DYK? Trees are also stormwater filters!

street trees are proven stormwater filters
Street trees are proven stormwater filters


Why all the fuss about managing stormwater? Simply put, stormwater pollutes waterways.

Stormwater runoff carries dirt, oil and other pollutants to rivers and streams. It can also cause erosion and flooding that harm properties and wildlife habitat.1

“Portland’s trees are also playing an underappreciated role every time it rains: They’re helping us prevent major flooding and avoid erosion; they are literally holding Multnomah County together.” 4

Traditionally, and still common throughout the country, stormwater is primarily managed through “grey” solutions such as massive construction and excavation projects that install giant pipes to divert the wastewater. Thinking green, Portland conducted a study and found there could be significant savings in the cost of the Big Pipe project by including green infrastructure along with wider sewer pipes.2 Other cities are catching on; Friends of Trees regularly receives inquiries from other cities (a recent call came from Louisville, KY) looking for more information about this partnership and its benefits.

Per an agreement between Portland Parks and Recreation and BES, “Portland’s Bureau of Environmental Services recognizes that, among the numerous environmental, economic, and social benefits trees provide, they can work for clean rivers by helping to manage stormwater where it falls. Planting trees can expand and enhance the urban forest canopy and help the city meet key goals of several plans,” including the City’s Climate Action Plan and Watershed Management Plan.3

In other words, BES recognizes the multiple bottom line trees deliver, and how essential trees are to a healthy, equitable and livable city. For more information about trees and stormwater management (and to check out a very cool interactive model that demonstrates trees’ impact), visit our friends at the Arbor Day Foundation. And when you can safely swim in a river or eat fish from a lake this summer be sure to thank the trees.

Read more about trees + stormwater.

  1. BES
  2. City of PortlandECONorthwest, et al reportNRDC report
  3. Portland Parks and BES agreement
  4. Multnomah County Trees Are Doing Much More Than We Think, OPB, 2019