Daniel H Doctor, Ph.D.
Daniel H. Doctor is a Research Geologist at the Florence Bascom Geoscience Center.
Dan is a research geologist conducting geologic mapping and specialized geologic research for the Appalachian Basin project. His current research interests include stratigraphy of the Appalachian Basin, landscape evolution within the Appalachian Valley and Ridge physiographic province, karst hydrology and geomorphology, sinkhole hazard studies, and paleoclimate records from karst regions.
Dan began a career with the USGS in 2002 as an NRC postdoc within the Isotope Tracers of Biogeochemical and Hydrologic Processes project of the National Research Program in Menlo Park, California. In 2006, he joined the Florence Bascom Geoscience Center in Reston, Virginia.
Professional Experience
Research Geologist (2006-present). U.S. Geological Survey, KARST Project, Eastern Geology and Paleoclimate Science Center, Reston, VA
Hydrologist (2004-2006). U.S. Geological Survey, Isotope Tracers Group, Water Resources Division, Menlo Park, CA
Postdoctoral Research Associate, National Research Council (NRC) (2002-2004). U.S. Geological Survey, Isotope Tracers Group, Water Resources Division, Menlo Park, CA
Project Analyst (2001). Lands and Minerals Division, Minnesota Department of Natural Resources (MN-DNR).
Education and Certifications
Ph.D. (2002) in Hydrogeology/Geochemistry, with Doctoral Minor in Water Resources Science, University of Minnesota, Dept. of Geology and Geophysics, Minneapolis, MN
Bachelor of Arts (1994) in Geology, Minor in Environmental Studies, Colgate University, Hamilton, NY (Magna Cum Laude, Phi Beta Kappa)
Science and Products
Filter Total Items: 42
A geodatabase representing a compilation of Cadwell, D.H., and others, 1991, Surficial Geology of New York; New York State Museum Map and Chart Series 40, scale 1:250,000, 5 sheets.
This Scientific Data Release is a spatial geodatabase representation of a compilation of Cadwell, D.H., Connally, G.G., Fleisher, P.J., Muller, E.H., 1988, Surficial geologic map of New York; Niagara sheet: New York State Museum Map and Chart Series 40, scale 1:250,000, 5 sheets., Muller, E.H., Cadwell, D.H., Connally, G.G., Young, R.A., 1986, Surficial geologic map of New York; Finger Lakes sheet
Geospatial files and tabular exposure estimates of sinkhole susceptibility for counties in the conterminous United States for current conditions and projections for the years 2070-2079 - Overview
These datasets support the conclusions in the journal article entitled "Current and future sinkhole susceptibility in karst and pseudokarst areas of the conterminous United States" as described in the abstract below: Sinkholes in karst and pseudokarst regions threaten infrastructure, property, and lives. We mapped closed depressions in karst and pseudokarst regions of the conterminous United State
Deep-learning-derived alluvium, shallow-to-exposed bedrock, and surficial sediment thickness map for the upper Neversink River watershed, New York
This dataset consists of a raster and surficial shapefiles for the Neversink River watershed, NY, that were generated using ArcGIS Pro's deep learning functionality. The shapefiles contain polygons that show the locations of shallow-to-exposed bedrock and alluvium-filled valleys, while the raster provides estimated minimum sediment thicknesses in the areas between the shallow/exposed bedrock and a
A geodatabase of Surficial Geology of the Allentown 30x60-Minute Quadrangle in Pennsylvania digitized from the original map of Braun, 1996
This Scientific Data Release is a spatial geodatabase representation of Braun, D. D., 1996, Surficial geology of the Allentown 30x60-minute quadrangle: Pennsylvania Geological Survey, 4th ser., Open-File Report 96-48, 17 p., 1 map, scale 1:100,000. These geospatial data depict surficial geologic materials in the Pennsylvania portion of the Allentown 30 x 60-minute quadrangle in eastern Pennsylvani
