In the recent century, a process of urbanization has increased globally. Previously rural or natural land have been converted into impervious surfaces to make way for housing, industries, and roads. This anthropogenic process has resulted in an increased amount of surface runoff from precipitation, so-called stormwater. Stormwater can accumulate a range of pollutants when it flows over the impervious surfaces of our cities. These pollutants can have a negative impact on the lakes and streams that receive the stormwater from the urban environments. To reduce the environmental problems associated with the content of stormwater, various techniques have been developed for stormwater treatment, with the aim of reducing the pollutant load in the runoff before it enters the receiving waterbody. One such technology is stormwater biofiltration, also known as bioretention. Stormwater biofilters were developed in the USA in the early 90's and they utilize the natural water remediation properties of plant-soil systems. They are generally characterized by a vegetated submerged filter bed with an underlying drainage layer. They have shown to be an effective method for stormwater pollutant removal. The treatment processes take place both in the vegetation and in filter material. As th ematerial choices and design of the biofilters can vary, so can its treatment performance. Stormwater biofilters have grown in popularity in the last decades since their development and numerous studies have been conducted to evaluate the systems’ treatment efficiency. However, knowledge gaps still exist regarding their implementation in colder climates and the suitability of different configurations and materials. This study examines the removal performance of total and dissolved heavy metals (Cd (cadmium),Cu (copper), Pb (lead) and Zn (zinc)), phosphorus, nitrogen and total suspended solids (TSS) in three stormwater biofilters in a Swedish climate, located in central Malmö. The current biofilters are designed with different configurations of their filter media and are built with 1) sand-basedfilter material 2) sand-based filter material with a submerged zone and 3) filter media consisting of 50% sand-based material in combination with 50% pumice. The results showed that the treatment capacity of the biofilters with a filter media of only sand (biofilter S) and with sand as well as a submerged zone (biofilter S_SZ) was similar for all pollutants. The reduction of total levels of metals (> 85 %) and TSS (>90 %) was consistently high and similar to levels achieved in previous studies for both temperate and colder climates. The removal of dissolved metals was lower in comparison to the removal of the total metal fractions, but the dissolved fractions were still generally reduced in the effluent. A positive removal of total phosphorus and total nitrogen was overall displayed in the effluent from the two biofilters; however,leaching was shown for the dissolved fractions. For nitrogen (N) species, the concentrations in the runoff were generally below the detection limit for the analysis making it difficult to establish probable removal percentages. For the biofilter S_P, which contained a mix of sand and pumice, the removal capacity was lowerfor all parameters compared to the other designs. Overall, the pollutant removal performances are regarded to be satisfactory for biofilters S andS_SZ and their implementation suitable for the given site. However, further investigations should be performed during warmer seasons, especially regarding the removal of nutrients.

Implementing optimal Low Impact Development (LID) practices has grown in popularity as a means of mitigating the adverse effects of urbanization and climate change. As such incorporating aspects of resilience for optimal LID design has become paramount. This study focuses on identifying the current LID optimization strategies and associated research gaps as well as assessing whether a quantitative approach to measure LID resilience exists. To do so, a systematic and bibliometric literature review on LIDs optimization and resilience is first conducted, based on which resilience, climate change, and uncertainty are recognised as hotspot keywords. The review also showed that no LID resilience quantification technique was available. Based on the latter outcome and to facilitate LID’s optimal design in future, this research proposes a new resilience quantification approach of LID by developing set of equations using Analytical Probabilistic Approach (APA) and continuous simulation approach using SWMM. The equations consider LID’s functionality and assess resilience using three indices: robustness, rapidity and serviceability. A new overall resilience index (the product of robustness and serviceability) and reliability index (the product of volumetric, occurrence, and temporal reliability) are proposed using different area ratios between contributing catchment and LID area to assure a resilient and safe LID system. LID costing tool of the Sustainable Technologies Evaluation Program (STEP) is subsequently utilized to estimate the capital cost of LID. Finally, a user-oriented design guideline is proposed for a cost-effective, resilient, and reliable LID system. Although this study adopts bioretention (BR) as a demonstration of the approach utility, the developed approach is applicable to any form of LID practices. / Thesis / Master of Applied Science (MASc) / There is a critical need to develop and implement optimal low-impact development (LID) practices in the field of stormwater management to mitigate the adverse effects of urbanization and climate change. This thesis is focused on developing quantitative resilient measurement approach of LID designs. A comprehensive literature review is first carried out, focusing on identifying various optimization methodologies, relevant gaps, and resilience assessment techniques. Subsequently, a novel resilience evaluation approach is developed, using bioretention (BR). By constructing a new reliability index, the entire BR system's reliability can also be assessed. Finally, a cost-effective, resilient and reliable design guideline for BR system is proposed. Although bioretention (BR) is used as an example in this study, the developed approach opens the gate to quantify the resilience of all types of LID practices.

