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Due to development of once natural landscapes, also referred to as urbanization, stormwater management has evolved in an effort to address and counteract impairment of waterways in the United States by extensively implementing best management practices (BMPs) or Green Stormwater Infrastructure (GSI). Facilities are installed without any requirement of long-term monitoring; instead relying on lab-tested or assumed pollutant removal efficiencies that often do not translate into field implementation and do not perform as intended and required by regulatory agencies. Monitoring studies have often been applied with variable standards, which lead to inconsistent results and inconclusive data. This study aims to synthesize essential components of a GSI monitoring program based on a review of existing programs (Technology Assessment Protocol – Ecology [TAPE], Technology Assessment Reciprocity Partnership [TARP], etc.). Data from past protocols was used in tandem with historic precipitation data to develop a methodology for creating a local or small region-specific protocol. This methodology was applied to the case study area of Fairfax, Virginia. Results from the study indicate that historic precipitation data and past protocol recommendations can be effectively applied in a local setting to create a more suitable protocol adapted for GSI monitoring in order to confirm designed efficiency. / Master of Science / Due to development of once natural landscapes, also referred to as urbanization, stormwater management has evolved in an effort to address and counteract impairment of waterways in the United States by extensively implementing best management practices (BMPs) or Green Stormwater Infrastructure (GSI). Facilities are installed without any requirement of long-term monitoring; instead relying on lab-tested or assumed pollutant removal efficiencies that often do not translate into field implementation and do not perform as intended and required by regulatory agencies. Monitoring studies have often been applied with variable standards, which lead to inconsistent results and inconclusive data. This study aims to synthesize essential components of a GSI monitoring program based on a review of existing programs (Technology Assessment Protocol – Ecology [TAPE], Technology Assessment Reciprocity Partnership [TARP], etc.). Data from past protocols was used in tandem with historic precipitation data to develop a methodology for creating a local or small region-specific protocol. This methodology was applied to the case study area of Fairfax, Virginia. Results from the study indicate that historic precipitation data and past protocol recommendations can be effectively applied in a local setting to create a more suitable protocol adapted for GSI monitoring in order to confirm designed efficiency.

Construction and maintenance can have huge implications on the long-term functioning of GSI facilities. GSI facilities investigated were bioretention, permeable pavement, sand filters, infiltration trenches, and vegetated swales. This study first highlights the most important construction and maintenance items based on relevant studies and state stormwater manuals. Fairfax County, VA was used as a case study to evaluate the County's current stormwater program and illuminate common maintenance issues found for each GSI type. Data analysis of 3141 inspection records illustrated particular deficiencies for each GSI type and that there are differences between public and private facilities, most likely depending on site conditions and frequency of routine maintenance. Sediment accumulation was found to be the most common maintenance issue (27.8% of inspections), supporting the importance of adequate pretreatment and good housekeeping when implementing GSI. The Northern Virginia Soil and Water Conservation District (NVSWCD) performed a study surveying 63 public bioretention facilities in which they measured ponding depth, filter media depth, ponding area, and infiltration rates. The NVSWCD concluded that deficiencies found in facilities could mostly be attributed to inadequacies during construction. By comparing current post-construction inspections performed by the County to the NVSWCD data, it was found that these County inspections are failing to detect these inadequacies in bioretention facilities from improper construction. It is recommended that MS4s thoroughly record and track construction and post-construction inspection items to improve the longevity of its facilities and better inform future decision making regarding GSI. / Master of Science / Studies have shown that the proper construction and maintenance of green stormwater infrastructure (GSI) is a critical factor concerning its long-term performance; however, little research has been conducted on the necessary protocols and frequency to ensure its longevity. Many MS4s and stormwater managers are implementing these facilities without providing the adequate institutional framework to ensure the proper construction and maintenance. This study concentrates on illuminating the construction and maintenance factors critical for the performance of GSI. Facility types investigated were bioretention, permeable pavement, sand filters, infiltration trenches, and vegetated swales. The effects of local site-conditions and level of routine maintenance on frequency of facility deficiencies was quantified using 3141 records of maintenance and inspection data from Fairfax County, VA. Sediment and debris accumulation were found to be the most common deficiency highlighting the importance of good housekeeping and pretreatment devices. The Northern Virginia Soil and Water Conservation District (NVSWCD) performed a comprehensive review of 63 bioretention facilities in which they inspected elements considered critical to pollutant removal performance including ponding depth, filter media depth, and infiltration rates. By comparing the findings from the NVSWCD to current post-construction inspections performed by the County, it was found that current inspection protocols are missing important design components of bioretention facilities. This study also highlights the importance of thorough and thoughtful databases to track and record inspection and maintenance data surrounding GSI. The proper construction and maintenance of GSI is ultimately dependent on a multitude of factors including site-conditions, facility design specifications, and institutional support.

