faculties, has inhibited the ad-

Research paper thumbnail of On the application of multilevel modeling in environmental and ecological studies

Ecology, 2010

This paper illustrates the advantages of a multilevel/hierarchical approach 2 for predictive mode... more This paper illustrates the advantages of a multilevel/hierarchical approach 2 for predictive modeling, including flexibility of model formulation, explicitly 3 accounting for hierarchical structure in the data, and the ability to predict the 4 outcome of new cases. As a generalization of the classical approach, the 5 multilevel modeling approach explicitly models the hierarchical structure in 6 the data by considering both the within and between group variances leading 7 to a partial pooling of data across all levels in the hierarchy. The modeling 8

Research paper thumbnail of Selected physical, chemical, and biological data used to study urbanizing streams in nine metropolitan areas of the United States, 1999–2004

US Geological Survey …, 2009

For more information on the USGS-the Federal source for science about the Earth, its natural and ... more For more information on the USGS-the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment, visit http://www.usgs.gov or call 1-888-ASK-USGS

Research paper thumbnail of Effects of Urban Development on Stream Ecosystems Along the Front Range of the Rocky Mountains, Colorado and Wyoming

For more information on the USGS-the Federal source for science about the Earth, its natural and ... more For more information on the USGS-the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment, visit http://www.usgs.gov or call 1-888-ASK-USGS.

Research paper thumbnail of Water-quality in the Albemarle-Pamlico drainage basin

Research paper thumbnail of Using Video to Communicate Scientific Findings -- Habitat Connections in Urban Streams

The U.S Geological Survey (USGS) National Water-Quality Assessment Program (NAWQA) provides infor... more The U.S Geological Survey (USGS) National Water-Quality Assessment Program (NAWQA) provides information about (1) water-quality conditions and how those conditions vary locally, regionally, and nationally, (2) water-quality trends, and (3) factors that affect those conditions. As part of the NAWQA Program, the Effects of Urbanization on Stream Ecosystems (EUSE) study examined the vulnerability and resilience of streams to urbanization. Completion of the EUSE study has resulted in over 20 scientific publications. Video podcasts are being used in addition to these publications to communicate the relevance of these scientific findings to more general audiences such as resource managers, educational groups, public officials, and the general public. An example of one of the podcasts is a film examining effects of urbanization on stream habitat. "Habitat Connections in Urban Streams" explores how urbanization changes some of the physical features that provide in-stream habitat a...

Research paper thumbnail of Responding to sea level rise and extreme events through climate change adaptation strategies: A case study using the network of Atlantic National Wildlife Refuges

Background/Question/Methods Coastal ecosystems and the services they provide to humans are especi... more Background/Question/Methods Coastal ecosystems and the services they provide to humans are especially vulnerable to climate-related impacts from sea level rise, coastal erosion, and extreme weather events such as hurricanes, as well as concomitant influences from human activities including land-use change, hardened shorelines, coastal barriers, habitat fragmentation, invasive species and other stressors. National Wildlife Refuges (NWRs) have responsibility for managing many coastal ecosystems, including the fragile habitats, migratory species and listed plant and animal taxa that may be dependent on these areas for all or part of their life cycles. The challenges inherent in these responsibilities became increasingly evident after Hurricane Sandy. The DOI Climate Science Centers (CSCs) are federal-University partnerships created to provide scientific information, tools and techniques that managers and others can use to anticipate, monitor and adapt to climate change. Results/Conclus...

Research paper thumbnail of Application of Multilevel Modeling in Study the Effects of Urbanization in Stream Ecosystems

The US Geological Survey conducted a study on the effect of urbanization on stream ecosystems (EU... more The US Geological Survey conducted a study on the effect of urbanization on stream ecosystems (EUSE) in nine different metropolitan areas of the country, using a gradient approach. The aim of the study was to understand the relation among distal (e.g., watershed and riparian scale) and proximal (stream segment and reach above the sampling point) stressors on stream biota (fish,

Research paper thumbnail of Multinomial regression for analyzing macroinvertebrate assemblage composition data

Research paper thumbnail of Effects of Urbanization on the Condition of Streams in the Piedmont of North Carolina: Responses of Benthic Macroinvertebrate Assemblages

