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1
Le, Normant Catherine. "Modélisation numérique tridimensionnelle des processus de transport des sédiments cohésifs en environnement estuarien." Toulouse, INPT, 1995. http://www.theses.fr/1995INPT014H.
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Cette these porte sur la modelisation numerique tridimensionnelle du transport en suspension des sediments cohesifs en estuaire. Dans un premier temps, le modele numerique telemac-3d, qui simule les ecoulements tridimensionnels en riviere et en mer, a fait l'objet de nouveaux developpements afin de representer les processus propres aux sediments fins (phenomene de floculation, mouvements de la creme de vase, consolidation du fond vaseux). L'etude d'un estuaire schematique a montre les capacites du code a simuler les phenomenes caracteristiques des environnements estuariens: propagation de la maree, intrusion saline et formation du bouchon vaseux. Le modele a alors ete applique a un cas reel: l'estuaire de la loire. Le bouchon vaseux reproduit par le modele presente des caracteristiques (position dans l'estuaire, deplacements au cours de la maree) similaires a celles observees en nature. Le modele de creme de vase a aussi ete teste et il s'est avere utile pour une bonne representation de la dynamique sedimentaire estuarienne
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Voltz, Baptiste. "Dynamique de la matière organique au sein dans les estuaires picards : caractérisation des faciès biosédimentaires et quantification des processus de minéralisation benthique." Thesis, Littoral, 2020. http://www.theses.fr/2020DUNK0579.
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Les estuaires assurent une production élevée et le transfert d'une grande quantité de matière organique (MO) du continent vers l'océan. Une étape importante pour comprendre les échanges de MO à l'interface continent - océan, le long de la côte française de la Manche Orientale, est d'établir un bilan de MO dans les trois plus grands estuaires : la Canche, l'Authie et de la Somme. Dans ce but, il a été réalisé une description sédimentologique et biologique du sédiment de surface et une caractérisation élémentaire et isotopique distinguant l'origine de la MO sédimentaire. La caractérisation du sédiment de surface a été réalisée, de l'étage proche subtidal à supratidal, le long de transects transversaux au fleuve, constituant un réseau de 36, 37 et 39 stations respectivement pour l'estuaire de la Canche, de l'Authie et de la Somme. A partir de cette approche cartographique, un transect représentatif dans l'estuaire de la Canche et de l'Authie a été sélectionné, dans le but de quantifier la minéralisation benthique de la MO sédimentaire, le long du gradient tidal et finalement d'établir un bilan de la dégradation de la MO à l'échelle de l'estuaire. A partir de la caractérisation sédimentologique et biologique du sédiment de surface, le paysage estuarien a été défini selon quatre faciès biosédimentaires : les bancs et plateformes sableuses, les vasières, le bas et le haut des prés salés. Il a été démontré que la répartition de la MO à l'échelle de l'estuaire est contrôlée par la distribution de ces différents faciès biosédimentaires. En effet, les sédiments sableux sont soumis à des contraintes hydrodynamiques importantes dans lequel le dépôt de la MO est limité. En revanche, la MO se dépose préférentiellement dans les lieux où les sédiments fins s'accumulent tels que les vasières et les prés salés. Ces deux environnements sédimentaires sont soumis à des contraintes hydrodynamiques plus faibles, plus particulièrement les prés salés, où la végétation favorise le dépôt et limite la remise en suspension de la MO sédimentaire. En effet, les fortes quantités de MO sédimentaire mesurées dans les prés salés sont issues de la contribution des halophytes en C3 dominant le haut des prés salés. Néanmoins, notre étude montre que la MO déposée le long du gradient tidal est aussi dépendant de l'apport de MO particulaire provenant des communautés phytoplanctoniques fluviatiles et marines/estuariennes. De plus, cette étude a mis en évidence des différences géomorphologique avec un état de maturité des prés salés avancée dans l'estuaire de la Canche, une progradation du pré salé en rive dans l'estuaire de l'Authie et une régression du pré salé, en rive nord dans l'estuaire de la Somme, issu d'un comblement avancé. A l'immersion et à l'émersion, les vasières et les prés salés ont une contribution plus importante que les sédiments perméables à la minéralisation benthique. Paradoxalement, le bilan de la minéralisation benthique, relève une contribution non négligeable des sédiments perméables dans l'estuaire de l'Authie, étant donné leur vaste répartition à l'échelle de l'estuaire. Il a été démontré que la variation spatiale de la minéralisation benthique repose sur les caractéristiques sédimentologiques des faciès biosédimentaires mais aussi sur les facteurs biologiques tels que la macrofaune benthique, le microphytobenthos et le système racinaire des halophytes. Cette thèse contribue à une meilleure définition du rôle des estuaires picards dans le cycle de la MO et permet un premier pas vers la quantification d'un bilan de MO dans les trois principaux estuaires de la Manche Orientale<br>Estuaries ensure a high production and transfer a large amount of organic matter (OM) from continent to ocean. To understand OM exchanges at the continent-ocean interface along the eastern English Channel coast, it is primordial to establish a mass balance OM budget in the three main estuaries : the Canche, the Authie and the Somme estuaries. In this frame, the sedimentary OM distribution and origin were studied by coupling a sedimentological description of surficial sediments and an elemental and isotopic characterization of the sedimentary OM. Such approach was carried out from near from subtidal to supratidal stages, along transects transversal to the main river channel, resulting in a sampling of 36, 37 and 39 stations respectively from the Canche, the Authie and the Somme estuaries. Based on this mapping approach, a representative transect was selected in the Canche and the Authie estuaries in order to quantify the sedimentary OM benthic mineralization along the tidal gradient and finally to establish an OM mineralization budget at the estuarine scale. Based on the sedimentological and biological characterization of sediments, the estuarine landscape was described according to four biosedimentary facies : sand flats, mud flats, low and high marshes. This study evidenced that the distribution of OM at the estuary scale is mainly controlled by the distribution of these biosedimentary facies. Indeed, sand flats are subject to intense hydrodynamic conditions in which sedimentary OM deposition is limited. On the other hand, OM is preferentially deposited in fine-grained sediments such as mud flats and salt marshes. Both of these sedimentary environments are subjected to lower hydrodynamic conditions, especially salt marshes, where vegetation enhances deposition and limits the resuspension of sedimentary OM. Indeed, the high quantities of sedimentary OM measured in salt marshes mainly originate from C3 halophytes dominating high marsh areas. Nevertheless, our study also evidenced that the deposition of sedimentary OM along the tidal gradient depends on the contribution of particulate OM from fluvial and marine/estuarine phytoplankton communities. Moreover, this study has demonstrated that various evolutions of the geomorphological features, with a mature salt marsh present in the Cancheestuary, a seaward prograding salt marsh on the north shore of the Authie estuary, a salt marsh retreat on the north shore of the Somme estuary resulting from an advanced sand infilling. The OM benthic mineralization campaigns demonstrated that during immersion and emersion periods, mud flats and salt marshes are the main contributors to total OM mineralization along the tidal gradient in contrast to sand flats. The spatial variation mainly depended on the sedimentological characteristics of each of biosedimentary facies but also on biological factors such as benthic macrofauna, microphytobenthos and root system of halophytes. The OM mineralization budget at the estuarine scale showed a significant contribution of sand flats in the Authie estuary given their wide distribution. This thesis contributes to a better definition of the role of "Picard" estuaries in the OM cycling and allows a first step towards the quantification of a mass balance OM budget in the three main estuaries of the eastern English Channel coast
3
Lesourd, Sandric. "Processus d'envasement d'un estuaire macrotidal : zoom temporel du siecle a l'heure ; application a l'estuaire de la seine." Caen, 2000. http://www.theses.fr/2000CAEN2049.
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La problematique de cette these engagee dans le cadre du programme seine-aval, est de comprendre et de caracteriser les mecanismes d'envasement de l'estuaire macrotidal de la seine. La cartographie de la couverture sedimentaire de rouen jusqu'a la baie de seine est presentee. Dans l'embouchure, les facies sedimentaires etaient grossiers au xixeme siecle et envases actuellement. Une interpretation de l'evolution a l'echelle du siecle est proposee. Une etude faciologique des depots est realisee. Les modalites de la sedimentation sont etudiees sur une courte echelle de temps. La variation de la nature des sediments superficiels est d'occurrence saisonniere. Le depot vaseux, d'extension maximale en crue, est partiellement remanie et deplace en etiage. L'etude du comportement mecanique des vases permet d'identifier les processus d'erosion. Les vases acquierent rapidement de fortes valeurs de cohesion et sont difficilement erodables par les seuls courants de maree. Les caracteristiques hydrosedimentaires des masses d'eau sont decrites. Le role des courants de maree dans la formation des structures turbides et le role du chenal nord dans le stockage et le transfert des mes sont etudies. L'etude morphosedimentaire de la vasiere nord a ete entreprise. Son fonctionnement hydrosedimentaire est etroitement lie aux crues, aux tempetes et a la divagation du chenal nord. L'etude geochimique des sediments fins et des mes a ete initiee. Elle caracterise un pole continental, un pole marin et des sources intra-estuariennes de particules. L'envasement actuel de l'estuaire de la seine est incontestable mais fluctuant. Il est lie au cycle complexe des particules fines, partiellement stockees en etiage, en partie expulsees en crue et deposees dans les faibles profondeurs. Les caracteristiques rheologiques et mineralogiques de ces vases expliquent leur preservation partielle. La partie superficielle des vases est remaniee ulterieurement et en partie reintroduite au sein de l'estuaire.
4
Orseau, Sylvain. "Dynamique sédimentaire d'un estuaire tropical sous influence amazonienne : Le cas de l'estuaire du Mahury." Thesis, Littoral, 2016. http://www.theses.fr/2016DUNK0450.
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La migration des bancs de vase observée le long des côtes Guyanaises génère des problématiques de navigation, particulièrement pour l'unique port de commerce de Guyane localisé dans l'estuaire du Mahury. La dynamique hydrosédimentaire de cet estuaire mésotidal et l'influence des bancs sur cette dernière sont très peu renseignées. Les principaux résultats de cette étude mettent en évidence l'importance relative du débit et des courants de marée sur la dynamique des sédiments fins. Bien que l'asymétrie de la marée soit dominée par le flot, les courants de jusant sont prédominants en saison humide et équivalents aux courants de flot en saison sèche. La dynamique des sédiments fins est gouvernée par la remise en suspension, bien que des épisodes de stratification puissent fortement atténuer la turbulence durant les premières heures du jusant. Les flux résiduels de sédiments sont généralement orientés vers l'amont durant la saison sèche et vers l'aval en saison humide, excepté lorsque les débits sont inférieurs aux moyennes saisonnières. L'évolution des fonds de l'estuaire sur 20 ans indique néanmoins une stabilité des dépôts et souligne la capacité de l'estuaire à évacuer les sédiments apportés durant la phase d'envasement. L'interdépendance entre l'estuaire du Mahury et le banc de Kaw sera ainsi soumise à discussion. Elle permettra d'évaluer la capacité du banc de Kaw à influencer la sédimentologie de l'estuaire et inversement d'évaluer la capacité de l'estuaire à perturber la migration du banc<br>The mud banks migration observed along the Guyanese coastline generates navigating issues, especially for the unique harbor of French Guiana located in the Mahury Estuary. The hydro-sedimentary dynamic of this mesotidal estuary and the influence of the mud banks migration is poorly documented. The main results have brought to light the relative importance of the river discharge and tidal currents on the fine sediment dynamics. Even though the tidal asymmetry is dominated by the flood, the ebb currents are predominant during the wet season and are equivalent to the flood currents during the dry season. The fine sediment dynamics are mainly governed by the resuspension even though some stratification events can highly damp turbulence during the first hours of the ebb. The residual fluxes of sediment are generally landward during the dry season and in the wet season when river discharges are lower than the seasonnal averages. However, the bathymetric evolution over 20 years indicates the stability of the deposits and underlines the estuary's capacity of flushing sediments brought from the mud bank. The interdependence between the Mahury Estuary and the Kaw mudbank will therefore be subject to discussion. It will allow us to evaluate the mud bank influence on the estuarine sedimentology or, inversely, evaluate the capacity of the estuary to interfere with the mud bank migration and slowing down its progression with the currents
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Cordier, Mateo. "Ecosystème estuarien et système économique régional: faisabilité d'une intégration par modélisation input-output : application au cas de l'habitat halieutique dans l'estuaire de la Seine." Doctoral thesis, Universite Libre de Bruxelles, 2011. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209905.
