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Impacts of Green Infrastructure Practices and Rainfall Characteristics on Sewershed Hydrology and Water Quality

Boening, Kathryn Margaret
http://rave.ohiolink.edu/etdc/view?acc_num=osu1595352797878418

Abstract Details

2020, Master of Science, Ohio State University, Food, Agricultural and Biological Engineering.
As urban populations continue to increase, new impervious surfaces are constructed that inhibit stormwater infiltration and increase stormwater runoff. Rainfall characteristics such as peak intensity and antecedent dry period also influence the stormwater quantity and quality generated by urban landscapes. Green infrastructure (GI) offers an alternative to traditional urban drainage through stormwater control measures (SCMs) which improve water quality in addition to reducing runoff volumes. The City of Columbus has implemented a multi-pronged sanitary sewer overflow mitigation project (Blueprint Columbus) that included retrofitting GI practices into existing neighborhoods. This presented a unique opportunity to examine the impacts of GI retrofits on sewersheds >10 hectares in size, to build upon the many previous studies which evaluated single SCMs or multiple SCMs treating a relatively small catchment (<5 ha). Two studies were performed: (1) a paired watershed analysis to compare hydrologic indicators at the sewershed-scale pre- and post-GI retrofit, and (2) an analysis of rainfall characteristics which impact runoff hydrology and water quality, and how these factors change following the implementation of sewershed-scale GI. To investigate the sewershed-scale hydrologic impacts imparted by GI SCMs, monitoring of rainfall and stormwater flow in sewershed outfalls began in four sewersheds in 2016. Three sewersheds were retrofitted with GI SCMs while one served as the control with negligible GI implementation. Linear regressions and analysis of covariance were utilized in a paired watershed approach to compare pre-GI and post-GI data. Decreases in peak flow rates (40-58%) and increases in lag-to-peak (6-64%) were observed in the treatment sewersheds post-GI. Decreases in stormwater volumes were initially observed in GI sewersheds. Installation of additional stormwater infrastructure improvement projects (i.e. downspout disconnections, sanitary sewer lateral lining, and sump pump installation) resulted in more stormwater being directed to the GI causing the outfalls to discharge runoff volumes that were not significantly different from those pre-GI. To examine effects of rainfall characteristics and implementation of GI SCMs on stormwater hydrology and water quality, factorial ANOVAs were used. Storm events were categorized based on three levels (low, medium, and high) of peak 5-minute rainfall intensity, rainfall depth and ADP. Runoff depth, peak flow rate, and concentrations and loads of representative nutrients, metals, and sediment were the response variables in the analysis. A strong and significant positive correlation was observed between rainfall depth and most hydrologic and water quality parameters. Peak rainfall intensity and ADP were significant positive drivers of runoff when they were examined together as an interaction term. GI SCMs were found to significantly decrease stormwater pollutant loads and flow rates for storm events across all levels but especially where moderate-to-high intensities and depths were observed. Post-GI, pollutant concentrations and loads as well as runoff depths were not significantly different across various rainfall characteristic levels. Thus, the significant trends pre-GI were no longer significant. The variation in the outfall responses became smaller after GI SCMs were installed; more uniform runoff hydrology and water quality could lead to more certainty regarding when sewersheds might exceed target reductions during future climate scenarios. These results confirmed that GI SCMs have substantive impacts on sewershed hydrology and water quality under a variety of rainfall characteristics, including storms that are larger than the water quality volume design storm.
Ryan Winston, Ph.D. (Advisor)
Jay Martin, Ph.D. (Advisor)
Gil Bohrer, Ph.D. (Committee Member)
101 p.
Civil Engineering; Environmental Engineering; Hydrology; Water Resource Management
Bioretention; Stormwater; Low Impact Development

Recommended Citations

Citations

  • Boening, K. M. (2020). Impacts of Green Infrastructure Practices and Rainfall Characteristics on Sewershed Hydrology and Water Quality [Master's thesis, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1595352797878418

    APA Style (7th edition)

  • Boening, Kathryn. Impacts of Green Infrastructure Practices and Rainfall Characteristics on Sewershed Hydrology and Water Quality. 2020. Ohio State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1595352797878418.

    MLA Style (8th edition)

  • Boening, Kathryn. "Impacts of Green Infrastructure Practices and Rainfall Characteristics on Sewershed Hydrology and Water Quality." Master's thesis, Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1595352797878418

    Chicago Manual of Style (17th edition)

osu1595352797878418
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