Made available in DSpace on 2015-02-24T19:48:41Z (GMT). No. of bitstreams: 1 FlavoESS.pdf: 7200814 bytes, checksum: 50030d58571208fd3287ef1805413e5f (MD5) Previous issue date: 2004-04-07 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / The estuaries are important investigation zones of the actual morphodynamic and of depositional facies of recent geological history. They are constituted in important receptor means of the coastal area sediments, where the evolutionary processes occur quickly. They are also attractive means for the development of anthropic activities, which in a disordered way interfere in the active processes in the sedimentary balance of the coastal areas. Among the human interventions, the alterations of the depositional environment of mangroves in areas of tropical estuary is deserving relevance, whose implications for the environment estuarine and the coastal adjacent, they are still far to be known. Due to the interest of the sedimentologic component in the comprehension of the processes linked to the evolution of the environments estuarine and coastal adjacent, this work, aimed at the understanding of the morphodynamic coastal phenomena that comprise the region of estuarine influence of the River Curimata? / RN. It was also evaluated in the morphodynamic context the implications due to alterations of the depositional environment of mangrove by anthropic activity. The Curimata? Estuary, located in the south portion of the oriental coast of Rio Grande do Norte, in the last decades has been objective of the overwhelming occupation of the shrimp farm in areas of mangroves, which were implanted with perspectives of development in a short to medium period. On the other hand, the estuary and its region of coastal influence lacks enough information to subsidize the planning and reorganization more effective of the surrounding activities. Thus, it was intended with this work to give a contribution target tothe maintainable use of the coastal resources of this region. A series of studies using data of orbital and acoustic remote sensing, as of sediments sampling, were executed in the gutter of the estuary. The obtained results starting from the interpretation of bathymetric maps, echo sounder graphics and of distribution of sediments made possible the location of the estuary based in morpho-sedimentar criteria. The estuarine tidal flat was dissected in environments of intertidal mangroves, supratidal mangroves and apicuns with base in the integration of data of sensor optic and of radar following by the field control. The adjacent coast that is influenced by the Curimata? estuary, was segmented according to their geomorphologic characteristics, where each segment had a point of observation of the beach morphodynamic, during the period from january/2001 to february/2002. Once every month, beaches profiles, collections of sediments in the beach zones, as measurement of hydrodynamic parameters were executed. The results of the observations of the tidal environment showed that the area of estuarine influence of the Curimata? begins to suffer negative sedimentary taxes, where in some beaches, the erosive processes are already observed. The granulometric characteristics of the beach sediments start to tend for the increase of thin sand in the erosive periods. The destruction of the depositional environments of mangroves of the Curimata? estuary, to the construction of shrimp farms, can be providing the diminution of the tidal prism of the estuary, enlarging the effects of the local increasing of the sea level, through the smaller supplying of sediments to the adjacent coast. Besides this, it was verified the possibility of the sanding of the tidal channel in the margins of the destroyed areas of mangroves, where very high taxes of sedimentation of thin materials were estimated in case of these areas were preserve / Os estu?rios s?o importantes zonas de investiga??o da morfodin?mica atual e de f?cies deposicionais de hist?ria geol?gica recente. Constituem-se em importantes meios receptores de sedimentos da zona costeira, onde os processos evolutivos ocorrem rapidamente. Por sua vez s?o tamb?m meios atrativos para o desenvolvimento de atividades antr?picas, que de forma desordenada interferem nos processos atuantes no balan?o sedimentar das ?reas costeiras. Dentre as interven??es humanas, as altera??es do ambiente deposicional de manguezal em ?reas estuarinas tropicais, vem merecendo destaque, cujas implica??es para o ambiente estuarino e o costeiro adjacente, ainda est?o distantes de serem conhecidas. Devido o interesse da componente sedimentol?gica na compreens?o dos processos associados ? evolu??o dos ambientes estuarinos e costeiros adjacentes, este trabalho objetivou a compreens?o dos fen?menos morfodin?micos costeiros que envolvem a regi?o de influ?ncia estuarina do Rio Curumata?