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Le modèle input-output régional environnementalisé développé dans la thèse de M. Cordier suggère qu’il serait possible de restaurer 25% des surfaces naturelles de nourriceries de poissons détruites dans l’estuaire de la Seine entre 1834 et 2004. Le modèle suggère que la mesure de restauration pourrait augmenter de 15% à 23% la biomasse de soles produite dans l’estuaire par rapport à une situation sans mesure. Quant à l’effet des coûts de restauration sur les agrégats macroéconomiques (PIB, emploi, etc.), il génère une diminution qui ne dépasse pas 0,5% par rapport à une situation sans mesure. Le modèle montre cependant que trois secteurs sont particulièrement touchés par la mesure, leur bénéfice étant considérablement réduit. Cela indique le compromis à réaliser entre les objectifs écologiques à long terme et les objectifs économiques sectoriels à court terme. La quantification des compromis par le modèle constitue un atout utile aux processus de décision participatifs multicritère / The regional green input-output model developed in Mateo Cordier's PhD shows that it seems possible to restore 25% of the natural areas of fish nurseries destroyed in the Seine estuary between 1834 and 2004. The model suggests that the restoration measure could increase between 15% and 23% the biomass of sole generated by the estuary compared to a situation without measure. Regarding the impact of restoration costs on macro-economic indicators (GDP, employment, etc.), it generates a decrease that does not exceed 0,5% compared to a situation without measure. However, the model shows that three sectors are particularly impacted by the measure. Their benefits are considerably reduced. This shows the trade-off that occurs between ecological targets on the long run and economic targets on the short run. The quantification of such trade-offs in the model is particularly useful to public participation in decision-making.<br>Doctorat en Sciences agronomiques et ingénierie biologique<br>info:eu-repo/semantics/nonPublished
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Verney, Romaric. "Processus de contrôle de la dynamique des sédiments cohésifs : Mesures in situ, mesures expérimentales et modélisation : Application à l'estuaire de Seine." Rouen, 2006. http://www.theses.fr/2006ROUES032.
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Les forçages hydrodynamiques influençant les vasières intertidales de l'estuaire de Seine ont été calculés dans le système Seine. Ces forçages induisent des érosions de plusieurs millimètres à plusieurs centimètres. La connaissance des processus d'érosion/dépôt a permis la réalisation d'un modèle semi-empirique 1DV de l'évolution des vasières intertidales. Les processus de floculation et de défloculation des matières en suspension (MES) naturelles de l'estuaire de Seine ont été étudiés en laboratoire. Les tests cinétiques effectués à partir du suivi annuel des MES ont permis d'évaluer les paramètres de contrôle de ces processus. Une hiérarchisation est proposée, désignant l'intensité turbulente, la concentration et la qualité des MES comme prépondérants. Un modèle multiclasse de floculation des MES naturelles a été développé. La comparaison de ce modèle aux cinétiques expérimentales a permis d'évaluer l'évolution de l'efficacité de collision selon la nature des MES<br>Hydrodynamic forcing parameters that influence intertidal ares have been determined in the Seine estuary. These parameters induce sediment erosion, ranging from few millimeters to several centimeters per tide. The knowledge of erosion and deposition mechanisms has led to the development of a semi-empirical 1DV numerical model, simulating the evolution of intertidal areas. Flocculation/deflocculation processes have been studied in lab from natural suspended particulate matter (SPM). Kinetic tests have been carried out with SPM sampled in the Seine estuary. This study has permitted to classify the controlling parameters, representing turbulence, SPM concentration and quality as the predominant parameters. A flocculation numerical model has been developed to simulate the dynamics of natural particles. The comparison of the experimental results and the simulation results allowed evaluating the variability of the collision efficiency as a function of SPM characteristics
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Normandeau, Alexandre. "Processus gravitaires tardi-quaternaires dans les canyons et chenaux sous-marins du Saint-Laurent (Est du Canada)." Doctoral thesis, Université Laval, 2015. http://hdl.handle.net/20.500.11794/25907.
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Tableau d'honneur de la Faculté des études supérieures et postdorales, 2014-2015<br>Les canyons et chenaux sous-marins sont formés par des courants de densité subaquatiques et sont les principaux conduits par lesquels les sédiments continentaux atteignent les milieux marins profonds. Plusieurs canyons et chenaux sous-marins incisent les marges de l’estuaire et du golfe du Saint-Laurent jusqu’à une profondeur de ≥ 300 m. Des données hydroacoustiques et sédimentologiques récemment acquises ont permis d’analyser en détail la morphologie et les processus sédimentaires tardi-quaternaires qui ont modifié l’architecture de ces systèmes turbiditiques. Quatre types de systèmes turbiditiques ont été identifiés en fonction de leur source respective de sédiments. Un premier type de système, alimenté par la dérive littorale, a été cartographié dans les secteurs de Sept-Îles, Les Escoumins et Tadoussac. La formation et l’évolution de ces trois systèmes semblent être étroitement liées à un apport sédimentaire provenant de l’érosion des rives avoisinantes. Vers la mi-Holocène, alors que la charge sédimentaire provenant des rivières a drastiquement diminué, l’érosion des fronts deltaïques a vraisemblablement contribué à alimenter ces systèmes turbiditiques. L’activité gravitaire est aujourd’hui dominée par des mouvements de masse qui permettent le transfert sédimentaire vers le niveau de base. Un second type de canyon a été découvert dans le secteur de Pointe-des-Monts. Bien qu’il ne reçoive pas d’apport sédimentaire, ce dernier est le seul où des formes en croissant, probablement associées à des courants supercritiques, ont migré récemment. Leur activité holocène peut être expliquée par des mouvements de masse épisodiques et des courants quasi-continus d’origine hydrodynamique se déplaçant sur le plancher marin. Des données sédimentologiques suggèrent que ces courants d’origine hydrodynamique seraient responsables de la formation des canyons. Deux autres types de chenaux et canyons ont été identifiés dans l’estuaire, soit des systèmes reliés aux rivières et aux glaciers. Ces deux types de systèmes ont été actifs majoritairement au début de l’Holocène, alors que la charge sédimentaire transportée vers l’estuaire était plus importante, permettant la génération de courants hyperpycnaux. Ainsi, cette recherche a permis de démontrer la variabilité morphologique des canyons et chenaux de l’estuaire et du golfe du Saint-Laurent ainsi que les différentes phases d’activité et types de processus gravitaires qui ont mené à la formation de systèmes turbiditiques dans un contexte tectonique et climatique similaire.<br>Submarine canyons and channels are formed by subaqueous sediment density flows and are the main conduits through which continental sediments reach deeper sedimentary basins. Numerous submarine canyons and channels incise the margins of the Estuary and Gulf of St. Lawrence, to a depth of ≥ 300 m. Multibeam bathymetry, acoustic backscatter, seismic reflection and sedimentological analysis have allowed examining in great detail the morphology and the late-Quaternary sedimentary processes within these systems. Four types of submarine fans were identified based on their respective source of sediment. A submarine fan located in ≤ 60 m deep in the Sept-Îles sector has illlustrated the role of longshore drift on the formation and evolution of such systems. Longshore drift, through submarine transverse bars and coastal sand bars, forced the formation of a submarine fan near 5 ka BP. Its activity is now dominated by the passage of low density/intensity flows forming sandwaves on the edge of the coastal shelf and high energy flows (probably slope failures) that allow the accumulation of sediment on the deeper submarine fan. Two other systems fed by longshore drift were identified in the Tadoussac and Les Escoumins sectors, where similar recent episodic activity has been described. A second type of canyon system was discovered in the Pointe-des-Monts sector. These canyons are sediment-starved and yet, they are the only systems in which crescentic bedforms recently migrated upslope. Their short- and long-term activity can be explained by slope failures and quasi-continuous hydrodynamic processes along the seafloor. Sedimentological data suggest that quasi-continuous flows of hydrodynamic origin are responsible for the formation of the canyons. Two other types of channels and canyons were identified in the St. Lawrence: systems fed by rivers and glaciers. Both types of systems were active mainly in the early-Holocene, when sediment supply to the St. Lawrence was greater. When sediment supply drastically diminished during mid-Holocene, erosion of deltaic fronts likely led to an increase in longshore-drift transport and the formation and/or continuated activity of the Sept-Îles and Les Escoumins systems.
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Yang, Chengfan. "Li isotope study of Yangtze River sediments : new constraints on climate, weathering and carbon cycle relationships." Electronic Thesis or Diss., Sorbonne université, 2020. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2020SORUS433.pdf.
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Au cours de ce travail, j’ai réalisé une série d'études dans le bassin du Changjiang (Yangtze), afin de mieux comprendre l'influence de ces effets.Tout d'abord, l'exploitation du barrage des Trois Gorges (TGD) a modifié la composition géochimique des sédiments en aval. Depuis 2003, les sédiments venant des hauts bassins ont été en grande partie retenus en amont, tandis que les sédiments précédemment déposés dans le bassin moyen-inférieur ont été progressivement remis en suspension. Ces processus expliquent l’évolution géochimique des sédiments exportés vers la mer de Chine. En deuxième partie, une étude systématique démontre que les compositions isotopiques en lithium des phases dissoutes et particulaires se comportent de façon conservative dans la zone de mélange de l'estuaire du Changjiang. Cependant, les phases échangeables ne représentent qu'une faible quantité de Li, ce qui explique son impact négligeable dans cette zone. Troisièmement, Cette étude confirme que dans les grands bassins versants, l'altération chimique peut réagir rapidement à de grandes amplitudes climatiques. Ceci est particulièrement bien illustré, dans la carotte CM97, par la période du Younger Dryas. Depuis 2 000 ans, les δ7Li des argiles s’accentuent clairement par rapport à la période précédente, à cause de l'érosion des sols de plaines induite par l'homme. En résumé, ces résultats apportent de nouveaux éclairages sur l'interprétation des proxys et sur la réponse de l'altération chimique aux variations climatiques, ce qui est essentiel pour mieux quantifier l’impact du l’altération continentale sur les climats passés et futurs de notre planète<br>In order to better understand the weathering-climate feedback, a series of studies was carried out in the Changjiang (Yangtze) Basin. First, the operation of the Three Gorges Dam (TGD) changed downstream sediment geochemical compositions. Before 2003, large amounts of upstream-derived sediments deposited and experienced further weathering in the mid-lower basin. Since 2003, strong riverbed sediment resuspension changed the roles of the mid-lower reaches from important sinks to major sources of sediments delivered to the sea. As a consequence, an intensified weathering intensity of downstream sediment was observed.Second, dissolved δ7Li exhibit a conservative behavior in the Changjiang Estuary. During the process of SPM transported offshore, weathering product flocculated and deposited, while primary minerals resuspended. The combined effect resulted in the UCC-like SPM δ7Li values. There is a Li isotope fractionation between the dissolved load and exchangeable phase. However, this process shows negligible impact on δ7Li of dissolved load and particulates. Third, weathering response to climate is complex in large river basins. During the Younger Dryas, the positive excursion of clay δ7Li is consistent with enhanced incongruent weathering, in response to temperature cooling. The minor variation of clay δ7Li at 11 – 2 ka likely indicate stable weathering and mile climate variation. Over the last 2 kyr, the fluctuation of clay δ7Li is mostly caused by intensification of human activities. In summary, this thesis sheds new lights on the weathering-climate feedback over geologic past, and provides perspectives on how human activities affect natural processes
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Trentesaux, Alain. "Enregistrement de processus sédimentaires pléistocènesExemples de plates-formes détritiques et de bassins profondsMer du Nord et mers de Chine." Habilitation à diriger des recherches, Université des Sciences et Technologie de Lille - Lille I, 2005. http://tel.archives-ouvertes.fr/tel-00140889.
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De leur source continentale à leur lieu de stockage ultime, les particules sédimentaires détritiques vont être produites en fonction de la nature et de l'intensité des processus continentaux : climat, contexte géodynamique. Sur les plates-formes, elles vont subir l'action des agents hydrodynamiques, vont se déplacer, constituer des corps sédimentaires qui seront préservés ou non selon la nature et l'intensité des processus : agitation s.l., apports sédimentaires, création d'espace par subsidence et variation du niveau marin... Enfin, dans les domaines océaniques profonds, elles vont se déposer.<br />L'objectif des travaux présentés dans ce mémoire est, par une approche sédimentologique, de reconstituer les conditions environnementales, tant sur les continents que sur les plates-formes, ayant conduit aux dépôts étudiés. Sur cette base, nous avons entrepris des études sur des dépôts du Pléistocène en mer du Nord ainsi que dans les mers de Chine de l'Est et du Sud. Cette époque, par sa proximité, permet des études à très haute résolution temporelle tandis qu'elle est caractérisée par des oscillations climatiques et eustatiques importantes et rapides. De plus, les dépôts les plus récents portent la trace de l'Homme.<br />Sur la plate-forme, l'étude des grands corps sableux, bancs et très grandes dunes, a permis de préciser les mécanismes de leur mise en place. A court terme, même dans les environnements dominés par la marée, l'importance de phénomènes sporadiques tels que les houles de tempêtes, a été démontrée. Ils impriment aux formes et à la structure des fonds marins leur marque tandis que les agents tidaux sont les pourvoyeurs du matériel sédimentaire. A plus long terme, ce ne sont plus les agents dynamiques qui conditionnent la préservation des corps sédimentaires mais la création d'espace disponible et l'importance des apports sédimentaires. Au niveau de l'estuaire de l'Authie, des séries de carottages nous ont aidé à mesurer les conséquences du mouvement vers le nord des divers ensembles sédimentaires sur le type de sédiment rencontré ainsi que sur les modifications d'un espace naturel convoité par l'Homme.<br />Dans les bassins profonds, en mer de Chine du Sud, nos études ont permis de préciser les sources du matériel sédimentaire et son transport en faisant la part des contributions éolienne, fluviatile et marine. L'étude des caractères sédimentologiques de la fraction détritique a permis également d'étudier la balance ntre l'érosion et l'altération sur les zones émergées ainsi que de voir quelle est la réponse des marqueurs détritiques aux changements climatiques globaux depuis 2 millions d'années.
