Theses and Dissertations
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Item Open Access Characteristics of curvilinear flows over tilting weirs: laboratory, computational, and field investigations(Colorado State University. Libraries, 2025) Pugh, Joseph E., author; Venayagamoorthy, Subhas Karan, advisor; Gates, Timothy K., advisor; Rastello, Marie, committee member; Niemann, Jeffrey D., committee member; Windom, Bret C., committee memberThe phenomenon of flow over a hydraulic control structure, such as a weir, is a cornerstone of open-channel hydraulics. These structures help regulate water levels in channels and reservoirs, measure discharge, and can even be used as grade control structures to manage channel morphology. The structural configurations that form the basis of centuries of research and application are the vertical sharp-crested weir and the rectangular free overfall. Tilting weirs, which span the range between these classical limits through an adjustable inclination angle, are increasingly being used in engineered systems for stage regulation and more recently, flow measurement. However, current rating methodologies for these structures are limited in scope and overly empirical. Furthermore, a unifying physical framework for the discharge coefficient of weirs that accounts for the constituent aspects influencing discharge characteristics is currently lacking. An investigation of the underlying fluid dynamics, including boundary layer development, flow separation, non-hydrostatic pressure distributions, and local energy loss has thus far seen limited application for weir flows. Motivated by the need for more accurate and physically interpretable discharge predictions and reliable control of water surface elevations, this dissertation seeks to revisit the classical weir discharge problem under the new light of advanced experimental techniques, apply this knowledge to the general case of the tilting weir, and work to close key knowledge gaps in the application of laboratory-derived rating equations to prototype-scale structures operating in the field. This research combines laboratory experimentation, computational fluid dynamics, and field-scale observations to construct a robust and generalizable framework for understanding the hydraulics of tilting weirs. Laboratory flume experiments were conducted using high-resolution velocity measurements from particle-image velocimetry (PIV) and acoustic-Doppler velocimetry (ADV), and were complemented by Reynolds-Averaged Navier-Stokes (RANS) computational fluid dynamics (CFD) simulations to examine flow field dynamics in detail across a generous range of flow cases. These efforts informed a new discharge equation for tilting weirs that accounts for the inclination angle of the structure, and was calibrated based upon more than 400 observations of flow over physical models at two unique laboratories. Practical limitations for flow measurement, concerned with scale effects occurring at low inertial states and the transition from weir to sill flow at high inertial states, were examined and accessible measurement recommendations were set forth to enhance accuracy. PIV results in conjunction with computational simulations helped elucidate the underlying fluid dynamics influencing these discharge characteristics. Finally, the laboratory-derived equation was applied to prototype-scale weirs operating within an irrigation system in Northern Colorado and adapted to reflect field-scale variability, such as approach channel conditions and localized energy losses due to flow separation. The key contributions of this work are as follows. The theoretical framework for the classical weir discharge coefficient (Cd) is revisited and new physical insight is provided by decomposing Cd into its contributing components, which are shown to account for the combined effects of kinetic energy, contraction, and local energy loss and together inform an understanding of Cd as a type of Froude number. Furthermore, a clear delineation of the transition from weir flow to the sill flow which occurs in the limit of the rectangular free overfall, is explained. This transition in regimes of discharge characteristics is analyzed in light of practical constraints for accurate flow measurement, and to inform the rating equation of the tilting weir, which operates within the physical limits of the vertical sharp-crested weir and rectangular free overfall. A generalized rating equation for tilting weirs is established, incorporating kθ as an inclination angle correction factor to the head term. This allows for the accurate prediction of discharge across the full spectrum of inclination angles observed in practice, harmonizing with classical theory at both operational limits. Laboratory results demonstrated consistent accuracy under different experimental configurations. Flow field analysis from experimental PIV and computational simulations revealed that boundary layer separation, turbulent mixing characterized by Reynolds stresses, vertical pressure gradients, and regions of high shear caused by large mean velocity gradients are the major factors influencing the discharge characteristics. Field application of the tilting weir discharge equation framework, with the addition of the field characteristics correction factor, kF, showed strong agreement with measured flows, indicating the robustness of the laboratory-derived approach and charting a path forward for future adaptions of lab-derived discharge relationships to field settings. A discussion of the kF correction factor reveals the viability of physical model experiments of weir flows to accurately capture the governing physics observed in the field, with the need for slight calibration and modification due to site-specific characteristics. Opportunities for future research include further validation of these results with additional physical models and computational simulations, investigating tilting weir blade characteristics such as curvature and surface roughness on the discharge characteristics to enhance functionality, and leveraging the tilting weir towards ecological goals such as a mechanism for sediment transport management and fish passage. This work advances the theoretical and practical understanding of flow measurement in general and tilting weirs specifically, laying the groundwork for further innovation in water resources engineering.Item Embargo Capturing the variability of rainfall intensity and its impacts on mountain hydrology(Colorado State University. Libraries, 2025) White, Phoebe, author; Nelson, Peter A., advisor; Davenport, Frances V., committee member; Morrison, Ryan R., committee member; Schumacher, Russ S., committee memberStorms in mountainous regions can develop quickly and cause significant flooding. Understanding how brief high intensity precipitation is influenced by terrain is important for evaluating the risk of flash floods and other natural hazards. The lack of precipitation gages in mountainous remote areas inhibits detailed monitoring of these hazardous events. As wildfires become more common in areas of complex terrain, increasing the likelihood of flash floods and debris flows, it is more important than ever to understand the potential for extreme precipitation. Precipitation estimates from remotely sensed data, such as radar and satellite, have improved in recent decades. Convection-permitting models also produce accurate precipitation estimates, that have outperformed interpolated gage datasets. In this dissertation, I examine the performance of these datasets at scales relevant to hazardous events in Colorado. Additionally, I