Stream Temperature, Dissolved Radon, and Stable Water Isotope Data Collected along Headwater Streams in the Upper Neversink River Watershed, NY, USA (ver. 2.0, April 2023)
This data release contains three data types that could potentially be used to infer spatiotemporal variability in groundwater discharge processes, along with other research and monitoring purposes: 1) Temporally continuous stream channel water temperature and adjacent streambank air temperature time series data (generally starting November 2020) as well as limited temperature data from May to Octo
Enhanced Terrain Imagery of the Sunbury 30 x 60 Minute Quadrangle from Lidar-Derived Elevation Models at 3-Meter Resolution
This imagery dataset consists of 3-meter resolution, lidar-derived imagery of the Sunbury 30 x 60 minute quadrangle Pennsylvania. It also covers part of the Delaware River Basin. The source data used to construct this imagery consists of 1-meter and 3-meter resolution Lidar-derived digital elevation models (DEMs). The lidar source data were compiled from different acquisitions published between 20
Enhanced Terrain Imagery of the York 30 x 60 Minute Quadrangle from Lidar-Derived Elevation Models at 3-Meter Resolution
This imagery dataset consists of 3-meter resolution, lidar-derived imagery of the York 30 x 60 minute quadrangle in Pennsylvania and Maryland. It also covers part of the Delaware River Basin. The source data used to construct this imagery consists of 1-meter and 2-meter resolution Lidar-derived digital elevation models (DEMs). The lidar source data were compiled from different acquisitions publish
Enhanced Terrain Imagery of the Hagerstown 30 x 60 Minute Quadrangle from Lidar-Derived Elevation Models at 3-Meter Resolution (ver. 1.1, February 2024)
This imagery dataset consists of 3-meter resolution, lidar-derived imagery of the Hagerstown 30 x 60 minute quadrangle in Pennsylvania, Maryland, and part of West Virginia. The source data used to construct this imagery consists of 1-meter resolution lidar-derived digital elevation models (DEMs). The lidar source data were compiled from different acquisitions published between 2016 and 2023. The d
Enhanced Terrain Imagery of the Harrisburg 30 x 60 Minute Quadrangle from Lidar-Derived Elevation Models at 3-Meter Resolution
This imagery dataset consists of 3-meter resolution, lidar-derived imagery of the Harrisburg 30 x 60 minute quadrangle in Pennsylvania. It also covers part of the Delaware River Basin. The source data used to construct this imagery consist of 1-meter and 3-meter resolution lidar-derived digital elevation models (DEMs). The lidar source data were compiled from different acquisitions published betwe
Enhanced Terrain Imagery of the Reading 30 x 60 Minute Quadrangle from Lidar-Derived Elevation Models at 3-Meter Resolution
This imagery dataset consists of 3-meter resolution, lidar-derived imagery of the Reading 30 x 60 minute quadrangle in Pennsylvania and parts New Jersey. It also covers part of the Delaware River Basin. The source data used to construct this imagery consists of 1-meter and 3-meter resolution Lidar-derived digital elevation models (DEMs). The lidar source data were compiled from different acquisiti
Enhanced Terrain Imagery of the Wilmington 30 x 60 Minute Quadrangle from Lidar-Derived Elevation Models at 3-Meter Resolution
This imagery dataset consists of 3-meter resolution, lidar-derived imagery of the Wilmington 30 x 60 minute quadrangle in parts of Pennsylvania, Maryland, Delaware, and New Jersey. It also covers part of the Delaware River Basin. The source data used to construct this imagery consists of 1-meter and 3-meter resolution Lidar-derived digital elevation models (DEMs). The lidar source data were compil
2015-2017 lidar-derived imagery of karst areas in Puerto Rico at 1-meter resolution
