Impervious Area Map

Why Is Impervious Area Important?

Impervious surface areas like rooftops, sidewalks, walkways, patio areas, driveways, parking lots, sheds and more that don't allow stormwater to do what it normally does - soak into the ground. View the impervious surface area on your property by viewing the map.

How to Read the Map

Stormwater Map

Understanding Map Elements

The map is based on 2015 Geographic Information Systems (GIS) data collected by the County and verified in 2018 with our own flyovers.


Select these buttons for more information about each area.

More Information Button

Impervious areas: Impervious areas are shown in red.

Impervious Area

Parcel Information: Select within your "black-line" property boundaries and an information box will appear.

Ready to See Your Impervious Area?

View the Map.

Understanding the Red Areas on Your Property

When we capture property information from aerial photography, we can't always shoot pictures of buildings from directly overhead. Please note: the impervious area calculations for buildings are based on the roof area centered over the building foundation. Because the angle of the image varies for every property, this method is the industry standard and ensures the most accurate measurement of building areas.

  • Side of a building: The image may show a side of a building in red. Don't worry - no one is charged for the side of the structure.
  • Part of roof is not in red: Since the calculations are based on the roof area centered over the building foundation, part of a roof may not be colored, but the measurement is still accurate.
  • Impervious surface area in the right-of-way: You may notice your driveway or sidewalk is outside of your property line. You are not charged for any surface outside of your property.

See something that shouldn't be considered impervious? Please read about appeals and contact us.

Surfaces considered to be impervious: roofs (of buildings including houses, sheds, garages and more), sidewalks, driveways, parking lots, paved areas, gravel, bricks, patios

Surfaces not considered to be impervious: yards, flower beds, gardens, lawn furniture.

Calculate Your Bill

House GraphicThe stormwater utility fee is based on the amount of impervious surface area on a property. Each billing unit will be set at $5 per 1,000 square feet of impervious area.

Read about credits and grants.


Notice an error? Get information about the appeals process.