One of my favorite elementary school memories was when mysterious dirt clods appeared all over my playground. At recess that day, my friends and I used the natural ammunition to play a cross between capture-the-flag and team dodgeball. The next day our teacher announced we couldn’t touch (or throw) the dirt clods. That was obviously impossible, so we weren’t allowed on the grass part of the playground for a while. But that first day was totally worth it, which is why I am pleased to report that those dirt clods are part of an elegant solution to stormwater issues.
Stormwater runoff increases as we create more places that shed rainwater (e.g. roads, parking lots, buildings). We can install bigger pipes to move the water away from cities, but this approach is expensive and disruptive and the stormwater still requires energy-intensive treatment. And bigger pipes don’t reduce the amount of stormwater, they just move the flooding somewhere else. Instead of trying to manhandle stormwater, more designers are using a Low Impact Development (LID) approach, striving to maintain pre-development watershed conditions using techniques such as green roofs and porous pavement.
After elementary school, I learned where my beloved dirt clods came from. More recently, I learned that aeration is an LID technique, a beautifully subtractive elegant solution. I think we tend to overlook subtraction and aeration works because of what is taken away, not anything that is added. Aeration is also cheap. A city can aerate a lot of parks for the price of one green roof. My only hope is that, for one day at least, they let the kids throw the dirt.