/RN. Tamb?m foi avaliada no contexto morfodin?mico as implica??es decorrentes das altera??es do ambiente deposicional de manguezal pela atividade antr?pica. O estu?rio Curimata?, localizado na por??o sul do litoral oriental do Rio Grande do Norte, nas ?ltimas d?cadas tem sido alvo da ocupa??o avassaladora da carcinicultura em ?reas em ?reas de manguezais, as quais foram implantadas com perspectivas de desenvolvimento a curto e m?dio prazo. Por sua vez, o estu?rio em pauta como a sua regi?o de influ?ncia costeira carecem de informa??es suficientes para subsidiar o planejamento e reordenamento mais eficazes das atividades de seu entorno. Assim, pretendeu-se com este trabalho dar uma contribui??o voltada ao uso sustent?vel dos recursos costeiros dessa regi?o. Uma s?rie de levantamentos utilizando dados de sensoriamento remoto orbitale ac?stico, como de amostragem de sedimentos, foram realizados na calha do estu?rio. Os resultados obtidos a partir da interpreta??o de mapas batim?tricos, sonogr?ficos e de distribui??o de sedimentos possibilitam a setoriza??o do estu?rio com base em crit?rios morfossedimentares. A plan?cie de mar? estuarina foi dissecada em ambientes de manguezais de intermar?, manguezais de supramar? e apicuns com base na integra??o de dados de sensores ?pticos e de radar seguidos do controle de campo. A costa adjacente que ? influenciada pelo estu?rio Curimata?, foi segmentada de acordo com suas caracter?sticas geomorfol?gicas, onde cada segmento teve um ponto de observa??o da morfodin?mica praial, durante o per?odo de janeiro/2001 a fevereiro/2002. Uma vez a cada m?s foram realizados perfis praiais, coletas de sedimentos nas zonas de praia, como medi??o de par?metros hidrodin?micos. Os resultados das observa??es do ambiente praial evidenciaram que a ?rea de influ?ncia estuarina do Curimata? passa a sofrer taxas de sedimenta??o negativas, onde em algumas praias j? s?o os processos erosivos. As caracteriza??es granulom?tricas dos sedimentos praiais passam a atender para o aumento de areias finas nos per?odos erosivos. A destrui??o dos ambientes deposicionais de manguezais do estu?rio Curimata? para constru??o de fazendas de camar?o, podem estar proporcionando a diminui??o do prisma de mar? do estu?rio ampliando os efeitos do aumento do n?vel do mar local, atrav?s do menor suprimento de sedimentos para a costa adjacente. Al?m disso, verificou-se a possibilidae do assoreamento do canal de mar? na margem das ?reas de manguezais destru?das, onde alt?ssimas taxas de sedimenta??o de materiais finos foram estimadas caso estas ?reas fossem preservadas

Made available in DSpace on 2015-03-13T17:08:12Z (GMT). No. of bitstreams: 1 GuilhermeCSP.pdf: 3646062 bytes, checksum: b5b07bc8d98389d97c55817c87e38a55 (MD5) Previous issue date: 2008-01-25 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / The research area is located on the county of Tibau do Sul, in the east coast of Rio Grande do Norte State, about 80km south of the capital Natal. The tourism represents the main income activity and Pipa beach is the most visited beach in the city, annually receives a large influx of domestic and foreign tourists. Some recent studies have reported the occurrence of coastal erosion in this littoral, being the main objective of the research, analyze the existing coastal erosion, through two methodologies, the geoenvironmental mapping and beach morphodynamics. The geoenvironmental mapping was done from oblique aerial photographs and field visits, which sought to carry out first the geomorphological mapping, with the purpose of analyzing features that suggest susceptible areas to erosion, as areas without protection of natural dunes, marine terraces, or sandstones (beach-rocks and ferruginous sandstones), areas with the presence of gullies and stretches where the sea-cliffs were in direct contact with the action of the sea, representing the beginning of the beach profile. In the morphodynamic study sought to carry out the survey of the physical and morphological characteristics, the analysis of sediment grain of the beaches and finally the analysis of the morphodynamic parameters to generate a table of risk to erosion by sector of the beach. The morphodynamic parameters were defined by the methodology proposed by Short (2006), in which considers different patterns of dynamism on beaches with characteristics favorable and unfavorable to erosive profiles. The maps indicated different levels of risk to the segments of the beaches analyzed, suggesting risk to erosion low and low to moderate only in areas north and northwest of the beaches of Madeiro and Curral, and levels of moderate and high risk sectors in the south and southeast of these beaches . The beach of Pipa showed moderate levels of risk and moderate to high at the ends and high risk to erosion in the central portion. The study of the coastal environment, its morphological evolution, and areas with problems of erosion, are of fundamental importance to assist coastal management policies, giving grants for planning activities undertaken in these regions / A ?rea da pesquisa localiza-se no munic?pio de Tibau do Sul, situado na costa leste do Estado do Rio Grande do Norte, cerca de 80 km a sul da capital Natal. O turismo representa a principal atividade geradora de renda e a praia de Pipa, a mais conhecida do munic?pio, recebe anualmente um grande fluxo de turistas nacionais e