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Thesis (MEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: The Swartvlei estuary and lake system is situated on the southern coast of the Western Cape Province of South Africa and forms part of the core conservation area of the Wilderness National Park. The Swartvlei system comprises two interlinked water bodies, namely Swartvlei Lake and Swartvlei estuary. SANParks have been monitoring this estuary closely over the past two decades, due to its importance to the ecology and to tourism. There are also low-lying properties on the perimeter of the Swartvlei estuary which run the risk of occasional flooding. Two of the major monitoring issues in this estuary system are the water level required for successful mouth breaching, and the influence of the water level on the low-lying properties. This study presents a preliminary analysis of the sediment budget across the Swartvlei estuary mouth. The objective of this study was to identify the various sediment contributory factors and to estimate the quantities that each individually contributed towards the defined sediment budget. / AFRIKAANSE OPSOMMING: Die Swartvlei meer en see monding is geleë aan die kaapse suidkus van Suid- Afrika. Dit vorm deel van die kern bewarings area van die Wilderness Nationale Park. Die Swartvlei sisteem bestaan uit twee verbinde, kern dele nl: Swartvlei meer en estuarium. Vir die afgelope twee dekades is hierdie area onder die noue toesig van SANParke as gevolg van die belangrikheid van die area met betrekking tot toerisme en ekologie. Daar is ook menigde laag liggende eiendomme aan die oewers, wat baie sensitief is vir watervlak stygings. Die optimum water vlakke benodig vir die uitskuring van die gety monding het ook implikasies vir die laag liggende eiendome en vereis noukeurige monitering. ‘n Voorlopige analise van die sediment begroting rondom die gety monding word deur hierdie studie voorgelê.

A seasonal and long-term analysis of the vertical structure of currents in the nearshore is conducted to determine the role of the wind in driving currents and consequently affecting littoral transport processes. Approximately ten years (January, 2002 – October, 2011) of nearshore current profiles are examined using the data collected with an Acoustic Doppler Current Profiler (ADCP) installed off of Spessard Holland North Beach Park located in Melbourne Beach, Florida. Additionally, wind data collected with a directional anemometer from September, 2002, until October, 2008, are used to further characterize the long-term hydrodynamic forcing. With the shoreline oriented nominally 17o west of magnetic north, both the current profiles and the wind vectors have been rendered into longshore and cross-shore components. The water level record from a NOAA tide station located at the Trident Pier at nearby Port Canaveral is utilized in establishing the water depth and conditioning the data for statistical analysis. Monthly mean vertical profiles reveal that during the winter months the surface currents are usually toward the south, and toward the north in the summer. In spring and fall, they are mixed, demonstrating a clear seasonality in both direction and intensity of the longshore current. Subjecting the longshore and cross-shore current data to Empirical Orthogonal Function Analysis reveals that the first spatial Eigenfunction accounts for more than 98% of the variability in the vertical profile of the longshore current, and more than 86% of the variability in the profile of the cross-shore current. However, there is a rotation of the current to the right (clockwise) with the rotation angle increasing and the variance decreasing with depth below the surface. The spiral structure of the water column follows a surface Ekman veering, but for very shallow water. The upper layer of the current is almost aligned with the direction of the wind. Monthly correlations between 2-hour average time series of longshore current and 2-hour average time series of wind speed reveal the seasonal patterns of the wind and longshore current in which the upper layer of the water column is highly correlated with the longshore component of the wind speed for most of the year and slightly less correlated for the lower layer of the water column. Most importantly, on average, wave height (Hmo) is larger when the longshore current is heading to the south (Hmo=0.95 m) than when the current is going to the north (Hmo=0.73 m). Additionally, there is a stronger correlation between southerly directed currents and incident wave energy flux than northerly directed currents and wave energy flux. These results indicate that the net long-term north-to-south sediment transport known to characterize the region is heavily influenced by wind-driven currents.

From the Proceedings of the 1982 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona - Nevada Academy of Science - April 24,1982, Tempe, Arizona / A prototypical computer simulation model has been developed to aid watershed managers in estimating impacts of alternative land management practices on nutrient and heavy metal losses due to transported sediment on forested watersheds of the southwestern United States. The model, called SEDCON, allows users at remote locations with modest computer terminal equipment and commonly available data to obtain reliable estimates of nutrient and heavy metal concentrations in suspended sediment originating on uniformly-stocked, forested watersheds in the Southwest. SEDCON has been structured in an interactive mode to facilitate its use by persons not familiar with computer operations. Written in FORTRAN IV computer language, the model requires approximately 5000 words of core. SEDCON is operative on a DEC-10 computer at the University of Arizona.

