Dissertations / Theses on the topic 'Stormwater management'

Executive Summary The project aims to create a cost-saving stormwater solution. The objectives are to build a dashboard for water level data and weather forecast analysis. Also, to simulate how the Climate Control Pump System, which rainwater tank in estate scale and single lot scale can affect the volume of stormwater runoff and the amount of groundwater infiltration throughout the year. Due to technical problems with the water level sensor when installed at the Environmental Technology Centre at Murdoch University, the water level in the rainwater tank was not recorded. Hence, the rainfall data from the Bureau of Meteorology was used to build the simulation for the Climate Control Pump System, which a rainwater harvest system integrated with weather forecast, water level sensor and automated pump. The water balance models of the simulation show that the annual stormwater runoff volumes can be reduced in both single lot scale and estate scale. It is also found out that a single lot scale is able to reduce the volume of stormwater runoff for more extended periods than estate scale. There are very little literature and research providing data for the cost and the size of stormwater treatment systems, which is unable to calculate the expenditure saved and the percentage of the extent that the stormwater treatment can reduce. However, some research suggested that the use of rainwater tanks for stormwater retention can reduce the size and cost of stormwater systems. Further improvement can be made on this project to gather more accurate data to compare the simulation and real-life result.

The Mulden-Rigolen system, a new urban stormwater management system implemented in Germany, has been examined in this study. The aim of this new system is to replace traditional sewer system for urban road runoff, by infiltrating the incoming water locally through a dual underground system: an active top soil layer and a deeper trench of packed gravel. For each site using this system, the characteristics of the soils in terms of pH, texture, organic matter, infiltration rate as well as Heavy Metals (Cd, Cr, Cu, Pb, Zn) and Phosphorus soil concentrations were successfully determined. The measured values for the soil characteristics were still, after an operation time of up to 15 years for some sites, globally in the range of the recommendation of the German Association for Water, Wastewater and Waste, except for organic matter in some sites, suggesting the need for a more cautious maintenance. Concerning heavy metals and phosphorus content, no alarming soil contamination was observed indicating that the studied “Mulden-Rigolen” systems were still acceptable in terms of soil pollution after several years of use, according to the Danish standards. If this system seemed to have a good flexibility and adaptability to different urban land uses, its treatment efficiency still has to be fully assessed. Indeed, only a primary evaluation of its performance war carried out through a simplistic model which brought up some questions about pollutant retention (especially in case of Zn). Further research (intact soil columns experiments, sequential extractions, on-site runoff sampling) would be necessary to fully determine how well this system works in terms of water treatment.

Thesis (M.C.P.)--Massachusetts Institute of Technology, Dept. of Urban Studies and Planning, 2012.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 115-132).
In urban planning and design, natural systems are a key element of explorations about how to design for sustainability. As part of these efforts, academics and practitioners have also begun to explore the ways in which the utilization of natural systems can and should change our approach to the design and function of urban areas and of infrastructure itself. As an entry point to explore the topic, this thesis focuses on stormwater management as one basic building block or fundamental component of multipurpose infrastructure development. An increasing number of cities will seek to implement green infrastructure approaches or stormwater best management practices (BMPs) in response to new regulation, desires to improve urban quality of life, and changes in attitudes about sustainability and climate change. However, a variety of urban conditions exist within and between cities, and it is therefore necessary to consider the range of possibilities for designing and implementing green infrastructure strategies in a range of built environments. At the same time, there is also the need to address other environmental, social, and cultural goals, such as creating assets from vacant land, improving the public realm, and creating connectivity through neighborhoods. This creates opportunities to develop multipurpose infrastructure projects that utilize natural systems to address multiple objectives. San Francisco, California; Lincoln, Nebraska; and Cleveland, Ohio represent three different types of urban conditions and serve as test locations to identify the factors that affect the development of multipurpose infrastructure. San Francisco has a dense urban environment, Lincoln expects continued horizontal growth through subdivisions, and Cleveland's decline in population has created a condition of vacancy throughout the city. These conditions present a range of constraints and opportunities and shape the planning, design, and implementation of multipurpose infrastructure based on stormwater management. As a result, they lead to three methods or approaches for planning and design of multipurpose infrastructure: the retrofitting city, the preemptive city, and the repurposing city. These three approaches highlight how stormwater management can serve as a basis to develop multipurpose infrastructure systems that function at a range of scales, serve multiples purposes and create additional value for communities.
by Ann-Ariel Vecchio.
M.C.P.

This report describes the design of the Ina Road Landfill Stormwater Management System. Such a system is required by the Arizona Department of Environmental Quality to efficiently and safely remove stormwater drainage from the landfill to better protect the environment and the public during storm events. Stormwater drainage systems are required at landfills to efficiently collect and remove stormwater, limit moisture that can penetrate waste, protect the integrity of the buried mass and the final cover system from washing out and reduce risk of flooding to neighboring property. The State requires that landfill stormwater management systems be designed to handle a minimum size storm event based on historical precipitation records.

Pervious pavements in car parks and driveways reduce peak discharge and the volume of runoff flowing in to urban drains and improve the water quality by trapping the sediments in the infiltrated water. This reduces the risk of pollutants such as suspended solids and particle bound chemicals such as phosphorous, nitrogen, heavy metals and oils and hydrocarbons entering receiving waters. The key objectives of the study are to establish relationships between rainfall and pervious pavement runoff and quantify improvements to infiltrated stormwater quality through the pervious pavement. The field experimental results were used to calibrate the PCSWMMPP model and to develop water flow and quality improvement transfer functions of the MUSIC model for concrete block and turf cell pavements. The research reported herein has demonstrated that pervious pavements can be introduced as a sustainable stormwater management initiative and as a key Water Sensitive Urban Design feature to deliver numerous benefits to the environment. The outcomes from the study will be useful in designing environmentally friendly car parks, pedestrian paths, light traffic drive ways, sporting grounds and public areas in the future. Land developers and local government authorities will be major beneficiaries of the study which has increased the understanding of the use of pervious pavements and explored a number of issues that previously inhibited the wider use of pervious pavements in practice.

This thesis shows the effect social learning has on various stakeholders involved in a project aimed at tackling a stormwater challenge in the city of Uppsala in Sweden and if social learning is a useful tool to address such an issue. Due to the onset of climate change societies are having to deal with increasingly complex issues. Finding sustainable answers to these challenges is proving difficult so alternative methods such innovation competitions much like the one studied in this paper are becoming attractive alternatives to conventional climate change mitigations approaches. By using an active participation method, this thesis attempts to study whether or not social learning is taking place in the innovation competition and if it is having an impact on the innovation competition. The study found that social learning is in fact taking place during the meetings which were attended but whether or not the resulting knowledge created as a result of the social learning was being used to the advantage of the stakeholders was compounded by communication issues outside of the project meetings.

