Walking to work in heavy rain a couple of weeks ago, it was impossible not to notice the rainwater streaming over roadways and into storm drains.
The rain made a constant drumming on my umbrella until I walked beneath a couple of large Douglas firs, at which point the drumming slowed to a drip, plunk, drip. While the sidewalk was not dry, these two large conifers were clearly intercepting, slowing and redirecting rain drops well before they hit the ground.
I think many Washingtonians view trees as landscape amenities that enhance the livability of our communities, however, they may not understand the full scope, value, and impact of the ecosystem services trees provide in urban areas.
Evergreen trees are particularly valuable in the Pacific Northwest. They reduce the volume of winter-time stormwater that reaches impervious surfaces and runs off into stormwater treatment facilities, or in many cases, directly into streams, rivers, and Puget Sound. Intercepting stormwater with trees and reducing volumes of runoff helps communities avoid or defer costly upgrades to stormwater infrastructure.
Of course, it is not always possible to plant Douglas fir, Ponderosa pine or other large-growing native conifer species in the confined spaces found within urban areas. Before you plant any large-maturing tree, make sure there is plenty of room above and below ground for it to reach its full potential.
Finding good places to plant big conifers in urban areas may be challenging, but it is worth the extra effort to incorporate these storm-water-mitigating trees into your community forest.
You can find out more about stormwater runoff and how trees help reduce stormwater at this link.
By Linden J. Lampman, program manager, DNR Urban and Community Forestry Program