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<p>Low Impact Development (LID) practices have been increasingly used to mitigate the adverse impacts of urbanization. Reliable methods are in need to provide hydrologic performance assessment of different types of LID practices. The purpose of this thesis is to develop a set of analytical models which can be used to assist the planning and design of commonly used structural LID practices such as green roofs, rain gardens, bioretention and permeable pavement systems.</p> <p>The analytical LID models are derived on the basis of exponential probability density functions (PDF) of local rainfall characteristics and mathematical representations of the hydraulic and hydrologic processes occurring in association with the operation of LID practices. Exponential PDFs are found to provide good fits to the histograms of rainfall characteristics of five cities located in different climatic zones. The mathematical representations are all physically based and most of the input parameters used in these representations are the same as those required in commonly used numerical models.</p> <p>The overall reliability of the analytical LID models are tested by comparing the results from these analytical models with results determined from long-term continuous simulations, in addition to that the accuracy of the analytical model for green roofs is also verified against observations from a real case study. The long-term rainfall data from the five cities and a variety of LID practice design configurations are used in the comparisons. The relative differences between the results calculated using the analytical LID models and the results determined from corresponding SWMM simulations are all less than 10%.</p> <p>The Howard’s conservative assumption is adopted in the development of the analytical models for rain gardens and permeable pavement systems. This assumption results in conservative estimations of the stormwater management performances of these LID practices. Instead of adopting the Howard’s conservative assumption, an approximate expected value of the surface depression water content of a bioretention system at the end of a random rainfall event [denoted as ] is derived and used in the development of the analytical model for bioretention systems. The use of is proven to be advantageous over the use of the Howard’s conservative assumption.</p> <p>The analytical LID models are comprised of closed-form mathematical expressions. The application of them can be easy and efficient as illustrated in the application examples. For a specific location of interest, with a goodness-of-fit examination of the exponential PDFs to local rainfall data and verification of the accuracy of the analytical LID models, these models can be used as a convenient planning, design, and management tool for LID practices.</p> / Doctor of Philosophy (PhD)

