A l’heure de la mondialisation, auteure d’une croissance sans limites de nos métropoles, la mobilité devient fer de lance ou symptôme de notre société. Le regard porté sur elle s’appuie sur les discours et théories qui ont retenu l’attention des chercheurs depuis les années 2000, et interroge les interrelations structurantes entre mobilité et espace public au prisme des phénomènes de métropolisation. L’espace public est ainsi questionné à travers une lecture morphodynamique faisant de la mobilité son nouveau cadre conceptuel. Cette approche fondée sur la primauté du mouvement amène à considérer l’espace à travers la notion de spatialité développée ici selon trois rapports spatiaux – abstrait-concret (« espace-substance »), scalaire-métrique (espace topologique), localisation-mouvement (espace de perception) – qui se déclinent en trois dimensions spatiales : l’espace-lieu, l’espace-liaison, l’espace-étendue. A travers cette proposition de lecture de l’espace émerge une redéfinition dynamique des catégorisations spatiales, jusqu’à présent fondées sur la typomorphologie, à partir d’une approche morphodynamique, c’est-à-dire qui tient compte des rapports entre les forces, les mouvements et les formes. Les modèles de représentation des métropoles sont ainsi requestionnés, au même titre que les dynamiques métropolitaines actuelles. Ce cadre théorique appliqué au concret rejoint l’hypothèse que si de prime abord les ancrages semblent traqués ils restent le socle de la mobilité, qui appliquée à l’espace urbain devient un vecteur de métropolisation au cœur d’un jeu d’organisation spatiale entre le local et le global. Il promeut un retour à la lenteur en réponse au paradoxe des modalités de déplacement dans les métropoles du XXIe siècle et met en évidence le modèle de la ville des courtes distances comme une nouvelle dynamique organisationnel de l’espace métropolitain. / Today, mobility is spearhead of our contemporary metropolises. This thesis consists in studying of interrelation between mobility and metropolitan public spaces. The main topic are focus the relation of mobility systems to metropolitan territories and places, through fields of knowledge and action as varied as architecture, engineering, geography, new technologies, and others. This thesis examines the structuring interrelations between mobility and public space in the light of metropolisation phenomena. Public space is questioned through a morphodynamic approach based on the primacy of movement and making mobility its new conceptual framework. That means to consider the notion of spatiality according to three relationships - abstract-concrete ("space-substance"), scalar-metric (topological space), location-movement (space of perception) - witch are declined in three spatial dimensions (little, medium and large) : the space-place, space-connection, extended-space. Through this analysis proposal emerges a dynamic redefinition of spatial categorizations - until now based on typomorphology - from a morphodynamic approach based on the relationships between forces, movements and forms. Consequently, the models of representation of the metropolises and the current metropolitan dynamics are challenged with crossing of spatial and temporal scales. This theorical framework is based on the assumption that if anchors seem tracked, its remain the base of mobility. Mobility becomes a vector for metropolisation in a game of organization between local scale and large scale. This values a return to the pedestrian scale because it seems that to go fast it's necessary to introduce the slowness. From my point of view, this case appears in the short distances city as a new dynamic model of organisation of the metropolitan space through distance control, urban diversity and multipolarity. An architecture of mobility as the fabric of the city, landscape and territory.

