Engineering Commons^™

Effects Of Climate Change On The Probability Of Urban Tree Failures From Wind Gusts, Samuel J. Woolsey

Electronic Thesis and Dissertation Repository

Trees grown in urban environments provide environmental, economic and psychological benefits to their surrounding communities. However, urban trees also pose significant risks since damaged trees can cause serious harm to people, housing, and infrastructure by falling on sidewalks, roads, houses or power lines. To better understand the risk posed to trees by wind, models have been developed that estimates the required wind speed needed to damage a tree or group of trees, and the likelihood that such a wind speed is met or exceeded annually. The importance of such models is rising each year as the associated risk grows as …

Spatiotemporal Changes Of Lagged Compound Dry And Wet Spells In The Northwest North America Under Climate Change, Reza Rezvani

Electronic Thesis and Dissertation Repository

Recently, an upsurge in the occurrence of hydroclimatic extremes and their temporal swings is observed in several regions around the world. Such transitions to the contrasting extremes such as the drought to flood in California (2016 – 17) has raised concerns about the increasing variability and rapid transitions between hydrological extremes and their associated compounding economic and environmental impacts. The intensification of the global hydrological cycle associated with climate change can further alter the drivers of such extremes and their interactions. Therefore, it is important to understand the characteristics of consecutive flood and drought events, including their spatiotemporal frequency and …

The Novel Application Of Electrical Resistivity Tomography For Spatiotemporal Monitoring Of Urban Stormwater Bioretention Systems, Darren Alvarenga

Electronic Thesis and Dissertation Repository

Bioretention systems are an increasingly popular low-impact development (LID) stormwater management approach that are used to reduce the water quantity and quality impacts of urban stormwater. The study investigated the feasibility and benefits of using non-invasive time-lapse electrical resistivity tomography (ERT) to understand the infiltration and soil moisture dynamics within bioretention systems. This was achieved through monitoring two field-scale operational bioretention systems in London, Ontario, Canada. High-resolution two-dimensional time-lapse ERT surveys were first completed during synthetic and natural rain events to assess the viability of time-lapse ERT to monitor soil moisture changes during events. Following this, three-dimensional ERT surveys were …

Compound Flooding Analysis Over The Canadian Coastal Regions, Farshad Jalili Pirani

Electronic Thesis and Dissertation Repository

The communities settling in the Canadian coastal regions are threatened by multiple flood-generating mechanisms including riverine, pluvial, and sea level forces. Reliable design flood estimation and risk assessment in these regions demand characterization of the interrelationships between different drivers as well as the corresponding compounding effects. In this study, as our first step, we assess the compound flood risks across Canada’s coasts considering eight bivariate flooding scenarios acquired from four flooding drivers including total water level, streamflow, precipitation and the skew surge at 41 sites located at three main regions of the Pacific, the Great Lakes (GL) and the Atlantic. …

Evaluation Of Fresh Groundwater Resources And Nitrogen Discharge To The Coastal Lagoon Of An Atoll Island, James D. Gale

Electronic Thesis and Dissertation Repository

Atoll island communities face socio-economic challenges together with environmental pressures imposed by climate change that are causing increased water quality degradation. Wastewater from domestic septic systems is released into the subsurface on Fongafale Islet, Tuvalu. It is unclear if this is contributing to high nitrogen (N) concentrations and eutrophication of the adjacent coastal lagoon. In this study, a variable-density groundwater flow and conservative contaminant transport model was developed in SEAWAT-2005 to simulate the salinity distribution and N transport through the Fongafale Islet aquifer. Model simulations evaluated the influence of tides, variable (interannual) recharge patterns, wastewater loading rates and wastewater source …

Exploring Valuable And Potentially Harmful By-Products Formed And/Or Released From Smouldering Treatment Of Sewage Sludge, Taryn Ashley Fournie

Electronic Thesis and Dissertation Repository

The presence of potentially toxic elements (PTEs) and emerging contaminants (e.g., per- and polyfluoroalkyl substances (PFAS)) makes sewage sludge management challenging. Due to their hazards, there is significant interest in thermal treatment technologies that can destroy these compounds, like incineration. However, incineration still poses several risks due to forming and/or releasing hazardous emissions (e.g., polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and PTEs). More recently, the use of smouldering has been introduced as a potential treatment technique for managing sewage sludge. Smouldering presents several advantages over traditional incineration due to its lower energy and pre-treatment requirements and potential for beneficial …

Carbon Injection To Support In-Situ Smouldering Remediation, Gillian Wilton

Electronic Thesis and Dissertation Repository

Per- and polyfluoroalkyl substances (PFAS) are a group of anthropogenic contaminants that are growing increasing concern due to their associated negative health affects. The properties of PFAS result in their persistence and stability which present challenges for remediation. Activated carbon is currently the most widely used method for PFAS treatment since carbon microparticle injection can be used for in-situ treatment; however, this method does not result in PFAS destruction. Thermal treatment is a promising post-treatment method that can be used with activated carbon as long as sufficient PFAS-destroying temperatures are achieved (> 900°C). A promising in-situ thermal treatment technology is …

Hydrogen-Rich Syngas Derived From Smouldering Biomass And Hydrocarbon Wastes, Joshua K. Brown