The overall aim of this work is to determine the ability of several types of in-sewer flow regulator to limit and attenuate, in conjunction with some type of storage unit, the flow of stormwater into a sewer system. The intended result of these devices is the reduction of overland flooding and downstream surcharge during storm events. Various stormwater management (SWM) techniques, practised both in the UK and abroad, were reviewed with particular emphasis on attenuation and control. Several types of flow regulators were tested where the choice was based on their popularity (i.e orifice plates and vortex), and novelty (i.e self regulating valve and throttle hose). A full size laboratory rig was built to allow experimentation and comparison of in-situ performance of several flow regulators. This system was capable of generating flows of up to 100 I/s which was controlled by a pneumatic valve interfaced to a dedicated PC. The flow characteristics(discharge and upstream head) were measured efficiently and accurately by two ultrasonic sensors. Investigation of the blockage performance of the vortex flow regulators indicated that these devices retained gross solids at higher heads (i. e. after formation of vortex) which either caused increase in discharge (up to 25% for a given upstream head) or reduced the outlet area (i. e. blockages). In terms of head/discharge relationships, the SRV offered optimum performance with consistent and near constant outflow (discharge changing 3% over 1m change in head). Vortex devices exhibited a linear relationship which is attributed to small changes in the air-core diameter. Comparisons were also made on the performance of these devices in terms of outlet opening, storage and passage of gross solids. A theoretical model was developed for the vortex regulator by combining the hydraulic properties of the free vortex with Bernoulli's equation and applying the principle of maximum discharge. In this way discharge could be predicted for a vortex flow regulator with an inlet opening in terms of upstream head and geometry of the device. The model was calibrated using the laboratory data and verified against independent data sets on blocked devices and from external sources.

A 0.2-hectare wetland was constructed in the floodplain of Opequon Creek in Northern Virginia as a best management practice (BMP) for stormwater management. The research goals were to 1) determine if wetland hydrology existed and quantify the role of groundwater exchange in the constructed wetland (CW) water budget, 2) estimate wetland hydraulic characteristics during overbank flows, and 3) quantify the event-scale nutrient assimilative capacity of the constructed wetland. CW water table elevations and hydraulic gradients were measured through an array of nested piezometers. During controlled flooding events, stream water was pumped from the creek and amended with nutrients and a conservative tracer in two seasons to determine hydraulic characteristics and nutrient reduction. Samples were collected at the inlet, outlet structure, and at three locations along three transects along the wetland flowpath. Water table elevation monitoring demonstrated that wetland hydrology existed on the site. The mean residence time of the wetland was found to be 100 min for flow-rates of 4.25-5.1 m3/min. Residence time distributions of the high and low marsh features identified a considerable degree of flow dispersion. Manningâ s n varied between macrotopographic features and was significantly higher in the spring event as compared to the fall event, likely due to the presence of rigid-stem vegetation. Average wetland n was 0.62. Total suspended solid concentrations decreased with increasing residence time during both experiments. Mass reduction of pollutants were 73% total suspended solids (TSS), 54% ammonia-nitrogen (NH3-N), 16% nitrate-N (NO3-N), 16% total nitrogen (TN), 23% orthophosphate-phosphorus (PO4-P), and 37% total P (TP) in the fall, and 69% TSS, 58% NH3-N, 7% NO3-N, 22% TN, 8% PO4-P, and 25% TP in the spring. Linear regression of mass flux over the event hydrograph was used to determine pollutant removal rates between the wetland inlet and outlet. Pollutant removal rates were determined through linear regression of mass flux and were higher in the spring event than in the fall. Dissolved nitrogen species were more rapidly removed than dissolved phosphorus. TSS, TP, and TN removal were greater and faster than dissolved nutrient species, suggesting that physical settling was the dominant removal mechanism for stormwater pollutants.
Ph. D.

Watershed-based stormwater management (WSM) has been proposed as more effective for stormwater management than traditional methods of controlling stormwater, which are carried out based on jurisdictional lines at the parcel-scale. Because WSM considers the watershed as a total unit, this method is considered to be more effective in reducing problems associated with stormwater management including environmental degradation and flooding. However, larger watersheds encompass smaller watersheds, and therefore WSM can be implemented at a wide range of scales. There has been little research on what scale is most appropriate, and more specifically, only a modest amount of work has taken stakeholder opinion into account.

The specific objectives of this study are to determine: 1) if watershed scale is an important factor in WSM, 2) whether stakeholder opinion has an effect on the appropriate scale used in WSM, and 3) what scale is most appropriate for WSM, if scale is an important factor. To meet these objectives, we delineated sub-watersheds within a watershed in southwestern Virginia, surveyed stakeholders within the watershed on their opinions of stormwater management methods, and compared the results at both watershed scales using statistical tests and decisions support software. The results of this study have important implications for geographic scale in WSM as well as the use of qualitative data in determining appropriate geographic scale in matters of implementation in the field of planning.
Master of Science

Protection of downstream channels and reduction in flooding can potentially be improved by evaluating alternative site stormwater management (SWM) strategies at a watershed scale and selecting the optimal strategy for a subject watershed. Tailoring a management strategy for a specific watershed may be worthwhile to minimize development costs and maximize downstream benefit. A hydrologic/hydraulic model for a watershed in Blacksburg, Virginia, is used to evaluate downstream results based on implementation of several alternative SWM strategies currently practiced within the United States. Results show none of the strategies meet the goal of maintaining the baseline goal at the watershed POI for the full range of design storms. Modification to the strategy that performs best at the watershed scale did meet the watershed goal for all design storms except the 1-year. For smaller storm events, it appears that increasing the volume of an initial capture and the drawdown time to release that volume does not increase performance downstream. This is potentially significant as extra dollars spent on site would not provide extra benefit downstream. When post-development peak runoff rates are detained to the predevelopment rate for larger storm events, whether based on a site or watershed focused strategy, the watershed goal can be met. A volume reduction strategy performs well, but implementation is hindered by soils with poor infiltration and the presence of karst. Other insight to watershed based management strategies, the role of regional facilities and predevelopment condition assumptions at the site scale to maintain a baseline condition downstream are discussed.
Master of Science

The effect of stormwater runoff on the water quality of Peters Creek was investigated. Creek water was sampled at rural, suburban and urban sites. Background and runoff samples were analyzed for sediment, nutrient and heavy metal concentrations. The area upstream of the suburban site was found to contribute the greatest contamination to the creek but the heavy metal contributions were accumulated throughout the watershed. The creek water contained sufficient nutrients to potentially contribute to the eutrophication of Smith Mountain Lake downstream. As the watershed has been developed, flooding has increased in frequency. The detrimental effects of runoff can be reduced in the watershed by clearing the trash from the creek bed, enforcing construction erosion control and creek bed alteration ordinances and by building a series of detention basins in the creek upstream from common sites of flooding.
Master of Science
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Much like other cities Stockholm has traditionally used a technical system for managing stormwater. With time this system has become overburdened and has led to large environmental concerns. To reach water quality goals set by the EU Stockholm needs to decrease pollution released to recipients by 70-80%.  Green infrastructure (GI) has increasingly been used as an alternative and addition to technical stormwater systems. Many studies have been conducted on different solutions and their stormwater management performance. The City of Stockholm have done research on numerous solutions to evaluate their performance in the context of Stockholm as well. However, implementation in the inner city is slow, thus this study explores why this is the case, and how Stockholm’s stormwater management goals can be reached. Stockholm predominately uses trees planted in plant beds using structural soil, and a combination of constructed wetlands and wet ponds for stormwater management. In new developments there is no real concern, as the GI can be included in planning at an early stage. Including these solutions in existing environments causes issues related to space, both above and below ground, and costs. Therefore, other solutions need to be found. This study explored green roofs, green walls and permeable pavements as possible options. Additionally, it found that finding new space that has previously not been used for GI could be an option. To mitigate financing issues new ways of promoting investment into GI from private property owners could be utilized, but that there also is a mismatch between supposed support for sustainable stormwater management on the political side and funds allocated. Finally, the study recommends that Stockholm takes the technical systems into account and explores what GI measures best work together with it to more effectively decrease pollution.