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L’objectif de cette thèse est le développement et la validation d’un outil numérique permettant d’évaluer la performance d’un ouvrage de décantation. L’approche Euler-Lagrange est retenue pour la modélisation de l’écoulement et du transport solide. De nouvelles conditions d’interaction particule/paroi permettent de restreindre le dépôt aux zones présentant des caractéristiques géométriques et hydrodynamiques favorables. Le modèle numérique est confronté à quatre jeux de données expérimentales. L’ensemble de ces expérimentations permettent d’investiguer une large gamme des paramètres représentatifs de l’écoulement et du transport solide. La comparaison des résultats numériques et expérimentaux permet de conclure sur la capacité du modèle à prévoir l’abattement des particules dans un ouvrage de décantation avec une précision de l’ordre de 5 pourcents lorsque les dépôts ont lieu sur l’ensemble du fond et de 10 pourcents dans le cas de dépôts localisés dans des zones préférentielles. / The objective of this thesis is the development and the validation of a numerical tool to estimate the trapping efficiency of settlers. The Euler-Lagrange approach is chosen to simulate the flow and the sediment transport. New particle/wall interaction conditions are developed to take into account the geometric and hydrodynamic characteristics to enable the deposit. The numerical model is compared to four sets of experimental data. All these experiments enable to study a wide range of parameters that describe the flow and the solid transport. The comparison between the numerical and experimental results shows that the model is able to estimate the trapping efficiency of particles in a settler with an accuracy of about 5 percent when the particles settle all over the bed of the basin and about 10 percent in case of located deposits.

The variability of the nearshore wave climate is investigated via the analysis of over 10 years of Acoustic Doppler Current Profiler (ADCP) data from a gauge deployed at Melbourne Beach, FL. Examples of large yearly variability in the significant wave height, peak period, mean direction and energy distribution are found in the data. Estimates of the averaged spectra for the entire record show that the average wave energy is distributed almost symmetrically with the peak being close to shore-normal. It was expected that the peak would be shifted towards the north of shore-normal considering net north to south longshore sediment transport at this location. Further analysis of the directional spectra partitioned into three directional windows reveals that waves from the southeast (avg. Hmo = 0.78 m) are less energetic than those from the northeast (avg. Hmo = 0.87 m), but they arrive from the south 53% more often. Additionally, energy-based significant wave height (Hmo), peak period (Tp) and mean period (Tmean) distributions are studied and modeled with notable success. Radiation stress (Sxy) estimates are computed using both rigorous integration as well as parameter-based approximations. These two estimates are correlated but the parameter-based approximation over predicts Sxy by 42%, because this method assigns all the wave energy into one direction (Ruessink et al., 2001). Finally, it is shown by the Sxy total average that the net longshore forcing at this location is indeed north to south, but yearly and seasonal variability were quite high. The results indicate that short-term wave records may not provide accurate information for planning purposes. For example, if only 3 months of data were collected at this site, there would be a 33% chance that the mean longshore forcing would be erroneously directed from south to north.

L’objectif de cette étude est de reconstruire le régime de l’érosion des chaînes himalayennes, et de relier ces paramètres aux variations climatiques globales et à l’intensité de la mousson. Dans ce travail, Les sédiments de 3 carottes prélevées dans la baie du Bengale pendant la mission MONOPOL ont fait l’objet d’analyses minéralogiques (XRD et granulométrie) et géochimiques (majeurs, traces, la composition isotopique du Nd et du Sr). La mise en âge des carottes, est basée sur les enregistrements de δ¹⁸O de foraminifères planctoniques (G. ruber), et des datations au ¹⁴C (AMS). Ces 3 enregistrements sédimentaires couvrent les derniers 180 ka. L'approche multi-traceur menée sur ces carottes, nous donne des informations essentielles sur les sources, afin de reconstruire les changements au cours du temps des sédiments transportés vers la partie proximale du cône sous-marin du Bengale, et de mieux comprendre ses liens potentiels avec les changements climatiques (mousson indienne et/ou des changements au niveau de la mer). Les résultats de cette étude, donnent également des clefs sur les processus d'altération chimique et de la dynamique du transport des sédiments au cours du temps. En outre, une étude à haute résolution, sur un site localisé sur la levée du chenal actif du cône sous-marin fournit des informations sur les changements dans le degré d'altération et la dynamique de transport des sédiments du système himalayen au cours de l'Holocène. Ainsi, il est possible de quantifier l'impact de la mousson d’été sur la sédimentation au niveau de la levée durant cette période climatique. Les résultats de cette étude ont été utilisés pour estimer les changements dans les sources sédimentaires (plaine Indo-Gangétique vs haute-chaine) et retracer l'altération chimique du matériel détritique au sein du bassin versant du système fluviatile du Ganges-Brahmapoutre. / The aim of this study is to reconstruct the erosional history of the Himalayan ranges, in order to connect these parameters to global climatic events and variations in the intensity of the monsoon. In this work, sediments from 3 marine cores collected in the Bay of Bengal, during the MONOPOL cruise were analyzed using mineralogical (XRD and grain-size) and geochemical (major, trace, Nd and Sr isotopic composition) methods. Chronological framework of studied cores were based on δ¹⁸O from planktonic foraminifera (G. ruber), and ¹⁴C ages dating (AMS). These cores cover the last 180 kyr. The multi-proxy approach conducted on these cores, gives us critical information about the source, to reconstruct the temporal variability of sediment export to the proximal northeastern Bengal Fan and its potential links to climatic changes (Indian monsoon and/or sea-level changes). Results also give insights on the chemical weathering processes and the dynamic of transport of the sediments through time as well. Moreover, a high-resolution study, on a site located on the active middle fan channel levee of the fan provides information on changes in the weathering pattern and the dynamic of transport of sediments from the Himalayan system during the Holocene. Thus, it is possible to quantify the impact effect of summer monsoon rainfall during that time interval. These results have been used to assess changes in the sedimentary sources (Indo-Gangetic plain vs highlands) and document the chemical weathering states of the detrital material within the Ganges-Brahmaputra river basin catchment.