Electronic Thesis and Dissertation Repository

In the face of climate change, the world is looking to new fuel sources to meet the surging global energy demand. Hydrogen has been proposed as a promising energy vector being both a net-zero carbon emitter and having one of the highest gravimetric energy densities of known fuels. Production of hydrogen, however, is difficult with many of the technologies which exist today failing to be economically feasible or environmentally sustainable. Smouldering has recently been developed as a cost effective and energy efficient technology for destruction of organic wastes. The unique reaction zones created within a smouldering system have the potential …

Wastewater Aeration Process Dynamic Modelling: Combined Mechanistic And Machine Learning Approach, Yuehe Pan

Electronic Thesis and Dissertation Repository

The aeration process is the largest energy consumer in wastewater treatment plants (WWTPs), and the optimization of the process based on computational models can offer significant savings for the plant. Recent theoretical developments have revealed that many of the parameters commonly assumed as constants in aeration modelling, in fact, have a dynamic nature; however, there still lacks a universal way to model these factors in an easy, accurate and timely manner. This work proposed a machine learning-based modelling approach to offer real-time estimations of the oxygen transfer rate, airflow demand, and energy consumption.

Utilizing the field data collected from Adelaide …

Evaluation Of The Impacts Of De-Icing Salts On The Performance Of Bioretention Media In Retaining Phosphorus From Urban Stormwater, Brennan S. Donado Visbal

Electronic Thesis and Dissertation Repository

Bioretention systems are a low impact development system that can remove pollutants such as phosphorus (P) from urban stormwater. P retention in bioretention systems is complicated in cold climate regions due to factors such as inputs of road de-icing salts. This study evaluates the impact of prolonged and periodic salt inputs on P retention by conducting column experiments using three different bioretention media with and without an amendment added. Non-amended columns showed net P release, whereas amended columns showed net P retention. While some non-amended columns showed prolonged salt exposure increases P release, the largest P release for all columns …

Characterizing The Concurrent Occurrence Of Tornadoes And Flash Floods Across Canada, Yeu Deck Ngui

Electronic Thesis and Dissertation Repository

Compound weather extreme events, such as tornadoes and flash floods, can significantly impact societies and infrastructure systems. Disaster response agencies provide instructions to the exposed communities to retreat to safety specific to the natural hazard. However, the instructions can become confusing if natural hazards demand conflicting responses. This study characterizes the compound tornado and flash flood (TORFF) events to assess and predict the simultaneous occurrence probability of such hazards across Canada in the long term. We quantify dependencies between the tornadoes and flash floods using ground-based and reanalysis datasets. Tornado data are available based on the recorded Fujita rating for …

Physical Investigation Of Downburst Winds And Applicability To Full Scale Events, Federico Canepa

Electronic Thesis and Dissertation Repository

Thunderstorm winds, i.e. downbursts, are cold descending currents originating from cumulonimbus clouds which, upon the impingement on the ground, spread radially with high intensities. The downdraft phase of the storm and the subsequent radial outflow that is formed can cause major issues for aviation and immense damages to ground-mounted structures. Thunderstorm winds present characteristics completely different from the stationary Gaussian synoptic winds, which largely affect the mid-latitude areas of the globe in the form of extra-tropical cyclones. Downbursts are very localized winds in both space and time. It follows that their statistical investigation, by means of classical full scale anemometric …

Erosion Control Of Steep Open Channels Using Articulated Concrete Blocks, Mohammadomid Marandi

Electronic Thesis and Dissertation Repository

Overtopping flow can undermine the stability of hydraulic structures including embankments and spillways through the shear stress and the subsequent soil erosion. Increased flow velocity can cause scour, which can result in the failure of dams, bridges, and overall open channel hydraulic structures. Sediment transport is another crucial issue in open channels that can cause severe socioeconomic and environmental consequences. Two general approaches are commonly considered for scour prevention. The first approach involves flow modifications to minimize the corresponding effects on the structures. The second approach is associated with bed armoring and placing physical barriers on the natural bedding such …

Engineering Cooling Time And Waste Heat Recovery For Thermal Treatment Beds, Ryan B. Morales

Electronic Thesis and Dissertation Repository

Applied smouldering systems harness fixed bed smouldering combustion to remediate contaminated soils and organic wastes. In this technology, contaminants/wastes are embedded or purposefully mixed into a fixed, porous medium, waste treatment bed. Then, a smouldering front is ignited and propagated through the bed, burning away the embedded contaminants/wastes as it travels. At the conclusion of smouldering treatment, only a clean, hot porous bed remains. Ahead of a following treatment cycle, the bed is cooled via air injection and off-loaded from the system to allow for the on-loading of more contaminated material. Due to large system sizes and high temperatures, cleaned …

Spatio-Temporal Variability Of Phosphorus Near The Groundwater-Stream Interface, Meghan Vissers

Electronic Thesis and Dissertation Repository

Agricultural practices can cause excess inputs of soluble reactive phosphorus (SRP) to freshwater catchments leading to eutrophication. This study evaluates spatio-temporal variability of SRP in an agricultural streambed including the influence of groundwater-stream interactions, and examines the associated geochemical and hydrological controls. High porewater SRP (>1000 µg/L) and high SRP sediment fractions were observed in low groundwater discharge zones, specifically in the shallow (≤ 0.1 m) streambed sediments. Porewater SRP concentrations were linked to iron redox cycling with SRP concentrations concordant with more reducing conditions. Porewater SRP varied temporally but distinct seasonal changes were not observed. The conditions in …