estrangeiros. Alguns estudos recentes relatam a ocorr?ncia de eros?o costeira em pontos desta regi?o litor?nea, sendo o objetivo principal da pesquisa, analisar a eros?o costeira existente, atrav?s de duas metodologias, o mapeamento geoambiental e a morfodin?mica praial. O mapeamento geoambiental foi realizado a partir de fotografias a?reas obl?quas e visitas a campo, onde buscou-se realizar primeiramente o mapeamento geomorfol?gico, com o objetivo de analisar fei??es que sugerem ?reas suscept?veis ? eros?o, como zonas sem prote??o natural de dunas, terra?os marinhos, ou arenitos (de praia e ferruginosos), ?reas com presen?a de ravinamentos e trechos onde as fal?sias encontravam-se vivas, ou seja, representando o in?cio do perfil praial, em contato direto com a a??o do mar. No estudo morfodin?mico buscou-se realizar o levantamento das caracter?sticas f?sicas e morfol?gicas, a an?lise granulom?trica dos sedimentos das praias e por fim a an?lise dos par?metros morfodin?micos para gerar uma tabela de risco ? eros?o por setor praial. Os par?metros morfodin?micos foram definidos atrav?s da metodologia proposta por Short (2006), em que considera diferentes padr?es de dinamismo em praias com caracter?sticas favor?veis e desfavor?veis a perfis erosivos. Os mapas indicaram diferentes n?veis de risco para os segmentos das praias analisadas, sugerindo risco ? eros?o baixo e baixo a moderado apenas nos setores norte e noroeste das praias do Madeiro e Curral, e n?veis de risco moderado a alto nos setores sul e sudeste destas praias. A praia de Pipa apresentou n?veis de risco moderado e moderado a alto nas extremidades e alto risco ? eros?o na por??o central. O estudo do ambiente costeiro, de sua evolu??o morfol?gica, e de ?reas com problemas de eros?o ? de fundamental import?ncia para auxiliar pol?ticas de gerenciamento costeiro, dando subs?dios para o planejamento das atividades desenvolvidas nestas regi?es

O presente trabalho propõe caracterizar a variabilidade espaço temporal dos prismas praias das praias do Lázaro, Domingas Dias e Sununga em relação às variáveis meteorológicas e oceanográficas, condicionadas pela passagem dos sistemas frontais, proporcionando à compreensão da evolução morfológica deste segmento costeiro da Enseada da Fortaleza e facilitar os próximos estudos para outras enseadas do litoral Norte do Estado de São Paulo. Para a caracterização morfodinâmica da face praial das praias da Sununga, Lázaro e Domingas Dias, no município de Ubatuba, São Paulo, foi utilizado o método de caminhamento com o uso de equipamento de precisão em posicionamento geográfico (DGPS), análises meteorológicas, análises granulométricas e modelo de padrão de incidência de ondas. Os principais resultados encontrados colaboraram para concluir que as praias do Lázaro, Domingas Dias e Sununga, embora estejam inseridas na mesma enseada, e possuam as mesmas características geológicas, meteorológicas e oceanográficas, se comportam de maneiras distintas frente aos processos dinâmicos de ondas geradas nos sistemas frontais, e nos sistemas de \"tempo bom\", devido ao nível de exposição a que ficam submetidos seus arcos praiais a incidência de ondas provenientes de distintas direções. O acompanhamento espaço temporal das três praias da enseada da Fortaleza, todas com suas faces praiais voltadas rumo aos quadrantes a sul, sob as mesmas condicionantes de origem climática, geológica, oceanográfica e antrópica, evidenciaram que a intensidade dos processos de perda e recuperação sedimentar destas praias não dependem apenas do grau de proteção, ou exposição, destes ambientes a ação mais direta das ondas mais esbeltas, mais energéticas, mas também da possibilidade de remobilização de sedimentos dentro do próprio prisma praial. / The purpose of this research is to characterize the spatio-temporal variability of Lázaro, Domingas Dias and Sununga\"s beaches, in Ubatuba, São Paulo, in relation to oceanographic and meteorological variables, conditional on the passage of frontal systems, to provide the understanding of the morphology evolution of this coastal segment of Fortaleza Bay, and to facilitate future studies on other bays of the northern coast of São Paulo. To characterize the morphodynamics of those beaches, we used the method of beach profile with precision equipment in geographical positioning (DGPS), meteorological and gain-size analyses and coastal modeling system (SMC). The main results collaborated to the conclusion that, although these beaches are inserted in the same cove and have the same geological, meteorological and oceanographic characteristics, they behave differently when compared to the dynamic processes of waves generated in frontal systems, and the \"good weather\" systems, due to the level of exposure of their bows beaches to waves originated from different directions, showing that the intensity of the loss and recovery of these sedimentary beaches not only depend on the degree of protection or exposure of these environments to the more direct action of more slender and more energy waves, but also on the possibility of remobilization of sediments inside the own praial prism.