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Webley, James A. C. "The ecology of the mud crab (Scylla serrata): their colonisation of estuaries and role as scavengers in ecosystem processes." Thesis, Griffith University, 2008. http://hdl.handle.net/10072/367091.
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Scylla serrata is a portunid crab which can attain a weight of over 2 kg and a carapace width exceeding 250 mm. It is distributed throughout the Indo-West Pacific extending down the east coast of Africa, and both the east and west coasts of Australia. In Australia it is commonly known as the mud crab because it occurs within muddy, mangrove-lined bays and estuaries. Mud crabs are generalist predators eating most small, slow moving animals which they can catch, but they are also vigorous scavengers. Being scavengers, they are readily caught in baited traps set by commercial and recreational fishers, and are the stock for these popular fisheries. Female crabs spawn offshore and larvae spend a period in the plankton where they develop into postlarvae or megalopae...<br>Thesis (PhD Doctorate)<br>Doctor of Philosophy (PhD)<br>School of Environment<br>Science, Environment, Engineering and Technology<br>Full Text
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Mahamod, Yusuff. "Sedimentary processes in the Dwyryd Estuary." Thesis, Bangor University, 1989. https://research.bangor.ac.uk/portal/en/theses/sedimentary-processes-in-the-dwyryd-estuary(ca0aea23-480c-4032-ba10-12a9adee740c).html.
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This study aims to describe and quantify the important sedimentary processes which control the dispersal and accumulation of sediment in the Dwyryd Estuary, adjacent to Tremadog Bay in West Wales. It is shown that sedimentation in the estuary is dominantly control by fast tidal currents, and in the bay by weak tidal currents. Landward transport of coastal sediments by tidal currents is the residual sediment transport path. The spatial distribution of textural parameters of the estuarine sediments is related to the strength of tidal currents as well as the morphology and bathymetry of the study area. The estuarine sediments, predominantly sand, are very similar in texture and mineralogy to the adjacent beach sediments but markedly different to the river sediments. However, the beach sediments are slightly coarser and more poorly sorted than the estuarine sediments. In contrast, sediment in the deeper parts of Tremadog Bay are finer than both the estuarine and beach sediments due to the presence of substantial admixture of mud. The grain size distributions of most of the sediments are neither lognormal nor log-hyperbolic reflecting the great variability of hydrodynamic conditions in the study area. Using previously published flume data, a new sediment transport rate formula in the form of a power law has been developed for computation of total sediment load from the bed mean grain size and flow parameters: Uc The exponent n varies from 2.7 (for 0.93 mm sand) to 4.18 (for 0.19 mm sand). This is in contrast to the Bagnold (1966) formula which regards the exponent value (equal to 3) as constant for all grain sizes. Sediment transport patterns depend on the asymmetry between flood and ebb tidal currents due to distortion of the tidal wave on entering the estuary. Estimates of sediment budgets from surveyed profiles suggest that large amounts of sand have been transported from coastal areas into the estuary, supporting the mineralogical evidence. The estimates are of the same order of magnitude as estimates using flow velocity data and the above sediment transport formula.
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Mendes, Renato Paulo dos Santos. "The Douro estuarine plume: detection, processes and dynamics." Doctoral thesis, Universidade de Aveiro, 2016. http://hdl.handle.net/10773/17073.
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Doutoramento em Física<br>O Douro é um dos maiores rios da Península Ibérica, constituindo a maior descarga de água
doce para o Oceano Atlântico na costa noroeste portuguesa. A sua pluma estuarina tem
particular relevância na dinâmica costeira e na modulação de fenómenos biogeoquímicos. São
objetivos desta dissertação contribuir para a compreensão dos processos físicos associados
à geração e propagação da pluma estuarina do Rio Douro no oceano, assim como para o
conhecimento dos seus padrões de dispersão e da forma como estes alteram a hidrologia
e a circulação costeira, considerando os agentes forçadores típicos deste fenómeno (caudal
fluvial, vento e maré) e índices climáticos relevantes. Para concretização destes objetivos
foram desenvolvidas e aplicadas metodologias inovadoras de processamento de dados de
deteção remota, assim como novas implementações estuarinas e costeiras de modelos
numéricos. Através de imagens MODIS, otimizadas para o estudo de fenómenos costeiros,
efetuou-se uma deteção rigorosa da pluma. Identificou-se uma relação entre o sinal túrbido
nLw555 e o caudal, demonstrando-se este produto como um bom proxy para a observação
da pluma no oceano. As escalas temporais e espaciais da pluma foram caraterizadas através
destas imagens, combinadas com dados de caudal fluvial, maré, vento e precipitação, e
também com índices climáticos relevantes. Para compreender a propagação da pluma e
caracterizar a sua dinâmica e impacto na circulação costeira, foi desenvolvida uma aplicação
3D de modelos estuarinos e costeiros com malhas aninhadas de resolução variável. Definiramse
e analisaram-se diferentes cenários de vento e descarga fluvial. A interação da pluma do
Rio Douro e do Minho foi ainda analisada através dos resultados de simulações baseadas num
evento de inverno. Os compósitos túrbidos mostraram que a pluma é facilmente detetada
quando o caudal é maior que 500 m3 s1. A descarga fluvial e o vento são os principais
forçadores da sua propagação, enquanto a maré é apenas importante na região próxima à
embocadura do estuário. Observaram-se relações a uma escala interanual entre a turbidez da
pluma e os índices climáticos East Atlantic e NAO, com uma correlação máxima identificada
com 1 e 3 meses de desfasamento, respetivamente. Com base nos resultados das simulações
efetuadas, a pluma é classificada como de larga escala e de adveção superficial, apresentando
características de uma pluma prototípica. Em condições de caudal moderado a elevado, a
descarga estuarina é suficiente para gerar uma corrente costeira para norte sem ação do
vento. Em eventos de ventos leste, a propagação da pluma é similar ao caso sem vento,
com um aumento da velocidade da corrente. Uma corrente costeira para sul é unicamente
identificada sob condições de forte vento de oeste. Ventos de norte tendem a estender
a pluma para o largo, com uma inclinação na direção sudoeste, enquanto ventos de sul
intensificam a corrente para norte, sendo a mistura das plumas do Douro e do Minho uma
consequência possível. A análise desta interação apontou a contribuição do Douro como
importante na estabilização da WIBP e nas trocas de água entre o oceano e as Rias Baixas.
A interação da pluma do Douro com estuários localizados a sul da sua foz e a confirmação in
situ da recirculação observada nos resultados numéricos afiguram-se como temas relevantes
para investigações futuras.<br>The Douro is one of the largest rivers of the Iberian Peninsula, representing the most
important freshwater input into the Atlantic Ocean (on the northwestern Portuguese coast).
Its estuarine plume has particular relevance on coastal dynamics and biogeochemistry. The
main goal of this dissertation is to contribute to increase knowledge on physical processes
associated with the generation and propagation of the Douro estuarine plume. The general
patterns of dispersion in the ocean and how the plume change hydrography and coastal
circulation were also evaluated, considering the typical drivers involved (river discharge, wind
and tide) and relevant climate indices. Innovative methodologies to process remote sensing
data, as well as new implementations of high-resolution estuarine and coastal numerical
models have been developed and applied. The plume was detected through MODIS images,
optimized for coastal studies. The relation between the turbid nLw555 signal and river
discharge was identified, demonstrating that this product is a good proxy for the observation
of the Douro estuarine plume in the coastal ocean. An interconnected approach, combining
these images, river discharge, tide, wind and precipitation data, as well as relevant climate
indices, was used to study the temporal and spatial scales of the plume. The implementation
of estuarine and coastal models with nested domains of variable resolution was developed
to understand the plume propagation and characterize its dynamics and impact on coastal
circulation. Using these applications, different scenarios of wind and river discharge were
defined and analysed. The interaction of the Douro and the Minho estuarine plumes was
further evaluated through simulations based on a winter event. Turbid composites showed
that the plume is easily detected when river discharge is greater than 500 m3 s1. River
discharge and wind are the main driver acting on the plume propagation, whilst tidal effect is
only important near the estuary mouth. A relation between turbid plume and climate indices
East Atlantic (EA) and North Atlantic Oscillation (NAO) was observed at inter-annual scale,
with a maximum correlation identified at 1 and 3-month lags, respectively. The Douro
estuarine plume is classified as large-scale and surface-advected, presenting characteristics
of a prototypical plume, based on the results of the numerical simulations. The estuarine
outflow is sufficient to generate a northward coastal current without wind action under
moderate-to-high river discharge conditions. Under easterly winds, the propagation pattern
is similar to the case without wind forcing, with a slight increase in the northward current.
A southward coastal current is only generated by strong westerly winds. Under upwellingfavourable
winds, the plume extends offshore with tilting towards southwest. Southerly
winds increase the velocity of the northward current, being the merging of the Douro and
Minho estuarine plumes a likely consequence. The analysis of this interaction pointed out
the Douro as an important contributor to the WIBP stabilization and in the water exchange
between ocean and Rias Baixas. The interaction of the Douro estuarine plume with estuaries
located south of its inlet and the in situ confirmation of the re-circulation bulge observed in
numerical results seem as relevant for future research topics.
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Marion, Claire. "Processus de sédimentation fine en domaine estuarien macrotidal : approche trans-disciplinaire et multi-échelles : application à l'estuaire de l'Authie, Nord de la France." Littoral, 2007. http://www.theses.fr/2007DUNK0188.
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Les mécanismes contrôlant la dynamique des sédiments fins en milieu estuarien sont complexes du fait de la multiplicité des processus en action et de leurs interactions diverses et encore souvent mal comprises. L’étude de la dynamique des sédiments fins regroupe quelques uns des enjeux environnementaux fondamentaux. En raison de leur forte affinité avec une large gamme de contaminants métalliques et organiques, les particules fines sont en mesure de concentrer la pollution provenant à la fois du bassin versant et du milieu marin et dont les risques respectifs sont croissants (agriculture, trafic maritime…). Leur accrétion mène à la formation de vasières puis à l’édification de marais maritimes, habitats d’importance communautaire au niveau européen. La pérennité de ces espaces ainsi que la biodiversité et la maintenance des ressources qu’ils contiennent sont cependant menacées par le comblement général des estuaires. Les travaux effectués lors de cette thèse ont permis de dégager quelques points clefs du fonctionnement d’un estuaire co-dominé par la houle et la marée en soulignant notamment les interactions entre les différents processus. Ils ont également permis d’appliquer un ensemble d’outils et de croiser les regards scientifiques par le biais d’une méthodologie transdisciplinaire. Les études à l’échelle de la marée ont mis en évidence l’influence significative mais restreinte de la houle au domaine d’embouchure, la mixité des masses d’eau et la présence d’un maximum de turbidité résultant d’un jeu d’asymétrie de la marée. Cette pompe tidale est en mesure de redistribuer les sédiments très largement au sein de l’estuaire, notamment par le biais de macroflocs. Les interactions entre la morphologie et les asymétries de marées sont complexes et, à travers le transport résiduel engendré, conditionnent l’évolution du système estuarien. La dynamique tidale est particulièrement bien enregistrée à travers la nature des dépôts et leurs rythmicité. Les suivis ont montré une constante disponibilité des MES dans les masses d’eau et le rôle clef de vecteur des chenaux de marée. Les apports de sédiments sur les zones intertidales se font ensuite selon les niveaux altimétriques. Les différents résultats ont mis en évidence l’importance de la spartine dans les mécanismes de piégeage des sédiments sur les marais salés et leur variabilité saisonnière mais également les répercussions que pouvaient avoir les forts taux de sédimentation sur les biocénoses benthiques à moyen terme. Sur une échelle plus longue, nous avons pu envisager les conséquences en termes d’élévation de cette accumulation en soulignant l’effet de la compaction du profil sédimentaire. Le volet stratigraphique, prenant en compte les conclusions de l’histoire holocène de la plaine maritime flamande, confirme le stade de comblement avancé de l’estuaire. Les recherches sur l’estuaire de l’Authie sont susceptibles de déboucher sur un modèle d’estuaire à dominance hydrodynamique mixte marée-houle, pertinent pour des estuaires macrotidaux tempérés situés dans des domaines à forte disponibilité en sables et répondant à ces critères hydrodynamiques (estuaire de la Manche). Les perturbations d’ordre climatique et la variabilité naturelle qui s’amorcent dans le cadre du changement global s’accompagnent d’une pression humaine de plus en plus forte sur les espaces estuariens. Ces risques devront nous obliger à appréhender les écosystèmes estuariens de manière holistique en les replaçant au niveau régional de la Manche mais également dans le contexte mondial<br>The mechanisms controlling fine sediments dynamics in estuaries are complex because of the multiplicity of active processes and their diverse interactions, most often not well understood. The study of fine sediment dynamics embodies a number of fundamental environmental issues. Due to their strong affinity with a large range of metallic and organic contaminants, fine-grained deposits are capable of concentrating pollutants from watersheds and from the sea, both of which are sources of increasing coastal zone hazards (from agriculture, maritime traffic. . . ). Accretion of estuarine deposits leads to mudflat formation, and then salt marsh establishment, thus forming habitats of supreme importance in the European community. The lasting biodiversity and resource value of these habitats are at risk from accelerated estuarine infilling. The objective of this thesis has been to highlight key points of the functioning of an estuary co-dominated by waves and tides, and to gain better insight into the interactions underlying fine-grained sedimentation processes. The approach is highly methodological, based on the application of a cross-disciplinaryassemblage of tools. The study shows that wave influence, though significant, is restricted to the esturary mouth. The esturary exhibits freshwater/salinity mixing and the presence of a turbidity maximum resulting from a combination of tidal asymmetries. This tidal pumping is capable of very widely redistributing the sediment within the estuary, notably via macrofloc dynamics. Interactions between tidal asymmetry and morphology are complex and, through generated residual transport, condition the evolution of the estuarine system. The tidal dynamics are particularly well recorded by the characteristics of deposited sediments and their clear rhythmic pattern. The monitoring has shown the constant availability of sediment in the water column and the key role of tidal channels as vectors of sediment circulation. The input of sediment over the intertidal zones is governed by elevation within the tidal frame. The different results have highlighted the importance of Spartina in sediment trapping mechanisms over salt marshes and their seasonal variability but also the medium-term impacts of high sedimentation rates on benthic biocoenoses. At longer timescales, investigation of the consequences of this accretion highlights the effect of compaction of the sedimentary profile. The stratigraphic input from this work takes into account conclusions from the Holocene history of the neighbouring Flemish coastal plain, and confirms the advanced stage of infilling of the Authie esturay. The research on the Authie estuary may be summarised by a model of an estuary with mixed wave-tide hydrodynamic dominance pertinent to temperate macrotidal estuaries located in sand-rich tidal seas with storm wave influence, which is precisely the case of English Channel estuaries. Climatic perturbations and natural variability initiated within the frame of global change result in increasing human pressures on estuaries, thus generating potential risks. Tacking these pressures and risks calls for a holistic approach to the study of estuarine ecosystems, not only at the regional scale of the English Channel, but also in the world context
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Coffey, Michael. "The behaviour of trace metals in the Humber Estuary, U.K." Thesis, University of East Anglia, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240991.
