Dissertations / Theses on the topic 'Storm morphology'

Accurate knowledge of the electron density structure of the Earth's upper atmosphere is crucial to forecasting the performance of transionospheric radio signals. For this research, we focus on storm-time structuring in the mid- to high latitude ionosphere where large gradients in electron density can cause severe degradation of communication and navigation signals. We begin in Chapter 2 with a review of the primary data sets and methods used to accomplish the collaborative, multi-instrument studies described in this dissertation. In Chapter 3, we compare observational techniques for tracking polar cap patches during a moderate geomagnetic storm interval. For the first time, we monitor the transportation of patches with high spatial and temporal resolution across the polar cap for 1--2~h using a combination of GPS TEC, all-sky airglow imagers (ASIs), and Super Dual Auroral Radar Network (SuperDARN) HF radar backscatter. Simultaneous measurements from these data sets allow for continuous tracking of patch location, horizontal extent, and velocity even under adverse observational conditions for one or more of the techniques. A focus is placed on the structuring of patches, particularly on the nightside ionosphere as they become wider in the dawn-dusk direction and develop narrow finger-like structures. In Chapter 4, we perform a superposed epoch analysis to characterize the average response of GPS TEC in the North American sector during more than 100 geomagnetic storms over a 13-year interval. For the first time a rigorous approach is used to fully separate storm-time, local time, longitudinal, and seasonal effects at midlatitudes where dense ground receiver coverage is available. The rapid onset of a positive phase is observed across much of the dayside and evening ionosphere followed by a longer-lasting negative phase across all latitudes and local times. Our results show clear seasonal variations in the storm-time TEC, such that summer events tend to be dominated by the negative storm response while winter events exhibit a stronger initial positive phase with minimal negative storm effects. A prominent magnetic declination effect is identified and examined in terms of thermospheric zonal winds pushing plasma upward/downward along magnetic field lines of opposite declination. Finally in Chapter 5 we summarize several co-authored studies which examined various storm-time phenomena utilizing GPS TEC mapping tools developed for this dissertation research, with topics including subauroral polarization stream (SAPS), storm enhanced density (SED), tongue of ionization (TOI), and polar cap patches.
Ph. D.

Gravel beaches and barriers occur on many high-latitude, wave-dominated coasts across the world. Due to their natural ability to dissipate large amounts of wave energy, gravel coasts are widely regarded as an effective and sustainable form of coastal defence. However, during extreme events waves may overtop, overwash, and even lower, the crest of the gravel beach, flooding the hinterland. In the evaluation of the safety of gravel coasts against flooding, coastal managers currently rely on models that have been shown in previous studies to be inaccurate. The research in this thesis attempts to improve the current predictive capacity of gravel beach storm response by developing a new process-based model to simulate storm impacts on gravel coasts. The numerical model developed in this thesis, called XBeach-G, is a morphodynamic, depth-averaged, cross-shore profile model, based on the XBeach model for sandy coasts (Roelvink et al., 2009). The model simulates the morphological response of gravel beaches and barriers to storms by solving: (1) intra-wave flow and surface elevation variations using a non-hydrostatic extension of the non-linear shallow water equations; (2) groundwater processes, including infiltration and exfiltration, using a Darcy-Forchheimer-type model; and (3) bed load transport of gravel using a modification of the Van Rijn (2007a) bed load transport equation to include flow acceleration effects, which are shown to be significant on coarse-grained beaches. The model is extensively validated for hydrodynamics, groundwater dynamics and morphodynamics using detailed data collected in physical model experiments, as well as data collected in the field on four natural gravel beaches in the UK and one in France. Validation results show that the model has high quantitative skill in simulating observed hydrodynamics on gravel beaches across a wide range of forcing conditions, in particular with regard to wave transformation, wave run-up and wave overtopping. Spatial and temporal variations in groundwater head are shown to be well represented in the model through comparison to data recorded in a physical model experiment. Validation of the morphodynamic component of XBeach-G shows that the model has high model skill (median BSS 0.75) in simulating storm impacts on five gravel beaches during ten storm events, with observed morphodynamic response ranging from berm-building to barrier rollover. The model is used to investigate hydrodynamic processes on gravel beaches during storms, where it is found that incident-band variance is elemental in the generation of wave run-up on gravel beaches. Furthermore, simulations of wave run-up during high-energy wave events show a distinct disparity between run-up predicted by empirical relations based on the Iribarren parameter and wave steepness, and run-up predicted by XBeach-G, where predictions by the empirical relations substantially underestimate observed wave run-up. Groundwater processes are shown, by means of sensitivity simulations, to strongly affect the morphodynamic response of gravel beaches and barriers to storms. The research in this thesis supports the hypothesis that infiltration in the swash is a key driver for the berm-building response of gravel beaches and helps to reduce erosion of the upper beach during storms. Through model simulations on a schematic gravel barrier it is shown that groundwater processes effectively increases the capacity of gravel barriers to withstand storms with 1-3 m higher surge levels than if groundwater processes did not occur. Reducing the width of a barrier leads to a lowering of this capacity, thereby reducing the resilience of the barrier to extreme storm events. Despite its strong influence on gravel beach morphodynamics, it is found that infiltration plays a relatively small role on wave run-up levels on most natural gravel beaches (median R 2% run-up level reduction of 8%). Application of the model in validation simulations and sensitivity simulations in this thesis, as well as in storm hindcast simulations discussed by McCall et al. (2013) shows the value of using the process-based XBeach-G model in coastal flooding analysis over the use of empirical tools. While no model can be considered entirely accurate, application of XBeach-G in all hindcast overwash simulations has lead to reasonable estimates of overtopping discharge and of morphological change, which is a significant improvement over the frequently substantial errors of the empirical tool designed for this purpose.