The effects of urbanization on the physical, chemical, and biological characteristics of streams ... more The effects of urbanization on the physical, chemical, and biological characteristics of streams in the North Carolina Piedmont were investigated as part of the U.S. Geological Survey's National Water-Quality Assessment (NAWQA) Program. Over 1,200 candidate basins (2-3rd order streams) were identified using a 30-m digital elevation model. A multimetric urban intensity index (UII) derived from population, infrastructure, land use, land

Research paper thumbnail of Responses of Benthic Macroinvertebrates to Urbanization in Nine Metropolitan Areas of the Conterminous United States

The effects of urbanization on benthic macroinvertebrates were investigated in nine metropolitan ... more The effects of urbanization on benthic macroinvertebrates were investigated in nine metropolitan areas (Boston, MA; Raleigh, NC; Atlanta, GA; Birmingham, AL; Milwaukee-Green Bay, WI; Denver, CO; Dallas-Fort Worth, TX; Salt Lake City, UT; and Portland, OR) as a part of the U.S. Geological Survey National Water Quality Assessment Program. Several invertebrate metrics showed strong, linear responses to urbanization when forest

Research paper thumbnail of Judging a Brook by Its Cover: The Relation between Ecological Condition of a Stream and Urban Land Cover in New England

Northeastern Naturalist, 2010

The US Geological Survey conducted an urban land-use study in the New England Coastal Basins (NEC... more 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 reppresented a gradient of urban intensity. Among various biological, chemical, and physical factors surveyed at each site, benthic invertebrate assemblages were sampled from stream riffl es 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 specifi c point-source stressors.

Research paper thumbnail of Effects of Urban Development on Water-Quality in the Piedmont of North Carolina--The NAWQA Urban Land-Use Gradient Study

AGU Fall Meeting …, 2004

A study of urban basins located in the Piedmont of North Carolina is underway as part of the US G... more A study of urban basins located in the Piedmont of North Carolina is underway as part of the US Geological Survey National Water-Quality Assessment (NAWQA) to determine the relation between level of urban development and water quality. Data were collected ...

Research paper thumbnail of Support of Total Maximum Daily Load Programs Using Spatially Referenced Regression Models

Journal of Water Resources Planning and Management, 2003

Research paper thumbnail of Urban streams across the USA: lessons learned from studies in 9 metropolitan areas

Journal of the North American Benthological Society, 2009

Studies of the effects of urbanization on stream ecosystems have usually focused on single metrop... more 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 (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, physicalhabitat, 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.

Research paper thumbnail of QUANTIFYING URBAN INTENSITY IN DRAINAGE BASINS FOR ASSESSING STREAM ECOLOGICAL CONDITIONS

Journal of the American Water Resources Association, 2000

RefDoc Refdoc est un service / is powered by. ...

Research paper thumbnail of NUTRIENT MASS BALANCE FOR THE ALBEMARLE-PAMLICO DRAINAGE BASIN, NORTH CAROLINA AND VIRGINIA, 1990

Journal of the American Water Resources Association, 1997

ABSTRACT: A 1990 nitrogen and phosphorus mass balance calculated for eight National Stream Qualit... more ABSTRACT: A 1990 nitrogen and phosphorus mass balance calculated for eight National Stream Quality Accounting Network (NASQAN) basins in the Albemarle-Pamlico Drainage Basin indicated the importance of agricultural nonpoint sources of nitrogen and ...

Research paper thumbnail of USE OF STAGE DATA TO CHARACTERIZE HYDROLOGIC CONDITIONS IN AN URBANIZING ENVIRONMENT

Journal of the American Water Resources Association, 2003

This paper presents the results of a study on the use of continuous stage data to describe the re... more 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. (KEY TERMS: hydrologic variability; watershed management; surface water hydrology; urban water management; stream ecology.)