The Ministry of Environment and Climate Change establishes design criteria for the sizing of Low Impact Development (LID) practices in the province of Ontario. The current sizing standards are based on the concept of the 90th percentile storm and require LIDs to provide enough storage capacity to store catchment runoff from a 25 mm rainfall event. The notion of 90th percentile storm means that 90% of all rainfall events have event volumes below a 25 mm rainfall event. This research examines the performance and cost of infiltration trenches and bioretention cells sized for alternative sizing standards ranging from 5–50 mm. Analytical probabilistic equations are used to determine the runoff reduction rates of infiltration trenches and bioretention cells, while the Sustainable Technologies Evaluation Program (STEP)’s LID Practices Costing Tool is used to estimate the overall cost of each LID. The costs are used to create a ratio denoted the fraction of maximum cost by dividing each cost by the cost of the 50 mm sized LID to receive a unitless ratio. This ratio is compared with the runoff reduction rates of both LIDs. Four different catchment sizes and various soil types are included to broaden the scope of the analysis and make the conclusions more dependable. Results indicate that the current sizing standard of 25 mm is probably too high and not cost-effective. In fact, depending on the type of soil and LID, little increase in performance occurs while there is a large increase in cost. A new methodology is proposed for setting sizing criteria for infiltration trenches and bioretention cells which focuses on achieving a desired capture efficiency instead of a required volume of rainfall. The method proposes using the capture efficiency, fraction of maximum cost and sizing criteria to determine what value is an economically more justifiable sizing standard based on individual catchment size and soil type. Use of the analytical probabilistic approach allows for the capture efficiency to be easily calculated and provides better sizing targets on a case by case basis. Recommending a specific capture efficiency can be more uniformly applied LID design in any soil conditions or any catchment size. This can reduce government spending when building LIDs and greatly reduce the possibility of over-design. / Thesis / Master of Applied Science (MASc)

Low impact development (LID) is an innovative stormwater management technique that was introduced in early 1990s. However, the transition to use of this more sustainable method has been slow due to technical, institutional, and regulatory barriers to LID adoption. The research questions for this study are: What constitutes LID adoption? Why do localities adopt LID? What are the major factors that influenced the level of LID adoption by local governments? Specifically, this study focused on motivations and key determinants of LID adoption by local governments. By answering these questions, we will have better knowledge about how to approach the adoption process of environmental innovations. The findings of the study will benefit any potential localities considering LID adoption. The theory of diffusion of innovations is applied as it is very flexible to investigate complex topics like environmental innovation involving multiple factors and environments. To explore the role of local governments in LID adoption, sub-theories like organizational innovation and policy adoption are reviewed. Based on these theoretical foundations, four constructs of variables which include innovation, organizations, motivations, and surrounding organizational context are investigated. The case study method is used for eight counties (Amherst, Bedford, Chesterfield, Fairfax, Isle of Wight, Roanoke, Stafford, and Spotsylvania) and two cities (City of Charlottesville, City of Roanoke) in Virginia. Key informants from each locality were selected for in-depth interviews and additional document reviews for each case are used to support multiple case studies. LID adoption consists of various forms such as regulations, practices, and plans. A combination of all forms of LID activities and programs was used to measure LID adoption level. Based on nine criteria (i.e., adoption mode, use of the term "LID" in local codes, code details, LID manuals, demonstration projects, number of LID projects after LID code adoption, education programs, task force, and incentives), localities with three levels of LID adoption have been determined. Influencing factors of innovation adoption varied depending on level of LID adoption (high, moderate, and low). Therefore, strategies to promote environmental innovation should be developed in relation to the level of innovation adoption. The research findings revealed two major determinants that influenced the level of LID adoption. One is strong champions, and the other is regulatory mandates. A champion-driven LID adoption model is found in high level LID adoption localities. Usually, individuals from local governments, NGOs, and development communities have played a critical role in LID adoption process. The local government organizations in this group are usually self-motivated for innovation adoption. Especially, the presence of strong champions was identified as a key factor to the higher level of innovation adoption. On the other hand, a regulation-driven LID adoption model is found in moderate to low level LID adoption localities. These localities are strongly influenced by state regulatory mandates. In these cases, external forces motivate local governments to adopt innovations. / Ph. D.