Meandering rivers provide fresh water and important aquatic ecosystem services, yet at the same time induce flood and erosion hazards. In the face of ongoing development pressure and changing climate, growing concern for meandering rivers has increased the demand to model accurately the flow and predict the sediment transport in a meandering river channel. Calibration and validation of these models based on comparable field-based data, as opposed to laboratory-scale experimental data, may decrease uncertainty and improve understanding of complex flow structures in natural meandering rivers. In this thesis, spatially intensive field data are utilized to develop appropriate calibration and validation methods for 3D meandering river models. Validated models are then applied to the study of morphodynamic processes and the influence of channel change on fish habitat availability in meandering rivers. This study presents a novel methodology for use of three-dimensional (3D) velocity for improved calibration of a 3D hydro-morphodynamic model. A natural tortuously meandering river was simulated using the Delft3D hydrodynamic model. A spatially intensive acoustic Doppler current profiler (ADCP) survey was conducted throughout the study river, providing fully 3D distributed velocities for model calibration. For accurate and realistic comparison of the fully 3D predicted and measured velocities, an algorithm was developed to match the location of each ADCP bin with 3D model grid points. The results suggest that different calibration approaches can result in different calibration parameterizations whose simulated results can differ significantly. It is shown that the model which was calibrated based on the proposed 3D calibration approach had the best model performance. Depending upon the nature and objectives of the numerical modelling exercise, the results demonstrate the importance of model calibration with spatially intensive field data. Given the importance of pressure gradients in driving secondary flow, it is worth studying how the modelled flow structures in a natural river bend can be impacted by the assumption of hydrodynamic pressure. Accordingly, the performance of hydrostatic versus non-hydrostatic pressure assumption in the Delft3D hydrodynamic modelling of a tortuously meandering river was studied. An Acoustic Doppler Velocimeter (ADV) was employed to measure the 3D flow field at a section in a sharp bend of the simulated river at two different flow stages. The field-based ADV data were employed to validate the simulated hydrodynamic models. The results indicate the surprisingly superior performance of the hydrostatic over non-hydrostatic Delft3D modelling of the secondary flow. It was determined that the non-hydrostatic routine employed in Delft3D was not mass conservative, which diminished model accuracy. Despite several decades of intensive study of the morphological changes in meandering rivers, less attention has been paid to confined meanders. This thesis includes a study of the meandering behavior of a semi-alluvial cohesive bed river over a 10-year period. We employed a paired sub-reach study approach, wherein one sub-reach is freely meandering and the second adjacent sub-reach is confined by a railway embankment. Channel migration and morphological changes of the channel banks along each of these sub-reaches were analyzed by comparing the historical aerial photography, light detection and ranging (LIDAR) data, bathymetric data obtained from a total station survey, and field examination. Moreover, two different spatially intensive ADCP surveys were conducted in the study area to find the linkage between the hydrodynamics and morphological changes in the two different sub-reaches. The unconfined sub-reach displayed a typical channel migration pattern with deposition on the inner bank and erosion on the outer bank of the meander bend. On the other hand, the confined sub-reach showed greater bank instabilities than the unconfined sub-reach. In the confined sub-reach, an irregular meandering pattern occurred by the evolution of a concave-bank bench, which was caused by reverse flow eddies. The results of this study could shed light on the potential impacts of channel confinement on bank retreat and river migration in comparable case studies. It is reasonable to expect that hydro-morphodynamic processes in rivers can affect fish habitat availability and quality, but the impact of river morphological changes on fish habitat is not well studied. Herein, we investigate the impact of morphological development of a cohesive meandering creek on the quality of fish habitat available for juvenile yellow perch (Perca flavescens) and white sucker (Catostomus commersonii). A 3D morphodynamic model was first developed to simulate the hydro-morphodynamics of the study creek over a 1-year period. Total station topographic surveys were conducted to provide bathymetric change data for calibration of the morphodynamic module. Successful calibration efforts indicated that the developed model could be reasonably employed to predict the hydro-morphodynamics of the study creek. Two fish sampling surveys were carried out at the beginning and the end of the study period to determine habitat utilization of each fish species in the study reach. ANOVA multiple comparison tests indicate that morphological development of the river was a significant factor for the habitat utilization of juvenile yellow perch, whereas juvenile white sucker habitat utilization was not significantly impacted by the changes in the creek morphology. It is shown that flow depth, depth-averaged velocity, and suspended sediment transport also significantly influenced presence of the juvenile yellow perch at the 5% significant level. As for the juvenile white sucker, the only significant factor was the depth-averaged velocity. The results of the developed 3D hydro-morphodynamic model were fed into a fish habitat model. Comparison of the predicted fish habitat map of the juvenile yellow perch with the results of fish sampling surveys confirms that the habitat quality was better predicted when the impact of morphological changes was taken into account in the fish habitat modelling. The results of the proposed methodology could provide some insights into the impact of sediment transport processes on the fish community. This has important implications for effective river management.

