The Bear Island Strait between Crosson and Dotson Ice Shelves in the Amundsen Sea Embayment sector of West Antarctica is an important junction for seawater exchange in the region. This work establishes that two previously distinct masses of seawater beneath the ice shelves now interact due to the thinning of the ice that separated them. A pathway connecting the water masses is revealed using reflection-seismic spot soundings to measure the bathymetry and water-column thickness beneath the ice in the Bear Island Strait. The spot soundings reveal a seafloor that is deep (> 800 m below sea level) and continuous to allow circulation of a layer of deep, warm and salty sub-ice water mass into the strait. However, the geometry of the water column through the strait may only allow one-way circulation of this layer from the Crosson side to the Dotson side, with Dotson to Crosson circulation constricted to upper, cooler water. Crosson to Dotson circulation could account for the observed high melt rates (~10 m/yr) at the grounding line of a Dotson pinning point, consistent with an inverted channel previously imaged on the underside of the Dotson Ice Shelf. By extension, the pathway through the Bear Island Strait allows water exchange between two large bathymetric troughs on the continental shelf. These results indicate previously unaccounted for avenues of regional ocean circulation and heat exchange likely to the influence the future deglaciation rate of the Amundsen Sea Embayment and West Antarctica. / Geology

This thesis focuses on the simulation of astronomic tides of the Pascagoula River. The work is comprised of five steps: 1) Production of a digital elevation model describing the entire Pascagoula River system; 2) Development of an inlet-based, unstructured mesh for inbank flow to better understand the basis of the hydrodynamics within the Pascagoula riverine system. In order to assist in the mesh development, a toolbox was constructed to implement one-dimensional river cross sections into the two-dimensional model; 3) Implementation of a sensitivity analysis of the Pascagoula River two inlet system to examine the inlet effects on tidal propagation; 4) Improvement of the inlet-based model by performing a preliminary assessment of a spatially varied bottom friction; 5) Implementation of an advection analysis to reveal its influence on the flow velocity and water elevation within the domain. The hydrodynamic model employed for calculating tides is ADCIRC-2DDI (ADvanced CIRCulation Model for Shelves, Coasts and Estuaries, Two-Dimensional Depth Integrated). This finite element based model solves the shallow water equations in their full nonlinear form. Boundary conditions including water surface elevation at the off-shore boundary and tidal potential terms allow the full simulation of astronomic tides. The improved astronomic tide model showed strong agreement with the historical data at seven water level monitoring gauge stations. The main conclusions of this research are: 1) The western inlet of the Pascagoula River is more dominant than the eastern inlet; however, it is necessary to include both inlets in the model. 2) Although advection plays a significant role in velocity simulation, water elevations are insensitive to advection. 3) The astronomic model is sensitive to bottom friction (both global and spatial variations); therefore, a spatially varied bottom friction coefficient is suggested. As a result of this successful effort to produce an astronomic tide model of the Pascagoula River, a comprehensive storm surge model can be developed. With the addition of inundation areas the surge model can be expected to accurately predict storm tides generated by hurricanes along the Gulf Coast.

Bathymetric mapping is an important tool for reservoir management, typically completed before reservoir construction. Historically, bathymetric maps were produced by interpolating between points measured at a relatively large spacing throughout a reservoir, typically on the order of a few, up to 10, meters or more depending on the size of the reservoir. These measurements were made using traditional survey methods before the reservoir was filled, or using sonar surveys after filling. Post-construction issues such as sedimentation and erosion can change a reservoir, but generating updated bathymetric maps is difficult as the areas of interest are typically in the sediment deltas and other difficult-to-access areas that are often above water or exposed for part of the year. We present a method to create complete reservoir bathymetric maps, including areas above the water line, using small unmanned aerial vehicle (sUAV) photogrammetry combined with multi-beam sonar data--both established methods for producing topographic models. This thesis presents methods to create accurate above-water shoreline models using images from sUAVs, processed using a commercial software package and a method to accurately knit sonar and Structure from Motion (SfM) data sets by matching slopes. The models generated by both approaches are point clouds, which consist of points representing the ground surface in three-dimensional space. Generating models from sUAV-captured images requires ground control points (GCPs), i.e., points with a known location, to anchor model creation. We explored issues with ground control spacing, masking water regions (or omitting water regions) in the images, using no GCPs, and incorrectly tagging a GCP. To quantify the effect these issues had on model accuracy, we computed the difference between generated clouds and a reference point cloud to determine the point cloud error. We found that the time required to place GCPs was significantly more than the time required to capture images, so optimizing GCP density is important. We found that we needed to mask water and areas related to distant regions and sky in images used for model creation. This is because water, objects in the far oblique distance, and sky confuse the algorithms that match points among images. Our sonar point clouds, while self-consistent, were not accurately georeferenced. We demonstrate a method using cross-sections of the transition between the above-water clouds and sonar clouds to geo-locate the sonar data and accurately knit the two data sets. Shore line topography models and integration of sonar and drone data is a niche area that leverages current advances in data collection and processing. Our work was applied at three different reservoirs to show that accurate post-construction reservoir bathometry maps can assist with reservoir management. A report is included that compares historical bathymetric maps with the current bathymetric maps at each of the three different reservoirs. A guide to perform the drone surveys is included in the report's appendix.