The goal of Low Impact Development (LID) is to mimic the pre-development hydrologic regime of a catchment through infiltration, filtration, storage, evaporation, and detention of post-development runoff using small-scale hydrologic controls close to the source. A LID facility located in Northern Virginia was examined for pollutant removal and hydrologic performance. The treatment train included four in-line grass swales followed by a bioretention cell with a gravel base. The facility retained 85% of the rainfall. Influent and effluent pollutant loads were calculated using three common substitution methods for datasets censored by values below the analytical detection limit. The Summation of Loads (SOL) method was used to facilitate understanding of how data censoring affected performance results when substitution methods were used. The SOL analysis showed positive removal performance for most nutrient species, sediment, oxygen demanding substances, selected trace metals and total petroleum hydrocarbons. Negative performance was observed for oxidized nitrogen, total dissolved solids and oil & grease. LID facility influent and effluent loads were also compared using the Effluent Probability Method (EPM). The EPM analysis showed statistically significant (p d 0.05) pollutant load removal performance over the entire range of sampled events for total suspended solids, total phosphorus, total nitrogen, total Kjeldahl nitrogen, ammonia nitrogen, chemical oxygen demand, copper, zinc and alkalinity. EPM analysis did not show significant removals of oxidized nitrogen, total dissolved solids, orthophosphate phosphorus and hardness. / Master of Science

Biofiltration systems like rain gardens and bioswales are an important tool for capturing andinfiltrating polluted runoff, but little data exists on their efficiencies within Mediterraneanclimates. A two-year study initiated in 2015 investigated water retention and pollutant loadingand retention in the Ballona Creek Rain Garden (BCRG). This 300 by 3 m biofiltration systemwas constructed by The Bay Foundation in 2011 along Ballona Creek in Culver City, Los AngelesCounty, California. The purpose of the garden was to capture and infiltrate runoff from lightindustrial and commercial operations bordering the Creek, thus reducing pollutants enteringthis waterway and flowing into Santa Monica Bay 9 km downstream. During storm events,runoff enters the garden via five inlets, and when filled, flows into the creek via two outlets.The goal of this study was to sample flows and pollutant concentrations in runoff entering andleaving the garden and then integrate these to calculate mass loading estimates. Flows weremeasured at all inlets and outlets using 90° V-notch weirs outfitted with Hobo water levelsensors to produce hydrographs. The following pollutants were measured at all flowing inletsand outlets two to three times per storm depending on its duration and intensity: fecalindicator bacteria (E. coli and enterococci), total suspended solids, metals (copper, zinc, andlead), and semivolatile hydrocarbons (polyaromatic hydrocarbons, diesel hydrocarbons, andmotor oil hydrocarbons). The summation of load method was used to calculate the mass ofcontaminants entering and leaving the garden for each storm event, and their percent capturewithin the garden. The BCRG was very effective at infiltrating runoff and sequesteringpollutants. The garden’s infiltration rates ranged from 73% to 100% (with 100% for many of thesmaller storms percent retentions were in the 80-90% range for all pollutants, with an average of 90% for allnine pollutants sampled. This suggests rain gardens and other Low Impact Development (LID)systems can be used successfully in urban Mediterranean climates like Los Angeles to promoteinfiltration, capture pollutants, and prevent polluted stormwater from reaching impaired waterbodies.

The use of the Internet and digital services has increased significantly during recent years, and as Human-Computer Interaction (HCI) field keeps on expanding, it is influencing aspects of our daily lives, though not always for the better. Researchers and practitioners, including a small number of designers, are addressing the growing concerns about the Internet’s environmental impact, such as electronic waste, increased energy use, resource depletion, and carbon footprint, which have emerged in recent years, and are calling for a more environment-friendly approach to web and app design. However, it is still a relatively new area of concern. This study evaluates existing guidelines for designing low-impact user interfaces in the mobile food delivery sector. First, the study investigates users’ food delivery habits and their impressions of low-impact interfaces. The findings from this section are then used to design a low-impact food delivery application (FDA) prototype and are tested with users to see how to make low-impact interfaces attractive for a possible change in user behaviors. This thesis builds on previous research about sustainable web design, but the focus area of this study is to investigate whether applied guidelines and low-impact design features are desired by users on mobile screens as well. The research reveals that low-impact features are indeed useful on smaller screens as well and users are generally open-minded and acceptive of front-end changes that have a more positive impact on the environment. However, it is crucial to communicate clearly about any low-impact modifications made to an application, due to the current low level of user awareness and knowledge in this field.