CORVALLIS, Ore. — As human populations continue to transition into an urban landscape, cities are faced with challenges in developing and maintaining balanced ecosystems. One newer innovation has those interested in these challenges looking up, literally: green roofs.

In western Oregon, the high presence of non-permeable surfaces like roads, buildings and parking lots results in a specific set of issues surrounding storm water run-off and water treatment facilities. These surfaces do not allow the heavy winter rains to penetrate into the ground. As a result, storm water run-off often overloads treatment facilities causing pollution and other contaminants to be deposited into area rivers.

Green roofs, or eco roofs, can mitigate storm water run-off and reduce the pressure on already stressed infrastructure. The subject of new research at Oregon State University, these roofs are planted with an array of succulents in an engineered growing medium that absorbs rainfall and slows the speed of storm water through wastewater treatment facilities.

"Storm water management is a primary reason that many city governments are interested in green roofs, said Erin Shroll, the lead researcher on OSU's Green Roof Technology project. "But there are a host of other benefits associated with the roofs ranging from better building insulation, to reductions in the urban heat island affect and increases in wildlife habitat."

Despite the benefits of green roofs, the science behind building successful green roofs is still in its early stages in the Pacific Northwest, and around much of the world, said Shroll.

"Each area in the city, and to a degree each portion of roof, has its own microclimate that creates a variety of conditions that must be considered before planting," said Shroll. "We're looking at what plants are most conducive to success in the northwest. It's a very regional study, but one that will tell us a lot about the intricacies of individual areas."

Shroll's study area includes 25 test plots at the Oak Creek Center for Urban Horticulture on OSU's campus and the roof of the Portland Building in downtown Portland. The campus test plots and the Portland roof have been covered with an engineered growing medium and planted with a variety of six different native plants. Shroll is irrigating the plots and documenting the amount of water necessary to keep the plants growing and healthy.

"We're really looking at how little water we can use to get the plants through the dry months so that when the rains start they are ready to start taking up moisture at a rapid rate," she said.

The OSU Green Roof Technology Project will host a tour of the Oak Creek test plots and a discussion about the role of green roofs in the urban environment on Oct. 3 from 5 p.m. to 7 p.m. at 844 SW 35th St., Corvallis, Ore. 97333. For more information contact Erin Shroll at, or (541) 207-6840.

Click photos to see a full-size version. Right click and save image to download.


Erin Shroll,