As praias urbanizadas são ambientes complexos devido à interação da ocupação antropogênica e dos processos costeiros. A ocupação costeira vem se caracterizando por alteração e deterioração da paisagem, processo mais intenso em grandes cidades litorâneas, onde casas e edifícios são construídos nas proximidades imediatas da orla. O presente trabalho analisa a morfodinâmica e processo de sobrelavagem das praias de Santos e Itararé, duas praias urbanizadas com a presença de obras na orla. Foram realizados levantamentos topográficos nas praias e modelagem de ondas (Delft 3D - Wave) para toda a baía durante os anos de 2015 e 2016. Cenários de sobrelevaçãoonda e nível do mar foram estipulando para o cálculo da sobrelevaçãototal e assim conhecer as condições que levam a sobrelavagem. A baía de Santos encontra-se aberta para sul, expondo a linha de costa para a ação de frentes frias. A variabilidade do clima de ondas, derivada das mudanças das suas condições meteorológicas formadoras, pode alterar a morfologia da praia. Em Santos e São Vicente as ondas de sul e sudeste apresentam maiores alturas de onda e são mais frequentes no outono e inverno quando temos mais frentes frias na região. Os resultados indicam relação entre a incidência de ondas com maior força de onda (W/m), associadas a frentes frias, em trechos mais inclinados das praias com perda de volume. A variedade de incidência das ondas ao longo da praia estudada mostra um decréscimo na força de onda, sendo maior em Itararé e caindo em direção a Ponta da Praia, com a presença de picos altos na Ponta da Praia. Justificando porque este trecho sofre mais variação de volume e perda de sedimento fato que pode estar associado a dragagem do canal do porto de Santos. Em ambos os trechos com maior declividade e menor faixa de areia apresentaram maior sensibilidade à ação das ondas e também maior chance de sofrer sobrelavagem, de todo o arco praial da baía de Santos a porção leste de Santos se mostrou a mais propícia a sofrer inundação.
Urbanized beaches are more complex environments due to the interaction of anthropogenic occupation and coastal processes. Coastal occupation has been characterized by alteration and deterioration of the landscape, being more intense in large coastal cities, where houses and buildings are built in the immediate vicinity of the beach border being subject to potentially high risk of erosion. The present work analyzed the morphodynamics and overwashing of the beaches of Santos and Itararé, two urbanized beaches with the presence of anthropogenic constructions in the beach border. Topographic surveys on both beaches and wave modeling (Delft 3D - Wave) were carried out for the entire basin during the years of 2015 and 2016. Wave run-up and sea level scenarios were stipulated for the calculation of the total water level and so determined conditions that lead to overwashing. The bay of Santos is open to the South, exposing the coast line for the action of cold fronts. The variability of the wave climate, derived from the changes of its formative meteorological conditions, can alter the morphology of the beach. In Santos and São Vicente, South and Southeast waves have higher wave height and are more frequent in autumn and winter when we have more cold fronts in the region. The results indicate the direct relationship between the incidence of waves with higher wave force (W/m), associated with cold fronts, with loss of volume along the beaches. The variety of wave incidence along the studied beach shows a decrease in wave force, being higher in Itararé and falling towards Ponta da Praia, in the area protected by the rocky promontory. However in Ponta da Praia we see high values of wave force, justifying why this stretch suffers more volume variation and loss of sediment, that we belive happends because of Port Channel. In both stretches with greater slope and lower sand range showed greater sensitivity to the action of the waves and also greater chance of overwash, of all the praial arc of the Santos bay, the Eastern portion of Santos was the most propitious to suffer flooding.