No description available.

Remote sensing studies based on satellite and aerial imagery have improved our understanding of the morphology and distribution of several shallow reefs along the Red Sea Arabian coast and of the benthic assemblages associated to them (Bruckner et al., 2011; Bruckner et al., 2012; Rowlands et al., 2016). However, data concerning the deeper benthic assemblages' composition and spatial distribution in the central Red Sea are still missing. Using high-resolution acoustic technology and an underwater remotely operated vehicle (ROV), we aim to map, describe, and classify the reefs found in Thuwal's coastal area, filling the information gap by producing the first benthic habitat map of this area and making progress towards the evaluation of shallow and upper mesophotic benthic resources in the Saudi Arabian Red Sea. High-resolution acoustic data was collected using a multibeam echosounder system, which generated a bathymetric model. Based on this, the seafloor features were classified into 12 morphotypes following a visual assessment. Based on the morphotypes classification, 28 sites were visually selected for ground-truthing data acquisition and characterization of the substrate and benthic assemblages using a remotely operated vehicle equipped with an ultra-short baseline (USBL) positioning system. With the information obtained from the bathymetry data and the ROV video transects, a Top-Down approach in which we analyzed, categorized, and classified the data was used to create Thuwal's reefs benthic habitat map in which 23 different benthic habitat types were identified. This research uncovered previously poorly studied reef morphologies in the Red Sea and their associated benthic assemblages. Moreover, this work will help improve the understanding of the spatial distribution of benthic communities located on Thuwal's reefs, giving a baseline with the potential to provide fundamental information that can be used for mapping, management, conservation, and future research at other Red Sea reef sites in Saudi Arabia.

Mathematical modeling of ocean waves is based on the formulation and solution of the appropriate equations of continuity, momentum and the choice of proper initial and boundary conditions. Under the influence of gravity, many free surface water waves can be modeled by the shallow water equations (SWE) with the assumption that the horizontal length scale of the wave is much greater than the depth scale and the wave height is much less than the fluid's mean depth. Furthermore, to describe three dimensional flows in the hydrostatic and Boussinesq limits, the multilayer SWE model is used, where the fluid is discretized horizontally into a set of vertical layers, each having its own height, density, horizontal velocity and geopotential. In this study, we used an explicit staggered finite volume method to solve single and multilayer SWE, with and without density stratification and bathymetry, to understand the dynamic of surface waves and internal waves. We implemented a two-dimensional version of the incompressible DYNAMICO method and compare it with a one-dimensional SWE. For multilayer SWE, we considered both two layer and a linear stratification of density, with very small density gradient, consistent with Boussinesq approximation. We used Lagrangian vertical coordinate which doesn't allow mass to flow across vertical layers. Numerical examples are presented to verify multilayer SWE model against single layer SWE, in terms of the phase speed and the steepness criteria of wave profile. In addition, the phase speed of the barotropic and baroclinic mode of two-layer SWE also verified our multilayer SWE model. We found that, for multilayer SWE, waves move slower than single layer SWE and get steeper than normal when they flow across bathymetry. A series of numerical experiment were carried out to compare 1-D shallow water solutions to 2-D solutions with and without density as well as to explain the dynamics of surface wave and internal wave. We found that, a positive fluctuations on free surface causes water to rise above surface level, gravity pulls it back and the forces that acquired during the falling movement causes the water to penetrate beneath it's equilibrium level, influences the generation of internal waves. Internal waves travel considerably more slowly than surface waves. On the other hand, a bumpy or a slicky formation of surface waves is associated with the propagation of internal waves. The interaction between these two waves is therefore demonstrated and discussed. / Thesis / Master of Science (MSc) / In the modelling of ocean wave, the formulation and solution of appropriate equations and proper initial and boundary conditions are required. The shallow water equations (SWE) are derived from the conservation of mass and momentum equations, in the case where the horizontal length scale of the wave is much greater than the depth scale and the wave height is much less than the fluid's mean depth. In multilayer SWE, the fluid is discretized horizontally into a set of vertical layers, each having its own height, density, horizontal velocity and geopotential. In this study, we used an explicit staggered finite volume method to solve single and multilayer SWE, with and without density stratification and bathymetry, to understand the dynamic of surface waves and internal waves. A series of numerical experiments were carried out to validate our multilayer model. It is found that, in the presence of density differences, surface waves for the multilayer SWE move slowly and get more steep than normal when they flow across bathymetry. Also, a positive fluctuations on free surface generates internal waves at the interior of ocean which propagate along the line of density gradient.

