Community Partner

City of Gresham

First Advisor

Joe Maser

Date of Award


Document Type


Degree Name

Master of Environmental Management (MEM)


Environmental Science and Management




Urban runoff -- Oregon -- Gresham -- Management, Incentives in soil conservation, Runoff -- Management -- Citizen participation, Stormwater infiltration -- Oregon -- Gresham




The City of Gresham is developing a Downspout Disconnection Program, which encourages homeowners to disconnect their roof downspouts from the storm sewer system and divert the stormwater onto their lawn or rain garden. Downspout disconnection is being evaluated for its effectiveness to help the city meet stormwater discharge requirements in their NPDES-MS4 permit from Oregon DEQ. This study reviewed current Natural Resources Conservation Service (NRCS) soil data and developed a suitability map showing High, Medium and Low suitability zones for on-site stormwater management. To validate the map, 55 soil textural classes and 11 infiltration rates were determined at residences throughout Gresham. When the results were compared with the published NRCS data, 73% of the soil textural classes and 100% of the infiltration rates were in agreement. A survey was mailed to 500 residents in the High suitability zone to determine homeowners' willingness to disconnect and to identify incentives which would help persuade them to disconnect their downspouts. Ninety-four (19%) surveys were returned. The three most popular incentives were 1) a $2.32/mo. stormwater utility fee discount (35%), 2) free materials (20%) and 3) a "how-to" guide (18%). By extrapolating the responses to the full proportion of residences in the High suitability zone, a $2.32 discount would cost the city $47,700 dollars per year in reduced stormwater fees (as well as additional resources needed to verify that each site qualifies) and is expected to divert approximately 33.6 million gallons (100 acre feet) of stormwater each year from the storm sewer system over the long-term.


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

Persistent Identifier