Impervious Surface Analysis Tool

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The Impervious Surface Analysis Tool (ISAT), a custom suite of easy-to-use scripts for ArcGIS, is used to calculate the percentage of impervious surface area within user-selected geographic areas, such as watersheds, municipalities, and subdivisions. ISAT uses imperviousness values to categorize areas as having good, fair, or poor water quality. A correlation between an increase in impervious surfaces and a decrease in water quality has been well established, and ISAT users may find the information derived from ISAT helpful in predicting how different management scenarios might impact local water quality.

output from the Impervious Surface Analysis Tool (ISAT) using arcgis 10


  • Calculates the percent impervious area and total impervious surface area of each selected polygon
  • Categorizes polygons to represent conditions of good, fair, and poor water quality based on calculated imperviousness
  • Incorporates land cover change scenarios to examine how changes influence impervious surfaces

Technical Specifications

  • ESRI ArcView 10.x
  • ESRI Spatial Analyst

Data Requirements

  • Raster-based land cover or land use grid
  • Polygon data set for which percentage of impervious surface is to be calculated
  • Set of land cover impervious surface coefficients, optionally calibrated for low, medium, and high population densities
  • Optional population density theme

Note: Tutorial and sample data are included when the tool is downloaded.


Provides a printable guide for self-paced training using sample data sets

Note: Tutorial and sample data are included when the tool is downloaded.

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ISAT for ArcGIS 10.x

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Previous Versions

Note for ArcGIS 9.2 and 9.3 Users: Besides installing the ISAT extension for ArcGIS 9.x, you must also install the ISAT patch for ArcGIS 9.2. The patch addresses several issues discovered with ArcGIS 9.2.

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