The following chapters presented here use modern ecological data and modern marine systems to evaluate past marine depositional settings and the preservation potential of various environments in the geological record. While the chapters in this dissertation vary in terms of study area, sedimentary systems (carbonate vs. siliciclastic), depositional environment, and organisms, all projects are based on developing and using quantitative models to evaluate the present as a means for understanding the past. Chapter one focuses on the preservation potential of rocky intertidal environments. The rocky intertidal zone is one of the most poorly preserved fossil-rich environments in the geological record. However in most coastal marine habitats today, it is one of the most diversity rich environments. Chapter one also focuses on the analytical advantages of hierarchical sampling of gastropod communities across San Salvador Island, the Bahamas to quantify community and species level preservation potential in rocky shore environments. Chapters two and three are based on the fossil-rich sedimentary deposits from the Po coastal plain in northeastern Italy. These deposits have been widely studied in terms of their sedimentology and stratigraphy, resulting in a highly resolved sequence stratigraphic architecture. The integration of sequence stratigraphy with paleobiology can enhance our understanding of spatiotemporal biotic patterns recorded in the fossil record. Used in conjunction with the highly-resolved stratigraphic framework, biotic patterns can be used to assess depositional cycles and bathymetry through time. Chapter two integrates sequence stratigraphic patterns and paleoecological data to develop bathymetric models across fossiliferous marine successions of the Po coastal plain, Italy. Chapter three evaluates the modern ecological dataset used to derive the bathymetric models. The last chapter also explores water depth distribution for selected taxa recorded in the Quaternary sediments and observed in present-day habitats. The dissertation research explored here demonstrates that modern ecological systems are essential to evaluating past geologic events. Through direct observation and quantitative analysis, I have learned that modern and fossil communities behave differently depending on environment (e.g. energy, salinity, water depth, etc.). These variables affect the distribution of living organisms today and through my research, delineate fossil distributions through time. With these observations, new questions have arisen about the latitudinal variability of rocky intertidal fossil preservation and extrapolating the quantitative bathymetric models to deeper time intervals. These questions will lead to future endeavors and pointedly add to the field of geology and stratigraphic paleobiology. / Ph. D.