investigate how considering the variability of natural rainfall observed in the mountains of Colorado influences runoff and erosion processes. Radar estimates of precipitation can fill the gaps in areas where gages are sparse, but the signal can be blocked by mountains, depending on where the storm is relative to the radar site. Because the error of radar estimates of precipitation can change based on where the storm is located in relation to the surrounding terrain and location of the radar, the reliability of these precipitation estimates is variable, adding to the difficulty of monitoring storms in mountains. To address this uncertainty, I developed a novel method of identifying where and when the radar estimates of precipitation are reliable, based on attributes of the region, rainfall, and storm events. The model can assist in deciding when to trust radar estimates of precipitation and in determining where more gages or radar sites are necessary. The error model uses the Multi-Radar Multi-Sensor (MRMS) product which incorporates radar, quantitative precipitation forecasts, and gage data at a high spatiotemporal resolution for the United States and southern Canada. For several time series samples of MRMS 15-minute intensity, various features related to the physical characteristics influencing MRMS performance are calculated from the topography, surrounding storms, and rainfall observed at the gage location. A gradient boosting regressor is trained and was used to predict a range of error throughout the mountains of Colorado during warm months. Mapping of this dataset by aggregating normalized RMSE over time reveals that areas further from radar sites in higher elevation terrain show consistently greater error. However, the model predicts larger performance variability in these regions compared to alternative error assessments. Precipitation gages provide high temporal resolution data; however, terrain induces significant variability in precipitation across Colorado. As a result, interpolated datasets or frequency analyses based on simple linear regression of gage data may fail to capture critical extremes. Anomalous precipitation events and variation at subdaily time scales are likely omitted from gage-based datasets due to low station density. To explore this uncertainty, I use several remotely-sensed and model-derived hourly datasets and re-evaluate the influence of terrain on the magnitude of subdaily precipitation intensity throughout Colorado. Precipitation–elevation relationships differ among basins: the Missouri and Arkansas show decreasing precipitation with elevation—an effect stronger for hourly than daily totals—whereas the Colorado and Rio Grande exhibit increasing precipitation with elevation, with daily totals rising more steeply and significantly than hourly ones. Gage‑based frequency studies, limited by sparse networks, miss the frequency of high intensity clusters along the Front Range and Pikes Peak shown by model data. Gage interpolation schemes might also fail to capture how particular terrain features, rather than elevation alone, affect precipitation development. After evaluating the capability of various datasets to represent precipitation variability in Colorado's mountains, I investigate how this variability impacts sediment mobility and runoff. Non-uniform rainfall profiles can result in significantly higher runoff and erosion rates compared to constant rainfall. In this study, I use a rainfall simulator capable of generating time varying intensity profiles similar to natural rainfall observed by gages in the mountains of Colorado. I examine the effects of time-varying rainfall intensity on both mulched and bare soil on a steeply sloped flume. The effectiveness of mulch varies markedly between fluctuating rainfall intensities and a steady intensity. The wood mulch treatment failed to significantly reduce total runoff under time-varying rainfall, though it did under constant rainfall. Erosion rates were reduced with mulch for all rainfall events, despite the increasing intensity rain event causing significantly more erosion on bare soil. Accounting for the variability of rainfall directly impacts management solutions for post-wildfire recovery. Rainfall variability in mountainous regions can be highly dynamic across both space and time, affecting surface processes in small plots and at larger scales. Accurately representing these fine-scale rainfall patterns remains challenging. Remotely sensed data and model outputs can complement or substitute gage data, especially when gages are sparse, enhancing the accuracy of rainfall estimates.Item Open Access Hybrid framework for analyzing reinforced concrete skewed and curved bridges with stochastic traffic loads(Colorado State University. Libraries, 2025) Chen, Luke, author; Guo, Yanlin, advisor; Mahmoud, Hussam, committee member; Chen, Suren, committee member; Atadero, Rebecca, committee member; Brandl, Alexander, committee memberReinforced concrete (RC) bridge with skewness or curvature geometry is a common alternative design to overcome terrain obstacle or facilitate highway alignments. Irregular bridge geometric configuration results in completely different performances under earthquakes, traffic loading or long-term distress (e.g., corrosion, fatigue) compared to straight bridges. A better understanding of performances of irregular bridges is crucial for their design and maintenance. In current practice, there is lack of systematic understanding of influence of bridge skew angle and curvature on the structural performance. Also, the existing analysis methods adopt oversimplified structural modeling techniques that prevent proper consideration of traffic loads distribution on irregular bridges. In light of these limitations in the existing studies, the objective of this dissertation is to advance the performance analysis methods of RC skewed and curved bridges under more realistic loading conditions. This dissertation proposes a hybrid framework that integrates detailed finite element (FE) modeling with stochastic traffic simulations to realistically assess the performance of RC skewed and curved bridges. The framework begins with seismic fragility analyses of bridge models under varied geometric configurations, identifying how skewness and curvature amplify vulnerability. A parametric study is conducted to investigate how different earthquake and traffic conditions affect the seismic performance of skewed and curved bridges. Then stochastic traffic loads are incorporated to study vehicle-bridge interactions under seismic events. Structural responses derived from these simulations are further utilized to conduct fatigue life assessments, accounting for both traffic-induced stresses and long-term deterioration like rebar corrosion. The proposed approach provides deeper insights into the combined effects of traffic, seismic loading, and fatigue on skewed and curved RC bridges, offering a more reliable basis for design, maintenance and retrofitting for these bridges.Item Open Access Application of time-lapse tTEM for groundwater monitoring and recharge in the San Luis Valley, Colorado, USA(Colorado State University. Libraries, 2025) Robinson, Julianne, author; Smith, Ryan G., advisor; Ronayne, Michael, committee member; Alves Meira Neto, Antonio, committee memberThe ability to measure groundwater availability, extraction, and recharge is becoming increasingly important as the climate changes and reliance on groundwater in water-stressed regions increases. Geophysical measurement methods like time-domain electromagnetic (TEM) surveys can address the need for