Modern urbanization results in profound changes to the landscape, specifically the proliferation of asphalt and concrete, and the displacement of agriculture and forestland. A temporal database of urban land transformations, depicting these changes, is needed by urban and regional planners, policy and decision makers, earth scientists, and global change researchers to measure trends in urban sprawl, analyze patterns of water pollution and sedimentation, understand the impacts of development on ecosystems, and develop predictive modeling techniques to better forecast future areas of urban growth.
The U.S. Geological Survey's EROS Data Center and NASA are working in collaboration to map urbanization as it occurred over time in selected metropolitan regions. Integrated and flexible temporal urban land characteristics databases for both the San Francisco Bay and the Baltimore-Washington regions have been compiled. These progressive geo-referenced databases of urban change are developed by merging information from historic maps, census statistics, commerce records, remotely sensed data, and digital land use data. USGS's rich data archives provided the bulk of the source material. Methodologies for interpreting, extracting, and compiling source information into each thematic data layer were developed. Information on urban development, principal transportation, hydrography, agricultural lands, forest lands, wetlands, and population density is being compiled in the geo-referenced database.
The San Francisco Bay and Baltimore-Washington databases provide a strong visual portrayal of urban growth patterns. The principal transportation data layer clearly demonstrates the influence that the transportation infrastructure (roads, railroads, and seaports) have exerted on population development. The hydrography data layer contributes to historical understanding by accentuating the loss of navigable rivers by siltation, the development of reservoirs for water supplies, and the changing shoreline resulting from harbor development and salt pond formation.
These datasets provide the information necessary for the geographic analysis of urban land use change. The historical perspective provides insight into the interactions of the physiographic and socio-economic variables that contribute to urban growth.
COLLABORATORS: USGS Mapping Applications Center, University of Maryland Baltimore County, U.S. Bureau of Census, Library of Congress.
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