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Dyson, Kirstie Elizabeth. "Biodiversity and ecosystem processes in heterogeneous environments /." St Andrews, 2008. http://hdl.handle.net/10023/698.
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Souza, Rogério Riker de. "Modelagem numérica da circulação de correntes de maré na Baía de Marajó e Rio Pará (PA)." Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/3/3147/tde-19092006-154712/.
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A região amazônica possui uma vocação natural para a navegação, uma vez que os rios desempenham um papel preponderante, sendo em muitos casos as únicas alternativas de transporte e comunicação. O trabalho se insere nesse cenário, tendo como objetivo maior a sistematização do conhecimento a respeito da circulação de correntes de maré na Baía de Marajó e Rio Pará (PA), com foco na Área Portuária de Vila do Conde. O melhor entendimento sobre as correntes de maré será um elemento importante para o planejamento portuário e hidroviário interior, além de propiciar um incremento na segurança e otimização nas operações portuárias. A sistematização da circulação das correntes de maré na área de estudo foi implementada através de modelagem numérica com a utilização do software MIKE21 HD de autoria do DHI, consistindo basicamente em um modelo bidimensional verticalmente integrado. Como subsídio à programação numérica, foi realizada uma revisão bibliográfica a respeito dos principais temas relacionados: correntes, maré e vento, bem como foram levantadas as principais bases de dados da região, utilizados na calibração e validação do modelo numérico. Em razão da escassez de dados disponíveis a calibração foi executada com dados do Porto de Vila do Conde, por meio de medições de intensidade e direção das velocidades das correntes nos anos de 1991 e 2001. A validação foi realizada através da Carta de Correntes de Maré, com ponto específico na Baía de Marajó. O programa mostrou-se consistente e aplicável à realidade, permitindo desta forma a obtenção de Cartas de Correntes de Maré para toda a área de estudo, bem como para a área foco.<br>In the amazonic region, navigation is the natural and leading, in some cases the only one possibility, role in the transportation network. In this scenario, the thesis has the main purpose of consolidating the knowledge about tidal currents pattern in Marajó Bay and Pará River (PA), considering Vila do Conde Harbour as the most important study area. A best knowledge about the tidal currents will be an important factor for port and waterway planning, contributing to increase the port operation safety and development. The tidal currents pattern was consolidated through numerical modelling using DHI MIKE 21 HD software, which is a bidimensional vertically integrated model. A bibliographical review was carried out about correlated themes: currents, tides and winds, and also was made a data base research, which was used in the numerical model calibration and validation. Due to the few data obtained, calibration was performed with Vila do Conde Harbour data, using current intensity and directions obtained in 1991 and 2001 surveys. The validation was performed using the Tidal Currents Chart, for a point in the Marajó Bay. The software results showed a consistent fit to the real condition, which made possible to get a Tidal Currents Chart of the whole area and for the focus area.
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Al-Enezi, Eqbal Hussain. "Modelling of phosphorus adsorption processes in estuarine and coastal water." Thesis, Cardiff University, 2011. http://orca.cf.ac.uk/54203/.
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This study consists of three parts: (i) Field work and data collection from the Loughor and Severn Estuaries. P adsorption increased with decreasing median sediment size in both estuaries. A positive correlation was found between the P adsorption in sediment and salinity in the Loughor Estuary, whereas a negative correlation was found in the Severn Estuary. Some factors, such as particle grain size, salinity, pH, organic matter, suspended sediment concentration and P concentration were found to control the exchangeable or loosely sorbed P (adsorbed P) in both estuaries. (ii) Laboratory experiments were conducted on P adsorption/desorption on different types on sediment, including Kaolinite, Silica, mud, silt, sand and suspended sediment. P adsorbed to the mud fraction than to the sand fraction. The adsorption coefficient (K<sub> d</sub>) and Maximum P adsorption (PS<sub>Max</sub>) for the mud fraction were 0.0091/g and 0.39 mg/g for the silt 0.007 l/g and 0.30 mg/g and the sand 0.001 l/g and 0.05 mg/g. (iii) Flume experiments were conducted in the hydraulic laboratory at Cardiff University, U.K. The main findings revealed that the velocity and the P concentrations in the water were important factors controlling the amount of P adsorbed processes on the sediment. The results from the field work and the laboratory experiments were similar to flume channel findings. These findings were used to develop new source term equations and these equations were added to the QUAL2E water quality model to improve the capability of the model to predict the P adsorption processes in a 2D computer model. These new equations were then used to simulate P concentrations in the estuarine environment using DIVAST.
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Abril, Gwenaël. "Dynamique du carbone dans les estuaires européens : processus de minéralisation et transfert continent-ocean-atmosphère." Bordeaux 1, 1999. http://www.theses.fr/1999BOR10577.
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Les transferts de carbone entre le continent, l'océan et l'atmosphère sont étudiés dans dix estuaires européens. Une grande partie du carbone organique (COrga) transporté par les fleuves est minéralisée dans les estuaires. Cette minéralisation qui affecte principalement la fraction particulaire est conditionnée par l'origine (phytoplancton fluviatile, rejets anthropiques, sols) et la labilité de ce COrga et le temps de résidence des particules. Les processus de minéralisation sont étudiés en détail dans deux estuaires macrotidaux. Dans la Gironde (France), les cycles de dépôt et de remise en suspension de crème de vase, aux échelles de temps tidale et lunaire, soumettent les matières en suspension à des oscillations oxique/anoxique. La matière organique particulaire est alors minéralisée alternativement par la respiration aérobie, la dénitrification et la réduction des oxydes métalliques. Dans la crème de vase, une dissolution de carbonate de calcium réduit significativement la quantité de CO₂ produite par la respiration, et la dénitrification produit de l'oxyde nitreux. Dans la zone hypoxique et très polluée de l’Escaut (Belgique, Pays-Bas), les processus d'ammonification, de nitrification et de dénitrification modifient les équilibres du système du carbone inorganique dissous par les échanges de protons qu'ils induisent. Les flux de CO₂ vers l'atmosphère mesurés sur les dix sites permettent d'estimer l'émission estuarienne européenne totale à 30-60. 10⁶ tC. An⁻¹, soit entre 5 et 10% des émissions industrielles du continent. Du fait d'une ventilation physique de CO₂ apporté par les fleuves, l'émission estuarienne de CO₂ excède la minéralisation de COrga. D'un estuaire à l'autre, les composantes du flux de CO₂ atmosphérique (activité hétérotrophe, nitrification, dissolution des carbonates et ventilation physique), varient fortement en fonction des caractéristiques des bassins versants et du temps de résidence<br>The transfer of carbon between the continent, the ocean and the atmosphere is investigated in ten European estuaries. A major fraction of the organic carbon (COrga) transported by rivers is mineralised in estuaries. This mineralisation affects in majority the particulate fraction and depends on the origin (fresh water phytoplankton, anthropogenic loads and soils) and the lability of this COrga and the residence time of particles. Mineralisation processes are investigated in two macrotidal estuaries. Ln the Gironde (France) because of fluid mud settling and resuspension cycles at tidal and neap-spring time scales, particulate material experiences oxic/anoxic oscillations. Particulate organic matter is mineralised alternatively by aerobic respiration, denitrification and metal-oxides reduction. Ln the fluid mud, a carbonate dissolution significantly reduces the quantity of CO₂ produced by the respiration and denitrification produces nitrous oxide. Ln the hypoxic and highly polluted area of the Scheldt (Belgium, the Netherlands), ammonification, nitrification and denitrification processes modify the equilibrium between the chemical species of dissolved inorganic carbon by producing and consuming protons. The CO₂ fluxes from the water to the atmosphere measured in the ten studied sites allow an estimation of the total European estuarine emission of 30-60. 10⁶ tC. Year⁻¹, corresponding to 5-10% of the anthropogenic emissions from the continent. Because of a physical ventilation of CO₂ carried by rivers, the estuarine·emission exceeds the mineralisation of COrga. From one estuary to the other, the origin of the total CO₂ atmospheric flux (heterotrophic activity, nitrification, carbonate dissolution and physical ventilation) appear to be very different, according to the characteristics of the hydrological basin and the residence time
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MacDonald, Daniel George 1970. "Mixing processes and hydraulic control in a highly stratified estuary." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/16902.
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Thesis (Ph. D .)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2003.<br>Includes bibliographical references (p. 207-214).<br>This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.<br>This thesis utilizes field data from the Fraser River Estuary, a highly stratified system located in southwestern British Columbia, Canada, to investigate the nature of mixing processes in a highly stratified environment, and to extend two-dimensional hydraulic theory to a three dimensional environment. During the late ebb, a stationary front exists at the Fraser mouth. Although densimetric Froude numbers in the vicinity of the front are supercritical in a frame of reference parallel to the local streamlines, the front itself is oriented such that the value of the Froude number is equal to the critical value of unity when taken in a frame of reference perpendicular to the front. This observation presents a robust extension of established two-dimensional, two-layer hydraulic theory to three dimensions, and implies similarity with trans-sonic flows, in that a Froude angle can be used to identify critical conditions in a manner similar to the Mach angle. Mixing processes were evaluated at the mouth during the late ebb using a control volume approach to isolate mean vertical entrainment processes from turbulent processes, and quantify the vertical turbulent salt and momentum fluxes. Observed turbulent dissipation rates are high, on the order of 10-3 m2s-3, with vertical entrainment velocities on the order of 2 x 10-3 m s' . Mixing efficiencies, expressed as flux Richardson numbers, are confined within a range from 0.15 to 0.2, at gradient Richardson number values between 0.2 and 0.25.<br>(cont.) These results are consistent with previous laboratory studies, but represent energetic conditions that are several orders of magnitude higher. In the estuarine channel, the variability of mixing processes was investigated through the tidal cycle using control volume and overturn scale methods. Spatially, mixing was observed to be more intense near a width constriction on the order of 25%. Temporally, more dominant mixing was observed during ebbs, due to increases in both vertical shear and stratification. Mixing is active and important throughout the tidal cycle, and was found to be the dominant process responsible for removing salt from the estuarine channel during the ebb.<br>by Daniel George MacDonald.<br>Ph.D .
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Thurston, William. "Turbulence as a mediator of processes in a macrotidal estuary." Thesis, University of Leeds, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.515412.
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Kenny, Carolyn. "Nitrogen transformation processes and nitrous oxide evolution in estuarine intertidal zones." Thesis, Royal Holloway, University of London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.417365.
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Smar, Daina. "An assessment of ecological processes in the Apalachicola estuarine system, Florida." Master's thesis, University of Central Florida, 2012. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5506.