cost-effective, high-resolution hydrostratigraphic data collection with greater spatial and temporal coverage than direct-sampling methods. Among other applications, these data can be used to map hydrostratigraphy and improve targeting of managed aquifer recharge. The application of TEM surveys for time-lapse studies could enable an expansion of the spatial and temporal scales of geophysical measurements, enhancing the capabilities in hydrologic applications such as delineating the infiltration front from groundwater recharge. Few studies have used mobile TEM surveys for time-lapse measurements. This study used geophysical datasets collected with towed time-domain electromagnetic (tTEM) surveys to track changes in subsurface resistivity at managed groundwater recharge sites in the San Luis Valley in south-central Colorado. Study sites were surveyed with tTEM approximately every six weeks over the course of the irrigation season to provide time-lapse datasets. Geostatistical tools were utilized to account for differences in measurement locations from survey to survey. Results show changes in subsurface resistivity consistent with recharge flows and observed soil water content throughout the irrigation season. Infiltration of recharge water at the study site followed lateral downward paths and was controlled primarily by the volume of recharge water applied. Minor variations were observed in lithology at depth, but the site had few geologic barriers to infiltration, making it a suitable location for managed recharge. This study demonstrates the capability of tTEM surveys to efficiently assess groundwater recharge over time through analysis of time-lapse measurements. This information can serve as an important addition to other forms of data to inform water management strategies, including managed aquifer recharge, in the San Luis Valley and other arid and semi-arid regions dependent on groundwater.Item Open Access Estimating fifty-two years of groundwater levels in different aquifer layers in the southern San Joaquin Valley, California(Colorado State University. Libraries, 2025) Pant, Susmita, author; Smith, Ryan, advisor; Bailey, Ryan, committee member; Frankell, Douglas P., committee memberOver the past century, California's San Joaquin Valley has faced dramatic groundwater level depletion. Significant spatial and temporal gaps in the records, unreliable measurements, and unknown depths to which most wells are drilled, hinder effective groundwater monitoring in the region. This study presents a novel method, which integrates a time series technique called Small Baseline subset (SBAS) with kriging to estimate yearly changes in groundwater levels, as well as total absolute head from 1971 to 2023 in the Southern San Joaquin Valley across two distinct aquifer layers – one shallow (mostly unconfined) aquifer and one deep (confined) aquifer. Firstly, 1,197 wells with known depths based on the depth of an extensive confining layer, the Corcoran Clay, were classified. Further, 348 wells with unknown depths, which were within the clay boundary, were categorized by examining the correlations and differences in the average yearly fluctuations of groundwater levels with the 1197 wells. Out of these 348 wells, 215 wells belonged to confined and 133 were assigned to mostly unconfined aquifers. 3,039 wells were outside the Corcoran Clay Layer, which were classified as mostly unconfined because they exhibited a similar distribution of seasonal groundwater fluctuations to the mostly unconfined group. For each of the aquifers, we used ordinary kriging to estimate groundwater level change over specific intervals (every 1, 2, 3, 4, 5, 6, 7, and 8 years for all wells with available data) across the study area. Using a system of linear equations, we then solved for the yearly change in groundwater level from 1971 to 2023. The mean reduction in groundwater level from 1971 to 2023 was observed to be 16 m for mostly unconfined aquifers and 23 m for confined aquifers. The groundwater levels declined sharply for both aquifers during drought periods because of the increased reliance on groundwater for irrigation. In addition, we used our predicted groundwater level data to estimate that a total of 21 km3 (0.8 to 2% of the total freshwater groundwater storage in the Central Valley) water was lost from the study area between 2015-2023, with most of the storage loss (76%) coming from mostly unconfined aquifers, followed by compaction of aquifer matrix (24%).Item Open Access Targeting salinity solutions: a national geospatial framework with regional salinity characterization for agricultural desalination planning(Colorado State University. Libraries, 2025) Laffite, Kenneth, author; Bailey, Ryan, advisor; Smith, Ryan, committee member; Andales, Allan, committee memberWater scarcity and rising salinity in agricultural areas present a major threat to the long-term sustainability of irrigation and the quality of water in river systems across the United States. This study aimed to identify suitable locations for implementing desalination technologies to enhance the availability of irrigation water and improve water quality in river systems throughout the contiguous United States, while addressing the insufficient characterization of salinity in these systems. GIS tools, machine learning, a river mass balance approach, and a hydrological model were utilized to generate spatial suitability models and subsequently to characterize salinity in a specific region in greater detail, both temporally and spatially. For the national assessment, national datasets on watershed boundaries, surface water salinity, groundwater salinity, irrigated lands, cropland cover, solar photovoltaic potential, and wind capacity factor were utilized to characterize watersheds and evaluate their suitability for implementing agricultural desalination powered by renewable energy sources, based on thresholds established in the literature. Several hotspot regions deemed suitable for agricultural desalination were identified, primarily in the western regions of the United States, including parts of the Rocky Mountain states (Colorado, Idaho, Montana, Utah, and Wyoming), most of Texas and Oklahoma in the Southwest, and throughout the Plains region in Kansas, Nebraska, Minnesota, North Dakota, and South Dakota. Additionally, sections of California and Florida, along with the lower Mississippi states. This emphasizes the extensive issues of freshwater salinization across the country and the potential of agricultural desalination as a source of freshwater. For one of the suitable regions (Colorado's Lower Arkansas River Valley), a detailed salt mass balance was applied along the river between Pueblo Reservoir in Colorado and Coolidge in Kansas (total distance =317.5 km) to quantify daily groundwater salt ion loadings for the 2000-2020 period, and determine the relative influence of upstream flow, canal diversions, tributary inflow, and groundwater discharge on salt mass within the Arkansas River. Random Forest modeling was used to estimate daily salt ion loads at gaging sites. A SWAT-MODFLOW model was then used to determine the influence of on-farm desalination on groundwater salt loadings to the Arkansas River. Two scenarios were selected: the first with no desalination applied, and the second with half desalination, meaning 50% of the salt ions in the irrigation water are removed. Although agricultural desalination showed no significant impact on the salinity of the river system, this research provides a framework for applying agricultural desalination and establishes a decision-support foundation for managing agricultural water