Elevated water levels and large waves during storms cause beach erosion, overwash, and coastal flooding, particularly along barrier island coastlines. While predictions of storm tracks have greatly improved over the last decade, predictions of maximum water levels and variations in the extent of damage along a coastline need improvement. In particular, physics based models still cannot explain why some regions along a relatively straight coastline may experience significant erosion and overwash during a storm, while nearby locations remain seemingly unchanged. Correct predictions of both the timing of erosion and variations in the magnitude of erosion along the coast will be useful to both emergency managers and homeowners preparing for an approaching storm. Unfortunately, research on the impact of a storm to the beach has mainly been derived from "pre" and "post" storm surveys of beach topography and nearshore bathymetry during calm conditions. This has created a lack of data during storms from which to ground-truth model predictions and test hypotheses that explain variations in erosion along a coastline. We have developed Coastal Lidar and Radar Imaging System (CLARIS), a mobile system that combines a terrestrial scanning laser and an X-band marine radar system using precise motion and location information. CLARIS can operate during storms, measuring beach topography, nearshore bathymetry (from radar-derived wave speed measurements), surf-zone wave parameters, and maximum water levels remotely. In this dissertation, we present details on the development, design, and testing of CLARIS and then use CLARIS to observe a 10 km section of coastline in Kitty Hawk and Kill Devil Hills on the Outer Banks of North Carolina every 12 hours during a Nor'Easter (peak wave height in 8 m of water depth = 3.4 m). High decadal rates of shoreline change as well as heightened erosion during storms have previously been documented to occur within the field site. In addition, complex bathymetric features that traverse the surf-zone into the nearshore are present along the southern six kilometers of the field site. In addition to the CLARIS observations, we model wave propagation over the complex nearshore bathymetry for the same storm event. Data reveal that the complex nearshore bathymetry is mirrored by kilometer scale undulations in the shoreline, and that both morphologies persist during storms, contrary to common observations of shoreline and surf-zone linearization by large storm waves. We hypothesize that wave refraction over the complex nearshore bathymetry forces flow patterns which may enhance or stabilize the shoreline and surf-zone morphology during storms. In addition, our semi-daily surveys of the beach indicate that spatial and temporal patterns of erosion are strongly correlated to the steepness of the waves. Along more than half the study site, fifty percent or more of the erosion that occurred during the first 12 hours of the storm was recovered within 24 hours of the peak of the storm as waves remained large (>2.5 m), but transitioned to long period swell. In addition, spatial variations in the amount of beach volume change during the building portion of the storm were strongly correlated with observed wave dissipation within the inner surf zone, as opposed to predicted inundation elevations or alongshore variations in wave height.