Stormwater runoff from existing impervious surfaces needs to be managed to protect downstream waterbodies from hydrologic and water quality impacts associated with development. As urban expansion continues at a rapid pace, increasing impervious cover, and climate change yields more frequent extreme precipitation events, increasing the need for improved stormwater management. Although green infrastructure such as bioretention has been implemented in urban areas for stormwater quality improvements and volume reductions, these systems are seldom monitored to validate their performance. Herein, we evaluate flow attenuation, stormwater quality performance, and nutrient cycling from eight roadside bioretention cells in their third and fourth years of implementation in Burlington, Vermont. Bioretention cells received varying treatments: (1) vegetation with high-diversity (7 species) and low-diversity plant mixes (2 species); (2) proprietary SorbtiveMediaTM (SM) containing iron and aluminum oxide granules to enhance sorption capacity for phosphorus; and (3) enhanced rainfall and runoff (RR) to certain cells (including one with SM treatment) at three levels (15%, 20%, 60% more than their control counterparts), mimicking anticipated precipitation increases from climate change. Bioretention water quality parameters monitored include total suspended solids (TSS), nitrate/nitrite-nitrogen (NOx), ortho-phosphorus (Ortho-P), total nitrogen (TN) and total phosphorus (TP), which were compared among bioretention cells’ inflows and outflows across 121 storms. Simultaneous measurements of flow rates and volumes allowed for evaluation of the cells’ hydraulic performances and estimation of pollutant load and event mean concentration (EMC) removal. We also monitored soil CO2 and N2O fluxes, as they represent a potential nutrient loss pathway from the bioretention cells. We determined C and N stocks in the soil media and vegetation, which are critical design elements of any bioretention, to determine the overall C and N balances in these systems. Significant average reductions in effluent stormwater volumes and peak flows were reported, with 31% of the storms events completely captured. Influent TSS loads and EMCs were well retained by all cells irrespective of treatments, storm characteristics, or seasonality. Nutrient removal was treatment-dependent, where the SM treatments consistently removed P loads and EMCs, and sometimes N as well. The vegetation and RR treatments mostly exported nutrients to the effluent. We attribute observed nutrient exports to the presence of excess compost in the soil filter media. Rainfall depth and peak inflow rate undermined bioretention performance, likely by increasing pollutant mobilization through the filter media. While the bioretention cells were a source of CO2, they varied between being a sink and source of N2O. CO2 fluxes were orders of magnitude higher than N2O fluxes. However, soil C and N, and plant C and N in biomass was seen to largely offset respiratory CO2-C and biochemical N2O-N losses from bioretention soil. The use of compost in bioretention soil media should be reduced or eliminated. If necessary, compost with low P content and high C: N ratio should be considered to minimize nutrients losses via leaching or gas fluxes. In order to understand trade-offs stemming from compost amendments, we conducted a laboratory pot study utilizing switchgrass and various organic soil amendments (e.g., different compost types and coir fiber) to a sandy loam soil contaminated with heavy metals and studied potential nutrient leaching and pollutant uptake. Addition of organic amendments significantly reduced metal bioavailability, and improved switchgrass growth and metal uptake potential. While no differences in soil or plant metal uptake were observed among the amendments, significant differences in nutrient leaching were observed.

Protection of water resources in a changing climate depends on bottom-up stewardship and adaptive management. From the ground up, a vital component is maintaining soil ecosystem services that regulate water, recycle nutrients, sequester carbon, provide food, and other benefits. Interacting spatial, social, and physical factors determine agricultural and stormwater management, and their impact on water. This dissertation explores these dimensions within a complex social-ecological system. The first chapter evaluates a participatory process to elicit solutions to complex environmental problems across science, policy, and practice. The second chapter studies on-farm soil assessment and its role in informing management decisions and supporting adaptive capacity. The third chapter investigates cross-scale dynamics of residential green stormwater infrastructure (GSI) for improved water resource management in a broader social-ecological context. Integrating participant feedback into current science, research, and decision-making processes is an important challenge. A novel approach that combines a Delphi method with contemporary “crowdsourcing” to address water pollution in Lake Champlain Basin in the context of climate change is presented. Fifty-three participants proposed and commented on adaptive solutions in an online Delphi that occurred over a six-week period during the Spring of 2014. In a follow-up Multi-Stakeholder workshop, thirty-eight stakeholders participated in refining and synthesizing the forum’s results. The stakeholders’ interventions from the crowdsourcing forum have contributed to the current policy dialogue in Vermont to address phosphorus loading to Lake Champlain. This stakeholder approach strengthens traditional modeling scenario development to include priorities that have been collectively refined and vetted. Healthy agricultural soils cannot easily be prescribed to farms and require knowledge and a long-term commitment to a holistic and adaptive approach. The second chapter addresses the questions: “to what extent do farmers use indicators of soil health, and does feedback inform management decisions?” A survey of farmers in two Vermont watersheds was conducted in 2016 showed relatively high use of fourteen soil indicators and high rankings of their importance. The finding that there were differences in use and perceived importance of soil indicators across management and land-use types has implications beyond the farm scale for agriculture, and the provision of ecosystem services. Soil management relates to broader adaptation strategies including resistance, resilience, and transformation that affects adaptive capacity of agroecosystems. Bottom-up adoption of environmental behaviors, such as implementing residential GSI, need to be understood in the context of the broader social-ecological landscape to understand implications for improved water management. A statewide survey of Vermont residents paired a cross-scale and spatial analysis to evaluate how intention to adopt three different GSI practices (infiltration trenches, diversion of roof runoff, and rain gardens) varies with barriers to adoption and household attributes across varying stormwater contexts from the household to watershed scale. Improved stormwater management outcomes at the watershed and local levels depend on management strategies that can be implemented and adapted along the rural-urban gradient, across the bio-physical landscape, and according to varying norms and institutional arrangements.