This raster dataset contains 1-meter lidar-derived imagery of 7.5 minute quadrangles in karst areas of Puerto Rico and was created using geographic information systems (GIS) software. Lidar-derived elevation data, acquired between 2015 and 2017, were used to create a 1-meter resolution working digital elevation model (DEM). To create this imagery, a hillshade was applied and a topographic position
Filter Total Items: 32
Analysis of hydrologic and geochemical time-series data at James Cave, Virginia: Implications for epikarst influence on recharge in Appalachian karst aquifers
The epikarst, which consists of highly weathered rock in the upper vadose zone of exposed karst systems, plays a critical role in determining the hydrologic and geochemical characteristics of recharge to an underlying karst aquifer. This study utilized time series (2007–2014) of hydrologic and geochemical data of drip water collected within James Cave, Virginia, to examine the influence of epikars
Authors
Sarah D. Eagle, William Orndorff, Benjamin F. Schwartz, Daniel H. Doctor, Jonathan D. Gerst, Madeline E. Schreiber
Karst mapping in the United States: Past, present and future
The earliest known comprehensive karst map of the entire USA was published by Stringfield and LeGrand (1969), based on compilations of William E. Davies of the U.S. Geological Survey (USGS). Various versions of essentially the same map have been published since. The USGS recently published new digital maps and databases depicting the extent of known karst, potential karst, and pseudokarst areas of
Authors
David J. Weary, Daniel H. Doctor
Instrumenting caves to collect hydrologic and geochemical data: case study from James Cave, Virginia
Karst aquifers are productive groundwater systems, supplying approximately 25 % of the world’s drinking water. Sustainable use of this critical water supply requires information about rates of recharge to karst aquifers. The overall goal of this project is to collect long-term, high-resolution hydrologic and geochemical datasets at James Cave, Virginia, to evaluate the quantity and quality of rech
Authors
Madeline E. Schreiber, Benjamin F. Schwartz, William Orndorff, Daniel H. Doctor, Sarah D. Eagle, Jonathan D. Gerst
Karst of the Mid-Atlantic region in Maryland, West Virginia, and Virginia
The Mid-Atlantic region hosts some of the most mature karst landscapes in North America, developed in highly deformed rocks within the Piedmont and Valley and Ridge physiographic provinces. This guide describes a three-day excursion to examine karst development in various carbonate rocks by following Interstate 70 west from Baltimore across the eastern Piedmont, across the Frederick Valley, and in
Authors
Daniel H. Doctor, David J. Weary, David K. Brezinski, Randall C. Orndorff, Lawrence E. Spangler
Hydrologic and geochemical dynamics of vadose zone recharge in a mantled karst aquifer: Results of monitoring drip waters in Mystery Cave, Minnesota
Caves provide direct access to flows through the vadose zone that recharge karst aquifers. Although many recent studies have documented the highly dynamic processes associated with vadose zone flows in karst settings, few have been conducted in mantled karst settings, such as that of southeastern Minnesota. Here we present some results of a long-term program of cave drip monitoring conducted withi
Authors
Daniel H. Doctor, E. Calvin Alexander, Roy A. Jameson, Scott C. Alexander
A semi-automated tool for reducing the creation of false closed depressions from a filled LIDAR-derived digital elevation model
Closed depressions on the land surface can be identified by ‘filling’ a digital elevation model (DEM) and subtracting the filled model from the original DEM. However, automated methods suffer from artificial ‘dams’ where surface streams cross under bridges and through culverts. Removal of these false depressions from an elevation model is difficult due to the lack of bridge and culvert inventories
Authors
John Wall, Daniel H. Doctor, Silvia Terziotti