Coastal cliff erosion is a widespread problem that threatens property and infrastructure along many of the world’s coastlines. The management of this risk calls for robust quantification of cliff erosion rates, which are often difficult to obtain along rocky coasts. Quantification of sea-cliff rates of retreat on annual to decadal time scales has typically been limited to rapidly eroding soft rock coastlines. Rates of erosion used for shoreline management in the UK are generally based on analysis of historic maps and aerial photographs which, in rocky coast environments, does not wholly capture the detail and timing at which the processes operate and the failures occur across the cliff face. The first stage of this study uses airborne LiDAR (Light Detection and Ranging) data at nine sites around a rocky coastline (Cornwall, UK) to gain a quantitative understanding of cliff erosion where average recession rates are relatively low (c. 0.1 m yr-1). It was found that three-dimensional volumetric changes on the cliff face and linear rates of retreat can be reliably calculated from consecutive digital elevation models (DEMs) several years apart. Rates of erosion ranged between 0.03–0.3 m yr-1. The spatial variability in recession rates was considered in terms of the relationship with the varying boundary conditions (rock mass characteristics, cliff geometries, beach morphology) and forcing parameters (wave climate and wave exposure). Recession rates were statistically correlated with significant wave height (Hs), rock mass characteristics (GSI) and the ratio between the two (GSI/Hs). Although the rates derived using airborne LiDAR are comparable to the longer term rates of retreat, the detail of erosion to the cliff-face provides additional insight into the processes occurring in slowly eroding environments, which are vital for understanding the failure of harder rock coastlines. In addition to this, the importance of the wave climate and rainfall needs further attention on a more localised scale. Monthly cliff face volume changes, at two particularly vulnerable sites (Porthleven and Godrevy, Cornwall, UK), were detected using a Terrestrial Laser Scanner (TLS). Using these volumes alongside information on beach profile, beach- cliff junction elevation changes and nearshore hydrodynamics have allowed an insight into how the cliffs respond to seasonal fluctuations in wave climate and beach morphology. Monthly variability in beach morphology between the two sites over a one-year survey period i  indicated the influence that beach slope and the elevation of the beach-cliff junction have on the frequency of inundation and the power of wave-cliff impacts. Failure mechanisms between the two sites ranged from rotational sliding of superficial material to quarrying and block removal over the entire cliff elevation, according to the extent of wave-cliff interaction. This particular survey period highlighted the sensitivity of cliff erosion to the variability in wave climate and beach morphology at two different locations in the south-west of the UK, where the vast majority (over 85% of the annual value) of cliff face erosion occurs during the winter when extreme storm waves prevail. Coastal cliff erosion from storm waves is observed worldwide but the processes are notoriously difficult to measure during extreme storm wave conditions when most erosion normally occurs, limiting our understanding of cliff processes. Over January-March 2014, during the largest Atlantic storms in at least 60 years with deep water significant wave heights of 6 – 8 m, cliff-top ground motions of a rocky cliff in the south-west of the UK (Porthleven, Cornwall) showed vertical ground displacements in excess of 50–100 μm; an order of magnitude larger than observations made previously. Repeat terrestrial laser scanner surveys, over a 2-week period encompassing the extreme storms, gave a cliff face volume loss 2 orders of magnitude larger than the long-term erosion rate. Cliff-top ground motions and erosion volumes were compared at two different locations, one a reflective beach with steeply shelving bathymetry (Porthleven, Cornwall) and the other an intermediate, low tide bar-rip beach with a wide coastal slope (Godrevy, Cornwall). Under similar wave conditions (6–8 m Hs and 15–20 s. Tp) the vertical ground motions were an order of magnitude greater at the cliffs fronted by steeply shelving bathymetry, where the breaking waves plunge right at the shoreline, with little prior dissipation, leading to large energetic runup impacting the cliff. These storm results imply that erosion of coastal cliffs exposed to extreme storm waves is highly episodic and that long-term rates of cliff erosion will depend on the frequency and severity of extreme storm wave impacts as well as the wave dissipation that occurs as a function of the nearshore bathymetry. Having recorded microseismic cliff-top motion on this scale for the first time and determined an effective method of monitoring the energetic wave impacts, this study emphasises how investigations of cliff behaviour during storms is not only obtainable, but paramount to understanding coastal evolution under extreme conditions.

This thesis applies concepts from Vladimir Propp’s model of the narrative structure of fairy tales (Propp’s morphology) to a story authoring tool for children. A computer story authoring application based on Propp’s morphology is developed and evaluated through empirical studies with children. Propp’s morphology is a promising model of narrative for a children’s story authoring tool, with the potential to give children a powerful mental model with which to construct stories. Recent research has argued for the use of computer-based interactive narrative authoring tools (which enable the construction of interactive narrative computer games in which the player can affect or change the plot) to support children’s narrative development, and a number of interactive narrative systems use Propp’s morphology as their underlying model of narrative. These interactive narrative tools have many potential learning benefits and a powerful motivational effect for children, who enjoy using them to create narrative games. The potential of an interactive narrative system based on Propp’s morphology to support children’s construction of narratives seems great, combining Propp’s rich narrative model with the motivational benefits of interactive narrative. Before the application of Propp’s morphology in an interactive narrative game creation tool to support children’s writing could be pursued, it was necessary to study children’s story writing with Propp’s morphology. How can Propp’s morphology be represented in a story authoring tool for children? Can children apply Propp’s abstract narrative concepts to the task of creating their own original stories? How does using Propp’s morphology affect the stories written by children? Using the Propp-based authoring tool that is presented in this thesis children were able to grasp Propp’s abstract concepts and apply them to their own story writing. The use of a story authoring tool based on Propp’s morphology improved some aspects of the narrative structure of the stories written by children, and children reported that they enjoyed using the tool and felt it was helpful to their story writing. This thesis lays the foundation and identifies the methods for further study of children’s appropriation of narrative structure by constructing stories using a story authoring tool based on Propp’s morphology.