Over the past several decades, flooding events in the United States have become the most frequent and costliest natural disaster. In the US, city and regional leaders are planning new water and flood mitigation infrastructure in response to the challenges of flooding, uneven urbanization, and racialized exclusion. Historically, projects to keep water out have never been universal or evenly applied. Yet, ‘learning to live’ with water, a key tagline in current sustainable development paradigms, masks how histories of racialized land development are entangled with contemporary water infrastructure projects and are productive of regional planning power. This dissertation centers racial capitalism in analysis of how contemporary water infrastructure projects are entangled with, and informed by, histories of racialized land development in the mid-Mississippi River Region. Through two case studies on flood mitigation infrastructure in eastern Missouri, I trace the historic development of infrastructures that shape the ongoing racialization of space, infrastructure (re)development and community vulnerability to flooding today. The case studies draw from a range of data, including archival research on histories of land and infrastructure development, participant observation of planning meetings, professional conferences, and local neighborhood initiatives, and field observations of the built environment. I argue that 1) scholarship concerned with social-environmental inequities should engage racial capitalism as a framework to “provincialize” urban theory and environmental racism as a means to theorize uneven infrastructural provisioning as a mode of urbanization that (re)produces social difference and value creation under racial capitalism, 2) the historical development of flood control in the Mississippi region was fundamental to the development of racial capitalism because it consolidated regional planning power through methods of social and environmental domination, and 3) contemporary infrastructural redevelopment and flood mitigation projects must contend with the path dependencies of structural racism to disrupt existing cycles of marginalization across social differences to deliver meaningfully on equity goals. Ultimately, this study finds that flood-mitigation infrastructures, including levees, floodways, and dams, on the Missouri River and gray and green stormwater infrastructure (GSI) in the City of St. Louis are embedded in broader social-environmental networks and regional power blocs, whose regional history and dynamics have created distinct patterns of uneven urbanization and vulnerability to flooding disasters. Because infrastructure projects are embedded in the built environment for decades, the social relations comprising their implementation, or lack thereof, reach into present and future development considerations. Thus, when planning projects fail to grapple with path dependencies of past infrastructure projects, they may reproduce structural racism and re-create patterns of uneven urbanization and vulnerability to flooding disasters. / Geography

Decisions of adopting best management practices made on residential properties play an important role in reduction of nutrient loading from non-point sources into Lake Champlain and other waterbodies in Vermont. In this study, we use Bayesian belief network (BBN) to analyze a 2015 survey dataset about adoption of six types of green infrastructures (GSIs) in Vermont’s residential areas. Learning BBNs from physical probabilities of the variables provides a visually explicit approach to reveal the message delivered by the dataset. Using both unsupervised and supervised machine learning algorithms, we are able to generate networks that connect the variables of interest and conduct inference to look into the probabilistic associations between the variables. Unsupervised learning reveals the underlying structures of the dataset without presumptions. Supervised learning provides insights for how each factor (e.g. demographics, risk perception, and attribution of responsibilities) influence individuals’ pro-environmental behaviors. We also compare the effectiveness of BBN approach and logistic regression in predicting the pro-environmental behaviors (adoption of GSIs). The results show that influencing factors for current adoption vary by different types of GSI. Risk perception of stormwater issues are associated with adoption of GSIs. Runoff issues are more likely to be considered as the governments’ (town, state, and federal agencies) responsibility, whereas lawn erosion is more likely to be considered as the residents’ own responsibility. When using the same set of variables to predict pro-environmental behaviors (adoption of GSI), BBN approach produces more accurate prediction compared to logistic regression.