Research paper thumbnail of Delineation and Evaluation of Hydrologic-Landscape Regions in the United States Using Geographic Information System Tools and Multivariate Statistical Analyses

Environmental Management, 2004

Hydrologic-landscape regions in the United States were delineated by using geographic information... more Hydrologic-landscape regions in the United States were delineated by using geographic information system (GIS) tools combined with principal components and cluster analyses. The GIS and statistical analyses were applied to land-surface form, geologic texture (permeability of the soil and bedrock), and climate variables that describe the physical and climatic setting of 43,931 small (approximately 200 km 2 ) watersheds in the United States. (The term ЉwatershedsЉ is defined in this paper as the drainage areas of tributary streams, headwater streams, and stream segments lying between two confluences.) The analyses grouped the watersheds into 20 noncontiguous regions based on similarities in land-surface form, geologic texture, and climate characteristics. The percentage of explained variance (R-squared value) in an analysis of variance was used to compare the hydrologic-landscape regions to 19 square geometric regions and the 21 U.S. Environmental Protection Agency level-II ecoregions. Hydrologic-landscape regions generally were better than ecoregions at delineating regions of distinct land-surface form and geologic texture. Hydrologic-landscape regions and ecoregions were equally effective at defining regions in terms of climate, land cover, and water-quality characteristics. For about half of the landscape, climate, and water-quality characteristics, the R-squared values of square geometric regions were as high as hydrologic-landscape regions or ecoregions.

Research paper thumbnail of Effect of Environmental Setting on Sediment, Nitrogen, and Phosphorus Concentrations in Albemarle-Pamlico Drainage Basin, North Carolina and Virginia, USA

Environmental Management, 1998

/ Environmental settings were defined, through an overlay process, as areas of coincidence betwee... more / Environmental settings were defined, through an overlay process, as areas of coincidence between categories of three mapped variables\Mland use, surficial geology, and soil drainage characteristics. Expert judgment was used in selecting factors thought to influence sediment and nutrient concentrations in the Albemarle-Pamlico drainage area. This study's findings support the hypothesis that environmental settings defined using these three variables can explain variations in the concentration of certain sediment and nutrient constituents. This finding underscores the importance of developing watershed management plans that account for differences associated with the mosaic of natural and anthropogenic factors that define a basin's environmental setting. At least in the case of sediment and nutrients in the Albemarle-Pamlico region, a watershed management plan that focuses only on anthropogenic factors, such as point-source discharges, and does not account for natural characteristics of a watershed and the influences of these characteristics on water quality, may lead to water-quality goals that are over- or underprotective of key environmental features and to a misallocation of the resources available for environmental protection.KEY WORDS: Environmental setting; Water quality; Watershed management; Nutrients; Sediment

Research paper thumbnail of Toward a Scientifically Rigorous Basis for Developing Mapped Ecological Regions

Environmental Management, 2004

Despite the wide use of ecological regions in conservation and resource-management evaluations an... more Despite the wide use of ecological regions in conservation and resource-management evaluations and assessments, a commonly accepted theoretical basis for ecological regionalization does not exist. This fact, along with the paucity of focus on ecological regionalization by professional associations, journals, and faculties, has inhibited the ad-

Research paper thumbnail of On the application of multilevel modeling in environmental and ecological studies

Ecology, 2010

This paper illustrates the advantages of a multilevel/hierarchical approach 2 for predictive mode... more This paper illustrates the advantages of a multilevel/hierarchical approach 2 for predictive modeling, including flexibility of model formulation, explicitly 3 accounting for hierarchical structure in the data, and the ability to predict the 4 outcome of new cases. As a generalization of the classical approach, the 5 multilevel modeling approach explicitly models the hierarchical structure in 6 the data by considering both the within and between group variances leading 7 to a partial pooling of data across all levels in the hierarchy. The modeling 8

Research paper thumbnail of Selected physical, chemical, and biological data used to study urbanizing streams in nine metropolitan areas of the United States, 1999–2004

US Geological Survey …, 2009

For more information on the USGS-the Federal source for science about the Earth, its natural and ... more For more information on the USGS-the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment, visit http://www.usgs.gov or call 1-888-ASK-USGS

Research paper thumbnail of Effects of Urban Development on Stream Ecosystems Along the Front Range of the Rocky Mountains, Colorado and Wyoming

For more information on the USGS-the Federal source for science about the Earth, its natural and ... more For more information on the USGS-the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment, visit http://www.usgs.gov or call 1-888-ASK-USGS.