Current Stormwater Practices and Future Implementation at Portland State University with the Uncertainty of Climate Change

Abstract

Stormwater runoff is one of the most critical environmental issues in urban areas and is only expected to worsen as climate change persists (EPA, 2016). When precipitation events occur, stormwater travels across impervious surfaces collecting soils and pollutants which can negatively impact water quality in receiving waters. Additionally, stormwater has human health impacts, specifically through flooding and the contamination of drinking water. According to the Intergovernmental Panel on Climate Change (IPCC), it has been determined that climate change will increase the frequency, intensity, and/or number of precipitation events in some regions, including the Pacific Northwest, and decrease in others (IPCC, 2018). One of the largest metropolitan areas in the Pacific Northwest is Portland, Oregon. Portland State University (PSU) is located in the heart of downtown Portland, where the percent of impervious surfaces are particularly high (81%). Consequently, precipitation events generate large amounts of stormwater that pollute the Willamette River. To combat stormwater runoff, PSU has made a concerted effort to increase the amount of stormwater green infrastructure (SGI), which work by mimicking natural processes of managing water, such as infiltration and retention, thus decreasing peak flows and flood risk by slowing and reducing stormwater discharges. Eighteen PSU buildings on campus have at least one type of SGI, and all these facilities treat 11% of the stormwater that falls on PSU impervious areas. The continued construction and maintenance of these systems is essential in creating a healthier urban environment. In collaboration with PSU's Campus Sustainability Office (CSO), we have created a comprehensive inventory of the SGI on campus and determined its effectiveness in reducing stormwater currently and in the future. To do this, we used the Environmental Protection Agency's Stormwater Management Model (EPA SWMM) to model PSU's buildings along with their various SGI facilities. We used current and future predicted precipitation data to estimate how stormwater runoff at the university will vary with climate change, and how the implementation of more SGI will help reduce this impact. PSU reduces 6.2% of stormwater runoff with its current number of SGI installations. Finally, we have proposed recommendations to the university based on these findings for the next 80 years.