Community Partner

City of Portland

First Advisor

Joseph Maser

Date of Award


Document Type


Degree Name

Master of Environmental Management (MEM)


Environmental Science and Management




Green roofs (Gardening) -- Oregon -- Portland, Green roofs (Gardening) -- Maintenance and repair




In 1999 the City of Portland (City) began to require that stormwater management facilities (SMF) be built when private property is newly developed or redeveloped (City Code Chapter 17.38). Proper maintenance and upkeep of SMFs is essential to ensuring they function appropriately. The City's Maintenance Inspection Program (MIP) is tasked with inspecting stormwater management facilities on private properties in order to ensure that they are being properly operated and maintained and to meet provisions of the City's NPDES Municipal Separated Storm Sewer System (MS4) permit.

Greenroofs are one type of SMF that are installed to satisfy this requirement. Understanding the long-term maintenance needs of a greenroof is essential to reaching MIP goals established by City Code and the MS4 permit. Data collection occurred between November 2011 and May 2013 at private properties in Portland, Oregon during routine maintenance inspections of stormwater management facilities for the City’s Maintenance Inspection Program (MIP). The objectives of this study are to:

  • Provide a summary of the type and frequency of greenroofs inspected in Portland as well as common issues, concerns from the property owners, and other information gained from greenroof inspections. This will also address questions such as
    - What does a typical Portland greenroof look like?
    - How deep is the growing media?
    - What types of plants are used?
    - What stressors act on the greenroofs?
    - Does replanting a greenroof eliminate stressors?

  • Inform property managers, architects, engineers, and maintenance personnel about some design techniques that may ease long-term maintenance input and expense. This study also aims to further scientific and systematic evaluation of greenroofs as an amenity and stormwater management facility.

Based on inspection results of greenroof plant communities, soil depth, stressor frequency, and replanting and replacing soil events; maintenance and design concerns are identified and recommendations are provided. Using the data collected, the typical greenroof has 1 to 7 inches of soil and an extensive design; it is most frequently vegetated by succulents and drains to either the CSO or the MS4. Most greenroofs are installed with growing media seven inches thick or less. Succulent plants are used most often both as a monoculture and in combination with other vegetation. Biological stressors act on greenroofs more often than any other type of stressor. Replanting does not eliminate stressors.


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A project submitted in partial fulfillment of the requirements for the degree of Master of Environmental Management.

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