GIS Completes an Impervious Surface Analysis for the Stormwater Management Program

Since 2008, Winnetka has seen more than average flooding in the community that has affected financial losses and destruction. Winnetka has brought it upon itself to alleviate the struggle with flooding by implementing a Stormwater Management Program. This program uses expert advisors to assess the land and systems to determine the best way to pay for a permanent solution. In the massive flooding of 2011, it caused approximately $7.6 million in uninsured damages! Winnetka’s goal is to substantially reduce structural flooding by 2017 with the implementation of the stormwater fee to pay for the system improvements. These fees are based on the impervious surfaces on each parcel of land. GIS was able to step in to complete a full analysis!


An Impervious Surface Analysis takes into account all impervious GIS data, Cook Co. data and Winnetka billing data and merges it all together based on PINs.  The list of impervious data that was merged is:

  • Building

  • Driveway

  • Miscellaneous Features (such as patios)

  • Parking Areas

  • Paths

  • Paved Areas

  • Private Roads

  • Sidewalks

The impervious surfaces were created from a fly-over of the Village by Ayers (contracted out by the Village). This was then brought together with Zoning Information, Cook Co. Assessor Data (Taxpayer information), Water Billing Data, Parcel Data and GIS Addresses. Checks and balances on the data were completed throughout the analysis to assure data and information accuracy. With this data, it can now be brought into the financial system, New World, and out to the residents of Winnetka. 

Without GIS, this analysis could not be completed with these accuracy levels and in the time that it was done. More is still to come with the Impervious Surface Analysis!