County staff have developed lower, middle, and upper options for impervious area limits. Each would have tradeoffs and benefits:

  • Less impervious area would create more space for trees and other plants. This can reduce reliance on human-made infrastructure to manage stormwater runoff and help provide all the other benefits of trees such as cooling, filtering pollution, and habitat.
  • When impervious area increases, stormwater runoff and pollution increase and the ‘urban heat island’ effect worsens.
  • Generally, when impervious area increases, tree canopy -- the land area that is covered by tree trunks, branches, and leaves -- decreases. Impervious area prevents water from reaching tree roots, which restricts a tree's ability to grow.
  • More impervious area, however, would give residents more flexibility with their property for meeting changing household needs through additions and improvements, such as walkways, patios, storage sheds, and parking. 

Review these slides for a deeper dive into the data on existing impervious area, tree canopy, equity, and other factors that inform the proposed impervious area limit options.

Row of three diagrams of rectangular residential lots (in this example, lots in the R-6 zoning district with older homes). The lots have varying amounts of impervious area (hard surfaces that keep rainwater from soaking into the ground) and area for planting trees. Above the diagram on the left are the words “Less Impervious Area.” Above the diagram on the right are the words “More Impervious Area.” Under the diagram on the left are “Option A (40% impervious area).” Under the middle diagram, “Option B (45% impervious area).” Under the diagram on the right, “Option C (50% impervious area).” Option A shows the least amount of impervious area (in features such as a house, a shed, and a driveway) and the greatest area for planting trees. Option C shows the greatest amount of impervious area and the least area for planting trees.

Click anywhere on the images above to enlarge all three.

Select one of the following options.

Use Tab to navigate between options, Space or Enter to select

Which impervious area limit option do you prefer?

Use Tab to navigate between options, Space or Enter to select
Select a response

I own a lot in a low density residential neighborhood. How would the impervious area limits affect me?

The proposed impervious area limits for lots with single-family homes would be categorized by zoning districts:

OptionsR-20R-10R-8R-6R-5R2-7
Lower25%30%35%40%45%45%
Middle30%35%40%45%50%50%
Upper35%40%45%50%55%55%
  • If your lot is at or just above the minimum required size for your zoning district, the proposed lower, middle, and upper limit options would be given as maximum percentages (%) of lot area.
  • If your lot is below the minimum required size for your zoning district (under-sized), or more than 140 percent of the minimum required size (over-sized), the proposed limit options would be given as maximum square feet (sf).

You can see how the limit options would apply to your lot using the Low Residential Study Map Viewer.

 

Map Viewer Instructions

Type your address in the search bar at the upper right.

Click on the small circle that appears over your property.

Click on the right-pointing arrow to expand the info box at the lower right.

For more information on the Low Residential Study, the development of the proposed impervious area limits, and the data used, visit the LRS website.