Braiding is a mesmerizing phenomenon since flow and sediment transport interact and are able to change the morphology of a channel in a rapid and complex fashion. Conventional two-dimensional morphodynamic models estimate bedload distribution using shear stress distribution. However, it is unclear if the use of such shear stress distributions is relevant or applicable for all situations when using two-dimensional morphodynamic modelling. This thesis strives to investigate whether shear stress distributions are useful to predict bedload transport pathways. This study focuses upon prediction of bedload transport pathways using a morphodynamic model (Delft3D) of an anabranch of the Rees River (New Zealand). Observed bedload transport pathways were compared to modelled bedload transport pathways in an attempt to validate the predictive ability of the model. Results show that there is a significant correlation between predicted bedload transport pathways and the apparent bedload transport pathways derived from the field measurements. Furthermore, bedload transport predictions were in good agreement with observed data in areas where the model’s predictions of high shear stress were comparable to field observations. However, substantial bedload transport predictions in low shear stress areas were not adequately captured by the model, suggesting that the observed pathways were not due to high shear stress, but rather to other sediment supply sources.

Sediment pulses are defined as large amounts of loose sediment that are suddenly deposited in river corridors due to the action of external factors or processes of natural or anthropogenic origin. Such factors and processes include landslides, debris flows from tributaries, volcanic eruptions, dam removal projects, and mining-related activities. Their occurrence is associated with a surplus in sediment load to downstream reaches, and therefore, with severe channel aggradation and degradation, significant floodplain deposition, increase in flood frequency, damage of infrastructure, and impairment of aquatic habitats. The main objective of this research is to develop a better understanding of the fundamental mechanisms that govern the propagation of these sediment-flow hazards in alluvial sand-bed rivers. Specifically, the study presented herein is divided into three separate parts to achieve this overarching goal. First, a component intended to improve the numerical modeling of morphodynamic processes in alluvial sand-bed rivers by proposing a novel solution methodology that applies either the decoupled or the coupled modeling approach based on local flow and sediment transport conditions. Secondly, a detailed numerical analysis to characterize the behavior of fine-grained sediment pulses (i.e. composed of granular material in the sand size range) in alluvial sand-bed rives by identifying the properties of these types of pulses, as well as the characteristics of riverine environments, that are most relevant to their downstream migration. And lastly, a case study application to assess the effect of the magnitude, duration, and frequency of severe hydrologic events on the overall propagation behavior of fine-grained sediment pulses in alluvial sand-bed rivers. Ultimately, this research aims to contribute towards reducing the uncertainty associated with the impact of these phenomena, and hence, improving the resilience of rivers corridors. / Ph. D.

Le littoral méditerranéen oriental du Maroc compris entre l’oued Kiss et le Cap des Trois Fourches s’étire sur près de 120 km. Ce littoral, objet de notre étude, est caractérisé par des unités morphologiques variées : embouchure, baies, lagune, plages, flèches sableuses, tombolo, falaises (vives et mortes). C’est une zone particulièrement intéressante pour l’étude et la compréhension de l’influence des processus naturels et anthropiques sur la dynamique sédimentaire. L’augmentation des activités industrielles et l’urbanisation croissante ont conduit ces dernières années à la construction de nombreux ouvrages le long de la côte, conduisant à des modifications dans la distribution des sédiments et à une dégradation de l’environnement naturel de certaines plages. L’étude sédimentologique couplée à l’analyse des photos aériennes de plusieurs missions a permis de caractériser les différents environnements de ce littoral, de reconstituer la dynamique des différents environnements sédimentaires et de souligner les facteurs, les processus hydrologiques et hydrographiques qui contrôlent ce littoral méditerranéen. Les analyses minéralogiques, en particulier l’étude des minéraux lourds, nous ont fourni des indications sur l’origine des sédiments, la nature du bassin versant fournisseur, également ont permis de mettre évidence deux secteurs morphosédimentaires de part et d’autre de l’embouchure de la Moulouya. Á l’Est, on trouve un secteur en démaigrissement et un secteur en accrétion est situé dans la partie Ouest de l’embouchure