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The following is a compilation of field data collected in 2011 and 2012 in Apalachicola, FL as part of a five year study assessing the ecological effects of sea level rise in the northern Gulf of Mexico. Many coastal communities, both natural and developed, will soon be working to mitigate the effects of sea level rise, if they are not already doing so. This thesis investigates the natural patterns of the Apalachicola estuarine system through the collection and analysis of in situ water, sediment, and biomass samples. Additionally, results of the field samples are presented and recommendations for additional sampling are given. The field methods and procedures developed in this study were designed to be repeated in other estuaries to build upon the work that has been conducted in Apalachicola. Water samples were tested for total suspended solids (TSS) and compared against hydrodynamic (tidal circulation and streamflow) and meteorological (wind and precipitation) characteristics. Streamflow was determined to influence a seasonal base level concentration of TSS. Wind strength and direction consistently influenced small TSS concentration fluctuations, an effect amplified by the shallow nature of the estuary. Tidal circulation appeared to have minor influences on TSS concentration fluctuations within the base level concentration range. Precipitation appeared to influence large TSS concentration fluctuations; however, due to limited data collection during storm events, more data is required to conclusively state this. Sediment cores throughout the lower Apalachicola River revealed that coarse particles settled out in upstream areas while fine particles tended to stay in suspension until low energy areas in the lower portions of the river or marsh system were reached. Finally, biomass samples were used to develop regression models utilizing remotely sensed data to predict biomass density in marsh areas with unprecedented accuracy. The documented patterns of this system are to be used as inputs and validation points to update an existing hydrodynamic model and to aid in the coupling and development of sediment transport and marsh equilibrium models. The field campaign developed and implemented here provides a foundation for this novel coupled modeling effort of estuarine systems. From the 2011 and 2012 sampling conducted, it is apparent that Apalachicola can be modeled as a closed system with river inflow and sediment influx as boundary conditions. Forcing local conditions should accurately represent the system. Ultimately, these models will be used to simulate future sea level rise scenarios and will provide useful decision making tools to coastal managers. Future work will include replicating water sampling in subsequent wet and dry seasons in Apalachicola, FL to confirm observed trends, in addition to implementing this sampling in Grand Bay, MS and Weeks Bay, AL. Additional biomass samples will be taken to validate the strong correlations found between remotely sensed data and in situ samples. In similar studies, it is recommended that water samples be taken to adequately represent influences from tidal cycles and riverine inflow. It is also recommended that spatially distributed biomass samples be taken to validate regression models.<br>M.S.<br>Masters<br>Civil, Environmental, and Construction Engineering<br>Engineering and Computer Science<br>Civil Engineering; Water Resources Engineering
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Mhashhash, Aisha Fowzi. "Laboratory and numerical modelling studies of sediment flocculation processes in estuaries." Thesis, Cardiff University, 2018. http://orca.cf.ac.uk/114776/.
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Surface water is one of the fundamental parts of the environment and needs to be protected from all pollution sources for human survival. Urban development and human activities have increased the contamination of coastal and estuarine water due to insufficiently treated sewage, runoff from fertilised agricultural area and lawns and releasing industrial pollutant directly into river and estuaries. Cohesive sediment in estuaries can act as either a source or a sink of many pollutants, such as nutrients and heavy metals. Understanding the interactions between sediment and nutrients in water bodies is important because high input rates of nutrients can negatively affect water quality. The prediction of both deposition and the resuspension of cohesive sediment in estuaries supports the understanding of their turbidity, which is important in terms of the biomass of these water bodies and many of the occurring biochemical processes and the morphological processes, which determine the suitability and maintenance of fairways and harbour basins. The complex ways in which hydrodynamic and biochemical parameters affect cohesive sediment are primary reasons for the poor representation of the deposition, erosion and settling of cohesive sediment processes in modelling tools within water estuaries. However, our current understanding regarding the accurate prediction of cohesive sediment transport processes is insufficient because of flocculation processes which occur under certain circumstances (e.g. the increase of salinity in the brackish zone of rivers, which leads to the formation of flocs that are both larger and less dense than individual particles). The phenomenon of flocculation is known to play a significant role in the sediment transport processes of settling, deposition and erosion of cohesive sediment. There is no unique equation that can be universally used to predict the deposition and suspension rates of cohesive sediment because each estuary is dynamically and physically different from another and this is particularly true for the highly dynamic estuary e.g. Severn Estuary. Therefore, this study focuses on gaining a better understanding of the transport processes of cohesive sediment, including a better inclusion of the flocculation processes by developing a new settling velocity equation for cohesive sediment including flocculation processes as a function of hydrodynamic parameters. It also aims to apply this equation to a numerical model IV and to test this refined model by simulating the flocculation phenomenon in the highly dynamic Severn Estuary. This study employed an extensive experimental setup using a small scale particle image velocimetry (PIV) system. The experimental research was carried out using suspended sediment samples from the Severn Estuary in the UK. A PIV system and an image processing routine were used to measure both floc size distribution and settling velocity. The experimental results indicate that both the floc size and the settling velocity are controlled by the interaction between turbulence and salinity at salinities of less than 10 ppt. At a salinity either equal to or more than 10 ppt, both the floc size and the settling velocity were functions of only turbulent shear stress. The new equations were successfully applied in the Delft3D model; the model results show that they aptly were able to match with observed suspended sediment distributions throughout the estuary. Overall, the developed model can be regarded as a basic tool for being applied to help manage the suspended sediment processes in the Severn Estuary and for assessing the potential impact of climate change and human interference such as tidal renewable energy schemes in this water body.
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Boonphakdee, Thanomsak. "Sources of organic matter and its transportation processes in a tropical river-estuary : the Bangpakong estuary, Thailand." Kyoto University, 2007. http://hdl.handle.net/2433/136568.
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Kyoto University (京都大学)<br>0048<br>新制・課程博士<br>博士(農学)<br>甲第13401号<br>農博第1656号<br>新制||農||948(附属図書館)<br>学位論文||H19||N4297(農学部図書室)<br>UT51-2007-Q802<br>京都大学大学院農学研究科応用生物科学専攻<br>(主査)教授 藤原 建紀, 教授 山下 洋, 教授 縄田 栄治<br>学位規則第4条第1項該当
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Weaver, Andrew John. "Numerical and analytical modelling of oceanic/atmospheric processes." Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/27560.
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Two problems in oceanic/atmospheric modelling are examined in this thesis. In the first problem the release of fresh water from a midlatitude estuary to the continental shelf is modelled numerically as a Rossby adjustment problem using a primitive equation model. As the initial salinity front is relaxed, a first baroclinic mode Kelvin wave propagates into the estuary, while along the continental shelf, the disturbance travels in the direction of coastally trapped waves but with a relatively slow propagation speed. When a submarine canyon extends offshore from the estuary, the joint effect of baroclinicity and bottom relief provides forcing for barotropic flow. The disturbance now propagates along the shelf at the first coastally trapped wave mode phase speed, and the shelf circulation is significantly more energetic and barotropic than in the case without the canyon. For both the experiments with and without a canyon an anticyclonic circulation is formed off the mouth of the estuary, generated by the surface outflow and deeper inflow over changing bottom topography. As the deeper inflow encounters shallower depth, the column of fluid is vertically compressed, thereby spinning up anticyclonically due to the conservation of potential vorticity. This feature is in qualitative agreement with the Tully eddy observed off Juan de Fuca Strait. A study of the reverse estuary (where the estuarine water is denser than the oceanic water) shows that this configuration has more potential energy available for conversion to kinetic energy than the normal estuary. Bass Strait may be considered as a possible reverse estuary source for the generation of coastally trapped waves. Model solutions are compared with field observations in the Bass Strait region and with the results of the Australian Coastal Experiment. The effects of a wider shelf and a wider estuary are examined by two more experiments. For the wider shelf, the resulting baroclinic flow is similar to that of the other runs, although the barotropic flow is weaker. The wide estuary model proves to be the most dynamic of all, with the intensified anticyclonic circulation now extending well into the estuary.
In the second problem the effect of the horizontal structure of midlatitude oceanic heating on the stationary atmospheric response is examined by means of a continuously stratified model and a simple two level model, both in the quasigeostrophic β-plane approximation.
Solutions are obtained for three non-periodic zonal heating structures (line source, segmented cosine, and segmented sine). Little difference is observed between the solutions for these two different models (continuously stratified and two level). There are two cases which emerge in obtaining analytic solutions. In case 1, for large meridional wavenumbers, there exists a large local response and a constant downstream response. In case 2, for small meridional wavenumbers, the far field response is now sinusoidal. A critical wavenumber separating these two cases is obtained. The effect of oceanic heating on the atmosphere over the Kuroshio region is examined in an attempt to explain the large correlations observed between winter Kuroshio oceanic heat flux anomalies, and the winter atmospheric surface pressure and 500 & 700 mb geopotential heights, both upstream and downstream of the heating region. In both models, the response is consistent with the observed
correlations. When western North Pacific heating and eastern North Pacific cooling are introduced into the models, a large low pressure response is observed over the central North Pacific. This feature is in excellent agreement with the observed correlations. A time dependent, periodic, two level model (with and without surface friction) is also introduced
in order to study the transient atmospheric response to oceanic heating. The height at which the thermodynamic equation is applied is found to be crucial in determining the response of this model. When the heating is entered into the model near to the surface, unstable modes are prevalent sooner than they would be when the heat forcing is applied at a higher level. As in the steady state models, two cases dependent on the meridional wavenumber ɭ emerge in the analysis. For small scale meridional heating structures (large ɭ), the response consists of an upper level high and a lower level low which propagate eastward with time. For large scale meridional heating structures (small ɭ) the response essentially consists of a wavenumber 3-4 perturbation superimposed on the solution for large ɭ.<br>Science, Faculty of<br>Mathematics, Department of<br>Graduate
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Budi, Santoso Eko. "Tidal anomalies at river entrances and the physical processes which generate them /." St. Lucia, Qld, 2004. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe17707.pdf.
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Yannaccone, John A. "Numerical simulation of the effects of sea level rise on estuarine processes." Thesis, Virginia Polytechnic Institute and State University, 1987. http://hdl.handle.net/10919/50072.
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The increasing concentration of carbon monoxide and other gases in the earth’s atmosphere is expected to cause temperatures on earth to increase. This condition, known as the greenhouse effect, could cause the sea level to rise due to the partial melting of the polar icecaps and the thermal expansion of the oceans. Such a rise in the sea level would affect the tides, currents, and sediment and salinity distributions within estuaries.
To see the nature of these effects, a parametric study was performed on the Rappahannock River in Virginia with a two-dimensional, laterally averaged, time-dependent numerical model which simulates the movement of water and suspended sediment in the estuary. The model is a systematic sequence of mathematical procedures derived from the mass-balance equation and the equation of motion. These equations are solved through an explicit finite difference scheme.
The astronomical tide, the increased height of the sea level due to the greenhouse effect and the additional tidal height due to a storm surge form the boundary conditions at the mouth of the river. Freshwater streamflows constitute the boundary condition at the upstream end of the estuary. A frequency analysis is performed for both the freshwater streamflows and the tidal heights. A procedure is developed which allows one to calculate the return period for various combinations of streamflow and tidal height.
The results from each run of the estuary model are reviewed to study the tidal hydraulics and the longitudinal and vertical distributions of the sediment and salinity with and without the sea level rise.<br>Master of Science<br>incomplete_metadata
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PERUGINI, ELEONORA. "The Application of Video-Monitoring Data to Understand Coastal and Estuarine Processes." Doctoral thesis, Università Politecnica delle Marche, 2019. http://hdl.handle.net/11566/263695.
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La presente tesi riguarda l’uso dei dati raccolti da una nuova stazione di video monitoraggio, denominata SGS allo scopo di accrescere la conoscenza dei processi idro-morfodinamici caratteristici di una spiaggia sabbiosa naturale tipica della costa Adriatica, in prossimità di un estuario. La stazione è stata installata all’interno del porto di Senigallia e ogni ora registra un video di dieci minuti a 2Hz. In questa tesi, sono stati elaborati i video raccolti dal 2015 al 2017. Le immagini derivanti sono state utilizzate in due differenti analisi: 1) lo studio della capacità di stimare la batimetria applicando il codice cBathy (un algoritmo ampiamente utilizzato per la valutazione della profondità dell’acqua tramite analisi inversa) ai dati ottici provenienti dalla stazione e 2) lo studio della dinamica di un sistema di barre sommerse. La stima della profondità dell’acqua varia, in termini di qualità, in funzione della posizione spaziale e delle condizioni ondose e si è osservata una generale sottostima della profondità in gran parte del dominio. Si è quindi eseguita una dettagliata analisi per comprendere il motivo di tale risultato. La causa principale è stata attribuita al grande angolo presente tra l’asse ottico della telecamera e la direzione di propagazione delle onde incidenti. Dei test sintetici sono stati usati per analizzare più in profondità questo aspetto. La procedura utilizzata può essere applicata anche per il progetto di nuove stazioni di video-monitoraggio. Per quanto riguarda la seconda analisi, le immagini disponibili permettono di ben identificare la complessa variabilità 3D (commutazione e biforcazione) del sistema di barre sommerse, sottolineando la capacità della stazione SGS di monitorare le caratteristiche del fondale dell’area oggetto di studio. Tre principali ordini di barre sono stati identificati in accordo con gli studi precedenti basati su dati raccolti da indagini in situ e la loro migrazione è stata correlata con il clima ondoso. Durante il periodo analizzato, è stata riscontrata una generale stabilità del sistema di barre in risposta a eventi di tempesta con onde provenienti da NNE, mentre è stato osservato un netto movimento delle barre verso il largo durante l’unica tempesta con onde provenienti da ESE. Il diverso comportamento è stato collegato alla diversa orientazione delle onde e alla riflessione delle onde provenienti da ESE dal molo del fiume.<br>The present thesis concerns the application of the data coming from a new video-monitoring station, called SGS, to improve knowledge of the hydro-morphodynamic processes on a typical natural sandy beach near an estuary along the Adriatic coast (Italy). The SGS station was installed in the Senigallia harbour and collects ten minutes of full-frame images at 2Hz each hour. In this work, the videos of the period 2015-2017 have been post-processed. The elaborated images have been used to perform two different analyses: 1) the study of the capability of the SGS data to estimate the water depth using cBathy (a widely used algorithm for depth-inversion) and 2) the study of the dynamics of a multiple sandbars system. The results of the first analysis varied in quality as a function of the location and wave conditions and a general underestimation of the depth has been found in a large portion of the domain. A detailed debugging analysis was carried out to find the reasons of this poor performance. The main source of error was found to be the large angle between the camera viewing direction and the direction of propagation of the incident waves. A synthetic analysis was performed to analyse in depth this aspect. The synthetic procedure can be applied also to design future shore-based video monitoring stations. With reference to the second analysis, the complex 3D-variability (switching and bifurcation) of the multiple sandbars system has been recognized from the images, this highlighting the capability of the SGS station to monitor the seabed features of the study field. Three orders of bars have been identified, in agreement with previous studies based on data collected by in-situ surveys and their motion has been correlated with the wave climate. In the analysed period, a general stability of the bar system in response to storm events with waves coming from NNE has been found, while a net offshore migration has been observed under the only storm with waves coming from ESE. The different behaviour has been related to the wave direction and to the reflection of the ESE waves off the wall of the nearby river pier.