Cities within California are beginning to incorporate urban agriculture into their land use designations. Prompted by residents and local organizations, cities are hoping to capture the benefits that urban agriculture provides. Research has shown that urban agriculture renews and beautifies neighborhoods, provides healthy food choices, increases public health, has the potential to help with stormwater runoff, creates jobs, and fosters community. In the last few years, several California cities have made headlines as they have adopted new zoning codes that include urban agriculture. In reviewing these new zoning codes and exploring the topic of urban agriculture, it became evident that just because an urban farm was small, organic and provided certain benefits that it was not free from impacting its surroundings. As more urban agricultural ventures are established within cities, planners have to carefully consider their effect. One such impact could be stormwater pollution. There is insufficient research to determine whether there is a relationship between urban agriculture and stormwater, however, studies on conventional agriculture and urban landscaping (mainly urban lawns) show that each of these areas pollute the local water bodies with sediment, chemicals, and nutrients. Is urban agriculture different? This thesis utilizes two case studies within California, the City of Oakland and the City of San Diego, to examine the similarities and differences between each city’s urban agriculture ordinances and evaluate whether or not the cities have adjusted stormwater requirements in parallel with these ordinances. Interview responses and site visits in each city were analyzed and compared to expound upon the approaches each city engaged. Using the collected data and analysis as a base, a set of guidelines was created for managing stormwater runoff from urban agriculture.

This thesis describes an integrated approach to infrastructure planning, watershed management and neighborhood livability for an urban basin in Portland, Oregon. After an examination of existing integrated approaches used in Oregon and British Columbia, this project outlines a framework for the analysis and planning of green infrastructure in the Oak Basin. After analyzing the conditions of the three systems that affect and are affected by green infrastructure (infrastructure - watershed - neighborhood), a green infrastructure plan was developed to meet systems needs. Additionally, site level designs reflect green infrastructure plan goals and targets as well as illustrating how these spaces can contribute to neighborhood livability.
Applied Science, Faculty of
Architecture and Landscape Architecture (SALA), School of
Graduate

Despite the runoff reduction efficiencies recommended by various regulatory agencies, minimal research exists regarding the ability of vegetated swales to simultaneously convey and reduce runoff. This study assessed the effect water quality swales distributed among upstream sub-watersheds had on watershed hydrology. The study was also posed to determine how certain design parameters can be dimensioned to increase runoff reduction according to the following modeling scenarios: base, base check dam height, minimum check dam height, maximum check dam height, minimum infiltration rate, maximum infiltration rate, minimum Manningâ s n, maximum Manningâ s n, minimum longitudinal slope, and maximum longitudinal slope. Peak flow rate, volume, and time to peak for each scenario were compared to the watershedâ s existing and predevelopment conditions. With respect to the existing condition, peak flow rate and volume decreased for all scenarios, and the time to peak decreased for most scenarios; the counterintuitive nature of this result was attributed to software error. Overall, the sensitivity analysis produced results contrary to the hypotheses in most cases. The cause of this result can likely be attributed to the vegetated swale design and modeling approaches producing an over designed, under constrained, and/or over discretized stormwater management practice.
Master of Science

Urbanization has considerably altered natural hydrology of urban watersheds by increasing runoff volume, producing higher and faster peak flows, and reducing water quality. Efforts to minimize or avoid these impacts, for example by implementing low impact development (LID) practices, are gaining momentum. Designing effective and economical stormwater management practices at a watershed scale is challenging; LIDs are commonly designed at site scales, considering local hydrologic conditions (i.e., one LID at a time). A number of empirical studies have documented hydrologic and water quality improvements achieved by LIDs. However, watershed scale effectiveness of LIDs has not been well studied. Considering cost, effort, and practicality, computer modeling is the only viable approach to assess LID performance at a watershed scale. As such, the United States Environmental Protection Agency’s Stormwater Management Model (SWMM) was selected for this study. It is well recognized that model predictions are plagued by uncertainties that arise from the lack of quality data and inadequacy of the model to accurately simulate the watershed. To scrutinize sensitivity of prediction accuracies to spatial resolution, four SWMM models of different spatial detail were developed for the Ballona Creek watershed, a highly urbanized watershed in the Los Angeles Basin, as a case study. Detailed uncertainty analyses were carried out for each model to quantify their prediction uncertainties and to examine if a detailed model improves prediction accuracy. Results show that there is a limit to the prediction accuracy achieved by using detailed models. Three of the four models (i.e., all but the least detailed model) produced comparable prediction accuracy. This implies that devoting substantial resources on collecting very detailed data and building fine resolution watershed models may not be necessary, as models of moderate detail could suffice. If confirmed using other urban watersheds, this result could benefit stormwater managers and modelers. All four SWMM models were then used to evaluate hydrologic effectiveness of implementing bioretention cells at a watershed scale. Event based analyses, 1-year, 2-year, 5-year and 10-year storms of 24-hours were considered, as well as data from October 2005 to March 2010 for a continuous simulation. The runoff volume reductions achieved by implementing bioretention cells were not substantial for the event storms. For the continuous simulation analysis, however, about twenty percent reductions in runoff volume were predicted. These results are in-line with previous studies that have reported ineffectiveness of LIDs to reduce runoff volume and peak for less frequent but high intensity storm events.

Stormwater user fees (SUFs) are an increasingly popular method of generating revenue for municipalities responsible for implementing complex stormwater regulations through the NPDES permit program. These fees can be created in a multitude of ways, including a flat fee for each parcel, charging by parcel area, charging based on a runoff factor, and many others. As a case study, eight SUFs were applied to the City of Roanoke and the Town of Blacksburg, both in Virginia, to determine the effect each SUF has on how land use type impacts the revenue composition. The City of Roanoke is larger and includes more industrial areas, but less multifamily impervious areas than Blacksburg, which translates differently in the SUFs. Residential parcels comprise the highest percentage of the revenue in all eight SUFs in Blacksburg and four in Roanoke. Open space parcels don't contain much impervious area yet account for up to 27% of the revenue. Industrial parcels comprise more of the revenue in Roanoke, averaging 11.1% compared to 4.6% in Blacksburg. A detailed digitized land cover dataset was compared to Blacksburg's land cover dataset, which resulted in maximum difference of $0.02 per parcel for residential parcel fees. Exemptions of large parcels in Roanoke, like the railroad and airport, if enacted would result in a maximum increase in fees of 15% and a shift of $7,491 of the monthly revenue to the residential parcels.
Master of Science