de la Moulouya. L'évolution morphodynamique de chacun de ces deux secteurs résulte des interactions entre les facteurs naturels et l’impact des aménagements réalisés sur cette portion de littoral / The Eastern Mediterranean coastline of Morocco ranging between Kiss and the Cap of the Three Fourches is stretched along nearly 120 km. This littoral, the object of our study, is characterized by varied morphological units: mouth, bays, lagoon, beaches, sand, tombolo, cliffs (formed and dead). It is a particularly interesting zone for the study and the comprehension of the influence of the natural and anthropic processes and sedimentary dynamics. During the last few years the increase in the industrial activities and the increasing urbanization led to the construction of many works along the coast, leading to modifications in the distribution of the sediments and to a degradation of the natural environment of certain beaches. The sedimentological study coupled with the analysis of aerial photographs (of several missions) made it possible to characterize the various environments of this littoral, to reconstitute the dynamics of the various sedimentary environments and to underline the factors, the hydrological and hydrographic processes which control this Mediterranean coastline. The mineralogical analysis, the study of heavy minerals in particular, provided indications on the origin of the sediments, the nature of the catchment supplier area and made it possible to put two morphosedimentary sectors obvious on both sides of the mouth of Moulouya. The morphodynamic evolution of each one of these two sectors results from the interactions between the natural factors and the impact from the installations carried out on this portion from littoral

O objetivo deste trabalho é avaliar as variações espaço-temporais da dinâmica morfo-sedimentar do sistema praial de Ilha Comprida-SP. Assim, para reconhecer os padrões de onda encontrados na região, resultados do modelo global de ondas WAVEWATCH III foram utilizados. Da mesma forma, levantamentos de campo periódicos foram realizados em cinco diferentes setores com obtenção de dados morfológicos e sedimentares. Simulações com o modelo numérico MIKE21 SW foram realizadas para reconhecer as tendências de transporte e distribuição de força de onda. Os resultados mostraram uma tendência geral de transporte para NE, com maiores valores para a região sul em relação a norte, com dois setores principais de divergência residual: centro-sul e norte. A divergência centro-sul apresenta um aumento e uma migração para sul nos meses mais energéticos, enquanto que a divergência norte apresenta uma manutenção espacial ao longo das estações. A distribuição de força de onda mostrou-se mais elevada nos setores centro-sul e norte, coincidindo com os pontos de divergência. Dados granulométricos mostraram baixa variabilidade temporal, mas possuem diferenças espaciais que refletem a hidrodinâmica local. Os dados volumétricos apresentam maiores valores médios nos setores centro-norte e menores no centro-sul e norte. De modo geral, os resultados mostram que ao longo de uma linha de costa exposta a um mesmo padrão de ondas, sua variabilidade é um reflexo de alterações hidrodinâmicas locais. Tais conclusões são importantes para o conhecimento do estado atual das praias e de sua evolução. / The aim of this study is to evaluate the spatial-time variations on the beach system of Ilha Comprida-SP. Therefore, the wave reanalysis database from the global wave generation model WAVEWATCH III was used to recognize the wave pattern for the region. Furthermore, periodic field works at five different sectors have been conducted to collect morphological and sedimentological data. The numerical model MIKE 21 SW has been applied to propagate waves onshore and recognize the transport tendency and the nearshore wave power distribution. Results show a transport trend to the NE, with the southern sector being larger than the northern sector in magnitude, with two main residual longshore drift divergence spots: in the central-southern and northern regions. Moreover, the central-southern divergence spot become larger and migrated to the south during the most energetic months, while the northern divergence spot kept its position throughout the year. Wave power results show two main areas with higher values that coincide with the observed longshore divergence spots. Sediment data presents low temporal variability, although spatial variations have been found reflecting the hydrodynamic conditions. The volumetric data shows largest values in the central-northern sector, being smaller in the central-southern and northern regions. In summary, the findings show that along this wide open stretch of coastline, exposed to the same offshore wave regime, its variability is a result of local hydrodynamic conditions. These results help in further understanding the island\'s long term evolution and current state of its beaches.