The work deals with nature prefigurations, which can be used in architecture. The first part is concerned with the bionics in architecture in general. There are introduced all available pieces of knowledge falling within this branch. The second part is focused on the nature prefiguration – tree. The tree was analyzed from different points of view. Suitable principles, which were found, were transformed to the field of architecture. On the basis of children's drawings the changing approach to “tree as a home” during adolescence was charted. The work can serve as a comprehensive supporting document for study of bionics for students of architecture and architects and also for the general public. The work should point out that nature is our great standard for any activity.

This study reports on the hypothesized raising of the low, front vowel /æ/, which is characteristic of a regional dialect vowel shift found in cities of the Midwest and Eastern North of the United States. The raising of this vowel is the primary change in a series of vowel shifts that have traditionally been attributed to this region of the U.S. The purpose of this study is to document the production of this vowel by residents of Portland, Oregon, in order to see what light it can shed on dialect research of the Pacific Northwest, especially across age groups to see if it can be implicated in language change. Data were collected by interviewing a convenience sample of twenty-four Portland speakers. Twelve females and twelve males from three different age groupings were interviewed. The interviews were tape recorded and portions of the tapes were analyzed. There was a two-part analysis of the data: 1) Formant measurements (in Hz) were measured with PCQuirer speech analysis software, 2) These measurements were plotted on a graph with Plotnik graphing software. The study found that /æ/ produced by Portland speakers is not following Labov's theory of language change and is therefore not raising. However, some initial speculations of the lowering and fronting of this vowel can be made by the data. The study found that the working class subjects produced a more fronted vowel, and that the younger subjects produced a more fronted and lowered variant of the vowel when compared to the other subjects. The study concludes that the patterns found do not clearly support Labov's paradigm of language change and are therefore only initial speculations.

El e-tailing es una nueva manera de compra que cada vez tiene mayor acogida en el cliente, se estima que en el 2021 las compras online representarán el 15.5% de las ventas de retail, debido a ello la mejor manera de contrarrestar la nueva modalidad de compra es a través del concept store debido a la atmósfera agradable que puede brindar el visual merchandising creando en el cliente una experiencia que no podrá vivirla a través de sus compras por internet. La investigación fue realizada a través del método mixto, llevándose a cabo la recolección y el análisis de datos cuantitativos y cualitativos. A la vez es una investigación de diseño transversal con un diseño transaccional correlacional. Para corroborar la información teórica se realizaron entrevistas a profundidad, focus groups y encuestas. La investigación cualitativa indica que los factores sensoriales como la vista, el oído, el tacto, el olfato y el gusto influyen en la intención de compra. A través de la investigación cuantitativa se pudo corroborar lo investigado cualitativamente, sí hay relación entre la intención de compra y los factores sensoriales, debido al rechazo de la hipótesis nula. El promedio de la correlación es de 0.499, lo que significa que es una correlación fuerte y cuanto más presente estén los cinco sentidos en la tienda, la intención de compra en las mujeres será más fuerte. La investigación es de gran utilidad para aquellas tiendas que brinden experiencia al consumidor, utilizando los sentidos generando una implicancia en la intención de compra.
E-tailing is a new way of buying that is increasingly welcomed by the client, it is estimated that in 2021 online purchases represent 15.5% of retail sales, due to this the best way to counteract the new modality of purchase is through the concept store due to the pleasant atmosphere that visual merchandising can offer, creating in the client an experience that can not be lived through its purchases over the internet. The research was conducted through the mixed method, carrying out the recollection and analysis of quantitative and qualitative data. At the same time, it is a transversal design research with a correlational transactional design. To corroborate the theoretical information, in-depth interviews, focus groups, and surveys were conducted. Qualitative research indicates that sensory factors such as sight, hearing, touch, smell and taste influence purchase intent. Through quantitative research it was possible to corroborate what was researched qualitatively, there is a relationship between purchase intention and sensory factors, due to the rejection of the null hypothesis. The average of the correlation is of 0.499, which means that it is a strong correlation and the more present the five senses are in the store, the purchase intention in women will be stronger. The research is very useful for those stores that provide consumer experience, using the senses generating an implication in the purchase intention.
Trabajo de investigación