salinity challenges.Item Open Access Linking floodplain processes to hydrologic modeling with SWAT+ gwflow in the Lower Arkansas River basin(Colorado State University. Libraries, 2025) Molloy, James, author; Bailey, Ryan, advisor; Morrison, Ryan, committee member; Ronayne, Michael, committee memberFloodplain landscapes play a significant role in hydrologic fluxes, including connectivity to the alluvial aquifer and the biogeochemical processing of solutes from irrigation return flows. Variable spatial extents and limited temporal occurrence of active floodplains make quantifying their hydrologic and biogeochemical impacts problematic. To investigate, a surface-subsurface modeling practice was implemented to simulate hydrologic processes at the watershed scale in the heavily managed Lower Arkansas River Valley (LARV) (Colorado, USA). The SWAT+ model accounts for spatial variability of landscape features while simulating the fundamental physical principles that govern hydrologic processes within a watershed, such as runoff, infiltration, soil water routing, crop uptake, soil lateral flow, groundwater storage and flow, and streamflow. Using the gwflow module of SWAT+ simulates groundwater head, storage, and fluxes in response to hydrology and irrigation at the surface, replacing the original groundwater module. The primary objective of this thesis is to improve the implementation of floodplain landscapes in a modified version of SWAT+ with gwflow; and to assess the role of floodplains in aquifer recharge in the LARV. The model is run for the 1992-2020 period, with fifteen parameters calibrated for streamflow. Most years, flooding is insignificant in the managed LARV, and few floodplain-linked cells become active along the Arkansas River corridor. Flood scenarios for 100-year and 500-year events were run to observe the effects of including floodplain-exchange in SWAT+ gwflow models. Water balances reveal that the hydrologic process with the largest daily groundwater flux may occur through active floodplains, with implications on the annual change in storage for an aquifer system. Groundwater contributes 13% to streamflows through the standard simulation period. During the month of a 500-year flood scenario, groundwater produced 8% of surface flows, up from 3% without integrating floodplains. Activating floodplains in the 500-year flood scenario provided an additional flux, increasing groundwater storage by 3.5 % that year. Results are largely dependent on how floodplain landscapes are delineated; findings show that incorporating floodplains and floodplain-channel interaction into models likely brings the simulation into a stronger accordance with the real stream-aquifer system, as seasonal groundwater head and fluxes (groundwater saturation excess flow, groundwater evapotranspiration, groundwater return flows) are influenced by river water seeping to the aquifer during periods of flooding. Doing so allows the LARV model, and other models that use the floodplain option, to be used for quantifying the effects of flooding events on hydrological processes, nutrient processes, and management of wetlands and cropping systems within the floodplain of a river valley.Item Open Access Loss of beaver dams decreases floodplain connectivity in Colorado headwater streams(Colorado State University. Libraries, 2025) Schultz, Kayla, author; Morrison, Ryan, advisor; Rathburn, Sara, committee member; Nelson, Peter, committee memberAs ecosystem engineers, beavers (Castor canadensis) modify river corridor form through dam building on lower order, low-gradient streams. The numerous geomorphic, ecological, and hydrological impacts of beaver dams are well documented, primarily through observations of active beaver systems. When beavers are removed from a system, their unmaintained dams wash out, altering the stream's hydrologic regime. The assumption that beaver dams increase floodplain connectivity is frequently presumed but has not been directly quantified. Moreover, many contemporary river restoration techniques aim to restore natural functions historically provided by beavers without fully understanding the hydrological benefits of past beaver activity. To address this knowledge gap, I quantified the change in floodplain connectivity caused by the loss of beaver dams at three headwater tributary sites in the Kawuneeche Valley, Rocky Mountain National Park, Colorado, USA. I developed two-dimensional steady-state hydraulic models to compare metrics of floodplain connectivity under historical (beaver-active) and present (no beaver activity) scenarios. The historical scenarios featured modeled beaver dams matching conditions in the year 1990 when beavers were present in the landscape. I simulated three low-to-moderate recurrence interval flood discharges to assess floodplain connectivity metrics, including the volume of water on the floodplain, the fraction of flow moving through the floodplain, the volumetric flux into the floodplain, and mean site and floodplain residence times. I found that the loss of beaver dams decreases floodplain connectivity across all connectivity metrics (up to a 96.5% loss in connectivity) except mean floodplain residence time, which increased in the absence of dams. Channel velocities also increased following the loss of beaver dams. Results from the sensitivity analysis show that the flow state and condition of the beaver dam, modeled here by the parameters porosity and drag coefficient, can have reach-scale impacts on floodplain connectivity. Notably, while I observed floodplain disconnection at each site, the magnitude of change varied depending on both site-specific characteristics (local topography, human impacts, etc.) and on the flood magnitude. I conclude that, in headwater streams, beaver dams play an important and quantifiable role in facilitating floodplain connectivity, and floodplain disconnection from the loss of dams has major implications for other ecological and geomorphic floodplain processes. Understanding the degree and variability to which beaver dams historically promoted floodplain connectivity is especially timely considering the increasing interest in beaver-related restoration.Item Open Access Drivers of stream channel erosion and deposition in post-fire watersheds(Colorado State University. Libraries, 2025) Thornton-Dunwoody, Alexander, author; Nelson, Peter, advisor; Kampf, Stephanie, committee member; Davenport, Frances, committee memberWildfires alter watershed hydrology and sediment dynamics, yet the relative importance of topographic, climatic, and vegetation controls on channel erosion remains poorly quantified. This study investigates the primary physical controls influencing channel erosion and following the Cameron Peak Fire (CPF) and East Troublesome Fire (ETF) in northern Colorado. Geomorphic change was quantified using digital elevation models of difference (DoDs) derived from structure-from-motion and LiDAR data, covering both cumulative (2023 – 2021/2020) and delayed (2023 – 2022) post-fire periods. Spatial stream network (SSN) models were applied to assess the influence of topographic, climatic, vegetation, and soil variables across hillslope, channel, and watershed scales. Results show that watershed and channel slopes were the strongest and most consistent predictors of both erosion and deposition. In contrast, stream power and drainage area exhibited site-specific and time-dependent effects. In CPF watersheds, high-intensity, short-duration storms increased sediment flux, whereas precipitation played a negligible role in ETF. Vegetation and soil variables—NDVI, clay content, and burn severity—were weak