A análise dos parâmetros morfométricos publicados buscou relacionar o comportamento morfodinâmico praial com o da barreira costeira holocênica no estado do Rio Grande do Sul (RS), para estabelecer de que maneira estes ambientes estão relacionados. Foram analisados os dados de 31 praias, de Torres ao Chuí, possibilitando uma revisão e reavaliação dos estágios morfodinâmicos, com a compartimentação destes locais em cinco grupos, baseados em sua morfodinâmica e mobilidade praial. O grupo 1 é composto pelas praias intermediárias de mobilidade moderada à alta, que estão em sua maioria localizadas no litoral médio do RS correspondente a barreira agradacional, com alto desenvolvimento de campos de dunas transgressivas e dunas frontais, e estão também associadas às praias com característica retrogradante da barreira, porção sul da barreira agradacional. O grupo 2 compõe as praias dissipativas, com estágio intermediário ocorrendo de maneira secundária, de moderada à alta mobilidade, associadas a barreira progradante do litoral norte. Este setor apesar de apresentar alto potencial de transporte sedimentar por ventos e por ondas não apresenta campos de dunas bem desenvolvidos, onde o aporte sedimentar favorece a progradação costeira. O grupo 3 é formado por praias intermediárias de baixa mobilidade, associadas à porção norte da barreira agradacional e às praias do litoral sul que representam a transição entre a barreira progradante e retrogradante. No litoral médio a associação da baixa mobilidade praial com a alta capacidade de transporte e disponibilidade sedimentar, resultante do transporte sedimentar pelo vento no sentido continental, permitiu o desenvolvimento de grandes campos de dunas transgressivos e de dunas frontais. O grupo 4 é constituído por praias dissipativas e secundariamente intermediárias, de baixa mobilidade, da barreira progradante do litoral sul, que não desenvolveu vastos campos de dunas, semelhante ao que ocorre na barreira progradante ao norte. O grupo 5 é formado por duas praias diferenciadas, onde o estágio intermediário predomina e o refletivo ocorre eventualmente no verão, e estão localizadas em barreiras retrogradantes. As praias dissipativas são responsáveis por remobilizar o maior volume sedimentar da antepraia ao ambiente praial, onde integra o processo de progradação costeira. A porção da barreira agradacional, responsável pelas maiores dunas frontais, apresenta a menor mobilidade, sendo que conforme sua mobilidade é aumentada em direção ao sul, os maiores campos de dunas transgressivas ocorrem. Os estágios intermediários possuem energia suficiente para transportar sedimentos da antepraia para a praia, enquanto que a formação ou não das dunas é influenciada pelo potencial de transporte do vento NE e pela orientação da linha de costa com relação a este vento. As barreiras retrogradantes estão associadas a estágios intermediários de mobilidade variável, sendo que os dois focos erosivos do estado estão associados à alta mobilidade, o qual deixa estes ambientes susceptíveis aos episódios de erosão durante a passagem de eventos de tempestades. Assim, o caráter erosivo da barreira pode estar associado tanto com a energia de ondas, quanto com uma antepraia irregular e um déficit sedimentar, que acarreta em variações na morfodinâmica praial. / The analysis of the morphometric parameters of the published works about beach morphodynamics in the State of Rio Grande do Sul had the objective to relate the morphodynamic behavior of the beach with the holocene coastal barrier, in order to establish how these environments are related. The data of 31 beaches were analyzed, allowing a review and reevaluation of the morphodynamic stages, with the compartmentalization of these sites in five groups, based on their morphodynamics and beach mobility. Group 1 is composed of intermediate beaches with moderate to high mobility, which are located in the middle coast corresponding to the aggradational barrier, with high development of transgressive dunes and foredunes, and, associated too with the beaches with retrogradational characteristics of the barrier. Group 2 consists of dissipative beaches, with intermediate stage occurring in a secondary way, being these from moderate to high mobility, associated with the progradational barrier of the north coast. This sector, despite to present a high potential for sediment transport by winds and waves, does not have well development dunefields, where the sediment budget supports coastal progradation. Group 3 is formed by intermediate beaches of low mobility, associated with the northern portion of the aggradational barrier and the beaches of the south coast that represent the transition between the prograded and retrograded barrier. In the middle coast, the association of low beach mobility with high transport capacity and sedimentary availability, and the resulting of the sedimentary transport by wind onshore, allowed the development of large transgressive dunefields and foredunes. Group 4 consists of dissipative and secondarily intermediate beaches, with low mobility, of the progradational barrier of the south coast, which, similar to what occurs in the progradational barrier of the north, did not develop largest dune fields. Group 5 is formed by two beaches with peculiar characteristics, where the intermediate stage predominates and the reflective occurs eventually in the summer, associated with the retrograded barrier. The dissipative beaches are responsible for remobilizing highs sediments volumes of the shoreface and provide to the beach environment, where, in this case, it is converted into coastal progradation. The portion of the aggradational barrier responsible for the largest frontal dunes presents the smaller mobility, and as its mobility is increased towards the south, the largest transgressive dunefields in the state occurs. The intermediate stages have enough energy to carry sediments from the shoreface to the beach, while the formation of the dunes is influenced by the transport potential of the NE wind and by the orientation of the coastline in relation to this wind. Retrograded barriers are associated to intermediary stages of variable mobility, and the two erosive hotspots of the state are associated with high mobility, which turns these environments susceptible to erosion episodes during the passing of storm events. Thus, the erosive character of the barrier may be associated with both wave energy and an irregular shoreface and a negative sediment budget, which leads to variations in beach morphodynamics.

