Land Use and Impervious Surface Area Change by County in Pennsylvania (1985-2000) as Interpreted Quantitatively by Means of Satellite Imagery

County averages of impervious surface area (ISA), and the urban and woodland fractions were determined for all 67 Pennsylvania counties from archived Landsat image data for the years 1985 and 2000. This paper focuses on changes in these quantities that occurred during the 15-year period, the patterns of development across the state, and the possible reasons for the changes. Changes in ISA suggest a movement of population away from the largest cities into less populated areas where land is more abundant and where taxes and land values are lower. Most counties experienced at least some gain in ISA, primarily in lowand mid-level density development (mainly housing). Other than a few exceptions, Lackawanna and Erie Counties, counties experiencing dominant growth in the high density categories were generally less developed and with less impervious surface area than the average.