The Green Infrastructure & Low Impact Development Series explores some of the Best Management Practices (BMPs) of Green Infrastructure and LID for both urban and rural applications. The IRWP is currently working with local cities, counties and organizations to implement green infrastructure and LID elements within the Illinois River Watershed. Watch for these demonstration projects in public spaces to see first-hand stormwater management in action!


Since impervious pavement is the primary source of stormwater runoff, Low Impact Development strategies recommend permeable paving for parking areas and other hard surfaces. Permeable paving allows rainwater to percolate through the paving and into the ground before it runs off. This approach reduces stormwater runoff volumes and minimizes the pollutants introduced into stormwater runoff from parking areas.

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 Three types of permeable paving.  Photo credit: (LEFT) LID – SEMCOG, (CENTER) Basalite, (RIGHT) East Central Community Council

There are three major types of permeable paving.

  • Paving stones (AKA unit pavers) are impermeable blocks made of brick, stone, or concrete, set on a prepared sand base. The joints between the blocks are filled with sand or stone dust to allow water to percolate downward. Some concrete paving stones have an open cell design to increase permeability.
  • Porous asphalt and pervious concrete appear to be the same as traditional asphalt or concrete pavement. However, they are mixed with a very low content of fine sand, so that they have 10%-25% void space.
  • Grass pavers (AKA turf blocks) are a type of open-cell unit paver in which the cells are filled with soil and planted with turf. The pavers, made of concrete or synthetic, distribute the weight of traffic and prevent compression of the underlying soil.

2_d-porous paving copyTypical cross-section for a porous pavers design.  Photo credit: Abbey Associates, Inc.

As with any stormwater design tool, it is best to evaluate the total functionality and cost for your application. Anticipated traffic intensities, purpose and location of tree planters or landscape beds are examples of site evaluation. Also, soil types and percolation rates will be important information to design appropriately. Not every space is suitable for permeable paving, but there are a lot that are!!

For case studies, examples and specifications, visit a helpful site we found, Interlocking Concrete Pavement Institute.

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 Permeable Paving is becoming a major tool for on-site stormwater management.  Photo credit: Pacific Interlock Pavingstone


The Illinois River Watershed Partnership works to improve and restore the Illinois River Watershed through public education, water quality monitoring, and conservation/restoration projects. Check out our website for current events that continue to educate stakeholders of the Illinois River Watershed about Green Infrastructure and Low Impact Development, as well as events that offer volunteer opportunities to make a positive difference!


Related Posts:

Green Infrastructure & LID Series: Tree Wells

10 Inspiring Ideas to Achieve a Water Smart Yard

Watershed Landscape: Rain Garden Design- Part I