As desembocaduras lagunares são sistemas costeiros dinâmicos e complexos em função de seu controle por diversos fatores ambientais, como amplitude de maré, energia de ondas e aporte fluvial. Essas variáveis atuam em conjunto produzindo condições hidrodinâmicas únicas e uma variedade de feições deposicionais. Estes sistemas, compostos por um canal principal e por deltas de maré, possuem fortes influências sobre a evolução da região costeira adjacente. O objetivo deste trabalho é avaliar a dinâmica da desembocadura de Cananéia, a fim de compreender os processos que governam as alterações morfológicas da região, considerando as prováveis influências do delta de maré vazante. Através de imagens aéreas e cartas náuticas históricas foi possível analisar as alterações morfológicas da desembocadura e do delta ao longo das últimas décadas. Posteriormente, foi aplicado o modelo numérico MIKE 21 para simular a propagação de ondas, a hidrodinâmica e o transporte sedimentar na região em duas situações batimétricas e em diferentes casos de ondas incidentes. Para tanto, utilizaram-se dados coletados in situ, resultados de modelos globais (WW3 e CFSR) e informações obtidas na literatura. Os resultados mostram alterações na morfologia da desembocadura com o predomínio de processos erosivos na margem norte, migração do canal e do delta para nordeste, aumento volumétrico do delta e avanço deste em direção ao oceano. Além disso, notou-se que a margem norte é exposta a maiores forças de onda e que, em ambas as margens, esta diminuiu ao longo do período analisado. Os resultados indicam a ação do delta de maré vazante como principal agente transformador de ondas, sendo a sua variação morfológica determinante para a ação das ondas nas margens do canal. A circulação é controlada predominantemente pela maré e o transporte de sedimentos, embora limitado, é aumentado sob o efeito sinérgico entre a ação de ondas e de maré. Devido a sua morfologia e hidrodinâmica, a margem norte é submetida à maior influência de ondas e de maré, resultando em processos erosivos. A dinâmica sedimentar reflete a complexidade deste ambiente. / Inlets are dynamic and complex coastal systems subjected to a variety of forces such as tidal range, wave energy and fluvial discharge. Combinations of these variables produce unique hydrodynamic conditions and a variety of depositional features. These systems, consisting of a main channel and tidal deltas, have strong influence on the evolution of the coastal zone. The aim of this study is to evaluate the dynamics of the Cananéia inlet in order to understand the processes that control the morphological changes in the region, considering the influence of its ebb-tidal delta morphology. Based on aerial photographs and historical nautical charts the morphological changes of the inlet and delta were analyzed over the last decades. Subsequently, the MIKE 21 numerical model was applied to simulate the wave propagation, the hydrodynamics and sediment transport in the region, for two different bathymetric situations and several wave scenarios. Therefore, we used in situ data, global model results (WW3 and CFSR) and information from the literature. Results show changes in the morphology of the inlet with the predominance of erosion on its northern margin, the migration of the channel and delta northeasterly, and the delta volume increase and its growth towards the ocean. Furthermore, it was noted that the northern margin is exposed to greater wave power and on both margins the wave power decreased over the analyzed period. The results show the action of the ebb tidal delta as the main transforming agent of the incoming waves and its morphological variation determines the action of the waves on the margins of the channel. The circulation is controlled predominantly by the tide and the sediment transport, although limited, is increased under the synergistic effect between the action of waves and tide. Due to its morphology and hydrodynamics, the northern margin is subjected to greater influence of waves and tide, resulting in erosional processes. The sediment dynamics reflects the complexity of this environment.

Impactos ambientais urbanos geram transtornos sociais diversos. Em muitos casos, a análise de impactos ambientais deveria ser pauta de reflexão cotidiana, inclusa nas políticas de planejamento urbano. Como suporte a essas políticas de planejamento urbano, numa perspectiva de aplicabilidade do conhecimento geomorfológico, destacam-se os mapeamentos temáticos em geomorfologia. Objetiva-se nesta pesquisa, de um modo geral, análises de impactos ambientais urbanos na bacia hidrográfica do arroio Feijó, utilizando-se do mapeamento geomorfológico de detalhe enquanto instrumento de referência, balizador e de síntese dessas análises. Apresentam-se AbSaber (1969), Ross (1992) e Fujimoto (2001), enquanto fundamentos teórico-metodológicos da pesquisa concretizada. Enquanto modos operacionais se destacam as atividades de levantamentos bibliográficos, de elaboração de documentos cartográficos, de trabalhos de campo e, embasadas nestas atividades, as análises. Compreender impactos ambientais urbanos requer o reconhecimento dos processos que os geraram e que, no seu próprio movimento, transformam-se. Impactos ambientais urbanos constituem-se ao longo do processo histórico, por julgamentos de valores de significâncias de efeitos perturbadores, de gêneses ou conseqüências antrópicas, no urbano ou para além, no ambiente, que, na promoção de mudanças ecológicas e/ ou sociais, coloquem em questão estados de auto-organização e/ ou de relativa estabilidade ambiental. A apreensão de impactos ambientais urbanos prima pela compreensão