or inconsistent predictors across models. These results underscore the primacy of topographic controls, particularly slope, over other commonly cited drivers, and suggest that post-fire erosion risk is more strongly associated with terrain steepness than with burn severity.Item Open Access The allocation of interstate ground water: evaluation of the Republican River Compact as a case study(Colorado State University. Libraries, 2004) Knox, Kenneth W., authorManagement of water resources is a demanding and complex challenge. The complexity is magnified when the source of water supply transcends local jurisdictions and extends across state boundaries to include multiple political interests, management authorities, and legal parameters. Interstate river compacts are used in the United States as an effective legal and administrative instrument to equitably distribute water within a multi-state river system. Of the forty-five interstate river compacts in the United States that focus upon the distribution of water supplies, only six include ground water within the distribution system -- even though ground water is an important and often the dominant source of water supply that is used within an interstate river basin.Item Open Access Design of baffled hydraulic jump stilling basins for dams(Colorado State University. Libraries, 2025) Moses, Dana Wesley, author; Thornton, Christopher, advisor; Crookston, Brian, committee member; Ettema, Robert, committee member; Julien, Pierre, committee member; Rathburn, Sara, committee memberThe hydraulic jump has been studied and used as a primary means of energy dissipation for hydraulic structures for well over a century. By the 1920s and 1930s, baffled hydraulic jump stilling basins were in widespread use as energy dissipators for large dams. These hydraulic jump stilling basins often consisted of toe blocks, a negative step and/or toe curve; one or more rows of baffle blocks; and a solid or dentated end sill. By the 1950's standard design guidance was developed by multiple agencies and universities. A comparison of the standard baffled hydraulic jump guidance illustrates a drastic difference in recommended stilling basin geometry with identical incoming flow conditions. For example, given the same incoming flow conditions, the height of baffle block determined for a U.S. Bureau of Reclamation standard design can be more than twice the block size for a standard outlet works stilling basin determined from US Army Corps of Engineers guidance. The use and/or geometry associated with chute blocks, number of rows of baffle blocks, length of basin, distance to baffle blocks, and end sill geometry have similar discrepancies. The current research includes a systematic physical model evaluation, performing over 400 individual experiments of the most often utilized baffled stilling basin design configurations. These experiments include 15 stilling basin configurations, each being evaluated for six discharge conditions and six tailwater scenarios. In addition, the USACE standard stilling basin configuration was evaluated for the general scour tendencies for discharges below and above the design discharge by means of mobile bed physical modeling. A numbered list of significant findings associated with the current research are provided below. Detailed descriptions of these significant findings and other conclusions and recommendations associated with the research objectives are provided subsequently. 1. The USACE (1992) stilling basin configuration is recommended for incoming Froude Numbers less than 4.5. 2. The Modified Type III stilling basin configuration is recommended for incoming Froude Numbers in the range of 4.5 to 8. 3. The stilling basin length and minimum required tailwater for the USACE (1992) and USBR (1984) can be expressed by unified equations. 4. A toe curve is not recommended for the hydraulic jump basin due to increase in length required and the decrease in jump stability. 5. Intermittent ramps associated with the tapered baffle block configuration are not recommended due to increase in downstream scour potential, decreased tailwater resilience, cost, general lack of observed cavitation damage, and unproven effectiveness in reducing cavitation damage. 6. Macro-scale turbulent structures exiting the stilling basin are the primary phenomenon controlling downstream scour potential. A maximum downstream attack angle of 15-degrees from horizontal was determined for the USACE (1992) stilling basin configuration for incoming Froude Numbers in the range of 3 to 5.Item Open Access Novel applications of data-driven approaches for understanding the impacts of household energy interventions(Colorado State University. Libraries, 2025) Brehmer, Collin, author; Carter, Ellison, advisor; Davenport, Frances, committee member; Keller, Kayleigh, committee member; Sharvelle, Sybil, committee memberAir pollution from household solid fuel combustion is associated with premature death, disease, and radiative climate forcing. Beginning in 2015, the Chinese government implemented the Clean Heating Policy in Northern China (CHP) with the goal to transition 70% of homes in the Beijing region from coal-based space heating to natural gas or electric-powered space heating. Studies of the impact of the CHP on air pollution and the potential mechanisms of action are limited. The continued use of a secondary solid fuel or heating device after the primary solid fuel heating stove is replaced with a cleaner alternative could weaken the impacts of the effort to replace the primary solid fuel stove. In Chapter 1, we identified heating events from biomass kang stoves as a proxy for stove use using a combination of manually labeled data and XGBoost modeling. We showed that biomass kang stove usage did not change because of the CHP and agreed with self-reported measures of heating duration. Our results demonstrated the capability of XGBoost to identify stove use events when trained on manually labeled event data and provided evidence that self-reported measures of stove use may be sufficient for understanding how secondary stove use changes as a result of a household energy intervention. Fine particulate matter air pollution (PM2.5) is of particular interest when evaluating household energy transitions since it is a product of incomplete combustion and is related to several health outcomes. We evaluated the impacts of the CHP on seasonal indoor, seasonal outdoor, and 24-hr personal PM2.5 exposure in 50 villages, 300 homes, and 500 participants during three years over a four-year period. The CHP had high uptake, with a significant decrease in coal usage in treated groups. We also observed a significant reduction in seasonal average indoor PM2.5 (22.2 [4.2, 40.3] µg/m3). Seasonal outdoor and 24-hr personal PM2.5 exposure did decrease over time but the decrease could not be attributed to the CHP due to similar decreases in treated and untreated groups. Our study suggests that the CHP yielded promising results in reducing indoor PM2.5 and provided valuable insights for household energy transitions worldwide. Given that most household energy interventions target one source of air pollution, using a mixture of sources as an outcome, like PM2.5, when only one of the sources of air pollution is targeted by the policy can make it hard to disentangle the effects of the policy if the variability in the non-targeted sources is high. Chapter 3 identified sources and their contributions to outdoor and personal PM2.5 exposure using chemical analysis and source apportionment. We used the concentration of the coal-containing source in outdoor and personal exposure