Harvesting stormwater to supplement water demands has attracted a growing interest in South Africa as concerns over the security of the country's water supply increase. Whilst stormwater harvesting has been shown to offer a viable alternative water resource, there are often concerns about its storage requirements due to space constraints in urban areas. Stormwater ponds offer a potential solution to these concerns. Since stormwater ponds are typically designed for the sole responsibility of attenuating the periodic peak stormwater flows that are associated with large storm events, they often remain underutilised. By introducing Real Time Control (RTC) systems to operate stormwater pond outlets, ponds could potentially be used to store stormwater. This could increase the benefits that stormwater ponds provide as well as offer a viable alternative water resource. To investigate the economic viability of harvesting stormwater from existing stormwater ponds, a case study was performed on a representative urban catchment – the Diep River subcatchment, located in Cape Town, South Africa. The catchment contains seven stormwater ponds, which could be retrofitted for harvesting purposes. Sixteen different stormwater harvesting scenarios were developed that modelled various non-potable demands in the vicinity as well as different storage and harvesting arrangements, created using RTC strategies, of the catchment's existing ponds. These scenarios were modelled using an assortment of modelling tools which include: a catchment stormwater model; water distribution network models; and a Life Cycle Cost Analysis (LCCA). The economic viability of harvesting stormwater from the Diep River subcatchment's stormwater ponds was most susceptible to the cost of the system's water distribution infrastructure. Consequently, stormwater harvesting was most economically viable if used to supply toilet, clothes washing and irrigation demands to residential properties situated in close vicinity to the system's harvesting pond as this minimised the extent of the water distribution network. The results also revealed that distributing storage amongst ponds situated throughout the catchment is an effective method of increasing the volume of stormwater a stormwater harvesting system could yield without reducing its economic viability. However, this is on the condition that the system only extracts stormwater from the most downstream pond in the catchment. Importantly, the study also revealed that the attenuation of peak flows of large storm events (up to 1-in-20 year return period), achieved when harvesting stormwater from the existing stormwater ponds would be comparable to what the ponds currently provide. The study concluded that harvesting stormwater from existing stormwater ponds is potentially viable. It also demonstrated an effective method to maximise a catchment's storage capacity using distributed storage. For stormwater harvesting to be viable however, stormwater should be used to supplement a large percentage of non-potable end-uses and requires significant uptake amongst catchment residents.

Stormwater runoff from developed land is a source of pollution and excessive flow to waterways. The most commonly employed practices for flow and volume control are stormwater ponds and basins (also referred to as detention and retention ponds). These structures can be effective at controlling peak discharge to water bodies by managing flow timing but are often ineffective at removing nutrients, particularly in dissolved forms. Pond morphology coupled with place-specific characteristics (like soil type and drainage area characteristics) may influence plant community composition in these water bodies. The interaction of physical, chemical, and biological elements in stormwater ponds may affect their water quality performance in more significant ways than previously understood. Floating treatment wetlands (FTW) are floating rafts of vegetation that can be constructed using a variety of materials and are an emerging technology aimed at improving the pollutant removal and temperature control functions of stormwater ponds. Previous studies with field research in subtropical and semiarid climatic regions found incremental nutrient removal improvement correlated with FTW coverage of pond surface area. However, data on their performance in cold climates is lacking from the literature. This dissertation presents data from a three-year study examining the performance of FTW on stormwater pond treatment potential in cold climate conditions and optimal vegetation selection based on biomass production, phosphorus (P) uptake, and root architectural characteristics that enhance entrapment functionality. To put the FTW pond performance data into context, results from a survey of seven permitted stormwater ponds in Chittenden County, Vermont and the ponds' associated variability in influential internal and external dynamics are also discussed. Pond morphology, drainage area land use, soil types, and biological communities are analyzed for correlative relationships to identify design factors that affect pond performance but are not controlled factors in stormwater system permitting.

In the Greater Vancouver Regional District (GVRD), non-point source pollution from an urban watershed and a diesel bus loop was assessed in terms of trace metal contamination in the stormwater runoff. In the Brunette River watershed study, Northwest Hydraulic Consultants (NHC) collected streambed sediment and suspended sediment from selected streams during 7 storm events over 2003. From 1993 to 2003, the major stormwater contamination happened in the most industrialized Still Creek. The streambed Cu, Mn, Fe, and Zn concentration increased by 1.5, 1.7, 1.9, and 1.1 times, respectively. And the suspended Cu, Mn, and Zn increased by a factor of 2.1, 4.2, and 1.5, respectively. The streambed sediment exceeded probable effect level in Still Creek and Stoney Creek to varying degrees with Cu and Zn. The land use is considered to be the origins of these toxicants. Statistically, the magnitude of suspended metal concentration in μg/l is negatively correlated with the drainage areas. While the — concentrations in mg/kg, especially for metal Cu and Zn, showed strongly and positively correlation with the traffic density. Positive correlation existed between the suspended metal loading (kg/yr) and the imperviousness and the catchment area. No apparent trend was observed in terms of export coefficient (g/ha/yr) and land use. 1062 tons of sediments were trapped by Burnaby Lake in 2003. This sediment overloading problem causes serious metal contamination in the lake. Stormwater runoff quality was monitored in 15 storm events from October 2004 to June 2005 in the diesel bus loop in the University of British Columbia. The dissolved Cu and Zn Event Mean Concentration (EMC) exceeded the EPA discharge criteria in 2 and 4 events each, which occurred in the dry season. Diesel bus traffic contributes' a large portion of Cu, Fe, Zn contamination since the average bus loop trace metal levels were much higher than the GVRD urban levels. The runoff trace metal concentrations are strongly related to the antecedent dry period, and are weakly related to the traffic density and the rainfall intensity. From the catch basin filter evaluation, high removal efficiencies on suspended metal/solids were achieved with low particulate loading in the filter chamber. The filter performed well for the dissolved metal removal before the non-reversible saturation was reached. Each kilogram of filter media has an absorption capacity of 52 gram oil and grease, 20 milligram Mn, and 16 milligram Zn.
Applied Science, Faculty of
Civil Engineering, Department of
Graduate

Urban stormwater management must address multiple social-ecological concerns as it adapts to present challenges and transitions towards sustainability. Concerns for physical stormwater infrastructure must be investigated and resolved in relation to diverse stakeholder perspectives. This research explored perspectives and barriers in urban stormwater management and their roles in the transition to sustainability. A dynamic simulation was developed to understand the systemic influence of environmentally friendly solutions on water quality in receiving environments in Project Twin Streams Catchment, West Auckland, New Zealand. Results showed that environmentally friendly solutions can reduce but not fully internalise the environmental impact of stormwater even in a catchment-wide implementation. Failure to integrate socialecological variables in the modelling process limits the usefulness of the model and the insights that can be gained. To address this, a qualitative modelling approach was undertaken that sought to understand pluralist perspectives in stormwater management and barriers that restrict the uptake of alternative solutions. Cognitive mapping was used to elicit and capture perceptions on problems and solutions in urban stormwater management. Three core perspectives were found to underlie contemporary stormwater management: conventional fixes, low impact solutions, and community development. These perspectives were diverse and conflicting. Conventional stormwater management created feedback loops that promoted the continuous construction of infrastructure to the detriment of environmental systems. Low impact solutions did not break this feedback loop. Community development failed to address urgent issues due to systemic delays. Importantly, none of the perspectives by themselves will lead to sustainable iv outcomes. This highlighted the need for integration of these different perspectives and approaches. Uptake of low impact solutions and community development was found to be hindered by physical, institutional, logistical and internal barriers. These barriers were caused by, and at the same time increased, the complexity inherent in stormwater management. Interactions between barriers were investigated and potential policy interventions suggested guiding managers in the development of effective policies that support the transition of urban stormwater management towards sustainability.