Au-delà de replacer les transformations du paysage commercial alimentaire dans deux contextes urbains différents, cette thèse a pour objectif de montrer qu’à travers le renouvellement de l’appareil marchand de proximité dans les centres-villes, il est possible de mettre en perspective les évolutions plus générales de la ville contemporaine. Qu’elle soit considérée compacte (Saragosse), ou au contraire diffuse (Toulouse), celle-ci présente des points forts et des faiblesses qui révèlent la difficulté de trouver une fabrique idéale de la ville ou plus modestement de promouvoir une organisation commerciale plus qu’une autre. La proximité redessinée au spectre du temps laisse ainsi entrevoir des réajustements incessants qui initiés par les mutations des formes, des formats, et des règlementations restent surtout insufflés par les aspirations versatiles des chalands. Exogènes ou endogènes, mobiles ou «assignés à résidence», ils restent au final, les principaux artisans de la reconfiguration globale de la ville par leur façon d’entreprendre l’espace urbain en général, mais aussi les territoires du quotidien. L’observation des pratiques les plus banales, permettent alors de pointer les disparités socio-spatiales les plus stigmatisantes
Commercial activities are key indicators of social and urban changes. Studying the evolution of grocery stores located in city centers, we concentrate our work on the geographic and social analysis of these commercial mutations in two different metropolitan areas. We compare and analyse these dynamics in Zaragoza (Spain), described as a compact city, and in Toulouse (France), considered as a critical example of uncontrolled urban sprawl. The weaknesses, forces and sustainability (in a social and environmental way) of these two urban morphologies are confronted. The contemporary idea of impulsing a perfect urban model, in a sense where all part of cities would be "close" in space and time by controlling the location of commercial activities, emerge as another urban utopia. Even if national and local authorities produce planning documents to reduce commuting related to shopping, consumers habits explain the major part of the urban recombinations observed. Finally, using a common indicator such as grocery stores enhance the usual social and spatial segregation our urban societies have to deal with

[For the Abstract, please see the PDF files below, namely "front.pdf"] CONTENTS. Chapter 1 Introduction. Chapter 2 Gross and microscopic visceral anatomy of the male Cape fur seal with reference to organ size and growth. Chapter 3 Age determination and growth in the male Cape fur seal: part one, external body. Chapter 4 Age determination and growth in the male Cape fur seal: part two, skull. Chapter 5 Age determination and growth in the male Cape fur seal: part three, baculum. Chapter 6 Suture age as an indicator of physiological age in the male Cape fur seal. Chapter 7 Sexual dimorphism in the adult Cape fur seal: standard body length and skull morphology. Chapter 8 Reproduction in the male Cape fur seal: age at puberty and annual cycle of the testis. Chapter 9 Diet and foraging behaviour of the Cape fur seal. Chapter 10(a) The Impact of the fur seal industry on the distribution and abundance of Cape fur seals. Chapter 10(b) South African Airforce wildlife rescue: Cape fur seal pups washed from Black Rocks, Algoa Bay, during heavy seas, December 1976. Chapter 11(a) Operational interactions between Cape fur seals and fisheries: part one, trawl fishing. Chapter 11(b) Operational interactions between Cape fur seals and fisheries: part two, squid jigging and line fishing. Chapter 11(c) Operational interactions between Cape fur seals and fisheries: part three, entanglement in man-made debris. Chapter 12 Concentrations of heavy metals (Cd, Cu, Pb, Ni & Zn) and organochlorine contaminants (PCBs, DDT, DDE & DDD) in the blubber of Cape fur seals. Chapter 13 Endoparasites of the Cape fur seal. Chapter 14(a) Preliminary investigations of shark predation on Cape fur seals. Chapter 14(b) Aggressive behaviour of an adult male Cape fur seal towards a great white shark Carcharodon carcharias. Chapter 15 Conclusions and future directions.

