By L. Peter MacDonagh, RLA, ISA, LEEP-AP

I have a lot of discussions about the role of trees, soil and stormwater in the urban environment — particularly, about how much more effective than your average stormwater system that they can be at managing daily rainfall events. Sometimes I encounter disbelief that this could be the case, so let me share an analogy I use to explain it.

The current stormwater system is on high alert 24/7. Every rain event, no matter how small, puts water in the pipes. This means that the stormwater pipes have less capacity for the big storms. It’s the same as if I call 911 every time I get a paper cut. There won’t be enough ambulances on the road to take care of the people with heart attacks and strokes.

If we have the small rain events — the paper cuts — taken care of by the non-emergency green infrastructure systems such as the urban forest, then we will then have enough capacity in the pipes for our big storms. By using trees and soil to manage small rain events, we are promoting a healthier urban forest and ensuring that there are enough ambulances for the emergencies.

Image: The Rabers