Portland Cement pervious concrete's ability to permit water infiltration has encouraged its use as a stormwater management tool. However, the material has suffered historically poor support due to a number of factors, including failures due to poor mix design and improper construction techniques, concern about lesser structural strength, concern about poor long term performance due to clogging of surface pores and undefined credit for stormwater management. This study focuses on long term performances of pervious concrete parking lots and their stormwater management credit. Before stormwater management credit could be estimated, it was necessary to develop a testing device to gather information from existing pervious concrete parking lots currently in use. Eight parking lots were examined to determine the infiltration rates of the pervious concrete, as well as to verify the soil makeup beneath pavement. A total of 30 cores were extracted from pervious concrete parking lots and evaluated for infiltration rates. Three of the sites had a pervious concrete section that included a gravel reservoir. Infiltration rates were measured using the application of an embedded single-ring infiltrometer. In an attempt to provide an estimate of credit, a mass balance model was created to be used for simulation of the hydrologic and hydraulic function of pervious concrete sections. The purpose of the model is to predict runoff and recharge volumes for different rainfall conditions and hydraulic properties of the concrete and the soil. The field derived hydraulic data were used to simulate infiltration volumes and rainfall excess given a year of rainfall as used in a mass balance operated within a spreadsheet. The results can be used for assessing stormwater management credit.
M.S.
Department of Civil and Environmental Engineering
Engineering and Computer Science
Civil Engineering

Thesis (M.C.P.)--Massachusetts Institute of Technology, Dept. of Urban Studies and Planning, 2010.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 79-83).
With their high concentrations of impervious surface, urban areas generate stormwater runoff that overwhelms existing infrastructure causing flooding, sewer overflows, water pollution, and habitat degradation. Under pressure to find cost-effective, environmentally sustainable, and socially responsible solutions to stormwater management, cities are looking to green infrastructure. The term "green infrastructure," when used for stormwater management, denotes design techniques, such as raingardens, green roofs, permeable pavement, street trees, and rain barrels, that infiltrate, evapotranspirate, capture, and reuse stormwater onsite. With the added benefits of improving air quality, land values, wildlife habitat, urban heat island, and urban aesthetics, some decision-makers view green infrastructure as a silver bullet solution to address climate change, water quality, and other urban issues. As cities move to create neighborhood- and citywide-scale green infrastructure plans, my thesis explores the common barriers that cities face when implementing green infrastructure, as well as tactics that have been used to overcome those barriers. The realities of implementation indicate that cities seeking to scale up green infrastructure should plan on expanding public participation and awareness-raising, strengthening interdepartmental coordination and partnerships within the community, building the technical capacity of the public and the government, and developing innovative ways to continuously engage and motivate individuals.
by Sarah A. Hammitt.
M.C.P.

In the United States, states are federally mandated to develop watershed management plans to mitigate pollution from increased impervious surfaces due to land development such as buildings, roadways, and parking lots. These plans require a major investment in water retention infrastructure, known as structural Best Management Practices (BMPs). However, the discovery of BMP configurations that simultaneously minimize implementation cost and pollutant load is a complex problem. While not required by law, an additional challenge is to find plans that not only meet current pollutant load targets, but also take into consideration anticipated changes in future precipitation patterns due to climate change. In this dissertation, a multi-scale, multiobjective optimization method is presented to tackle these three objectives. The method is demonstrated on the Bartlett Brook mixed-used impaired watershed in South Burlington, VT. New contributions of this work include: (A) A method for encouraging uniformity of spacing along the non-dominated front in multiobjective evolutionary optimization. This method is implemented in multiobjective differential evolution, is validated on standard benchmark biobjective problems, and is shown to outperform existing methods. (B) A procedure to use GIS data to estimate maximum feasible BMP locations and sizes in subwatersheds. (C) A multi-scale decomposition of the watershed management problem that precalculates the optimal cost BMP configuration across the entire range of possible treatment levels within each subwatershed. This one-time pre-computation greatly reduces computation during the evolutionary optimization and enables formulation of the problem as real-valued biobjective global optimization, thus permitting use of multiobjective differential evolution. (D) Discovery of a computationally efficient surrogate for sediment load. This surrogate is validated on nine real watersheds with different characteristics and is used in the initial stages of the evolutionary optimization to further reduce the computational burden. (E) A lexicographic approach for incorporating the third objective of finding non-dominated solutions that are also robust to climate change. (F) New visualization methods for discovering design principles from dominated solutions. These visualization methods are first demonstrated on simple truss and beam design problems and then used to provide insights into the design of complex watershed management plans. It is shown how applying these visualization methods to sensitivity data can help one discover solutions that are robust to uncertain forcing conditions. In particular, the visualization method is applied to discover new design principles that may make watershed management plans more robust to climate change.

Thesis (M.S.) -- University of Maryland, College Park, 2008.
Thesis research directed by: Dept. of Civil and Environmental Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.

In Washington, DC, historical data are used to adequately size for rainfall events, and efforts to increase stormwater management requirements are fought against by internal stakeholders. In urban planning, extreme rainfall events, that may occur more frequently than expected, are often not a consideration when designing for green infrastructure facilities. The purpose of this case study was to explore how internal and external stakeholders influence stormwater management policies related to extreme rainfall events in Washington, DC. The power and politics organization theory, which focuses on how individuals obtain influence, and the resource dependency theory, which explores how organizations benefit from sustainability, were used as the theoretical framework in this study. The case study analysis was conducted via phone interviews; through phone interviews, data were collected from 4 policymakers (i.e., external stakeholders), 5 real estate developers (i.e., internal stakeholders) and 3 internal team members (i.e., internal stakeholders) and analyzed thematically. All the stakeholders believed that it is not necessary to design the green infrastructure systems to the extreme rainfall event; however, the developers said that they would design their green infrastructure systems larger if required by policy. The results of the study showed that each group'€™s effect works in a cyclic fashion to each other. Recommendations for future studies include to expand and increase stakeholder participation. This collaboration and better communication can help in developing more efficient stormwater management policies for a better city, which is an implication for positive social change.

This project was a step forward in developing new knowledge relating to the optimisation of the flood mitigation measures adaptation against climate change and urbanisation impacts by considering their uncertainty. The generic outcomes of this study are expected to contribute to the optimisation of design of flood mitigation measures into the future based on costs and the capability to reduce the flood damage.