measurements as the outcome in policy analysis models and compared the findings to the models where total PM2.5 was the outcome. We found a significant reduction in personal exposure to the coal containing source (-7.75 [-13.4, -2.14] µg m-3), which contrasts with our findings that the CHP had no impact on personal exposure to total PM2.5. This work demonstrates how additional granularity in the air pollution outcome can serve as a better outcome than a mixture of sources.Item Open Access Development of data integration strategies to improve interdisciplinarity in hazards research(Colorado State University. Libraries, 2025) Johnston, Blythe, author; van de Lindt, John W., advisor; Guo, Yanlin, committee member; Mahmoud, Hussam, committee member; Shields, Martin, committee memberNatural hazards are inherently interdisciplinary problems that pose risk to human life, property and prosperity. To provide holistic and actionable solutions in the face of these hazards, a more integrated approach to hazards research is needed. The current state of the hazards and disaster research continues to work more in disciplinary silos with progress being made around the world. This progress is ongoing, and this dissertation contributes to the investigation of these cross- and trans-disciplinary spaces in the context of natural hazards research and how they can be further fused and progressed, with a specific focus on data integration and modeling techniques that inform the complex problem of outmigration characterization following a hazard event. For contextualization, this dissertation first presents prior attempts at data integration. With the commonly echoed best practice of data integration from the earliest stages of data creation, a set of tools are developed for more interdisciplinary data collection in geographically large field studies. These tools are then implemented for the creation of a multi-community dataset tracking damage and recovery following the December 2021 Midwest Tornado Outbreak. This data can be utilized in the training and parameterization of long-term post-event models such as outmigration prediction. Modeling techniques for using the knowledge and data acquired in this field study are explored to arrive at actionable and predictive data for enhanced interdisciplinary hazards research. These modeling techniques include the combination of top-down and bottom-up approaches, linear multi-regression modeling, agent-based modeling, and hindcasting. Some or all these techniques are used to first develop a sheltering model to determine the viability of community tornado shelters during an event similar to that seen in the field study, and establish the knowledge needed to undertake the more complex outmigration model. The datasets and modeling techniques created and acquired are then leveraged to develop a top-down and bottom-up outmigration model after a hazard event that predicts rate of gross outmigration, gross inmigration, net migration, and demographic change following a hazard event. With this set of tools and resources, this dissertation aims to tangibly propel the task of interdisciplinarity in disaster and natural hazards research with the set of tools and resources provided here culminating in the development of a model for predicting long-term population flow following an event.Item Embargo Examining social equity in transportation asset management: current status and integration approaches(Colorado State University. Libraries, 2025) Khalife, Fawzi Ghazi, author; Atadero, Rebecca, advisor; Ozbek, Mehmet, advisor; Grigg, Neil, committee member; Arneson, Erin, committee member; Malin, Stephanie, committee memberTransportation is a critical component of the built environment, vital for ensuring access to essential services and opportunities. In the U.S., transportation systems have expanded significantly since the rise of the automobile and the development of the Interstate Highway System. While these advancements have enhanced connectivity and accessibility, they have also had detrimental effects on many communities. Research shows that low-income and racially minoritized groups are disproportionately impacted by displacement, pollution, and substandard transportation infrastructure. This disparity has raised concerns about social equity among transportation professionals, which commonly refers to the fair distribution of benefits and burdens associated with transportation systems. Transportation asset management (TAM) is one subsector of transportation where social equity remains overlooked. TAM is centered on the operation and maintenance of transportation systems, traditionally prioritizing economic factors while giving minimal attention to social and equity factors in decision-making. To address this issue, this dissertation explores the integration of social equity – referred to as equity in this study – within TAM, identifies strategies for effectively incorporating equity into TAM practices, and analyzes the challenges faced in this process. This research is organized into three studies designed to highlight equity-related issues in TAM and promote the integration of equity into TAM practices. The first study (Chapter 2) investigated the incorporation of equity within TAM by analyzing the 2019 TAM plans from all U.S. states. The findings revealed that equity remains neglected in these plans, with many in the sector failing to integrate equitable practices. This underscored the need for further research on equity in the context of TAM. Additionally, the study reviewed existing guides and sustainability rating systems that can assist in managing assets to promote equity. These resources provide definitions and indicators of equity that TAM professionals can utilize as a foundation, allowing them to adapt and expand upon these frameworks to address the specific needs of their communities and achieve equitable outcomes. The second study (Chapter 3) involved conducting interviews with professionals engaged in integrating equity into transportation to gain deeper insights into the challenges they encounter. Recognizing that transportation sectors outside of asset management have made greater progress in integrating equity into practice, this study included a diverse sample of 29 professionals from local governments, community-based organizations, and departments of transportation. This approach reflects the varied backgrounds and expertise of those engaged in equity work within the transportation sector. Utilizing semi-structured interviews and thematic analysis, the author categorized equity-related challenges into four themes: definitions, metrics and data, community engagement, and organizational challenges. This research enhances the understanding of these challenges and explores strategies for effectively addressing them, facilitating the successful integration of equity across various transportation sectors, including TAM. The third study (Chapter 4) surveyed TAM engineers and professionals to understand whether and how equity is currently incorporated in their practices and decision-making processes. The respondents provided information about their work in TAM and equity, sharing their expert opinion on equity-related issues. The findings indicated that while equity remains neglected within TAM, there are existing efforts and initiatives that could be enhanced to promote equity. Respondents noted that there is not a singular approach to advancing equity in TAM and that several challenges hinder the process, particularly in measuring equity, securing funding for equity programs, and defining equity in the context of TAM. This