Abstract

As green stormwater infrastructure (GI) practices become more widely implemented, it is important to develop a full understanding of both the positive and negative ways that GI practices may influence environmental and human health. Additionally, as climate change leads to shifts in precipitation patterns, it is necessary to understand how the resulting changes in stormwater runoff volume, soil moisture, and vegetation species composition will impact both biogeochemical cycling and the production of ecosystem services and disservices. The overall objective of this study was to compare green stormwater infrastructure practices by weighing the tradeoffs that exist between negative impacts such as greenhouse gas production and the positive impacts provided by ecosystem services including recreational and educational infrastructure and opportunities, carbon sequestration and other regulating ecosystem services, and habitat provisioning for biodiversity support. In this study, six types of GI practices were examined: green roofs (n = 3), wet ponds (n = 2), dry ponds (n = 4), bioretention basins (n = 3), rain gardens (n = 3), and vegetated swales (n = 3). Rates of potential production of methane (CH4) and carbon dioxide (CO2) greenhouse gases were measured using anaerobic soil incubations. Soil samples were also analyzed for organic matter, moisture, and C and N content. Vegetation surveys were used to determine percent cover and Shannon diversity (H) of all plant species and percent cover of native, non-native, and invasive plant species. A rubric was used to assess availability of two categories of cultural ecosystem services: recreational and educational opportunities at each site. A comparative cradle-to-grave life cycle assessment (LCA) was conducted for evaluation of the environmental and human health impacts associated with the materials, construction, maintenance, operation, and end-of-life decommissioning of a selection of the GI sites included in this study. A hypothetical situation involving one example of conventional stormwater management infrastructure, an underground pre-cast concrete detention basin, was included in the LCA for comparison to GI practices. All measurements were highly variable between study sites, even between sites of the same GI type. Two sites, a green roof and a vegetated swale, exhibited significantly higher production rates for CH4 and CO2 and contained significantly higher organic matter and C and N content than all other sites. Linear regression results suggest that higher rates of potential production of CH4 and CO2 are driven by increased soil organic matter, and to a lesser extent, by increased soil moisture. Average soil C and N were lowest for the wet pond and bioretention basin GI categories and highest in the green roofs, and soil C and N were both correlated with production rates of CH4 and CO2 gases. LCA results indicate that for most sites, the majority of total life cycle negative environmental impacts were caused during the construction and decommissioning phases. One green roof had much higher impacts compared to the other sites and the highest global warming impacts. When compared to all GI types included in this study, vegetated swales had the highest vegetation species diversity, the highest potential for providing cultural ecosystem services, the highest % carbon content, only moderate potential production rates of CH4 and CO2, and low total lifecycle impacts as measured by the LCA. Although there were tradeoffs for all GI types and despite variations between individual sites; when considering all factors, vegetated swales were the GI type which provided the highest ratio of benefits to negative impacts.

Library of Congress Subject Headings

Urban runoff--Management--Environmental aspects; Urban runoff--Management--Health aspects; Ecosystem services

Publication Date

8-2021

Document Type

Thesis

Student Type

Graduate

Degree Name

Sustainable Systems (MS)

Department, Program, or Center

Sustainability (GIS)

Advisor

Carmody McCalley

Advisor/Committee Member

Callie Babbitt

Advisor/Committee Member

Thomas Trabold

Campus

RIT – Main Campus

Plan Codes

SUSTSY-MS

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