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Rouas, Guy. "Étude et modélisation par éléments finis des processus hydrosédimentaires estuariens." Compiègne, 1996. http://www.theses.fr/1996COMPD884.
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L'objet de ce travail a consisté à proposer et développer une gamme de modèles pour la simulation des processus hydrosédimentaires en estuaires. Dans une première partie, un modèle bidimensionnel vertical aux éléments finis résolvant les équations couplées de l'hydrodynamique, du transport du sel et des sédiments en suspension, et enfin de l'évolution des fonds soumis à l'érosion et au dépôt a été établi. La fermeture du système nécessite l'écriture de relations constitutives complémentaires exprimant les termes turbulents, la vitesse de chute moyenne du sédiment en fonction de sa concentration et les flux d'échange au fond notamment. Un ensemble de cas tests analytiques et comportementaux ont été traités afin de valider le modèle. La réalisation d'une campagne d'essais en laboratoire pour l'étude des phénomènes de transport d'une vase de Gironde en écoulements turbulents a permis d'établir les lois de vitesse de chute du matériau d'une part et de vérifier la capacité du code à reproduire, les phénomènes de stratification induits par les effets gravitaires d'autre part. Dans une deuxième partie, une étude théorique et expérimentale fondée sur l'approche des milieux diphasiques a été conduite pour l'étude du dépôt et de la consolidation des vases en eau calme. Un modèle monodimensionnel fournissant l'évolution de la distribution verticale des concentrations au cours du temps a ainsi été développé puis calibré à partir d'essais en colonne de sédimentation.
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Emptage, Matthew Robert. "Radionuclide distribution in relation to sedimentary processes in the Esk estuary, UK." Thesis, Lancaster University, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357310.
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Gomes, Filho Jose Gerardo Ferreira. "Pre- and post-settlement processes influencing the distribution of barnacles along estuarine gradients." Thesis, University of Plymouth, 2007. http://hdl.handle.net/10026.1/2409.
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Estuaries are the interface between freshwater systems and the sea, with clearly recognizable changes in the distribution of organisms along various environmental gradients from riverine to fully marine conditions. This thesis studied ecological processes affecting the distribution of marine species along estuarine gradients using both field and laboratory experiments with barnacles as a tractable model system. Elminius modestus Darwin, Semibalanus balanoides Linneaus, Chthamalus montagui Southward are the most common barnacle species found in the intertidal of British estuaries. Surveys performed in the Plym and the Yealm Estuaries revealed that E. modestus occurred furthest up estuaries and was dominant along most of their length, with the exception of sites closest to the sea; C. montagui had the most restricted degree of penetration up-estuary; and S. balanoides occurred at low abundances, with limits of penetration located between those of C. montagui and E. modestus. Transplants of adult specimens to sites along the marine-to-freshwater gradient revealed that E. modestus was better adapted to environmental conditions found in inner areas of the estuaries than C. montagui and S. balanoides. Survival of the latter two species was negatively correlated with deposition of silt and decreasing salinity. Laboratory experiments showed that, in contrast to the other two species, E. modestus was highly tolerant to burial by silt. A comparison of observed distributions along the gradients with survivability showed that C. montagui was able to survive in areas where adults were absent, indicating that early life cycle stages were a potential limiting factor to the distribution of this species. Examination of patterns of cyprid settlement and recruitment to the benthic phase reinforced the suggestion that pre-settlement processes contribute to restrictions in the distribution of both C. montagui and S. balanoides. The abundance of these species, post-settlement, was also affected by physico-chemical conditions in the upper estuary. Pre-settlement processes did not limit the distribution of E. modestus and post-settlement processes appeared to be more important in limiting its abundance at sites closest to the sea.
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Ali, Ayub. "Physical Processes of a Shallow Subtropical Estuarine System : Coombabah Lake, Gold Coast, Australia." Thesis, Griffith University, 2010. http://hdl.handle.net/10072/366810.
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Estuaries are of immense importance to many communities. It has been estimated that
60 to 80 % of commercial marine fishery resources depend on estuaries for part, or all
of, their life cycle. The characteristics of estuarine flow, water quality and sediment
conditions are important as they play a critical role in the functionality and health of
these systems. This study utilised both field data and numerical modelling technique to
help enhance our understanding of the physical processes of a very shallow subtropical
estuarine system.
This study first quantified various salt flux components within the shallow subtropical
estuarine system Coombabah Lake in Gold Coast, Queensland, Australia to better
understand the system’s physical processes for assisting future management decisions in
this ecologically and economically significant region. Residual water transport was
identified as the dominant factor influencing residual salt transport, which alternates
direction frequently.
This study then developed a new simple and robust traversing system to measure flow
properties within estuarine bottom boundary layers to estimate two important
parameters used in numerical modelling of aquatic systems: bed shear stress and bed
roughness height. Four commonly-employed techniques: (1) Log-Profile; (2) Reynolds
stress; (3) Turbulent Kinetic Energy; and (4) Inertial Dissipation used to estimate bed
shear stresses from velocity measurements were also compared. Bed shear stresses
estimated with these four methods agreed reasonably well; of these, the Log Profile
method was found to be most useful and reliable for the unstratified conditions studied.
A three-dimensional hydrodynamic model with unstructured meshes utilising the
MIKE3 FM modelling system and simulated the hydrodynamic regime was set up for
Coombabah Lake to assist with enhancing our understanding of the hydraulic properties
within this shallow sub-tropical estuarine system. The sensitivity of calibration
parameters of a very shallow estuarine model was also investigated. The model utilised
the hydraulic data collected by the newly developed traversing system and that collected
during the first part of the study used to examine salt flux dynamics. The hydrodynamic
regime of the lake was found to be favourable for settlement of suspended sediments.
The results also revealed that the correct bathymetry is the most important parameter for
accurate modelling, followed by appropriate bed roughness in the numerical scheme for
very shallow environments.
This study finally provided an understanding of the sediment dynamics within
Coombabah Lake and the surrounding waters. It utilised ten days of observed
hydrodynamic and sediment data and employed the three-dimensional model with
unstructured meshes utilising the MIKE3 FM modelling system. Sediment dynamics of
the lake were found to be dominated by advection process driven by tides with wave
and wind playing minor roles – even though the system was shallow. Simulation results
agreed well with field data and supported the aforementioned findings. Correlation
between TSS and turbidity was very poor; therefore, the employed automatic data
logging system (turbidity meters) was determined inappropriate for the estimation of TSS concentration in the very shallow subtropical estuarine system.<br>Thesis (PhD Doctorate)<br>Doctor of Philosophy (PhD)<br>School of Engineering<br>Science, Environment, Engineering and Technology<br>Full Text
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Geronilla, Kristina. "Re-presenting the Waterfront: revealing the intersection of human and natural processes." Thesis, Virginia Tech, 2004. http://hdl.handle.net/10919/35894.
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Water and waterfronts are appealing to almost any person, as a visitor or designer. This study challenges the author's design processes and understanding of the landscape as the sculpted meeting ground, intersecting human and natural physical processes. It progresses from assumptions through collaborated ideas of others in a literature review through case studies of various waterfront situations and finally to the design project of the Jones Point waterfront in Alexandria, Virginia. Here the intermingled aspects from cultural activities over time and local, physical movement of land by water are assessed to be revealed and enhanced for the visitor's benefit, use, and connection with place. For it is the author's belief that the landscape and space can be sculpted, experienced, and imagined for the purpose of connecting us to a larger framework of living systems on this planet and beyond. The design extends the city to the waterfront and vice versa with an understanding of both physical processes and cultural choices to the point of being unable to distinguish action from reaction.<br>Master of Landscape Architecture
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Narvaez, Diaz Carla. "Green urchin demography in a subartic ecosystem : patterns and processes." Doctoral thesis, Université Laval, 2018. http://hdl.handle.net/20.500.11794/33303.
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Dans les environnements littoraux de l’Atlantique Nord, les densités importantes d’oursin vert Strongylocentrotus droebachiensis ont entraîné la décimation des laminaires et l’apparition de grandes étendues dénudées où la biodiversité et les services écosystémiques sont fortement limités. Par contre, l’oursin vert a une grande valeur commerciale et son élevage en aquaculture représente une activité pour laquelle un intérêt grandissant est observé. Toutefois, il s’agit malheureusement d’une pêcherie ayant une évolution temporelle en dents de scie. Une gestion appropriée des populations d’oursins pourrait aider à atteindre un meilleur équilibre entre l’abondance de cette espèce et les laminaires. Ainsi, les laminaires pourraient recoloniser les zones d’où elles ont été complètement broutées par les oursins, ce qui améliorerait la qualité des oursins favorisant leur exportation. La présente thèse rassemble de l’information relative aux interactions écologiques et aux facteurs environnementaux déterminants la démographie des oursins à différentes échelles spatiales dans l’Estuaire et le Golfe du Saint-Laurent (EGSL, Canada). Dans l’EGSL, il n'y a aucun des mécanismes usuels de contrôle des populations d’oursins (prédation, mortalité en masse et pêche). Il en résulte que les oursins dominent les régions infra littorales depuis des décennies. Un inventaire extensif décrivant la structure des populations (c.-à-d., fréquences de la taille, abondance et biomasse) à plusieurs échelles spatiales (c.-à-d., profondeur, site) a montré une importante variabilité spatiale. La densité et la biomasse mesurées dans l’EGSL sont parmi les plus importantes rapportées pour cette espèce. De plus, les laminaires sont limitées aux sites exposés et peu profonds. Une étude faite en mésocosme sur le terrain couplée à une expérience comportementale a montré que la compétition intraspécifique déterminée par la taille joue un rôle important sur la structure des populations via la réduction du taux de croissance et de la production de gonades chez les petits individus, ainsi que sur leur comportement d’approvisionnement. Un changement ontogénique intéressant a été observé quant à l’importance relative du type de compétition, qui passe d’une combinaison d’interférence et d’exploitation chez les petits oursins à une compétition par exploitation seulement chez les oursins de taille moyenne. Finalement, nous avons évalué l’exactitude de la technique de sclérochronologie consistant à estimer l’âge des oursins à partir du compte des bandes de croissance observables sur leur squelette. Des expériences en laboratoire ont démontré qu’en plus d’une importante variabilité dans la déposition des bandes entre les différents composants du squelette, plusieurs facteurs de stress environnementaux (p. ex., apport alimentaire limité, périodes d’hyposalinité, température de l’eau) peuvent induire la déposition de bandes de croissance additionnelles. De plus, une revue de littérature a montré que malgré son utilisation fréquente, seule la moitié des études ayant eu recours à cette technique ont tenté de valider les prémisses sur lesquelles celle-ci est basée. Une analyse plus approfondie de la méthodologie de ces études révèle également que lorsque présentes, les études de validation étaient inadéquates. Ainsi, la sclérochronologie chez les oursins ne devrait pas être utilisée pour déterminer l’âge des individus sans qu’avant une méthode permettant de générer une estimation répétable, exacte et précise, à partir des bandes de croissance, ne soit élaborée. L’information récoltée dans le cadre des études démographiques a des applications écologiques importantes et permet d’améliorer les prédictions des modèles de dynamique des populations dans un monde en changement constant. Cette thèse fait avancer notre compréhension des caractéristiques individuelles intrinsèques, les interactions écologiques et les facteurs environnementaux associés à L’EGSL qui déterminent les processus (c.-à-d., taux de croissance des populations, mortalité) et les caractéristiques (c.-à-d., abondance, âge) démographiques chez l’oursin.<br>In North Atlantic nearshore environments, high densities of the green urchin Strongylocentrotus droebachiensis have led to the decimation of kelp beds and created extensive barren grounds with reduced biodiversity and ecosystem services. However, green urchins have a high commercial value, and there is a growing interest in aquaculture farming, but unfortunately, their extraction is a classic example of a boom - and - bust fishery. Correct management of urchin populations could thus help create a better equilibrium bet ween urchin populations and kelp beds, allowing the kelp to re-colonize places where it has been completely grazed by urchins and increasing the quality of urchins for export. This thesis collects information about the underlying ecological interactions and environmental factors that affect urchin demography at different spatial scales in the Saint Lawrence Estuary and Gulf (SLEG, Canada). In the SLEG there is no control of urchin populations by the usual means (i.e., predation, mass mortality and harvest), so subtidal environments have been dominated by urchin barrens for decades. An extensive survey across different spatial scales (i.e., region, depth, and site) revealed high variability in urchin population structure (i.e., size - frequency, abundance, and biomass). Density and biomass were among the highest recorded for this species, and kelp beds were limited to exposed shallow sites. Field-based mesocosm and behavioural experiments showed that size-asymmetric intraspecific competition may have an important role in structuring these populations by reducing the growth rate and gonad production of small urchins, as well as affecting their foraging behaviour. Interestingly, there is an ontogenetic change in the relative importance of the type of competition (i.e., interference and exploitative) as it moves from interference and exploitative in small urchins to only exploitative in medium urchins. Finally, we evaluated the accuracy of sclerochronology, a technique used to estimate urchin age that involves counting skeletal growth bands. Under laboratory conditions, several environmental stressors (e.g., food limitation, low salinity periods, water temperature) can induce the deposition of additional growth bands, and band deposition varies among different skeletal components. Moreover, a literature review showed that despite the common use of sclerochronology, only half of the studies that have used it have attempted to validate its basic assumptions, and of those, the methodology used for the validation attempts were judged inadequate for most studies. Thus, sclerochronology should not be used for aging urchins until it provides consistently accurate and precise interpretations of growth bands. Information collected in population demography studies has an important role in informing ecological applications and improving predictions of urchin population dynamics in a constantly changing world. This thesis greatly furthers our understanding of how individual intrinsic characteristics, ecological interactions and environmental factors interact in the SLEG to shape urchin population demographic processes (i.e., growth rates, mortality) and characteristics (i.e., abundance, age).