Bed topography identification in open channel and glacier flows is of paramount importance for the study of the respective flows. In the former, the knowledge of the channel bed topography is required for modelling the hydrodynamics of open channel flows, fluvial hydraulics, flood propagation, and river flow monitoring. Indeed, flow models based on the Shallow Water Approximation require prior information on the channel bed topography to accurately capture the flow features. While in the latter, usable bedrock topographic information is very important for glacier flow modellers to accurately predict the flow characteristics. Experimental techniques to infer the bed topography are usually used but are mostly time consuming, costly, and sometimes not possible due to geographical restrictions. However, the measurement of free surface elevation is relatively easy. Alternative to experimental techniques, it is therefore important to develop fast, easy-to-implement, and cost-effective numerical methods. The inverse of the classical hydrodynamic problem corresponds to the determination of hydraulic parameters from measurable quantities. The forward problem uses model parameters to determine measurable quantities. New one-shot and direct pseudo-analytical and numerical approaches for reconstructing the channel bed topography from known free surface elevation data is developed for one-dimensional shallow water flows. It is shown in this work that instead of treating this inverse problem in the traditional partial differential equation (PDE)-constrained optimization framework, the governing equations of the direct problem can be conveniently rearranged to obtain an explicit PDE for the inverse problem. This leads to a direct solution of the inverse problem which is successfully tested on a range of benchmark problems and experimental data for noisy and noiseless free surface data. It was found that this solution approach creates very little amplification of noise. A numerical technique which uses the measured free surface velocity to infer the channel bed topography is also developed. The one-dimensional shallow water equations along with an empirical relationship between the free surface and the depth averaged velocities are used for the inverse problem analysis. It is shown that after a series of algebraic manipulation and integration, the equation governing the inverse problem simplifies to a simple integral equation. The proposed method is tested on a range of analytical and experimental benchmark test cases and the results confirm that, it is possible to reconstruct the channel bed topography from a known free surface velocity distribution of one-dimensional open channel flows. Following the analysis of the case of one-dimensional shallow water flows, a numerical technique for reconstructing the channel bed topography from known free surface elevation data for steep open channel flows is developed using a modified set of equations for which the zero-inertia shallow water approximation holds. In this context, the shallow water equations are modified by neglecting inertia terms while retaining the effects of the bed slope and friction terms. The governing equations are recast into a single first-order partial differential equation which describes the inverse problem. Interestingly, the analysis shows that the inverse problem does not require the knowledge of the bed roughness. The forward problem is solved using MacCormack’s explicit numerical scheme by considering unsteady modified shallow water equations. However, the inverse problem is solved using the method of characteristics. The results of the inverse and the forward problem are successfully tested against each other. In the framework of full two-dimensional shallow water equations, an easy-to-implement and fast to solve direct numerical technique is developed to solve the inverse problem of shallow open channel flows. The main underlying idea is analogous to the idea implemented for the case of one-dimensional reconstruction. The technique described is a “one-shot technique” in the sense that the solution of the partial differential equation provides the solution to the inverse problem directly. The idea is tested on a set of artificial data obtained by first solving the forward problem. Glaciers are very important as an indicator of future climate change or to trace past climate. They respond quickly compared to the Antarctica and Greenland ice sheets which make them ideal to predict climate changes. Glacier bedrock topography is an important parameter in glacier flow modelling to accurately capture its flow dynamics. Thus, a mathematical technique to infer this parameter from measured free surface data is invaluable. Analogous to the approaches implemented for open channel flows, easy-to-implement direct numerical and analytical algorithms are developed to infer the bedrock topography from the knowledge of the free surface elevation in one space dimension. The numerical and analytical methods are both based on the Shallow Ice Approximation and require the time series of the ablation/accumulation rate distribution. Moreover, the analytical method requires the knowledge of a non-zero glacier thickness at an arbitrary location. Numerical benchmark test cases are used to verify the suitability and applicability of the algorithms.

L'objectif de la thèse est de développer une méthode de modélisation 3D des tunnels canaux en service, afin de les documenter de manière précise. Le levé des structures est effectué en dynamique depuis un bateau, avec un ensemble de caméras au-dessus de l'eau et un sonar pour la partie immergée. La construction du modèle 3D doit combiner des données acquises dans deux milieux différents, en l'absence de signal GPS pour la localisation du système de mesure. L'approche proposée exploite pleinement les capacités du calcul photogrammétrique, à la fois pour construire le modèle 3D de la voûte et pour estimer la trajectoire du bateau, laquelle permet de géoréférencer les profils de points sonar. L'application du procédé en vraie grandeur dans le tunnel de Niderviller a permis d'obtenir un premier modèle 3D. L'analyse de la méthode a mis en jeu une technologie innovante de mesure sonar statique, nécessitant le développement de traitements appropriés. Elle a permis de jauger les capacités du sonar à numériser les canaux, d'évaluer les trajectoires estimées par photogrammétrie et de comparer quantitativement le modèle obtenu à un modèle de référence préalablement construit. / The aim of this thesis is to develop a 3D modeling method for canal-tunnels in service, in order to document them accurately. The survey of the structures is carried out dynamically from a boat, with a set of cameras above the water and a sonar for the submerged part. The construction of the 3D model must combine data acquired in two different environments, in the absence of a GPS signal to locate the measurement system. The proposed approach makes full use of the capabilities of photogrammetric computation, both to build the 3D model of the vault and to estimate the trajectory of the boat, which allows georefencing of sonar point profiles. The application of the process to field test data acquired in the Niderviller tunnel allowed a first 3D model to be obtained. The analysis of the method involved an innovative static sonar measurement technology, requiring the development of appropriate treatments. It enabled to assess the capacity of the sonar for canal surveying, to evaluate the trajectories estimated using photogrammetry and to compare quantitatively the obtained model with a previously constructed reference mode