Stormwater treatment is commonly performed with a combination of approaches including the utilization of natural systems and engineered devices. Before using a proprietary treatment instrument it is required to verify its performance and efficiency in reducing different pollution components including the TSS. Different states have developed strategies and regulations for accepting new instruments. In this thesis the stormwater management plan of the City of Portland, Oregon(2008), is analyzed in order to improve the current regulations. These rules apply to new technologies which are proposed by vendors to be used in Portland's stormwater treatment plans. Each requirement which should be met by the applying vendors is thoroughly analyzed followed by a comparison with the Stormwater management plan(2008)regulations of the state of Washington the so called Technology Assessment Plan-Ecology TAPE (Howie, 2011). Because of the similarities in the climate and land use between these two testing frameworks in order to evaluate the potential applicability of data submitted by vendors who had devices approved by Washington, to be utilized by Portland. The treatment of total suspended solids (TSS) is the focus of this thesis since it is central to the testing process and since most of the other pollutions are attached to TSS and will get treated if TSS is treated. The overall analysis shows that Portland adopts more restrictive requirements on the characterization of stormwater event samples to be treated by a technological instrument while Washington's restriction are more stringent on the efficiency of total suspended solid removal, in which it demands higher standards on the treatment of TSS compared to Portland's efficiency requirements. In order to study practical context in which regulations are administrated by Portland, rainfall data from 66 gauges covering the period of 1980-2011 was studied and the impacts of seasonality, land use, land form, periods of no rain before and after an event and Portland's Modified Performance line on the number of accepted rain events were analyzed. The results which were accepted by state of Washington were also compared with the results accepted by the city of Portland on Portland's Standard Performance line. Our seasonality study suggests that Portland's requirements are unnecessarily restrictive which results in the disqualification of many otherwise useful stormwater events, sometimes allowing no natural events to be available for testing in dry years. The analysis of land use showed that land use has no statistically significant impact on the concentration levels of TSS, thereby indicating that land use restrictions in the testing rules could be usefully relaxed. Decreasing the interevent no-rain period significantly increases the total number of events providing sufficient data to assess the performance of treatment facilities. We also showed that many more events become suitable for performance testing if events separated by one hours or less are considered a single, longer event. Finally we identified a statistical relationship between number of forecasted accepted stormwater events and the total average daily precipitation in a given year.

Sustainable Built Environments Senior Capstone Project
During Tucson rainstorms, many roads and neighborhoods experience high levels of flooding on the city’s street networks. This phenomenon creates unsafe road conditions, damage to the road infrastructure, and excessive urban stormwater runoff that is potentially polluted. The vast quantities of impervious surfaces in the urban landscape impede the rainwater’s ability to infiltrate the ground, thus resulting in increased volumes of runoff during a rainstorm. Stormwater management is used by municipalities and communities to address the previously mentioned adverse impacts of stormwater runoff. Various techniques and strategies used in stormwater management include, low impact development (LID), green infrastructure, and better site design (BSD) strategies implemented during design stages to reduce stormwater runoff levels. In addition, local governments can establish stormwater utilities and policies in order to help address and better manage the issue of stormwater runoff within urban areas. The primary research questions of this study will include: What are the most effective best management practices and techniques to address urban runoff? What combination of best management practices and government policies will be the more effective in addressing Tucson’s urban runoff problem? Accordingly, this study will examine a variety of policies and techniques to address stormwater runoff, and then, based on this information, provide a suggestion of the best practices and techniques that may be feasible for implementation in Tucson.

Two pilot size bioretention boxes were constructed for field investigations at the Risvollan Urban Hydrological Research Station in Trondheim. The seasonal pollutant retention, hydraulic lag times, and rainfall runoff versus snowmelt chemo dynamics have been studied with respect to zinc, copper, and lead. The field investigations were divided into four parts; a long term continuous hydrologic performance, heavy metal retention of rainfall runoff during different seasons, and heavy metal retention from roadside snowmelt. The chemo dynamic pathways through the system were investigated for the warm versus the cold season, and rainfall runoff versus snowmelt. Overall the results showed consistent high retention of particles and total metals with respect to concentrations and mass removal, with more than 90% mass removal of total zinc and more than 85% mass retention of lead, while copper retention varied from 46% to 86% by mass. However increases in dissolved fractions through the system for all events in the case of copper and for the snowmelt events in the case of zinc could lead to an increase of bioavailable dissolved metals in the outflow which is not desirable. The top mulch layer was identified as the largest sink of metals and particles, which helped avoid clogging the soil due to high particle concentrations in the inflow. The plants did show some ability to retain and absorb metals in the roots and shoot, however this was less than 5% of the total metal retention. The plants had a more important function in improving root zone infiltration, and rejuvenating the system in the spring every year, making it a valuable green space in the urban landscape. Snow storage was also considered and it was found that snow storage, dependent on annual snow volume, quickly became a deciding design parameter with respect to sizing.

The separation of stormwater from the sewage waste stream has been implemented in many cities to minimize combined sewer overflows (CSOs) during periods of heavy rain. In the absence of treatment, discharges from separated sewer/stormwater outfalls are also very damaging to aquatic environments as they typically carry numerous nonpoint source pollutants and alter the delicate geomorphology of natural watercourses. A new strategy has emerged during the past few decades that focuses on absorbing, infiltrating and detaining stormwater to reduce peak flows and filter out nonpoint source pollution, thereby addressing CSOs, stormwater runoff pollution and flooding at the same time. An increasing number of cities in the United States and Canada have devised comprehensive plans to incorporate these methods into their overall wastewater management strategies. In an effort to eliminate CSOs and build resilience against flooding the City of Vancouver has committed over $1 billion to separate all of its remaining combined sewer/stormwater infrastructure by 2050. In contrast, Seattle and Portland (Oregon), two cities with similar rainfall patterns and levels of urbanization are following strategies that utilize a combination of targeted conventional stormwater infrastructure upgrades and GI to minimize CSOs, stormwater runoff pollution and flooding. As the City of Vancouver moves forward with its city-wide Integrated Stormwater Management Plan, this thesis contends that its sewer separation project should be revised to also include a comprehensive network of GI. The primary investigatory goal of this thesis is to identify and analyze the social, institutional, economic and technical barriers encountered by Portland and Seattle to the implementation of GI and the key factors that enabled its implementation. This is accomplished through interviews conducted with key staff members from Portland’s Bureau of Environmental Services (BES) and Seattle Public Utilities (SPU), supported by a review of recent literature. It was found that Portland and Seattle overcame a variety of social, institutional, economic and technical barriers through the use of cost effective pilot projects, extensive public consultation, slowly changing the internal culture towards GI within municipal departments, offering financial incentives and through increasing the profile of their projects through awards and competitions.
Applied Science, Faculty of
Community and Regional Planning (SCARP), School of
Graduate