de processos ambientais através de análises multidimensionais as mais articuladas possíveis. As diretrizes para estruturação de mapeamentos geomorfológicos de detalhe, destacando-se os elementos de abordagem acordados pela Comissão de Pesquisa em Mapeamento Geomorfológico da União Geográfica Internacional (UGI), dados morfográficos, morfométricos e morfocronogenéticos do relevo, quando acrescidas das leituras morfodinâmicas do relevo, acredita-se, para o caso da bacia hidrográfica do arroio Feijó, bem embasam análises de impactos ambientais urbanos. Abordagens de dados hidrográficos, geológicos, pedológicos, pluviométricos, sócio-históricos e socioeconômicos contribuem na estruturação do mapeamento geomorfológico da bacia hidrográfica do arroio Feijó e, a partir deste, ao reconhecimento de proeminentes impactos ambientais urbanos na bacia hidrográfica em questão. No contexto do mapeamento geomorfológico, reconhecem-se padrões, unidades e geometrias de vertentes do relevo da bacia do Feijó, assim como, formas de processos atuais; também, reconhecem-se aspectos pedológicos e das vertentes de indicações morfogenéticas relativamente recentes do relevo, as quais, sensivelmente alteradas no processo de ocupação antrópica da bacia hidrográfica: há aumento do fluxo por terra e conseqüente redução da infiltração. Verifica-se alteração do sistema hidrológico da vertente e conseqüentemente do curso fluvial. Com a intensa alteração dos processos morfogenéticos, marcados pelo acréscimo dos fluxos superficiais, há um colapso na funcionalidade dos canais, com os solapamentos de margens, assoreamentos e transbordamentos dos mesmos. Visando-se atenuar os problemas decorrentes destas situações, entre outras práticas, utiliza-se do processo de retificação dos cursos fluviais, que se torna permanente. Desse modo, impõe-se a busca das gêneses, das funções e das relações, numa melhor compreensão de impactos ambientais. Há de se considerar essa busca uma constante entre as variáveis das dinâmicas ambientais, dentre elas, indica-se, das morfodinâmicas do relevo da bacia hidrográfica do arroio Feijó. / Urban environmental impacts generate various social disorders. In many cases, the analysis of environmental impacts should be the agenda for everyday discussion, included in urban planning policies. As support to these policies of urban planning in a perspective of applicability of geomorphologic knowledge we highlight the thematic mappings in geomorphology.This research, at large, aims at the analysis of urban environmental impacts in the Feijó stream hydrographic basin, using geomorphologic mapping detail as a reference tool, demarcation, and synthesis of these analyses. Ab\'Saber (1969), Ross (1992), and Fujimoto (2001) are presented in the theoretical and methodological research done. Highlighted as operating modes are the activities of research in literature, elaboration of cartographic documents, field work, and based on these activities, the analyses. Understanding urban environmental impacts requires the recognition of the processes that generated them and that, in their own movement, transformed them. Urban environmental impacts form, along the historical process, by judgments of value of significance of disruptive effects, of genesis or anthropogenic consequences, in the urban city or beyond, in the environment, which, in promotion of ecological and/or social changes, questions states of selforganization and/or of relative environmental stability. The apprehension of urban environmental impacts stands out by understanding environmental processes through the most possibly articulated multidimensional analysis. Guidelines for structuring geomorphologic detail mapping, highlighting the elements of approach agreed upon by the Committee of Geomorphologic Mapping Research of the International Geographical Union (IGU), morphographic, morphometric, and morphocronogenetic data of the relief, when the morphodynamic readings of the relief are added, is believed, in the case of the Feijó stream hydrographic basin, to well underlie analysis of environmental impacts. Hydrographic, geological, pedological, pluviometric, socio-historical, and socio-economical data approaches contribute to the structure of the geomorphologic mapping of the Feijó stream hydrographic basin and, from this, the recognition of outstanding environmental impacts in the urban hydrographic basin concerned. In the context of the geomorphologic mapping standards, units and geometries of sections of the Feijó hydrographic basin relief are recognized, as well as forms of current processes, pedological aspects and areas of relatively recent morphogenetic indications of the relief are also recognized which, significantly altered in the process of human occupation of the hydrographic basin: there is an increased flow by land and a consequent reduction of infiltration. Change in the hydrological system of the slope is verified, and consequently of the course of the river. With intense alteration of the morphogenetic processes, marked by the increase in superficial flows, there is a collapse in the functionality of the canals, with the undermining of the banks, silting, and their flooding. Aiming at mitigating the problems arising from these situations, among other practices, the process of rectification of river courses is used, which becomes permanent. Thus, the search for the genesis, functions, and relations are imposed, for a better understanding of environmental impacts. One should consider this as a constant search among the variables of environmental dynamics, among which, the morphodynamics of the relief of the Feijó stream hydrographic basin is indicated.