understanding of equity in TAM can empower TAM professionals to better understand and advance equity in their work. This dissertation offers a deep understanding of equity in the context of transportation and TAM. It concludes by offering insights and resources that enable engineers and professionals in TAM to define and measure equity in their work, implement actionable strategies, and develop plans to advance equity while managing associated challenges. The findings aim to assist TAM professionals in refining their practices to better address community needs and deliver equitable outcomes, ultimately advancing social justice through transportation infrastructure and assets.Item Open Access Evaluating personal PM2.5 and black carbon exposure variability in Beijing's rural communities(Colorado State University. Libraries, 2025) Hirst, Kennedy, author; Carter, Ellison, advisor; L'Orange, Christian, committee member; Bareither, Christopher, committee memberExposure to air pollution is a major public health concern, with PM2.5 and black carbon (BC) linked to adverse health outcomes. To reduce emissions of PM2.5 and BC, the Chinese government implemented the Coal-to-Clean Energy Policy (CCEP) in 2016, reducing indoor PM2.5 concentrations. However, its effect on personal exposure remains unclear. This study evaluated the role of time-activity patterns in personal exposure to PM2.5 and BC in the context of the policy. Data from the Beijing Household Energy Transition study (winters of 2018-2022) included 252 participants with concurrent indoor and personal PM2.5 measurements and GPS- based time-activity data. Geofencing classified participant locations, and generalized linear models assessed exposure determinants. Model performance was evaluated using indoor PM2.5 data with and without time-activity adjustments. Personal PM2.5 exposure averaged 52.9 μg/m3, while BC averaged 1.6 μg/m3. The best PM2.5 model used indoor PM2.5 over the full sampling period (AIC: 489.06, adjusted R2: 0.59). The top BC model used indoor PM2.5 averaged only while participants were home (AIC: 407.59, adjusted R2: 0.25). On average, participants spent 20.0 hours at home per day (95% CI: 19.4, 20.7). Despite these time-activity trends, the lack of reductions in personal exposure were not explained by time-activity patterns, indicating that other influential factors may be impacting exposure, or the available data was insufficient to fully capture exposure variability. Enhanced time-activity monitoring is necessary to improve exposure assessments and better inform air quality interventions.Item Open Access Evaluating sources of volatile organic compounds in Colorado workplaces via positive matrix factorization(Colorado State University. Libraries, 2025) Lippmann, Jadelyn, author; Carter, Ellison, advisor; Burt, Melissa, committee member; Atadero, Rebecca, committee memberRecognition of the health risks associated with exposure to volatile organic compounds (VOCs), particularly in indoor environments, has increased the need for a stronger understanding and management of air quality. Exposure to VOCs, emitted from various sources like building materials, office equipment, and consumer products, have been linked to both acute and chronic health outcomes, including respiratory issues and carcinogenic effects. While research on residential indoor air quality is extensive, fewer studies have characterized VOC exposure, particularly in workplaces, where people may spend a significant portion of their time. The work presented in this thesis addresses this knowledge gap through analysis of a comprehensive empirical study of VOC concentrations in 50 diverse workplaces across the State of Colorado. The study presented herein, which is part of a broader initiative led by Colorado State University in partnership with the Colorado Department of Public Health and Environment (CDPHE), utilized weeklong air sampling with SUMMA canisters and analyzed 61 target VOCs via EPA Method TO-15. Positive Matrix Factorization (PMF) modeling was employed to identify and apportion the sources of VOCs, providing insights into the relative contributions of indoor and outdoor pollutants. The findings inform further understanding of patterns of indoor VOCs measured in workplaces, as well as the design and implementation of targeted interventions to improve indoor air quality in occupational settings, particularly in underserved communities. Ultimately, this work contributes to advancing exposure science and supports healthier, and more sustainable indoor environments where people work.Item Embargo GeoStable Tailings laboratory mixture trial(Colorado State University. Libraries, 2025) Jagerhorn, Emily Clarice, author; Scalia, Joseph, IV, advisor; Bareither, Chris, advisor; Sanford, William, committee memberThis study focused on GeoStable Tailings, a homogeneous mixture of tailings and waste rock. The research evaluated (i) the influence of laboratory placement methods on mixture dry density and (ii) the influence of mixture characteristics (mixture ratio and tailings solids content) on hydraulic and mechanical behavior of GeoStable Tailings. Laboratory testing was conducted to assess dry density, air permeability, penetration resistance, and slump for different GeoStable Tailings mixture ratios, tailings compositions, solids contents, and placement methods. Standard Proctor compaction, drop chute, and loose placement methods were used to represent a range of compaction energies. Placement of GeoStable Tailings with standard Proctor compaction yielded specimens that were more consistent in the engineering behavior, whereas specimens placed via the drop chute or loose placement were more variable. Results indicate that standard Proctor compaction produces more consistent engineering behavior, whereas drop chute and loose placement exhibit greater variability. Whole tailings with solids contents above 80% and mixture ratios between 1.0 and 2.0 demonstrated optimal performance in minimizing air permeability, ensuring trafficability, and maintaining structural integrity. Underflow tailings exhibited a broader range of viable mixture ratios and solids contents, with enhanced stability and reduced deformation potential. Findings from this research contribute to the development of practical design guidelines for field applications of GeoStable Tailings, supporting the integration of tailings and waste rock as a sustainable alternative to traditional tailings management.Item Open Access Numerical model of sediment transport in sediment bypass tunnels: influence of transverse slope in tunnel bend(Colorado State University. Libraries, 2025) Brown, Jesse, author; Thornton, Christopher I., advisor; Ettema, Robert, advisor; Dumitache, Ciprian, committee memberSediment Bypass Tunnels (SBTs) convey sediment around reservoirs, increasing reservoir lifespan by greatly reducing reservoir sedimentation and, thereby, mitigating consequent loss of reservoir water-storage capacity. To keep SBTs small and economical in cross-section, SBTs convey super-critical flows. Consequently, SBTs convey super-critical flows with large sediment loads, typically containing high concentrations of coarse particles of sediment that can cause abrasion of SBT liners. Especially vulnerable are SBT reaches where secondary currents develop, notably SBT bends. The sediment abrasion that occurs along the invert of a bend requires expensive, frequent replacement of the invert's concrete liner. Consequently, the abrasion rate of inverts and, therefore, bend flow fields are of interest to SBT designers. SBT design variables such as sediment-size