Les bassins de rétention sans plan d'eau permanent (bassins "secs") sont largement répandus pour diminuer les aspects négatifs du ruissellement urbain sur le milieu récepteur. À l'heure actuelle, de tels bassins sont conçus avec un contrôle statique, ce qui signifie que leur fonctionnement est seulement basé sur une limitation de leur débit maximal de sortie. Le Contrôle en Temps Réel (CTR) du degré d'ouverture de leur vanne de sortie permettrait d'améliorer leurs performances. Le travail présenté ici a notamment permis le développement de scénarios de CTR d'un bassin de rétention sec situé à l'exutoire d'une petite zone urbaine (3.5 km2) sur le territoire de la Ville de Québec, au Canada. Le ruissellement et sa concentration en Matières En Suspension (MES) ont été simulés par le modèle SWMM5, dans lequel la formulation du lessivage de surface a été améliorée dans le cadre de ce travail. Les stratégies de gestion en temps réel proposées utilisent comme information les données du réseau pluviométrique, la mesure de la hauteur d'eau dans le bassin de rétention et, dans certains des scénarios, des prévisions météorologiques. Les prévisions de pluie peuvent en effet s'avérer intéressantes pour une large gamme d'utilisateurs, comme ceux impliqués dans la prévention des crues, et la gestion de l'eau de manière générale, puisqu'elles permettent une certaine anticipation du comportement du système. Les prévisions de pluie d'ensemble fournissent de plus une description explicite et dynamique de l'incertitude liée à la prévision. Cependant, de telles prévisions sont à l'heure actuelle disponibles à des échelles trop grandes pour être directement compatibles avec des modèles hydrologiques mis en œuvre sur de petits bassins versants. Cette thèse de doctorat s'est donc de plus penchée sur la désagrégation spatiale du système de prévision d'ensemble Canadien, afin de rendre les prévisions d'ensemble de pluie plus appropriées à l'échelle du petit bassin urbain pour lequel des règles de CTR du bassin de rétention ont été élaborées. Pour cela, diverses variantes de la méthode statistique de désagrégation spatiale proposée par Perica et Foufoula-Georgiou (1996b) ont été comparées, pour faire passer les prévisions d'ensemble globales de pluie (émises par Environnement Canada) d'une résolution de 100 km par 70 km à celle de 6 km par 4 km. Cette technique permet d'augmenter la variance des hauteurs de pluie prévues à l'intérieur d'un pixel original lors de la désagrégation, tout en préservant la valeur moyenne initialement prévue pour la pluie sur ce pixel. Ces prévisions d'ensemble de pluie ont été émises par le système de prévision d'ensemble global Canadien, dans sa forme opérationnelle en 2009. La méthode statistique de Skaugen (2002) a également été appliquée à ces prévisions, et a mené à la production de prévisions d'ensemble ayant une résolution de 10 km par 7 km. Pour comparaison, des méthodes plus simples comme celle de l'interpolation bilinéaire, ont aussi été appliquées. Cette dernière permet le raffinement des prévisions globales de pluie sans augmenter la variance des hauteurs de pluie lors du processus de raffinement spatial. Les produits météorologiques désagrégés ont été évalués d'un point de vue météorologique et hydrologique, en utilisant différents scores et diagrammes. Pour l'évaluation météorologique, neuf jours présentant d'importants évènements de précipitation ont été utilisés pour comparer les hauteurs de pluie prévues à celles observées par le réseau de pluviomètres de la ville de Québec. Des prévisions hydrologiques d'ensemble avec un pas de temps compris entre 3 et 24 heures ont été mises en œuvre sur une période de 3 mois, avec les prévisions d'ensemble originales et celles issues de la désagrégation. Cette chaîne de prévision hydro-météorologique opérationnelle a été élaborée en utilisant les modèles GR4J et SWMM5. Ces modèles ont été mis en œuvre sur 4 bassins situés dans la région de Québec, avec une taille comprise entre 5 et 350 km2. L'évaluation hydrologique s'est basée sur la comparaison des débits prévus avec ceux observés. Les résultats obtenus avec la méthode de Skaugen (2002) ne se sont pas révélés aussi intéressants que ceux basés sur la technique de Perica et Foufoula-Georgiou (1996b). Avec cette dernière, les conclusions principales de ce travail de thèse sont: 1) la qualité globale des prévisions est préservée lors du processus de raffinement, et 2) les produits désagrégés par cette méthode qui permet d'augmenter la variance des hauteurs de pluie présentent une qualité similaire à celle des produits désagrégés par la méthode de l'interpolation bilinéaire. En revanche, la variance et la dispersion des différents membres des prévisions d'ensemble se sont avérées largement améliorées pour les produits désagrégés par la méthode de Perica et Foufoula-Georgiou (1996b), ce qui représente un avantage considérable comparativement à la méthode de l'interpolation bilinéaire. Ces résultats ont été confirmés du point de vue hydrologique. Par conséquent, il est avancé à l'issue de ces travaux de doctorat que la méthode de désagrégation statistique de Perica and Foufoula-Georgiou (1996b) représente une manière intéressante pour réduire le problème d'incompatibilité existant entre les résolutions des modèles météorologiques globaux et le haut degré de précision parfois requis dans la représentation spatiale des champs de précipitation par les modèles hydrologiques semi-distribués et par ceux montés sur de petits bassins versants. Les stratégies de CTR mises en place pour le bassin de rétention sec étudié ici ont permis une amélioration significative de ses performances - l'efficacité d'enlèvement des MES est passée de 46 à 90% - tout en restant sécuritaire (du point de vue du risque de débordement) et en prenant en compte une contrainte liée au risque de prolifération de moustiques. Cependant, les prévisions de pluie désagrégées ne se sont pas révélées supérieures aux prévisions originales du modèle d'ensemble global Canadien, dans ce contexte spécifique de gestion en temps réel. Les différentes prévisions considérées ont en effet mené à des résultats similaires pour les performances de ce bassin de rétention soumis à des règles de CTR.
Dry detention ponds are commonly implemented to mitigate the impacts of urban runoff on receiving water bodies. They currently rely on static control through a fixed limitation of their maximum outflow rate. Real-Time Control (RTC) allows optimizing their performance by manipulation of an outlet valve. This thesis developed several enhanced RTC scenarios of a dry detention pond located at the outlet of a small (3.5 km2) urban catchment near Québec City, Canada. The catchment's runoff quantity and Total Suspended Solids' (TSS) concentration were simulated by the SWMM5 model with an improved wash-off formulation. The control procedures rely on rain gauge data, on measures of the pond's water height, and, in some of the RTC scenarios, on rainfall forecasts. Rainfall forecasts are indeed valuable to a wide variety of end users in the field of flood risk assessment and water management, as they allow some anticipation of the behaviour of the system under consideration. Ensemble rainfall forecasts thus provide an explicit and dynamic assessment of the uncertainty in the forecast. However, for hydrological forecasting, their low resolution currently limits their use to large watersheds. Therefore, this thesis explores rendering the Canadian Ensemble Prediction System's (EPS's) rainfall forecasts more appropriate for hydrological modeling of such a small urban catchment as the one studied here. To bridge this spatial gap, various implementations of the spatial statistical downscaling method proposed by Perica and Foufoula-Georgiou (1996b) were compared, bringing Environment Canada's (EC's) global Ensemble Rainfall Forecasts (ERFs) from a 100-km by 70-km resolution down to 6-km by 4-km, while increasing each pixel's rainfall variance and preserving its original mean. These ERFs were issued by the Canadian Global Ensemble Prediction System (GEPS) in its 2009 operational version. The statistical downscaling method of Skaugen (2002) was also applied to these ERFs, producing rainfall fields with a resolution of 10 km by 7 km. For comparison purposes, simpler methods were also implemented such as the bi-linear interpolation, which disaggregates global forecasts without modifying their variance. The downscaled meteorological products were evaluated, using different scores and diagrams, from both a meteorological and a hydrological view points. The rainfall forecasts were compared against nine days (presenting strong precipitation events) of observed values taken from Québec City's rain gauge database. Ensemble Hydrologic Forecasts (EHFs) with a time step of 3 and 24 hours were performed over a 3-month period for the original and disaggregated rainfall forecasts. This hydro-meteorological operational forecasting chain was conducted using hydrological models GR4J, a modified version of GR4J, and SWMM5. These models were implemented on four catchments ranging between 5 and 350 km2, and located in the Québec City region. The hydrological evaluation was based on the comparison of forecasted flows to the observed ones. Results obtained with the method of Skaugen (2002) were not as interesting as those based on the technique of Perica and Foufoula-Georgiou (1996b). This is due to the fact that with the method of Skaugen (2002), the final rainfall field corresponds to the average of ten downscaled fields, what tends to dampen the variance added through the disaggregation process. For the technique of Perica and Foufoula-Georgiou (1996b), the most important conclusions are: 1) the overall quality of the forecasts is preserved during the disaggregation procedure and 2) the disaggregated products using the variance-enhancing method are of similar quality than bi-linear interpolation products. However, variance and dispersion of the different members are, of course, much improved for the variance-enhanced products, compared to the bi-linear interpolation, which is a decisive advantage. These results were confirmed by the hydrological evaluation. The disaggregation technique of Perica and Foufoula-Georgiou (1996b) hence represents an interesting way of bridging the gap between the resolution of meteorological models and the high degree of spatial precision sometimes required (in the precipitation representation) by semi-distributed hydrological models and by models built on small watersheds. RTC strategies of the studied dry pond allowed for a substantial improvement of the performance compared to those with its current static control– the TSS removal efficiency increased from 46 to about 90% - while remaining safe and taking a mosquito-breeding risk constraint into account. However, the downscaled rainfall forecasts were not superior to the original ones (issued by the Canadian GEPS) in this context, as they led to the same performance for the RTC scenarios relying on rainfall forecasts.

