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Delaware River Basin Project

Twentieth-Century Land Surface Changes in the Delaware Water Gap Basin, a GIS Snapshot Approach

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Links to individual projects:
Modeling Urban Expansion in the Philadelphia Metropolitan Area; A Cellular Automata Approach
Historical land-use data from the twentieth century was used as input to the SLEUTH land-use change model, a Cellular Automata model developed by Keith Clarke at the University of California at Santa Barbara, to produce projections of urban expansion in the Philadelphia metropolitan area.

Twentieth-Century Land Surface Changes in the Delaware Water Gap Basin, a GIS Snapshot Approach
Methods of integrating land-surface data and measuring change with time are being tested on historical land use/land cover data of the Delaware Water Gap watershed area in Pennsylvania.

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Delaware Water Gap
The Delaware Water Gap is a "gap" or gorge that formed as the Delaware River cut through the rocks of the Appalachian Mountains. Today, the gorge is a scenic part of the Delaware Water Gap National Recreation Area.

As the only systematically-collected maps of the entire nation, detailed enough to show local conditions, the USGS historical topographic maps can uniquely offer historical documentation of topographical data for the United States during the 20th century. From these data, researchers can extract and compile land use and land cover conditions and changes affecting global, regional, and local environmental problems. Land use changes affect biodiversity, water quality, forest cover, and nutrients; landscape changes mask previous landscapes, upon which our personal, regional, and national identities were built. This study offers two types of sources for detecting land use and land cover change in the Delaware Water Gap watershed; historical topographic mapping and Geographic Information System (GIS) data drawn from those maps. Both of these types of data can be downloaded here. The comparison of these mapping data for the same location between different editions reveals changes on the landscape that are important for various geographic purposes.

National topographic mapping "once-over coverage," or the completion of a 1:24,000 scale quadrangle map series covering the entire United States was performed by the USGS from the late 1880s up to about 1991. Mapping began with surveyors going to the field with plane tables and alidades, and after the 1930s with aerial photographs, to establish ground control and to classify features on the photography. The photos were used in stereoplotters (introduced in the 1940s) for photogrammetric compilation. Bushkill PA-NJ

Digital Raster Graphics (DRGs) are scanned images of published topographic quadrangle maps. The file names of the DRGs are composed of the name of the quadrangle and the years of the original edition of its publication. To identify the name of the quadrangle that covers the area of your interest in the basin, please refer to the index map. The geographical area that each DRG covers varies. Until the 1940s, maps were published mostly as 15' by 15' quadrangles when the transition to 7.5' by 7.5' maps was started and continued through the 1990s. Some maps from the 1940s were published by the Army Map Service in partnership with the USGS, and occasionally maps were published at other scales, such as 1:25,000.

The massive effort required to complete map coverage of the nation meant that revisions and maintenance of the maps was sometimes delayed. However, the information was checked and considered reliable for the publication date of each map edition. When a map edition was photo-revised or reprinted, the file name in the data base may have just the last two digits of the edition year and photo-revisions or its reprinting. The USGS map production documentation is unclear as to whether or not reprints of editions incorporated changes since the original or latest publication date; some have been determined to have changes, and others don't. Not all of the published maps, as documented from production records, can be located in this database. Some maps have a date stamped in the collar; that is presumably the date the map was added to the library collection.

The digitized land use/land cover data were classified according to a modified Anderson Land Use/Land Cover data categorization system. The table of land use/land cover classes has added codes that appear in the data attribute tables. The land use/land cover data files may contain topological errors, such as polygon slivers, as a result of the digitizing process. (Download the free Adobe Reader)

More technical information on these data is available from the metadata file.


This project was partly funded by NASA Research Announcement 00-OES-08NASA Carbon-0000-0270 Carbon Cycle Science and Related Opportunities in Biology and Biogeochemistry of Ecosystems and Applications (NRA-00-OES-08) awarded to the Delaware River Basin Collaborative Environmental Monitoring and Research Initiative. Some maps were made available courtesy of the Map Collection, Free Library of Philadelphia, and the Map Division, New York Public Library. Nathan Piekielek, National Park Service , contributed important technical comments about the land use/land cover database.

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Page Last Modified: Monday, 14-Jan-2013 19:26:19 EST