distribution, invert-liner type (usually concrete), flow cross-section dimensions, tunnel slope and bend radius can affect sediment abrasion in an SBT, doing so by influencing flow field, secondary currents, and patterns of sediment abrasion. This study focuses on sediment abrasion of SBTs:1. The flow field generating secondary currents associated with free-surface flows along SBT bends; and 2. Banking of an SBT invert to reduce sediment abrasion. The concept of invert-banking was proposed in personal communications with Dr. Ismail Albayrak of the Federal Institute of Technology (ETH), Zurich, Switzerland. The concept was floated during a SBT site inspection in April 2024. The problem of sediment abrasion is a problem for hydraulic structures in mountainous regions such as Switzerland and parts of the United States (e.g., Muller-Hagermann et al. 2020; Melesse et al. 2023). The present study uses the Computational Fluid Dynamics (CFD) code OpenFOAM to create a numerical model of an existing SBT for which hydraulic-model and field data and observations exist. The numerical model was used with the solver interFoam, and the renormalization group (RNG) k-ε turbulence flow assumption, the volume of fluid (VOF) method, and a Discrete Element Model (DEM) coupling. Of focal interest in the modeling was the pattern of secondary flow in a bend whose invert had variable transverse sloping. The prototype bend selected for this study is Switzerland's Solis SBT. The pattern of secondary flow in the bend affected the distribution of sediment across the bend's invert and, therefore, the sediment abrasion experienced by the bend. The Solis SBT, part of the sediment control system used for Solis Reservoir, was chosen for this study because of data and observations availability. Built in 2012, the invert of a bend in the Solis SBT has experienced severe abrasion owing to sediment. This study recommends a small amount of banking in the Solis SBT and other tunnels with similar hydraulic properties. Even a 1% to 2% slope appears to have a substantial effect in distributing the sediment evenly.Item Open Access Geomorphic impacts of large wood restoration in an urban Colorado stream(Colorado State University. Libraries, 2025) Schoner, Bijoux, author; Morrison, Ryan, advisor; Rathburn, Sara, committee member; Alves Meira Neto, Antônio, committee memberThe effects of urbanization on river systems lead to degradation and simplification, reducing beneficial ecosystem functions. Prior to urbanization, many rivers in the Mountain West were geomorphologically complex, hydrologically interconnected, interspersed with large wood, and connected to their floodplains, providing numerous ecosystem services that led to functional resilience. Process-based restoration techniques are being implemented to reintroduce and support these lost functions in both rural and urban areas as an alternative to form-based restoration. Minimal research around process-based techniques has been done in urban systems and understanding how this approach impacts geomorphic response in varied biomes provides practitioners a basis to evaluate future projects. The objective of this study is to analyze the effects of a large wood process-based restoration in an urban Colorado corridor (Cache la Poudre River, Fort Collins, CO) by monitoring changes in 1) site erosion and deposition, 2) geomorphic unit heterogeneity, 3) large wood volume and porosity, 4) evaluate whether monitoring geomorphic units is an adequate metric of project success, and 5) to compare restoration techniques throughout the site by analyzing sediment changes. Additionally, I review and recommend monitoring methodologies and discuss how water policy affects restoration in Colorado. The site restoration included reconnecting the floodplain, reconstructing site bathymetry, and adding large wood to both the floodplain and active channel. Following restoration construction and one runoff season, digital elevation models were analyzed to delineate geomorphic units and compare restoration approaches. iPad LiDAR was collected at six constructed large wood structures to determine volumetric and porosity changes. Sediment analysis shows net aggradation of sediment around structures, supporting the project goal of mitigating an impending head cut. Large wood analysis results varied based on structure location within the channel and with respect to other large wood structures. The accumulation and dispersion of wood throughout the site was captured by newly formed islands induced by restoration. Both the largest patch index and patch density heterogeneity metric either stayed consistent or increased after the runoff season. This restoration project demonstrates to policymakers the geomorphological, ecosystem, and social benefits while showcasing the low-risk nature of carefully designed process-based restoration using large wood. Greater utilization of large wood in urban restoration more broadly supports the ecosystem services that benefit the communities that live in and around the river.Item Open Access Ex post facto analysis of the Sedgwick Sand Draws Project: a case study of the small watershed program(Colorado State University. Libraries, 1999) Ward, Jason P., author; Ruff, James, advisor; Grigg, Neil, committee member; Wilkins-Wells, John, committee memberThe Sedgwick Sand Draws Project is a flood control project completed in 1992 to provide floodwater damage protection for agricultural and municipal lands in Sedgwick County, which lies in extreme northeastern Colorado along the South Platte River. Funding and technical support for the project was provided by the U.S. Soil Conservation Service (SCS) under the Watershed Protection and Flood Prevention Act, commonly referred to as The Small Watershed Program. Short duration, high intensity thunderstorms occur in mid to late summer in the upland portions of the Sand Draws Watershed near the Colorado- Nebraska border. Runoff from these storms is channeled into upland sand draws that drain into the developed alluvial floodplain below. Before project average annual floodwater damages were estimated at $220,050. An ex post facto method was proposed for evaluating the damage reduction benefits of a watershed flood control project. Using economic, hydrologic and engineering principles, damage-frequency curves developed in the proposal phase of a project are used to estimate actual damage reduction benefits. Estimates are made by adjusting the damage-frequency curves to reflect a current economic time base and evaluating damages produced by hydrologic events that have occurred during the period of analysis. Other performance indicators, such as site inspections, historical crop yields, changes in land use, disaster relief application rates, and interviews with local community members are also used in the evaluation. The ex post facto evaluation principles were applied to the Sand Draws project as a case study. However, lack of information in the SCS Sand Draws proposal required a technique for estimating the original damage-frequency curves. A method for estimating the curves from minimal known information was developed and used for the Sand Draws project. The period of analysis was from completion of the project in June 1992, to the latest date of available data, September 1997. Hydro logic analysis of the watershed identified seven damage producing rainfall events during this period. It was estimated that the project has produced a total of$3,556,628 in damage reduction benefits resulting in average annual benefits of $592,771. Benefit-cost analyses and a look at other performance indicators were also evaluated.