The alongshore variability of beach-dune systems and the response and recovery from extreme storms remains poorly understood. The height and extent of foredunes along barrier islands varies over a range of spatial scales, implying that during extreme storms, the beach-dune system should respond in different ways depending on the elevation and volume of the dunes relative to the storm surge. The purpose of this study is to use Ground-Penetrating Radar (GPR) and vibra-cores to investigate the internal structure of small, intermediate and large dunes along a 2.5 km transect of beach in Padre Island National Seashore, TX with particular attention to storm impacts. A series of dune normal and parallel GPR profiles were collected to capture the variation in beach-dune morphology at the three sites. Site locations were chosen along a transition from dissipative to intermediate beach states. Following the Sallenger (2000) storm impact model, the small dune is defined by low-lying topography that is susceptible to overwash and inundation depending on the size of the storm surge. The large dune is characteristic of the “collision regime”, while the intermediate dune represents a transition between “overwash” and “collision regimes”, with the underlying assumption that all three dunes would be impacted by the same level of surge during a single storm event. Results from the GPR survey suggest that each site contains a bright, laterally continuous radar reflector that is interpreted with the aid of the sedimentary data as an erosional layer. Different characteristic radar facies and sequence boundaries provide evidence as to how each dune evolved through and after the storm. Results from XRF scans and grain size analysis show a direct comparison between the GPR reflectors at the storm surface and spikes in calcium counts from XRF scans to distinct changes in grain size parameters at the same depth. It is argued that the location of each shell layer corresponds to a storm surface generated during a single storm, which means it is possible to interpret different recovery mechanisms. The presence of the storm layer across the backbeach and dunes provides evidence for the height and extent of the surge during the storm event. The data suggests that the small dune was overtopped by the surge, experiencing minimal erosion and recovery. The intermediate dune was completely eroded by the surge, but showed the greatest recovery of all the dune sites. The large dune was scoured at the base with marginal impact along its crest and shows minimal recovery after the storm. These results suggest that the evolution (i.e., transgression) of a barrier island varies considerably over short distances.

Storm surge, the pileup of seawater occurring as a result of high surface stresses and strong currents generated by extreme storm events such as hurricanes, is known to cause greater loss of life than these storms' associated winds. For example, inland flooding from the storm surge along the Gulf Coast during Hurricane Katrina killed hundreds of people. Previous storms produced even larger death tolls. Simultaneously, dune, barrier island, and channel erosion taking place during a hurricane leads to the removal of major flow controls, which significantly affects inland inundation. Also, excessive sea bed scouring around pilings can compromise the structural integrity of bridges, levees, piers, and buildings. Modeling these processes requires tightly coupling a bed morphology equation to the shallow water equations (SWE). Discontinuous Galerkin finite element methods (DGFEMs) are a natural choice for modeling this coupled system, given the need to solve these problems on large, complicated, unstructured computational meshes, as well as the desire to implement hp-adaptivity for capturing the dynamic features of the solution. Comprehensive modeling of these processes in the coastal zone presents several challenges and open questions. Most existing hydrodynamic models use a fixed-bed approach; the bottom is not allowed to evolve in response to the fluid motion. With respect to movable-bed models, there is no single, generally accepted mathematical model in use. Numerical challenges include coupling models of processes that exhibit disparate time scales during fair weather, but possibly similar time scales during intense storms. The main goals of this dissertation include implementing a robust, efficient, tightly-coupled morphological model using the local discontinuous Galerkin (LDG) method within the existing Advanced Circulation (ADCIRC) modeling framework, performing systematic code and model verification (using test cases with known solutions, proven convergence rates, or well-documented physical behavior), analyzing the stability and accuracy of the implemented numerical scheme by way of a priori error estimates, and ultimately laying some of the necessary groundwork needed to simultaneously model storm surges and bed morphodynamics during extreme storm events.
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Thesis (M.S.)--Florida State University, 2008.
Advisor: Joseph F. Donoghue, Florida State University, College of Arts and Sciences, Dept. of Geological Sciences. Title and description from dissertation home page (viewed Sept. 26, 2008). Document formatted into pages; contains xvi, 171 pages. Includes bibliographical references.