Imprevious Surface Calculation

The project area of the site is being updated. This page is in work.



Surface analysis


  • Improve the efficiency and effectiveness of calculating the percentage of impervious surface on any given area of land


  • LandSat
  • TBD

Output maps are available in the District group in the map Gallery

Current project document (Word) (PDF)




Surface Water Management

In 2012, King County Surface Water Management (SWM) brought a small group of residents together to provide advice on a possible SWM fee increase.

In the fee structure, SWM calculates the percentage of impervious surface on commercial properties and provides discounts for high quantities of pervious surface.

For rural properties, both residential and commercial, SWM is unable to determine the percentages with enough accuracy to offer fee reductions when theres a large amount of pervious surface.

One of the recommendations the resident group made was to use GIS to improve the efficiency and effectivenets of calculating the percentage of impervious surfaces.