Ce travail porte sur la morphodynamique des bancs de galets alternés dans une rivière de montagne aménagée. Le site expérimental est un tronçon long de 8 km de la rivière Arc située dans les Alpes françaises. Une analyse des cartes historiques, des photos aériennes et des relevés topographiques montre que le lit de la rivière a évolué d’un style en tresse vers un lit rectiligne avec des bancs alternés contraints entre deux digues. Au milieu des années 1990, le lit de la rivière a été aplani pour former des profils trapézoïdaux. Cependant, les bancs alternés ont réapparu en moins de dixans. Une analyse des facteurs contrôlant leur formation est fournie. Les observations de terrain et l’analyse numérique 1D suggèrent que le motif de bancs alternés représente un état de quasi équilibre du tronçon. D’autre part, la topographie d’un sous-tronçon incluant un banc de galets aété mesurée 18 fois entre 2006 et 2012. Une méthodologie de construction des MNT basée sur leslignes directrices et incluant une estimation de l’erreur a été proposée pour une application aux litsde rivières. La technique de différenciation des MNT a été utilisée pour détecter les changements morphologiques du banc. Ainsi, la morphodynamique du sous-tronçon a été étudiée en la reliant aux principaux processus qui la contrôlent tels que l’hydrologie, les formes des hydrogrammes, la répartition des contraintes de cisaillement, les apports amont en sédiments et l’énergie du coursd’eau. La forme des hydrogrammes de crue ainsi que les apports en sédiments semblent être lesprincipaux facteurs influençant le bilan sédimentaire sur le site étudié. En outre, des modélisationsnumériques 2D hydro-sédimentaires ont été utilisées pour appréhender la dynamique du banc. Lessimulations ont révélé l’importance de l’interaction entre les sédiments fins et les galets sur ladynamique globale du banc. / The current research investigates the morphodynamics of gravel alternate bars in an engineeredmountainous river. The experimental site corresponds to an 8 km long reach of the Arc River, in the French Alps. An analysis of historical maps and recent aerial photographs and topographic campaigns shows that the original braided river bed has evolved to a straight bed with alternate bar system constrained within two embankments following two centuries of man-made engineeringprojects. In the mid 1990s the river bed was flattened to fit a trapezoidal cross-sectional design. However, alternate bars re-appeared in less than ten years. An analysis of the controlling factors of bar formation and evolution is provided. Field observation and 1D numerical analysis suggest that the alternate-bar pattern represents a quasi-equilibrium state of the river bed. A singlegravel bar within the reach was monitored 18 times from 2006 to 2012. A methodology of DTM construction based on breaklines is proposed for river beds and an error estimation is presented. DTM differencing technique was used to detect morphologic changes of the gravel bar. Therefore, the gravel bar and main channel dynamics were analyzed relative to main controlling processes suchas extreme hydrologic events, sediment supply, hydrograph shape, bed shear stress distribution andriver energy. Sediment supply and hydrograph shape appeared to be the main factors influencing the study site sediment budget. Moreover, 2D numerical modelling of water flow and sediment transport was performed. Sensitivity analysis was conducted to yield results in agreement with observations. Simulations revealed the relevance of the interaction between fine sediments and gravels on the bar dynamics.

The morphodynamics of an inlet channel draining an estuary or bay are governed by a complex system of temporally and spatially varying physical processes, including wind, waves, tides, sediment transport, and both tide and wave driven currents. In addition, sediment availability and characteristics in conjunction with underlying geologic framework bear on the morphology and morphologic behavior of an inlet system. This study examines the morphodynamics, sediment transport patterns and time-series morphologic change of John’s Pass and Blind Pass, two structured tidal inlets that collectively make up a dual-inlet system sharing the tidal prism of northern Boca Ciega Bay, in Pinellas County, Florida. To quantify wave and tidal forcing and response mechanisms an array of hydrodynamic sensors were deployed over a 12 month period at both inshore and offshore locations. In order to capture morphologic changes and quantify volumetric changes within the inlets, bathymetric surveys of the inlets were conducted in 2010, 2011, 2012, and 2014. Similarly, bi-monthly beach survey data for the same range of time was acquired in order to quantify volumetric changes along adjacent stretches of beach. In addition to gaining insights into sediment pathways based on morphologic and volumetric variability, those data were also used to develop a regional sediment budget along the studied stretch of coast. To gain insights into the morphodynamics of the dual-inlet system, bathymetric and hydrodynamic data was used to develop a numerical model of the dual inlet system. Numerical model simulations based on existing or baseline conditions were compared with numerical simulations employing synthetic bathymetric and hydrodynamic conditions in order to examine inlet behavior under a range of different morphological and hydrodynamic conditions. John’s Pass is the dominant of the two inlets. It exhibits mixed-energy straight morphology and captures ca 81% of the available tidal prism. The inlet has a well-developed mature ebb shoal, and actively bypasses sediment from one side of the inlet to the other supplying sediment to the downdrift littoral system. Blind Pass captures less than 20% of the available tidal prism, and while also exhibiting mixed-energy morphologic characteristics has a less well developed ebb shoal that currently has not fully established a sediment bypassing system. Both inlets channels and ebb shoals have been dredged on multiple occasions to provide sediment for the nourishment of nearby chronically eroding stretches of beach. Dredge pits excavated along the distal margins of the ebb shoals are infilling at rates substantially slower than expected due to limited sediment transport along those regions of the ebb shoal, while inlet channel dredge pits infill at rapid and expected rates. The objective of this study was to characterize the morphodynamics of the dual-inlet system with the aim of identifying sediment pathways and bypassing mechanisms, and quantify a balanced regional sediment budget in order to design more sustainable approaches to inlet management.