Karst in the United States: A digital map compilation and database
This report describes new digital maps delineating areas of the United States, including Puerto Rico and the U.S. Virgin Islands, having karst or the potential for development of karst and pseudokarst. These maps show areas underlain by soluble rocks and also by volcanic rocks, sedimentary deposits, and permafrost that have potential for karst or pseudokarst development. All 50 States contain rock
Authors
David J. Weary, Daniel H. Doctor
Karst geomorphology and hydrology of the Shenandoah Valley near Harrisonburg, Virginia
The karst of the central Shenandoah Valley has characteristics of both shallow and deep phreatic formation. This field guide focuses on the region around Harrisonburg, Virginia, where a number of these karst features and their associated geologic context can be examined. Ancient, widespread alluvial deposits cover much of the carbonate bedrock on the western side of the valley, where shallow karst
Authors
Daniel H. Doctor, Wil Orndorff, Joel Maynard, Matthew J. Heller, Gerolamo C. Casile
Automated determination of the stable carbon isotopic composition (δ13C) of total dissolved inorganic carbon (DIC) and total nonpurgeable dissolved organic carbon (DOC) in aqueous samples: RSIL lab codes 1851 and 1852
The purposes of the Reston Stable Isotope Laboratory (RSIL) lab codes 1851 and 1852 are to determine the total carbon mass and the ratio of the stable isotopes of carbon (δ13C) for total dissolved inorganic carbon (DIC, lab code 1851) and total nonpurgeable dissolved organic carbon (DOC, lab code 1852) in aqueous samples. The analysis procedure is automated according to a method that utilizes a to
Authors
Kinga M. Révész, Daniel H. Doctor
Coupled hydrological and biogeochemical processes controlling variability of nitrogen species in streamflow during autumn in an upland forest
Autumn is a season of dynamic change in forest streams of the northeastern United States due to effects of leaf fall on both hydrology and biogeochemistry. Few studies have explored how interactions of biogeochemical transformations, various nitrogen sources, and catchment flow paths affect stream nitrogen variation during autumn. To provide more information on this critical period, we studied (1)
Authors
Stephen D. Sebestyen, James B. Shanley, Elizabeth W. Boyer, Carol Kendall, Daniel H. Doctor
Comparison of age distributions estimated from environmental tracers by using binary-dilution and numerical models of fractured and folded karst: Shenandoah Valley of Virginia and West Virginia, USA
Measured concentrations of environmental tracers in spring discharge from a karst aquifer in the Shenandoah Valley, USA, were used to refine a numerical groundwater flow model. The karst aquifer is folded and faulted carbonate bedrock dominated by diffuse flow along fractures. The numerical model represented bedrock structure and discrete features (fault zones and springs). Concentrations of 3H, 3
Authors
Richard M. Yager, Niel Plummer, Leon J. Kauffman, Daniel H. Doctor, David L. Nelms, Peter Schlosser
An evaluation of automated GIS tools for delineating karst sinkholes and closed depressions from 1-meter LIDAR-derived digital elevation data
LiDAR (Light Detection and Ranging) surveys of karst terrains provide high-resolution digital elevation models (DEMs) that are particularly useful for mapping sinkholes. In this study, we used automated processing tools within ArcGIS (v. 10.0) operating on a 1.0 m resolution LiDAR DEM in order to delineate sinkholes and closed depressions in the Boyce 7.5 minute quadrangle located in the northern
Authors
Daniel H. Doctor, John A. Young
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Filter Total Items: 42
A geodatabase representing a compilation of Cadwell, D.H., and others, 1991, Surficial Geology of New York; New York State Museum Map and Chart Series 40, scale 1:250,000, 5 sheets.