As lagoas de estabilização compõem sistemas de tratamento de águas residuárias sujeitos à variação de eficiência decorrente, dentre outros fatores, das variações climáticas. A variação de eficiência e da estratificação em lagoas de estabilização, localizadas em ambiente subtropical, em diferentes épocas do ano, foi o principal objetivo dessa pesquisa. Para essa finalidade, a eficiência de dois sistemas de lagoas de estabilização localizadas no Vale do Ribeira de Iguape (SP) - nas cidades de Jacupiranga e Pariquera-Açu - foi determinada, em período sazonal (quatro épocas do ano) e semanal (três dias consecutivos), assim como perfis de temperatura, condutividade elétrica, pH e oxigênio dissolvido e aspectos ambientais (temperatura do ar, radiação solar, direção e velocidade do vento e precipitação) foram mensurados. Além disso, aspectos operacionais, tais como, volume de lodo, de água, vazão e tempo de detenção teórico foram mensurados a fim de caracterizar apenas as lagoas facultativas. Alterações no comportamento sazonal destas variáveis e padrões de similaridade entre eficiência de cada lagoa e estratificação térmica foram analisadas através da ferramenta estatística análise do componente principal (PCA). Observou-se, principalmente, que a variação sazonal de eficiência foi relevante, sendo que, em julho/06 a qualidade do afluente e do efluente foi diferente das outras épocas do ano, ou seja, houve variação sazonal de variáveis físicas e químicas. Variação diária foi observada em janeiro/06, época de maiores precipitações e maior homogeneidade térmica. Na PCA, a estratificação térmica foi significativa, ou seja, esteve relacionada com outras variáveis. A vazão e tempo de detenção, nas lagoas facultativas, estiveram dentro de faixas observadas em outras lagoas de estabilização e o volume de lodo não ultrapassou 3% do volume das lagoas. / Stabilization ponds compose systems of wastewater treatment citizens to the variation of efficiency decurrent, amongst other factors, of the climatic variations. The variation of efficiency and stratification in stabilization ponds, located in subtropical environment, at different seasons, was the main objective. For this purpose, the efficiency of two stabilization ponds systems located in the Vale do Ribeira de Iguape (SP) - in cities as Jacupiranga and Pariquera-Açu - was determined, in sazonal period (four seasons) and weekly (three days consecutive), as well as temperature, electric condutivity, pH and dissolved oxygen profiles and environment aspects had been measured (air temperature, solar radiation, direction and speed of the wind and precipitation). Moreover, operational aspects, such as, volume of sludge, volume of water, outflow and theoretical detention times had been measured in order to characterize only the facultative ponds. Alterations in sazonal behavior of these variables and standards of similarity between efficiency and thermal stratification had been analyzed through the tool statistics análise do componente principal (PCA). It was observed, mainly, that the sazonal variation of efficiency was important, so, in July/06 the quality of the affluent and effluent was different to the other seasons, in other words, it was observed sazonal variation of physical and chemical variable. Daily variation happened in January/06, time of more precipitations and thermal homogeneity. In other analysis with PCA, the thermal stratification was significant and it was related with other variable. The outflow and detention times, in the facultative ponds, had been similar others facultatives ponds and the volume of sludge did not exceed 3% of the volume of water in the ponds.