The impervious surfaces of built landscapes create stormwater runoff that causes water quantity and quality problems downstream, upsetting natural hydrology and harming aquatic ecosystems. Green stormwater infrastructure (GSI) includes practices that reduce the amount of stormwater runoff and the pollutants it carries utilizing plants, soils, and other materials to capture, store, reuse, infiltrate, evapotranspire, and filter stormwater. GSI helps to restore developed landscapes, mimicking natural hydrologic processes and providing important water treatment functions as well as beneficial green spaces in urban areas. However, there are many challenges associated with the implementation and maintenance of GSI in our communities and cultures. This research explores the human side of implementing GSI, investigating current maintenance capacities in rural and urban settings, and exploring multifunctional benefits of GSI to provide both biophysical and cultural ecosystem services (CES). Research goals include characterizing the current state of GSI implementation and maintenance in municipalities in the State of Vermont (USA) and eliciting lessons that can inform GSI design practices and policies. Multifunctional GSI design objectives that provide and enhance CES are described, revealing opportunities to instill values and a sense of stewardship for the health wellbeing of people and ecosystems. The first chapter provides relevant topical background to set the stage for the latter two chapters. The second chapter analyzes results from a survey of municipal officials in Vermont that occurred as part of NSF-EPSCoR-funded Basin Resilience to Extreme Events project research on stormwater management. The survey included questions about GSI and maintenance practices in place and perceptions of visual appeal and ability to maintain bioretention systems shown in landscape visualizations. Results show that visual appeal and perceived maintainability of vegetated bioretention practices do not appear to be significant barriers to adoption and operation, but stormwater policy and funding are shown to be both significant barriers and solutions to implementing and maintaining GSI in Vermont municipalities. Additionally, urban and rural towns provide very different contexts for implementing and maintaining GSI in Vermont and characteristics of development patterns and maintenance capacity should be considered in policy, regulations, outreach, and education. The third chapter offers a literature review, guided by a CES framework, of design elements that can be included in GSI to create multifunctional urban green spaces. CES categories of aesthetic, recreation, education, sense of place, social capital, and stewardship benefits framed a set of design elements, principles, practices, and documented benefits to guide multifunctional design of GSI. Findings include the importance of participatory processes to elicit diverse landscape values, visible water pathways, biodiversity, spaces for creative use, accessibility, interaction with water, interpretive signage, and artful and biophilic design features to enhance feelings of preference, pleasure, relaxation, learning, connection, and inclusion. The health and wellbeing of water and people must be integrated into the design of GSI for cities to be ecologically functional and culturally meaningful to their populations.

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Urban stormwater runoff is both an environmental threat and a valuable water resource. This dissertation explores the use of two stormwater management strategies, namely green stormwater infrastructure and stormwater real-time control (RTC), for capturing and treating urban stormwater runoff. Chapter 2 focuses on clean bed filtration theory and its application to fecal indicator bacteria removal in experimental laboratory-scale biofilters. This analysis is a significant step forward in our understanding of how physicochemical theories can be melded with hydrology, engineering design, and ecology to improve the water quality benefits of green infrastructure. Chapter 3 focuses on the novel application of unsteady transit time distribution (TTD) theory to solute transport in a field-scale biofilter. TTD theory closely reproduces experimental bromide breakthrough concentrations, provided that lateral exchange with the surrounding soil is accounted for. TTD theory also provides insight into how changing distributions of water age in biofilter storage and outflow affect key stormwater management endpoints, such as biofilter pollutant treatment credit. Chapter 4 focuses on stormwater RTC and its potential for improving runoff capture and water supply in areas with Mediterranean climates. We find that the addition of RTC increases the percent of runoff captured, but does not increase the percent of water demand satisfied. Our results suggest that stormwater RTC systems need to be implemented in conjunction with context-specific solutions (such as spreading basins for groundwater recharge) to reliably augment urban water supply in areas with uneven precipitation. Through a combination of modeling and experimental studies at a range of scales, this dissertation lays the foundation for future integration of TTD theory with RTC to improve regional stormwater management. / Doctor of Philosophy / Urban stormwater runoff contains a variety of pollutants. Conventional storm drain systems are designed to move stormwater as quickly as possible away from cities, delivering polluted runoff to local streams, rivers, and the coastal ocean – and discarding a valuable freshwater resource. By contrast, green stormwater infrastructure captures and retains stormwater as close as possible to where the rain falls. Green stormwater infrastructure can also help remove pollutants from stormwater through physical, chemical, and biological treatment processes. This dissertation describes two modeling approaches for understanding and predicting pollutant removal processes in green stormwater infrastructure (Chapters 2 and 3). Chapter 4 explores the implementation of smart stormwater systems, which use automated controllers and sensors to adaptively address stormwater management challenges. Through a combination of modeling and experimental studies at a range of scales, this dissertation lays the foundation for future improvements to regional stormwater management.