This Scientific Data Release is a spatial geodatabase representation of a compilation of Cadwell, D.H., Connally, G.G., Fleisher, P.J., Muller, E.H., 1988, Surficial geologic map of New York; Niagara sheet: New York State Museum Map and Chart Series 40, scale 1:250,000, 5 sheets., Muller, E.H., Cadwell, D.H., Connally, G.G., Young, R.A., 1986, Surficial geologic map of New York; Finger Lakes sheetGeospatial files and tabular exposure estimates of sinkhole susceptibility for counties in the conterminous United States for current conditions and projections for the years 2070-2079 - Overview
These datasets support the conclusions in the journal article entitled "Current and future sinkhole susceptibility in karst and pseudokarst areas of the conterminous United States" as described in the abstract below: Sinkholes in karst and pseudokarst regions threaten infrastructure, property, and lives. We mapped closed depressions in karst and pseudokarst regions of the conterminous United StateDeep-learning-derived alluvium, shallow-to-exposed bedrock, and surficial sediment thickness map for the upper Neversink River watershed, New York
This dataset consists of a raster and surficial shapefiles for the Neversink River watershed, NY, that were generated using ArcGIS Pro's deep learning functionality. The shapefiles contain polygons that show the locations of shallow-to-exposed bedrock and alluvium-filled valleys, while the raster provides estimated minimum sediment thicknesses in the areas between the shallow/exposed bedrock and aA geodatabase of Surficial Geology of the Allentown 30x60-Minute Quadrangle in Pennsylvania digitized from the original map of Braun, 1996
This Scientific Data Release is a spatial geodatabase representation of Braun, D. D., 1996, Surficial geology of the Allentown 30x60-minute quadrangle: Pennsylvania Geological Survey, 4th ser., Open-File Report 96-48, 17 p., 1 map, scale 1:100,000. These geospatial data depict surficial geologic materials in the Pennsylvania portion of the Allentown 30 x 60-minute quadrangle in eastern PennsylvaniStream Temperature, Dissolved Radon, and Stable Water Isotope Data Collected along Headwater Streams in the Upper Neversink River Watershed, NY, USA (ver. 2.0, April 2023)
This data release contains three data types that could potentially be used to infer spatiotemporal variability in groundwater discharge processes, along with other research and monitoring purposes: 1) Temporally continuous stream channel water temperature and adjacent streambank air temperature time series data (generally starting November 2020) as well as limited temperature data from May to OctoEnhanced Terrain Imagery of the Sunbury 30 x 60 Minute Quadrangle from Lidar-Derived Elevation Models at 3-Meter Resolution
This imagery dataset consists of 3-meter resolution, lidar-derived imagery of the Sunbury 30 x 60 minute quadrangle Pennsylvania. It also covers part of the Delaware River Basin. The source data used to construct this imagery consists of 1-meter and 3-meter resolution Lidar-derived digital elevation models (DEMs). The lidar source data were compiled from different acquisitions published between 20Enhanced Terrain Imagery of the York 30 x 60 Minute Quadrangle from Lidar-Derived Elevation Models at 3-Meter Resolution
This imagery dataset consists of 3-meter resolution, lidar-derived imagery of the York 30 x 60 minute quadrangle in Pennsylvania and Maryland. It also covers part of the Delaware River Basin. The source data used to construct this imagery consists of 1-meter and 2-meter resolution Lidar-derived digital elevation models (DEMs). The lidar source data were compiled from different acquisitions publishEnhanced Terrain Imagery of the Hagerstown 30 x 60 Minute Quadrangle from Lidar-Derived Elevation Models at 3-Meter Resolution (ver. 1.1, February 2024)
This imagery dataset consists of 3-meter resolution, lidar-derived imagery of the Hagerstown 30 x 60 minute quadrangle in Pennsylvania, Maryland, and part of West Virginia. The source data used to construct this imagery consists of 1-meter resolution lidar-derived digital elevation models (DEMs). The lidar source data were compiled from different acquisitions published between 2016 and 2023. The dEnhanced Terrain Imagery of the Harrisburg 30 x 60 Minute Quadrangle from Lidar-Derived Elevation Models at 3-Meter Resolution