Geoindicadores correspondem a medidas de magnitude e freqüência de processos geomorfológicos superficiais que variam num período inferior a cem anos e se baseiam em análises, diagnósticos e procedimentos para monitoramento do meio ambiente. Assim, o conceito de geoindicador foi adotado nesta pesquisa para formulação e sistematização de indicadores de processos morfodinâmicos e intervenções antropogênicas (uso e ocupação do solo) na bacia do ribeirão Pirajuçara, com 73 km2, que abrange os municípios de São Paulo, Taboão da Serra e Embu, na Região Metropolitana de São Paulo (RMSP). Sua escolha considerou a existência de áreas significativas de produção de sedimentos e o histórico de ocorrências de inundações. Os indicadores foram aplicados em três escalas de análise: bacia do ribeirão Pirajuçara (1:50.000), bacia do ribeirão Poá (afluente principal do ribeirão Pirajuçara) (1:25.000), e sub-bacias de dois afluentes de primeira ordem do córrego Poá (1:5.000). A proposta apresentada reúne 21 (vinte e um) indicadores em quatro categorias: situação de equilíbrio, intervenções antropogênicas, dinâmica das vertentes, e dinâmica fluvial, para cada uma das quais foram descritos os parâmetros de registro de cada indicador. Esse modelo poderá subsidiar a elaboração de planos de monitoramento para prevenção e controle de processos morfodinâmicos em bacias hidrográficas em áreas urbanas e/ou rurais. / Geoindicators are measures of magnitude and frequency of surface geomorphological processes that vary significantly over a period of less than 100 years and are used in environmental monitoring assessment. Geoindicators have been adopted in this research in order to select and systematize the morphodynamic processes and anthropogenic action (land use occupation) in the Pirajuçara Watershed which drains an area of 73 km2, and includes parts of São Paulo, Taboão da Serra and Embu cities, in São Paulo Metropolitan Region (RMSP). The reason for selecting this watershed was the presence of significant erosion areas and the historical records of floods. The indicators have been applied in three scales of analysis: Pirajuçara watershed (1:50.000), Poá watershed - the main subwatershed of Pirajuçara (1:25.000) and two subwatersheds of first order of Poá (1:5.000). This research presents 21 indicators in four classes: equilibrium state; anthropogenic action; hillslope dynamic and fluvial dynamic, and describes for each indicator its characteristics. This proposal may be used to support the elaboration of monitoring plans to prevent and control the morphodynamic processes for watersheds in urban and/or rural areas.