Master of Regional and Community Planning
Department of Landscape Architecture/Regional and Community Planning
Huston Gibson
Green infrastructure is an emerging concept which utilizes vegetated systems rather than traditional gray infrastructure for stormwater management. Conducting a literature review revealed the effectiveness of incentive based planning, the benefits of green infrastructure, information on bioswales and wetlands, stormwater management, Portland, and planning implementation strategies. Portland, Oregon, was selected as the area of study because of its widespread application of green infrastructure. Seeking to understand the reasoning behind the implementation of this atypical civic infrastructure, existing policies in the city’s Comprehensive Plan and the Zoning Code were analyzed. A policy analysis was conducted through itemizing the relevant policies in the Comprehensive Plan and the Zoning Code. Additionally, six in-depth phone interviews were conducted with Portland base planning-related professionals utilizing a snowball sampling technique to qualitatively understand the policies and circumstances that enabled the implementation of the city’s bioswales and wetlands. Findings were revealed through using the grounded theory methodology of coding and memoing to analyze the responses from the interviews. According to the policy itemization and phone interviews, the Comprehensive Plan and Zoning Code were not the reasons for Portland’s green infrastructure implementation, as hypothesized. Instead, green infrastructure was evident due to a need for compliance with the U.S Environmental Protection Agency’s Clean Water Act, and a resulting Stormwater Management Manual created by the city. Additionally, other reasons for implementation included strong leaders, active citizens, and incentives and grants. The city encountered several challenges with implementation including costs, a technical lack of information, and opposition from members against using green infrastructure, which were all ultimately overcome. Lessons learned from this case study of Portland point to four policy recommendations for other cities wanting to implement green infrastructure to help alleviate pollution and flooding: the need for design having a general Comprehensive Plan and detailed Stormwater Management Manual, experimentation to generate and monitor data, collaboration, and funding.

Developments that have been taking place on Cal Poly campus over the years have altered the natural hydrology of the area. Stormwater management practices could help reduce the impacts of these developments. Computer models can help to design effective and economical stormwater management solutions at a watershed scale. As such, the objective of this study was to develop a stormwater management model for Cal Poly campus. The model was developed based on the utility data obtained from the university and other watershed data available from open sources. Field surveys were conducted to address some anomalies in the utility data, and streamflow monitoring was performed. The model was calibrated using the streamflow data measured during this study. The calibration effort significantly improved the prediction accuracy of the model. The calibrated model was then used to analyze the hydrologic performance of implementing LID systems for two projects that Cal Poly plans to build. Permeable Pavements (PPs) and Bioretention Cells (BRCs) were the LID types examined. The LIDs were evaluated based on peak flow and runoff volume reductions they would achieve. The potential reductions were compared for current conditions and the proposed project if LIDs were implemented, and for inflows to the LIDs and outflows from the LIDs. The results indicate that implementing a PP system for the proposed student apartment at the current H-1 and R-1 parking lots and a BRC system for the proposed engineering project facilities at the current H-2 parking lots will significantly reduce peak flow and runoff volume. Overall, the developed model will help the university with the traditional stormwater management practices such as flood control and to identify effective LID practices for future developments. Limitations of the current model and recommendations on how to improve the model are also discussed.

This dissertation develops a new distributed split-flow stormwater management strategy and compares its site design feasibility and construction cost to existing stormwater management methods. The purpose of the split-flow strategy is to manage stormwater by preserving predevelopment flows in terms of rate, quality, frequency, duration and volume. This strategy emulates the predevelopment hydrology: it retains and infiltrates additional runoff volume created by development by using bioretention and paired weirs as proportional flow splitters connected to small infiltration facilities distributed throughout a site. Results show that 1) the distributed split-flow stormwater management strategy can provide a higher level of environmental protection at comparable construction cost to existing detention-based methods, 2) split-flow systems are less expensive to construct than current truncated hydrograph-based bioretention and infiltration systems and 3) non-point source water pollution-reduction objectives, currently achieved with either detention with first flush or comparable bioretention and infiltration systems, could be achieved in a more cost-effective manner using distributed split-flow stormwater management strategy.
Ph. D.

Historically, the primary objective of traditional stormwater best management practices (BMPs) was to attenuate peak runoff discharges from urban areas. There has been growing demand to construct BMPs that improve stormwater runoff quality to reduce pollutant loading into downstream water bodies. A BMP located in Herndon, Virginia was retrofitted in 2009. Previously a dry detention pond, the new BMP design contains permanent wet pools as well as elements of Low Impact Development practices. A performance analysis was conducted on the retrofit to determine if the BMP was removing pollutants from stormwater runoff. Two mass-based methods were utilized for the performance analysis: the Summation of Loads Method and Effluent Probability Method. The Kaplan-Meier method and Robust Regression on ordered statistics (ROS) were used to make it possible to include censored datasets in the analysis. Analysis with the SOL method showed removal of suspended sediment, nitrogen, iron, and copper. Export of dissolved solids, phosphorus, organic carbon, and manganese was observed. The results of the Effluent Probability Method showed statistically significant reductions of sediment, iron, and copper across the entire range of monitored storm event sizes (p-value≤0.05). There was no statistical difference between the influent and effluent loads of nitrogen. Negative performance of dissolved solids, phosphorus, organic carbon, and manganese were observed for the entire range of monitored storm event sizes. The results of both methods indicated that the BMP retrofit is effectively removing sediment but failing to achieve significant nutrient reductions. This may be due to the creation of anoxic conditions from the oxygen demand of the micropool sediments and microbial degradation of vegetation within the BMP. Removal of the sediment bed and harvesting of the vegetation would likely improve the performance of the BMP.
Master of Science

Includes abstract.
Includes bibliographical references.
Sustainable urban Drainage Systems (SuDS) are increasingly being implemented around the world. A common barrier to the wider use of SuDS in South Africa is the uncertainty regarding their total cost. The need for reasonable predictions of life cycle cost is vital, both in terms of ensuring the viability of the proposed projects as well as to allow for comparison with more conventional designs that have historically relied on concrete pipes and culverts to transport the stormwater to nearby receiving water bodies as quickly and efficiently as possible.