Ces travaux visent à inscrire le monitoring des plages récifales de l'île de La Réunion dans la « Stratégie Nationale de Gestion Intégrée des Zones Côtières » (2012). Elle oriente les recherches vers une démarche labellisée sur le long terme qui se concrétise par la mise en place de protocoles de mesures normalisés déployés sur des sites ateliers. Le site de l'Ermitage devient, en 2012, le premier site atelier en zone tropicale et de type bioclastique labellisé à l'échelle nationale (AllENVI, puis INSU en 2014). La dynamique des plages d'arrière-récif demeure à ce jour peu étudiée à travers le monde. Les plages bioclastiques de La Réunion sont le produit de récifs coralliens décrits comme dégradés par les biologistes depuis les années 80. Elles sont confrontées à une très forte anthropisation. Des formes marquées d'érosion se lisent dans ces paysages littoraux. La révision des protocoles de suivi de la topographie des plages tout en exploitant les suivis historiques, vise à illustrer la pluralité des dynamiques en contexte d'arrière-récif. La diversité des processus et des échelles spatio-temporelles impliqués dans le fonctionnement hydro-sédimentaire des plages récifales nécessite la mise en œuvre de méthodes d'observation in situ adaptées, comparables et reproductibles. Dans cette étude nous exploitons surtout les suivis topographiques des plages à l'échelle évènementielle, saisonnière et pluriannuelle. Par l'analyse morphologique et volumétrique des séries de profils topographiques, la variabilité morphosédimentaire en zone intertidale et supratidale est décrite. La significativité de la mesure de la mobilité du trait de côte est également questionnée. / Long-term assessment of beach morphodynamic is a great challenge to understand future trajectories of these landforms. In France, in 2012, a national strategy for an integrated management of shoreline has been adopted. This one lead to creation of research labels (SOERE and SNO) which aim to sustain scientific researches dedicated to sandy beach morphodynamic in response to various hydrodynamics forcing. Shoreline monitoring on selected pilot sites is conducted within network where normalized protocols and high quality data are guaranteed at long-term scale. The French coastline also extend in tropical zone through its ultramarine territories. Tropical shoreline are among the most sensitive environment however they remain poorly studied. Since, 2012, Reunion island, a French department in Indian Ocean, integrated the SOERE network. Coral reef and coral beaches which preferentially developed on the western coast are frequently threatened by major swell event associated with tropical cyclones or long period swell. Since now, the beach trend evolution and morphogenic processes have not been quantified. However past monitoring exists which has consisted in topographic measurement along beach profile based on empirical protocols which produced biaised data. Since its integration within SOERE network, DGPS survey are now conducted along the different coral beach compartments of Reunion Island at seasonal and post-storm scale. This study aims to capitalize historical and DGPS beach topographic data in order to quantify long term and post-storm beach response and recovery from Cap Champagne to Trou d'Eau.