A key goal of tsunami research is to quantitatively reconstruct flow parameters from paleotsunami deposits in order to better understand the geohazards of coastal areas. These reconstructions rely on grain-size and thickness measurements of tsunami deposits, combined with simple models that allow an inversion from deposit characteristics to wave characteristics. I conducted flume experiments to produce a data set that can be used to evaluate inversion models for tsunami deposition under controlled boundary conditions. Key variables in the flume experiments are sediment grain-size distribution, flow velocity and depth, and depth of water ponded in the flume before the tsunami bore was released. Physical experiments were run in a 32 m-long outdoor flume at The University of Texas at Austin. The flume has a head box with a specialized mechanical lift gate that allows instantaneous release of water to create a bore. Various sediment mixtures (silt to very coarse sand) are introduced to the upstream end of the channel as a low dune positioned just below the lift gate. The bore entrained the sediment mixture, producing an unambiguous suspension-dominated deposit in the downstream half of the channel. Deposits were sampled for grain-size and thickness trends. The experimental results capture characteristics of many recent and paleotsunami deposits, including consistent fining in the transport direction. In addition to overall fining, trends in deposit sorting and coarse (D95) and fine (D10) fractions reveal the importance of sediment-source grain-size distribution on tsunami deposit attributes. / text

A investigação dos movimentos morfológicos da embocadura de canais e de linhas de praia pode ser instrumental para a descrição da influência de processos costeiros de curto prazo. A Lagoa do Peixe (LP) encontra-se dentro do Parque Nacional da Lagoa do Peixe (PNLP), 344 km², litoral médio da Planície Costeira do Rio Grande do Sul. O objetivo desse trabalho foi descrever o comportamento morfodinâmico da embocadura do canal, sua instabilidade, geometria, caracterização geomorfológica e a análise da variabilidade da posição da linha de praia adjacente, entre 1987 e 2009. A partir do conjunto de imagens LANDSAT (1973 a 2009) e de técnicas de geoprocessamento, foram analisadas as características morfológicas e a dinâmica do canal. O movimento de curto prazo na linha de praia foi avaliado a partir de imagens LANDSAT TM vetorizadas (1987 e 2009) pelo método dos pontos extremos. Os resultados foram comparados a modelos numéricos, possibilitando a descrição de um canal de maré com um mecanismo de assoreamento morfodinâmico. A região do PNLP sofre a influência da variabilidade do seu regime de precipitação sazonal, onde o maior volume de chuvas ocorre no inverno. Esse regime pluviométrico é associado às correntes litorâneas de SW, que tem de maior capacidade de deriva que as correntes de NE, mais frequentes no verão. A abertura natural do canal ocorreu no biênio: 1997-1998, onde os totais de precipitação anual foram de 400 mm acima da média para a região do PNLP (1265 mm). O assoreamento do canal da LP esta relacionado à diminuição do volume de chuvas. Com a aproximação do verão, o transporte de sedimentos, promovido pelos ventos e correntes de NE, é menos competente, porem de maior frequência, contribuindo para a formação de pontais que se desenvolvem no sentindo das correntes. A análise da variabilidade da posição da linha de praia adjacente ao PNLP acusou um processo progradante ao norte do canal (até 40 m) e retrogradante ao sul (máximo 80 m). Esses resultados são compatíveis com outros resultados oferecidos pela literatura respectiva. / The investigation of morphological change in lagoonal inlets and shorelines can be instrumental to describe the influence of short term coastal processes. The Lagoa do Peixe (LP) is set within the Parque Nacional da Lagoa do Peixe (PNLP), 344 km², located on the mid-section of the Rio Grande do Sul coastal plain. The objective of this work was to describe the morphodynamic behavior of inlet, its instability, geometry and geomorphologic characteristics, as well as an analysis of the variability of the adjacent shoreline position, between 1987 e 2009. A set of LANDSAT images (from 1973 to 2009) and geoprocessing techniques were employed to analyze the morphologic characteristics and dynamics of the LP channel. Short term movements of the shoreline were evaluated from the vectorized LANDSAT TM imagery (1987 and 2009), using the extreme points method. The results were compared to numerical models, which made it possible to describe a tidal inlet with a morphodynamic sedimentation mechanism. The PNLP region is influenced by the variability of its precipitation regime, in which larger precipitation volumes occur in winter. This pluviometric regime is associated to the longshore SW currents which have a greater drifting capacity than the NW currents, more frequent in summer. The natural opening of the channel occurred in the two-year periods of 1997-1998, where total annual precipitation was 400 mm above the average for the PNLP region (1265 mm). LP channel sedimentation is related to the lowering of rain volumes. With the progression of summer, sediment transport promoted by wind and NE currents, is less competent, although more frequent, contributing to the formation of spits that develop siding the currents. Analyses of the variability of PNLP adjacent coastline position indicated a progradation process to the north of the channel (up to 40 m) and a retrogradation process to the south (maximum of 80 m). These results are compatible with other assessments offered by the respective literature.