Climate models have anticipated higher future extreme precipitations and streamflows for various regions. Urban stormwater facilities are vulnerable to these changes as the design assumes stationarity. However, recent climate change studies have argued about the existence of non-stationarity of the climate. Distribution method adopted on extreme precipitation varies spatially and may not always follow same distribution method. In this research, two different natural extremities were analyzed for two separate study areas. First, the future design storm depth based on the stationarity of climate and GEV distribution method was examined with non-stationarity and best fit distribution. Second, future design flood was analyzed and routed on a river to estimate the future flooding. Climate models from North American Regional Climate Change Assessment Program (NARCCAP) and Coupled Model Intercomparison Project phase 5 (CMIP5) were fitted to 27 different distribution using Chi-square and Kolmogorov Smirnov goodness of fit. The best fit distribution method was used to calculate design storm depth as well as design flood. Climate change scenarios were adopted as delta change factor, a downscaling approach to transfer historical design value to the climate adopted future design value. Most of the delta change factor calculated were higher than one, representing strong climate change impact on future. HEC-HMS and HEC-RAS models were used to simulate the stormwater infrastructures and river flow. The result shows an adverse effect on stormwater infrastructure in the future. The research highlights the importance of available climate information and suggests a possible approach for climate change adaptation on stormwater design practice.

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

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

No description available.

Master of Landscape Architecture / Department of Landscape Architecture/Regional and Community Planning / Laurence A. Clement / Contemporary design of the urban environment focuses increasingly upon the quality of space found within the public right-of-way. Landscape architects and urban planners are beginning to ask new questions that deviate from the conventional streetscape designs of the latter half of the 20th century. Under the mantra “complete the streets,” communities all across America are calling for a paradigm shift towards multimodal, pedestrian-scaled urban rights-of-way. At the same time, existing stormwater and combined sewer infrastructure is nearing the end of its productive lifespan in cities all across the country and world. The direct costs associated with repairing this infrastructure combined with the indirect costs of poor water quality and a greater frequency and intensity of flooding events downstream present a strong argument for developing new, innovative ideas about how to best design the stormwater infrastructure of tomorrow. The reintegration of ecological processes into the urban fabric will act as a catalyst for the appreciation of genius loci (spirit of the place) and user meaning while mitigating downstream flooding, increasing water quality, and extending the lifespan of existing stormwater infrastructure. By studying the hierarchical categorization of urban rights-of-way according to increased levels of user orientation, this research project aims to clearly articulate a new theoretical framework for expanding upon the current discourse surrounding “complete streets” and “green streets” theory. In the long-term, it is both economically and socially profitable for cities to use ecological processes to reclaim auto-oriented, urban rights-of-way as valuable public space for the health, safety, and welfare of all their users.

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.

Compaction of urban soil where stormwater infrastructures are built reduces infiltration, vegetation growth, and stormwater treatment capacity. Biochar—a carbonaceous porous material produced by pyrolysis of organic waste – can be used as a soil amendment to improve the function of stormwater infrastructure in addition to the proven benefit of increased pollutant removal. However, the benefits depend on the biochar’s properties such as particle size distribution and concentration. Further, because biochar’s particle size distribution is altered by compaction, the hydraulic functions of compacted biochar amended soil is unknown. Herein, we examined the effect of biochar concentrations (0-6% w/w) and particle sizes (unsieved, sieved to < 2mm, and to < 0.5 mm) on water retention and saturated or unsaturated hydraulic conductivity of compacted stormwater media amended with biochar. Our results show the particle size of biochar plays a critical role in whether or not compaction is alleviated: while increasing concentration of unsieved biochar increased hydraulic conductivity up to 3% biochar, increasing concentration of fine biochar (< 2 mm) resulted in consistent decline in hydraulic conductivity under compaction. The results indicate that large biochar particles can effectively dissipate the compaction energy, while the fine biochar under compaction increased clogging by generating more fines that occupy the pores. Water retention improved regardless of the size distribution of added biochar, indicating that addition of biochar would reduce the irrigation requirement to maintain plant health in dry climate or water-stressed conditions. Overall, the results indicate that biochar addition can be effective in mitigating the negative impacts of compaction on stormwater infrastructures, depending on the proportion of coarse biochar. / Geology

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.