Improving Root-Zone Compaction with Pervious Driveways | Shades of Green Blog

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Hi there! Welcome to the PawPaw Patch blog, a place to learn and grow. We've been up to this for a while, so I want to share what we've learned in the field so we can accelerate change together. Stay a while and say hello!

Hi, I'm Brandy.

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Improving Root-Zone Compaction with Pervious Driveways

Jan 19, 2021

Here are a few ecologically-sound driveway upgrades you can do to create pervious surface while protecting tree roots from compaction.

You probably wouldn’t guess it, but driveways are high on the priority list for many of our clients. There is a broad spectrum of ecologically-sound options, all of them pervious.

On the more costly end of the spectrum, you can consider using materials such as lattice pavers with groundcover infill, like this:

And there are less expensive options, such as geogrid with an aggregate infill, like this:

 

geogrid aggregate

But, aside from the various material choices in renovating your driveway, I want to talk to you about one unexpected application of a previous driveway⏤to reduce root zone compaction. I’m going to show you two examples of projects we’ve done that illustrate this:

APPLICATION #1

This first project features a farm access road that cuts through a forested area on the property. The drive cut through mature trees, and due to the compaction created by the vehicles and the direction of the road down the slope, the water began carving away at the topsoil and eroding the trees’ root zone. Then, the now exposed roots were subject to vehicle traffic, which was noticeably impacting their health. The clients wanted to formalize an access road to the back of the property and develop a solution that wouldn’t involve digging down to damage the tree roots further.

Instead, we built the roadbed up above the existing grade and added pervious lattice pavers with a groundcover infill. The benefit was twofold: we stabilized the slope and kept the soil from eroding, and we protected the tree roots from further compaction by spreading out the force of traffic into the lattice grid rather than at a single point of impact.

APPLICATION #2

Another example of this technique was a recently project completed. The existing asphalt driveway was built when the trees were small, and as they matured, the roots heaved up, buckling the asphalt and exposing them to compaction from repeated traffic.

Our solution was to remove the asphalt and build the new driveway up above grade. We added a geogrid with aggregate infill, which had two benefits: the geogrid prevents compaction by creating a spongy base that absorbs impact. The new driveway gave the roots more room to grow, infiltrating water and stabilizing soil.

 

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