This imagery dataset consists of 3-meter resolution, lidar-derived imagery of the Harrisburg 30 x 60 minute quadrangle in Pennsylvania. It also covers part of the Delaware River Basin. The source data used to construct this imagery consist of 1-meter and 3-meter resolution lidar-derived digital elevation models (DEMs). The lidar source data were compiled from different acquisitions published betweEnhanced Terrain Imagery of the Reading 30 x 60 Minute Quadrangle from Lidar-Derived Elevation Models at 3-Meter Resolution
This imagery dataset consists of 3-meter resolution, lidar-derived imagery of the Reading 30 x 60 minute quadrangle in Pennsylvania and parts New Jersey. It also covers part of the Delaware River Basin. The source data used to construct this imagery consists of 1-meter and 3-meter resolution Lidar-derived digital elevation models (DEMs). The lidar source data were compiled from different acquisitiEnhanced Terrain Imagery of the Wilmington 30 x 60 Minute Quadrangle from Lidar-Derived Elevation Models at 3-Meter Resolution
This imagery dataset consists of 3-meter resolution, lidar-derived imagery of the Wilmington 30 x 60 minute quadrangle in parts of Pennsylvania, Maryland, Delaware, and New Jersey. It also covers part of the Delaware River Basin. The source data used to construct this imagery consists of 1-meter and 3-meter resolution Lidar-derived digital elevation models (DEMs). The lidar source data were compil2015-2017 lidar-derived imagery of karst areas in Puerto Rico at 1-meter resolution
This raster dataset contains 1-meter lidar-derived imagery of 7.5 minute quadrangles in karst areas of Puerto Rico and was created using geographic information systems (GIS) software. Lidar-derived elevation data, acquired between 2015 and 2017, were used to create a 1-meter resolution working digital elevation model (DEM). To create this imagery, a hillshade was applied and a topographic position - Maps
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Filter Total Items: 32
Analysis of hydrologic and geochemical time-series data at James Cave, Virginia: Implications for epikarst influence on recharge in Appalachian karst aquifers
The epikarst, which consists of highly weathered rock in the upper vadose zone of exposed karst systems, plays a critical role in determining the hydrologic and geochemical characteristics of recharge to an underlying karst aquifer. This study utilized time series (2007–2014) of hydrologic and geochemical data of drip water collected within James Cave, Virginia, to examine the influence of epikarsAuthorsSarah D. Eagle, William Orndorff, Benjamin F. Schwartz, Daniel H. Doctor, Jonathan D. Gerst, Madeline E. SchreiberKarst mapping in the United States: Past, present and future
The earliest known comprehensive karst map of the entire USA was published by Stringfield and LeGrand (1969), based on compilations of William E. Davies of the U.S. Geological Survey (USGS). Various versions of essentially the same map have been published since. The USGS recently published new digital maps and databases depicting the extent of known karst, potential karst, and pseudokarst areas ofAuthorsDavid J. Weary, Daniel H. DoctorInstrumenting caves to collect hydrologic and geochemical data: case study from James Cave, Virginia
Karst aquifers are productive groundwater systems, supplying approximately 25 % of the world’s drinking water. Sustainable use of this critical water supply requires information about rates of recharge to karst aquifers. The overall goal of this project is to collect long-term, high-resolution hydrologic and geochemical datasets at James Cave, Virginia, to evaluate the quantity and quality of rechAuthorsMadeline E. Schreiber, Benjamin F. Schwartz, William Orndorff, Daniel H. Doctor, Sarah D. Eagle, Jonathan D. GerstKarst of the Mid-Atlantic region in Maryland, West Virginia, and Virginia
The Mid-Atlantic region hosts some of the most mature karst landscapes in North America, developed in highly deformed rocks within the Piedmont and Valley and Ridge physiographic provinces. This guide describes a three-day excursion to examine karst development in various carbonate rocks by following Interstate 70 west from Baltimore across the eastern Piedmont, across the Frederick Valley, and inAuthorsDaniel H. Doctor, David J. Weary, David K. Brezinski, Randall C. Orndorff, Lawrence E. SpanglerHydrologic and geochemical dynamics of vadose zone recharge in a mantled karst aquifer: Results of monitoring drip waters in Mystery Cave, Minnesota