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Qu, Wenchuan. "Studies on nitrogen cycling processes in Lake Illawarra, New South Wales, Australia." Access electronically, 2004. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20050302.161641/index.html.
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Schneider, Suzanne Zvalaren Willey Joan D. "Mercury sources and cycling processes in the Cape Fear River estuary, North Carolina." Chapel Hill, N.C. : University of North Carolina at Chapel Hill, 2009. http://dc.lib.unc.edu/u?/etd,2906.
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Thesis (Ph. D.)--University of North Carolina at Chapel Hill, 2010.<br>Title from electronic title page (viewed Jun. 23, 2010). "... in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Marine Sciences." Discipline: Marine Sciences; Department/School: Marine Sciences.
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Bronikowski, Jason Lee. "Sedimentary environments and processes in a shallow, Gulf Coast Estuary-Lavaca Bay, Texas." Texas A&M University, 2004. http://hdl.handle.net/1969.1/1098.
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Sedimentation rates in sediment cores from Lavaca Bay have been high within the last 1-2 decays within the central portion of the bay, with small fluctuations from river input. Lavaca Bay is a broad, flat, and shallow (<3 m) microtidal estuary within the upper Matagorda Bay system. Marine derived sediment enters the system from Matagorda Bay, while two major rivers (Lavaca & Navidad) supply the majority of terrestrially derived sediment. With continuous sediment supply the bay showed no bathymetric change until the introduction of the shipping channel. Processes that potentially lead to sediment transport and resuspension within the bay include wind driven wave resuspension, storm surges, wind driven blowouts, and river flooding. These processes were assessed using X-radiographs, grain size profiles, and 210Pb and 137Cs geochronology of sediment diver cores. In six cores the upper 10 cm of the seabed has been physically mixed, where as the rest showed a continuous sediment accumulation rate between 0.84-1.22 cm/yr.
Sidescan sonar and subbottom chirp sonar data coupled with sedimentological core and grab samples were used to map the location and delineate the sedimentary facies within the estuarine system in depths >1 m. Five sedimentary facies were identified in Lavaca Bay and adjacent bays, they are: 1) estuarine mud; 2) fluvial sand; 3) beach sand; 4) bay mouth sand; and 5) oyster biofacies. Of the five facies, Lavaca Bay consists primarily of estuarine mud (68%).
Pre-Hurricane and post-Hurricane Claudette cores were obtained to observe the impact to the sedimentary processes. The north and south Lavaca Bay were eroded by 10 cm and 2-3 cm, respectively. Cox Bay and Keller Bay saw a net deposition of 2-3 cm.
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Yasin, Ahmad Raza. "Sedimentary deposits, processes and evolution of the sandy, macrotidal Duddon Estuary, northwest England." Thesis, University of Reading, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292903.
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Larcombe, Piers. "The post-glacial evolution and present-day sedimentary processes of the Mawddach Estuary." Thesis, Bangor University, 1992. https://research.bangor.ac.uk/portal/en/theses/the-postglacial-evolution-and-presentday-sedimentary-processes-of-the-mawddach-estuary(45824215-5e60-4c6b-b29e-017319409c81).html.
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The Mawddach Estuary and Barmouth Bay now occupy what was a deeply incised glaciated valley at the last ice maximum. This valley is now filled by a complex suite of sediments, up to 75m thick at the present estuary mouth, which record increasing marine influence. A regressive coastline is also present today. In the Bay, Welsh glacial drifts were eroded to form deep depressions, infilled by complex cross- stratified Late- or Postglacial sediments, overlain by a parallel-stratified sequence, perhaps formed behind a coast-parallel morainal barrier. Net sediment transport of the fine sand in the Bay is shoreward, controlled by a strong mesotidal and wave regime. Calculated sediment transport rates infer long term sediment accumulation rates of 82mm per year for the estuary as a whole, but repeated surveys suggest much spatial variation within the estuary. Waves greatly enhance sediment transport in the bay, by approximately 30 times in storms, when coarse sand is mobilised. The estuarine sand fines landward, from medium- to very finegrained. Grain size and petrological evidence suggest sediment is derived from erosion of glacial deposits in Cardigan Bay. A highly skewed tidal wave creates strong flood currents and net flood sediment transport throughout the estuary and in the southwest portion of the bay. The estuary is generally well-mixed, and the tidal wave is a standing wave with a progressive component. The estuary comprises a two part hydrodynamic system, with decreased currents and sediment transport inland of a hard rock constriction. Intertidal megaripples dominate large areas of the seaward portion of the estuary. They show very complex morphological and dynamic behaviour over a lunar cycle. Detailed velocity profile measurements over these megaripples, show complex relationships of bedform to flow. Flow parameters show considerable scatter, and have only weak correlations with bedform morphology or migration. Within each flood-ebb cycle, the relationship of shear velocity to roughness length appears related to the underlying bedforms. Natural variation of megaripple behaviour is a major factor in limiting palaeoflow estimates from deposits of intertidal megaripples. A concluding chapter discusses the relationship between sea-level, sedimentation, and estuarine hydrodynamics, through the Holocene. Sea level rise brought drowning and erosion of coastal glacial complexes, leading to conditions allowing spit formation and growth, with, in the estuary, increased tidal asymmetry, salinity and low water elevation. Fine-grained estuarine sedimentation was initiated in the sheltered back-barrier region, intertidal flats and supratidal marshes prograded, and tidal channels were progressively restricted towards the northern side of the estuary mouth. Within the modern estuarine sand wedge, preserved estuarine sedimentary structures may exhibit an upwards-increasing expression of flood- directed sediment transport.
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Gao, Guanghai. "Numerical modelling of hydrodynamic and sediment-bacteria interaction processes in estuarine and coastal waters." Thesis, Cardiff University, 2008. http://orca.cf.ac.uk/54738/.
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A study has been undertaken to investigate and improve the representation and modelling of a range of various hydrodynamic, biochemical and sediment transport processes relating to the transport of enteric bacteria organisms in estuarine waters. In this study a relatively simple turbulence model was first further investigated to predict the complex three-dimensional flow structure in a flume with vegetation. The main purpose of this part of the study was to try and acquire accurate velocity profiles of complex flows without the need for a more advanced two-equation turbulence model, requiring values for a number of unknown coefficients and extra computing cost. The results showed that the simple two layer mixing length model was capable of giving more accurate complex velocity profile predictions, with the advantage of requiring limited coefficient data. Formulations developed through earlier studies for dynamic decay rates were then refined and included in the numerical model. The model predictions were tested against field data, with good agreement being obtained. Further refinements to the representation of the transport of bacteria through the flow field were included in the model by the novel addition of the interaction of bacteria with the sediments by partitioning the total bacteria into their free-living and attached phases using a dynamic partitioning ratio. This ratio was related to the suspended sediment concentrations. The novel method used in this study was to include the re-suspension and deposition of the absorbed bacteria with the sediments and this approach has been tested against analytical solutions for steady uniform flow conditions, and published field and experimental data. The model was then applied to the Severn Estuary. After calibration against available data sets the model was then run for different scenarios to investigate the effects of different hydro-environmental conditions on the bacteria distributions in the Severn Estuary. The model was finally used to investigate the impact of the proposed Cardiff-Weston tidal barrage on the hydrodynamic, the sediment transport and bacterial processes within the Severn Estuary. The results showed that the barrage would reduce the currents, as well as significantly reducing the suspended sediment concentrations and bacteria concentration levels in the estuary.
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Pidduck, Emma Louise. "The importance of micro-scale processes on the release of macro-nutrients from estuarine suspended sediments." Thesis, University of Plymouth, 2016. http://hdl.handle.net/10026.1/5378.
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The quality of water within an estuary is inseparable from the component parts; suspended particulate matter (SPM) and the balance of macro-nutrients. Long-term temporal variations and the horizontal advection of both SPM and macro-nutrient concentrations are well-constrained, but the vertical fluxes associated with micro-scale processes, such as turbulence and flocculation, are poorly constrained. The importance of three micro-scale processes on the interactions between SPM and inorganic macro-nutrients, nitrate (NO–3 ), ammonium (NH+4) and phosphate (PO3 –4 ), are examined in four field campaigns and five laboratory experiments. Field campaigns were conducted in two turbid estuaries. One field campaign was conducted in the Seine estuary, France, and three campaigns in the Tamar estuary, U.K., in order to consider the effects of seasonal variations (spring, summer and autumn). Physical conditions measured included current velocity, turbidity, turbulence and particle size, were recorded using a suite of oceanographic instrumentation. Five different laboratory studies were conducted using the same mini annular flume, with different background conditions. Inorganic macro-nutrients were measured spectrophotometrically on a continuous flow analyser (for NO – 3 and PO3 –4) and fluorimetry (NH +4). Three hypotheses are presented as potential mechanisms controlling the release and uptake of macro-nutrients from sediments. Mechanism One (M1) described an exchange process between inorganic macro-nutrients and flocculation/disaggregating particles. It was hypothesised that flocculating particles would decrease water column macro-nutrient concentrations, and vice versa. In this study, flocculation was observed in both field sites, but there was no significant relationship between flocculation and macro-nutrient concentration. Similarly, the five laboratory studies demonstrated no statistically significant relationships between flocculation and macro-nutrient concentrations. Mechanism Two (M2) hypothesised that turbulence would enhance the release portion of the exchange processes described in M1. Furthermore, it was proposed that increased turbulence would break bonds between macro-nutrients and the surface of particle faces. Turbulence was observed to limit the floc size in all experiments (both field and laboratory), but this study determined that it did not promote a significant release mechanism for inorganic macro-nutrients. However, this study observed that turbulence played a key role in the vertical distribution of PO 3 – 4 and NH +4. In both the Seine and Tamar estuaries, surface and near-bed concentrations were observed to be statistically significantly different (p = < 0.05). Finally, Mechanism Three (M3) hypothesised that increased salinity provides additional salt water cations that would enhance flocculation and M1. This study measured an increase in floc size with increasing salinity in but did not enhance the proposed M1. Instead, as with turbulence, differences in water density as a result of the salinity affected the vertical distribution of NO –3. This research concluded that micro-scale processes have no significant impact on the water-column concentration of inorganic macronutrients. Instead, it was observed that two of the three micro-scale processes, turbulence and salinity, play a key role in the vertical distribution of inorganic macro-nutrients in the Tamar and Seine estuaries.
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Duffy, B. "Phase transfer processes affecting the chemistry of iron and manganese in river-estuary systems." Thesis, University of Southampton, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356766.
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Davis, Edgar V. "Circulation and transport processes for the Pocomoke River a tributary to partially mixed estuary /." College Park, Md. : University of Maryland, 2005. http://hdl.handle.net/1903/3264.
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Thesis (M.S.) -- University of Maryland, College Park, 2005.<br>Thesis research directed by: Marine, Estuarine, Environmental Sciences Graduate Program. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Cahyono, M. "Three-dimensional numerical modelling of sediment transport processes in non-stratified estuarine and coastal waters." Thesis, University of Bradford, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.520623.