Large-scale bed features are often encountered in coastal waters, and include sandbanks and spoil heaps. The morphodynamic development of such features involves complicated nonlinear interactions between the flow hydrodynamics, sediment transport, and bed profile. Numerical modelling of the morphodynamic evolution and migration of large-scale bed features is necessary in order to understand their long-term behaviour in response to changing environmental conditions. This thesis describes detailed measurements of the morphodynamics of sand mounds in unidirectional and oscillatory (tidal) flows, undertaken at the U.K. Coastal Research Facility (UKCRF). High quality data were collected, including water velocities, water levels and overhead images. The parameters tested are: three types of mound shape (circular and elliptical in plan shape, and Gaussian, cosine and triangular in cross-section); underlying fixed or mobile bed conditions; and initial crest height (submerged, surface-touching and surface-piercing). Peak flow velocities are about 0.5 m/s, the sand median grain size is 0.454 mm, and transport occurring mostly as bedload. When analysing the data, the bed contours are determined by digitising the shoreline at different water levels. From these plots, the volume, height, and centroid position of the mound are calculated. A large-scale fit method, based on a Gaussian function has been used to separate small-scale ripples from the large-scale bed structure during the evolution of an isolated sand mound or spoil heap. The bed profile after the ripples are removed is comparable to typical predictions by shallow-flow numerical solvers. The UKCRF experiments investigated the morphodynamic response of a bed mound to hydrodynamic forcing: shape changes, migration rates, volume decay and sediment transport rates. The measured migration rate and decay of a submerged sand mound in the UKCRF are found to be in satisfactory agreement with results from various theoretical models, such as the analytical solution derived by De Vriend. Numerical predictions of mound evolution by a commercial code, PISCES, are also presented for a fully submerged sand mound; the bed evolution is reasonably similar to that observed in the UKCRF. The data provided as a result of the research reported in this thesis provide insight into the behaviour of sand mounds in steady and unsteady flows at laboratory scale, and should also be useful for benchmark (validation) purposes to numerical modellers of large-scale morphodynamics.

La plupart des côtes de la Terre reculent et 80% sont rocheuses. La prévision du recul des falaises littorales est primordiale afin d’anticiper les risques futurs pour les aménagements littoraux. Cependant, la compréhension de ce recul est difficile car de nombreux paramètres le contrôlent. Des expériences en canal à houle de petite échelle ont été effectuées où nous avons mis en place un massif de sable humide soumis à l’attaque des vagues par sapement. Le but est de comprendre comment l’effet des vagues contrôle l’érosion des falaises. La technique de mesure par ombroscopie a été employée et nous a permis de détecter la surface du sable et la surface libre en fonction du temps. Nous avons ainsi analysé l’influence du forçage des vagues (F, ξ) (où F est le flux d’énergie des vagues incidentes au large et ξ est le paramètre de similitude de “surf”) sur la vitesse de recul de la falaise et sur la profondeur des évènements d’effondrement. La vitesse de recul de la falaise augmente linéairement avec le flux d’énergie F. Les débris de falaise érodés changent la morphologie du fond, les types de morphologie du fond dépendent fortement du paramètre de similitude de “surf” au déferlement, ou encore du paramètre de Dean Ω. Des profils du fond instationnaires présentant une oscillation auto-entretenue de la barre sédimentaire ont été observés. Nous avons de plus étudié l’effet de la granulométrie du sable utilisé : pour un sable plus fin, la falaise est plus cohésive et s’effondre au cours d’évènements de plus grande ampleur. Etonnamment, le recul de la falaise est plus important pour du sable fin. Ceci est probablement dû à une modification de la morphologie du fond conduisant à une dissipation de l’énergie des vagues moins importante. Le volume de sable injecté dans le système a finalement été quantifié, la barre sédimentaire a d’abord été prélevée périodiquement et il a été observé que la vitesse de recul de la falaise vr est constante. Puis, la hauteur de falaise a été modifiée, le recul des falaises est plus important pour des petites falaises. Il semblerait que l’instationnarité d’un profil du fond se déclenche à partir d’un volume seuil de sable érodé. / Most of the Earth coasts recedes and 80 % are rocky. Prediction of sea-cliff recession is essential to anticipate future risks for coastal development. However, it is difficult to understand this recession because many parameters control it. In addition, both the space and time scales are too big for the different mechanisms of cliff erosion to be fully analysed. Experiments in a small-scale wave flume were conducted in which a massif made of wet sand is submitted to wave attack. The aim is to understand how cliff erosion is wave-controlled. The technique of shadow graph measurements was used to detect the time evolution of sand and water surfaces. We have analyzed the influence of wave forcing (F, ξ) (where F is the incident offshore wave energy flux and ξ is the surf similarity parameter) on the cliff recession rate and on collapse event size. The cliff recession rate increases linearly with the wave energy flux F. The eroded cliff materials change the bottom morphology ; the types of bottom morphology strongly depend on the surf similarity parameter at the breaker point, or the Dean parameter Ω. Bottom profiles characterized by unsteady self-sustained sandbar oscillation were observed. In addition, we studied how sand granulometry change the system evolution. Finer the sand is, more cohesive is the cliff and bigger are cliff collapses. Contrary to what was expected, cliff recession is more important for a finer sand : this could be due to a more dissipative bottom morphology built by fine sands. The sand volume within the system changes following cliff collapses and a sandbar removal during particular experiments. The cliff recession rate is constant when the sandbar is removed and decreases with cliff height. It seems that the unsteadiness of the bottom profile is activated when the volume of eroded sand exceeds a threshold value.