Caves provide direct access to flows through the vadose zone that recharge karst aquifers. Although many recent studies have documented the highly dynamic processes associated with vadose zone flows in karst settings, few have been conducted in mantled karst settings, such as that of southeastern Minnesota. Here we present some results of a long-term program of cave drip monitoring conducted withiAuthorsDaniel H. Doctor, E. Calvin Alexander, Roy A. Jameson, Scott C. AlexanderA semi-automated tool for reducing the creation of false closed depressions from a filled LIDAR-derived digital elevation model
Closed depressions on the land surface can be identified by ‘filling’ a digital elevation model (DEM) and subtracting the filled model from the original DEM. However, automated methods suffer from artificial ‘dams’ where surface streams cross under bridges and through culverts. Removal of these false depressions from an elevation model is difficult due to the lack of bridge and culvert inventoriesAuthorsJohn Wall, Daniel H. Doctor, Silvia TerziottiKarst in the United States: A digital map compilation and database
This report describes new digital maps delineating areas of the United States, including Puerto Rico and the U.S. Virgin Islands, having karst or the potential for development of karst and pseudokarst. These maps show areas underlain by soluble rocks and also by volcanic rocks, sedimentary deposits, and permafrost that have potential for karst or pseudokarst development. All 50 States contain rockAuthorsDavid J. Weary, Daniel H. DoctorKarst geomorphology and hydrology of the Shenandoah Valley near Harrisonburg, Virginia
The karst of the central Shenandoah Valley has characteristics of both shallow and deep phreatic formation. This field guide focuses on the region around Harrisonburg, Virginia, where a number of these karst features and their associated geologic context can be examined. Ancient, widespread alluvial deposits cover much of the carbonate bedrock on the western side of the valley, where shallow karstAuthorsDaniel H. Doctor, Wil Orndorff, Joel Maynard, Matthew J. Heller, Gerolamo C. CasileAutomated determination of the stable carbon isotopic composition (δ13C) of total dissolved inorganic carbon (DIC) and total nonpurgeable dissolved organic carbon (DOC) in aqueous samples: RSIL lab codes 1851 and 1852
The purposes of the Reston Stable Isotope Laboratory (RSIL) lab codes 1851 and 1852 are to determine the total carbon mass and the ratio of the stable isotopes of carbon (δ13C) for total dissolved inorganic carbon (DIC, lab code 1851) and total nonpurgeable dissolved organic carbon (DOC, lab code 1852) in aqueous samples. The analysis procedure is automated according to a method that utilizes a toAuthorsKinga M. Révész, Daniel H. DoctorCoupled hydrological and biogeochemical processes controlling variability of nitrogen species in streamflow during autumn in an upland forest
Autumn is a season of dynamic change in forest streams of the northeastern United States due to effects of leaf fall on both hydrology and biogeochemistry. Few studies have explored how interactions of biogeochemical transformations, various nitrogen sources, and catchment flow paths affect stream nitrogen variation during autumn. To provide more information on this critical period, we studied (1)AuthorsStephen D. Sebestyen, James B. Shanley, Elizabeth W. Boyer, Carol Kendall, Daniel H. DoctorComparison of age distributions estimated from environmental tracers by using binary-dilution and numerical models of fractured and folded karst: Shenandoah Valley of Virginia and West Virginia, USA
Measured concentrations of environmental tracers in spring discharge from a karst aquifer in the Shenandoah Valley, USA, were used to refine a numerical groundwater flow model. The karst aquifer is folded and faulted carbonate bedrock dominated by diffuse flow along fractures. The numerical model represented bedrock structure and discrete features (fault zones and springs). Concentrations of 3H, 3AuthorsRichard M. Yager, Niel Plummer, Leon J. Kauffman, Daniel H. Doctor, David L. Nelms, Peter SchlosserAn evaluation of automated GIS tools for delineating karst sinkholes and closed depressions from 1-meter LIDAR-derived digital elevation data
LiDAR (Light Detection and Ranging) surveys of karst terrains provide high-resolution digital elevation models (DEMs) that are particularly useful for mapping sinkholes. In this study, we used automated processing tools within ArcGIS (v. 10.0) operating on a 1.0 m resolution LiDAR DEM in order to delineate sinkholes and closed depressions in the Boyce 7.5 minute quadrangle located in the northernAuthorsDaniel H. Doctor, John A. Young - News