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Details are given herein of the development, refinement and application of a higher-order accurate 3-D finite difference model for non-cohesive suspended sediment transport processes, in non-stratified estuarine and coastal waters. The velocity fields are computed using a 2-D horizontal depth-integrated model, in combination with either an assumed logarithmic velocity profile or a velocity profile obtained from field data. Also, for convenience in handling variable bed topographies and for better vertical resolution, a δ-stretching co-ordinate system has been used. In order to gain insight into the relative merits of various numerical schemes for modelling the convection of high concentration gradients, in terms of both accuracy and efficiency, thirty six existing finite difference schemes and two splitting techniques have been reviewed and compared by applying them to the following cases: i) 1-D and 2-D pure convection, ii) 1-D and 2-D convection and diffusion, and iii) 1-D non-linear Burger's equation. Modifications to some of the considered schemes have also been proposed, together with two new higher-order accurate finite difference schemes for modelling the convection of high concentration gradients. The schemes were derived using a piecewise cubic interpolation and an universal limiter (proposed scheme 1) or a modified form of the TVD filter (proposed scheme 2). The schemes have been tested for: i) 1-D and 2-D pure convection, and ii) 2-D convection and diffusion problems. The schemes have produced accurate, oscillation-free and non-clipped solutions, comparable with the ULTIMATE fifth- and sixth-order schemes. However, the proposed schemes need only three (proposed scheme 1) or five cell stencils. Hence, they are very attractive and can be easily implemented to solve convection dominated problems for complex bathymetries with flooding and drying. The 3-D sediment transport equation was solved using a splitting technique, with two different techniques being considered. With this technique the 3-D convective-diffusion equation for suspended sediment fluxes was split into consecutive 1-D convection, diffusion and convective-diffusion equations. The modified and proposed higher-order accurate finite difference schemes mentioned above were then used to solve the consecutive 1-D equations. The model has been calibrated and verified by applying it to predict the development of suspended sediment concentration profiles under non-equilibrium conditions in three test flumes. The results of numerical predictions were compared with existing analytical solutions and experimental data. The numerical results were in excellent agreement with the analytical solutions and were in reasonable agreement with the experimental data. Finally, the model has also been applied to predict sediment concentration and velocity profiles in the Humber Estuary, UK. Reasonable agreement was obtained between the model predictions and the corresponding field measurements, particularly when considered in the light of usual sediment transport predictions. The model is therefore thought to be a potentially useful tool for hydraulic engineers involved in practical case studies
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Larsen, Genevieve Ruth. "Modelling hydrodynamic processes within Pumicestone Passage, Northern Moreton Bay, Queensland." Thesis, Queensland University of Technology, 2007. https://eprints.qut.edu.au/16634/1/Genevieve_Larsen_Thesis.pdf.
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Estuaries can be considered as vital natural resources and are unique ecosystems at the interface between terrestrial and marine environments. The increase of population density centred on these coastal features and associated anthropogenic activities such as trade, industry, agriculture and recreation can adversely affect these sensitive environments.
The Pumicestone Passage, located in northern Moreton Bay, Australia, is one such estuarine environment where there are concerns about degradation of water quality resulting from rapid land use change. These changes are both immediate to the Passage and within its wider catchment. Of notable concern are the outbreaks of Lyngbya (a toxic blue-green algae) in the Passage itself and near its interface with Deception Bay to the south. Other factors of concern are increased suspended and dissolved loads, and maintenance of ecosystem integrity.
In this study, numerical modelling, graphical methods and water surface elevation and current velocity parameter calculations are used to describe hydrological processes in the Pumicestone Passage. A hydrodynamic model is developed using the modelling software SMS and RMA2 as a foundation for future hydrodynamic and water quality modelling. In addition, observed data are used to interpret general hydrodynamic behaviour in the passage, and determine various parameters for use in model development and calibration. Tidal prediction is also discussed and used for model calibration.
To support the modelling and for preliminary interpretation of hydrodynamic processes within the Passage, measurements were made in the field of (a) water surface elevation variation at 17 sites; (b) tidal current velocities in four of the tributary creeks and at the northern boundary; (c) volumetric flow rates at two cross-sections within the Passage; and (d) cross-sectional bathymetry at sites where tidal current velocities were measured in the creeks.
In general, examination of the observational data reveals a number of important processes in the Pumicestone Passage. Almost all sites within Pumicestone Passage and its tributaries are flood dominant indicating that tidal storage and bottom friction effects are significant. Mesotidal ranges occur at sites close to the southern boundary of the passage, however, bottom friction greatly reduces the tidal response at the remaining sites which results in microtidal ranges. The influence of both the southern and northern tides can be seen in the deformation of tidal waveforms in the central passage. Extensive intertidal areas at and inside the northern inlet to the Passage markedly reduce tidal ranges in the northern estuary and its tributary creeks.
Issues involved in hydrodynamic model development and performance are discussed. Overall, model results for the southern estuary have satisfactory correlation with observed data whereas model results for the northern estuary are less satisfactory. In addition, water surface elevation variation model results are generally more accurate than tidal current velocity model results. Reasons for the differences between model and observed values are considered and possible solutions given. Factors discussed relate to boundary condition locations, resolution of bathymetric and geographical data, mesh development methods and parameter assignment.
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Larsen, Genevieve Ruth. "Modelling hydrodynamic processes within Pumicestone Passage, Northern Moreton Bay, Queensland." Queensland University of Technology, 2007. http://eprints.qut.edu.au/16634/.
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Estuaries can be considered as vital natural resources and are unique ecosystems at the interface between terrestrial and marine environments. The increase of population density centred on these coastal features and associated anthropogenic activities such as trade, industry, agriculture and recreation can adversely affect these sensitive environments. The Pumicestone Passage, located in northern Moreton Bay, Australia, is one such estuarine environment where there are concerns about degradation of water quality resulting from rapid land use change. These changes are both immediate to the Passage and within its wider catchment. Of notable concern are the outbreaks of Lyngbya (a toxic blue-green algae) in the Passage itself and near its interface with Deception Bay to the south. Other factors of concern are increased suspended and dissolved loads, and maintenance of ecosystem integrity. In this study, numerical modelling, graphical methods and water surface elevation and current velocity parameter calculations are used to describe hydrological processes in the Pumicestone Passage. A hydrodynamic model is developed using the modelling software SMS and RMA2 as a foundation for future hydrodynamic and water quality modelling. In addition, observed data are used to interpret general hydrodynamic behaviour in the passage, and determine various parameters for use in model development and calibration. Tidal prediction is also discussed and used for model calibration. To support the modelling and for preliminary interpretation of hydrodynamic processes within the Passage, measurements were made in the field of (a) water surface elevation variation at 17 sites; (b) tidal current velocities in four of the tributary creeks and at the northern boundary; (c) volumetric flow rates at two cross-sections within the Passage; and (d) cross-sectional bathymetry at sites where tidal current velocities were measured in the creeks. In general, examination of the observational data reveals a number of important processes in the Pumicestone Passage. Almost all sites within Pumicestone Passage and its tributaries are flood dominant indicating that tidal storage and bottom friction effects are significant. Mesotidal ranges occur at sites close to the southern boundary of the passage, however, bottom friction greatly reduces the tidal response at the remaining sites which results in microtidal ranges. The influence of both the southern and northern tides can be seen in the deformation of tidal waveforms in the central passage. Extensive intertidal areas at and inside the northern inlet to the Passage markedly reduce tidal ranges in the northern estuary and its tributary creeks. Issues involved in hydrodynamic model development and performance are discussed. Overall, model results for the southern estuary have satisfactory correlation with observed data whereas model results for the northern estuary are less satisfactory. In addition, water surface elevation variation model results are generally more accurate than tidal current velocity model results. Reasons for the differences between model and observed values are considered and possible solutions given. Factors discussed relate to boundary condition locations, resolution of bathymetric and geographical data, mesh development methods and parameter assignment.
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Ali, Elham Mahmoud. "Processes and conditions influencing phytoplankton growth and bloom iniation in a macrotidal estuary, Southampton Water." Thesis, University of Southampton, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.274569.
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Thomas, Shaun. "The response of anaerobic prokaryotic processes and communities in Severn Estuary sediments to environmental change." Thesis, Cardiff University, 2014. http://orca.cf.ac.uk/69981/.
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The Severn Estuary in the south-western UK is one of the most tidally dynamic environments on the planet. However, despite this the sediments of the estuary remain relatively understudied with regards to their biogeochemical potential. The aim of this project was to investigate how the constantly changing sedimentary environment in the estuary, in which millions of tonnes of sediment are eroded and deposited over the tidal cycle, affects the prokaryotes within the sediments and the processes they control, and also to determine what effect environmental changes in the estuarine system might have on these processes. The study showed that the sediments of the Severn Estuary have high rates of sediment oxygen demand (SOD) indicating a high degree of organic matter (OM) degradation. However, the sediments have low rates of the anaerobic processes that are expected to dominate in shallow marine systems (e.g. sulphate reduction and methanogenesis), suggesting that most OM degradation must be linked to processes further up the redox cascade. The sediments also showed a lack of microbial guild depth zonation, with methanogenesis occurring above or alongside sulphate reduction. Both of these unusual factors can be linked to the regular re-suspension of the estuary’s sediments by tidal action, resulting in large-scale oxidation and mixing of the sediment column and the suppression of anaerobic processes while potentially stimulating aerobic and dysaerobic activity. This same mixing would also distribute guilds of organisms throughout the sediment, creating isolated pioneer populations with a general lack of competition. Re-suspension is also likely responsible for the high cell counts that persist to significant depth around the estuary, as the mixing of sediment and entrainment of OM would produce high and homogeneous cell profiles upon deposition, which in turn can be linked to the high SOD of the estuary’s sediments. Despite this dominance of aerobic and dysaerobic processes throughout most of the estuary some isolated sites do show increased rates of anaerobic processes, particularly at locations that have undergone significant environmental change. These include fluidised mud pools in the deeper areas of the estuary, salt marsh peat deposits at St Brides Wentlooge (especially within the “activated interface”) and Cardiff Bay, an anthropogenic lake and former mudflat environment which shows significant methanogenic potential. Overall this study has shown that the dynamic conditions in the Severn Estuary promote the activity of aerobic and dysaerobic prokaryotic groups over the anaerobic groups traditionally thought to dominate in shallow marine sediments. However, this promotion is not uniform across the estuary, instead varying with topography/bathymetry and the degree of sediment disturbance.
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Charoenvattanaporn, Jiraporn. "Processes influencing phytoplankton growth and primary production in shallow temperate estuary Christchurch Harbour, United Kingdom." Thesis, University of Southampton, 2016. https://eprints.soton.ac.uk/403350/.
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The aim of this research project was to identify the factors controlling the phytoplankton community and primary production in the shallow temperate estuary of Christchurch Harbour and the two river systems flowing into the estuary. Christchurch Harbour is a small shallow micro-tidal enclosed estuary situated on the south coast of England. It is fed by the rivers Stour and Hampshire Avon, and exchanges with coastal waters through a narrow channel at Mudeford. An intensive programme of monitoring both the water quality and phytoplankton communities was undertaken at weekly intervals from April 2013 to April 2014 at the lowest river gauging stations on the Hampshire Avon at Knapp Mill and the Stour at Throop plus a further station at Iford Bridge just above the tidal limit of the estuary. In addition a similar set of measurements were made on the same dates at the entrance to the estuary at Mudeford Quay at low tide. During Spring/Summer 2014 eight estuarine surveys were conducted at fortnightly intervals with measurements of water quality, phytoplankton abundance, and production made at six stations along a transect throughout the estuary. The riverine phytoplankton community in terms of carbon biomass and accessory pigments displayed a distinctive pattern of seasonal succession. A diatom group maximum was observed in spring and chlorophyte peak in summer. The nano-sized diatom (2.0 – 20.0 ?m), Stephanodiscus sp., dominated the phytoplankton assemblage, reaching 4.4 × 104 cells mL-1 and a chlorophyll concentration of 98.8 ?g L-1 on the Stour river during spring when river discharge had reduced following the winter flow peak. The summer chlorophyte bloom was composed of Chlamydomonas spp., reaching 7.9 × 104 cells mL-1 and followed the diatom spring bloom. Multivariate analysis revealed that water temperature, river discharge, silicate, and phosphate concentration were major factors controlling phytoplankton carbon biomass at all the river study sites. At Mudeford Quay, inorganic nutrient concentrations (nitrate, phosphate, and silicate) were generally low during periods of reduced river discharge, but increased during the winter high river flow periods. A chlorophyll a maximum was observed during the late spring and decreased during the autumn and winter similar to conditions on the rivers at Throop and Knapp Mill. Phytoplankton carbon biomass and accessory pigment concentration displayed a similar pattern. Diatoms dominated the phytoplankton biomass and community throughout most of the sampling period and were inversely correlated to silicate concentrations. The dinoflagellate Kryptoperidinium foliaceum was observed in high abundance during summer months at high salinity values and the freshwater diatom Stephanodiscus spp. dominated during the spring. During the estuarine transect surveys conducted over high tide, high chlorophyll ‘bloom’ events (chlorophyll up to 98 ?g L-1) were detected in the middle of the estuary in waters of salinity values over 30. Reduced river discharge in summer months led to an increase in higher salinity water in the mid estuary with these associated peaks in phytoplankton abundance. Different populations of estuarine phytoplankton were observed over the course of the summer with dinoflagellate blooms dominated by K. foliaceum, occurring in the mid-estuary followed by Cryptomonas spp. blooms. Multivariate analysis revealed that irradiance attenuation coefficient (k), salinity, oxygen saturation, temperature, nitrate, and silicate were the major factors controlling phytoplankton carbon biomass during the transect surveys. The results of the present study have provided an improved understanding of the factors controlling the production and distribution of estuarine phytoplankton communities in the shallow temperate, Christchurch Harbour estuary.
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Vinson, Joshua S. "Role of oxygen and salinity on biogeochemical processes controlling mercury and monomethylmercury flux from estuarine sediments." View electronic thesis, 2008. http://dl.uncw.edu/etd/2008-2/r1/vinsonj/joshuavinson.pdf.
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