Biological invasions provide a unique opportunity to study the mechanisms that regulate community composition and ecosystem function. Invasive species that are also ecosystem engineers can substantially alter physical features in an environment, and this can lead to cascading effects on the biological community. Aquatic-terrestrial interface ecosystems are excellent systems to study the interactions among invasive ecosystem engineers, physical features, and biological communities, because interactions among vegetation, sediment, and fluids within biophysical feedbacks create and modify distinct physical features. Further, these systems provide important ecosystem services including coastal protection afforded by their natural features. In this dissertation, I investigate the interactions and feedbacks among sand-binding beach grass species (a native, Elymus mollis (Trin.), and two non-natives, Ammophila arenaria (L.) Link and A. breviligulata Fernald), sediment supply, and dune shape along the U.S. Pacific Northwest coast. Dunes dominated by A. arenaria tend to be taller and narrower compared to the shorter, wider dunes dominated by A. breviligulata. These patterns suggest an ecological control on dune shape, and thus, coastal vulnerability to overtopping waves. I investigate the causes and consequences of these patterns with experiments, field observations, and modeling. Specifically, I investigate the relative roles of vegetation and sediment supply in shaping coastal dunes over inter-annual and multi-decadal time scales (Chapter 2), characterize a biophysical feedback between beach grass species growth habit and sediment supply (Chapter 3), uncover the mechanisms leading to beach grass coexistence and whether A. breviligulata can invade and dominate new sections of coastline (Chapter 4), and examine the non-target effects resulting from management actions that remove Ammophila for the recovery of the threatened Western Snowy plover (Charadrius alexandrinus nivosus) (Chapter 5). I found that vegetation and sediment supply play important roles in dune shape changes across inter-annual and multi-decadal time scales (Chapter 2). I determined that a biophysical feedback between the beach grass growth habits and sediment supply results in species-specific differences in sand capture ability, and thus, is a likely explanation for differences in dune shape (Chapter 3). I found that all three beach grass species can coexist across different sediment deposition rates, and that this coexistence is largely mediated by positive direct and indirect species interactions. I further determined that A. breviligulata is capable of invading and dominating the beach grass community in regions where it is currently absent (Chapter 4). Combined, these findings indicate that A. breviligulata is an inferior dune building species as compared to A. arenaria, and suggest that in combination with sediment supply gradients, these species differences ultimately lead to differences in dune shape. Potential further invasions of A. breviligulata into southern regions of the Pacific Northwest may diminish the coastal protection ability of dunes currently dominated by A. arenaria, but this effect could be moderated by the predicted near co-dominance of A. arenaria in these lower sediment supply conditions. Finally, I found that the techniques used to remove Ammophila for plover recovery have unintended consequences for the native and endemic dune plant communities, and disrupt the natural disturbance regime of shifting sand. A whole-ecosystem restoration focus would be an improvement over the target-species approach, as it would promote the return of the natural disturbance regime, which in turn, would help recover the native biological community. The findings from this dissertation research provide a robust knowledge base that can guide further investigations of biological and physical changes to the coastal dunes, can help improve the management of dune ecosystem services and the restoration of native communities, and can help anticipate the impacts of future beach grass invasions and climate change induced changes to the coast. / Graduation date: 2012 / Access restricted to the OSU Community at author's request from Sept. 22, 2011 - March 22, 2012