Ce travail de thèse s’inscrit dans le contexte général de l’étude de la dynamique de la frangelittorale. Le but de ce travail de thèse était l’étude des couplages entre les ondes de surface (vagues, ondeslongues dont les ondes infra-gravitaires), les variations du niveau marin et les courants ainsi que les variationsà haute-fréquence du niveau d’eau sur la plage et les déplacements de la nappe phréatique au sein de la plagesableuse. L’approche retenue est essentiellement expérimentale in-situ.La campagne de mesure ROUSTY201412 a permis de récolter un jeu de données hydro- morphodynamiquesconsidérable, qui viendra alimenter l’étude des plages sableuses dans de nombreux domaines. Elle permeten particulier de décrire l’ensemble d’une saison hivernale sur un même site soumis à une grande variété declimats de houles et de vents, ce qui en fait un jeu de données unique dans le contexte méditerranéen.Dans cette thèse nous nous intéressons à trois domaines d’étude : la dynamique de la surface libre avecl’analyse des relations existantes entre les différentes échelles (vagues, variations du niveau marin, ondeslongues, wave-setup, ...), la structure et l’évolution du courant ainsi que le lien avec la dynamique de surface,et la circulation souterraine dans la nappe de plage et en particulier sous la zone de swash. / This PhD work is part of the general context of littoral dynamic study. The purpose of this workwas to study couplings between surface waves (waves and long waves including infra-gravity waves), sea waterlevel variations and currents, as well as high-frequence water level variations on shoreline and groundwatermovements within sandy beaches. The approach is mostly experimental in-situ.The field campaign ROUSTY201412 allowed the collection of a substantial hydro- morphodynamic dataset,supplying sandy beaches studies in several fields. In particular, it will allow, on a same site, the descriptionof a full winter season under various waves and winds climates, making it a unique dataset in Mediterraneancontext.In this PhD, we are interested in three fields : free surface dynamics, including multi scale relations analysis(waves, water level variations, long waves, wave-setup, ...), currents structure and evolution linked withsurface dynamics, and groundwater circulation within the coastal aquifer and particularly under the swashzone.

Made available in DSpace on 2015-02-24T19:48:40Z (GMT). No. of bitstreams: 1 MarceloSC.pdf: 3390549 bytes, checksum: 96946e2e3e5bc8f4dcb5b4714f27c462 (MD5) Previous issue date: 2005-10-10 / This thesis describes the general behavior of the northern shore of the State of Rio Grande do Norte relating beach profile morphology with hydrodynamic and sedimentological parameters. The Macau and Serra Oil Field are inserted on this area and are under accelerated coastal erosion. At these oil fields are installed oil wells from PETROBRAS, nowadays located directly in the shoreline, under constant attacks of coastal processes (e.g. waves, tides and currents), which promote an intense morphodynamic variability of this sandy coast. The area was monitored for 24 months in three different stations (P01, P02 and P03). The methodology applied involved current techniques of beach profiles, hydrodynamical processes, remote sensing and geophysics. A synthesis of results obtained through the use of different time scales (monthly, lunar cycle, seasonal, annual) from a coastal dynamics study is presented. The average wind direction corresponded to 77?Az (NE). The steepness of the berm and of the shoreface, as well as coastal current direction, do not present major changes, with an average of 36? for the steepness of the berm, 15? for the shoreface and 15? for the coastal current direction. This data set allows us to infer that the months of larger coastal erosion were November/2000 and April/2001, because of the largest wave parameter during this time. The months of worse coastal erosion in this area are related with the increasing wavy energy. This in turn, seems to be related to seasonal climatic variations, with the wave energy and tide currents speed increasing during months of minor precipitations (June to January). The months of worse coastal erosion were September and November, when the largest wave parameters and speed currents are measured in the area. Since these months are included on the period of minor precipitations, we related the coastal erosion to seasonal climatic variations. The results obtained during these 24 months of monitoring confirms a situation of accentuated erosion, mainly in Profile 03 (Barra do Corta-Cachorro), where the wave height, period, and coastal current speed are always larger than the values found in Profile 02 (Macau5). Probably these values are more expressive in Profile 03, because it does not present any natural structure of protection against the wave impacts, as the barrier island located at Ponta do Tubar?o, or the sand banks in front of Macau5. The transport of the sediments occurs from East to West, and the sand accumulation is more pronounced on Profile 03 intertidal zone, where there are embrionary dunes in dryer months. The tidal currents speed, on the other hand, is more accentuated in the Macau5 area (Profile 02). At Ponta do Tubar?o, the tidal currents presented a preferential direction for NE, at times of flood, currents and for NW, at times of ebb current; at Barra do Corta-Cachorro the direction of the currents were predominantly for NW, independent of the tide phase, coinciding with the preferential direction of the longshore current. This currents inversion at Ponta do Tubar?o is attributed to the presence of the Ponta do Tubar?o island barrier and by the communication channel of the lagoon with the sea. The tide currents are better observed in protected areas, as in the Ponta do Tubar?o, when they present inversion in their direction accordingly to the flood and ebb tide. In open areas, as in Barra do Corta-Cachorro, the tide currents are overprinted by the longshore currents. Sediment analysis does not show important modifications in grain size related to seasonality (dry- and rainy seasons). On the foreshore and backshore zones, the sediments vary from fine to medium sand, while in the shoreface they very from fine to very sands. The grains are mostly spheres, varying from sub rounded to sub angled. Quartz is the main component alongside Feldspat and heavy minerals as accessory components. Biogenic content is also present and mainly represented by mollusks fragments. The calculated sediment transport show values around 100 m3/day. The morphodynamic studies indicated that this is a reflexive area from October to April, and intermediate from May to September. The Relative Tide Range-RTR for this area is 4 < RTR < 15, and so classified in the mixed wave-tide group. Having this exposed we can affirm that the more active natural factors in this area are the currents, followed by the tides and the winds. The anthropic factors are exclusively local and punctual (Macau and Serra Oil Field). Taking in account the economic importance of the area, as well as the intensity of coastal processes acting on this shore, it is important a continuity of the monthly environmental monitoring looking for variations on longer-period cycles. These data have been stored on the geo-referenced database of the projects MARPETRO and PETRORISCO (REDE 05), aiming to model the coastal and sea environment, susceptible to oil spills and their derivatives / Esta tese contempla a caracteriza??o da din?mica costeira dos campos petrol?feros de Macau e Serra, localizados no litoral setentrional do Estado do Rio Grande do Norte. Estes campos petrol?feros est?o inseridos em uma costa de mesomar? sob a a??o da eros?o costeira. As instala??es do campo Macau foram constru?das no in?cio dos anos 80 do s?culo passado a uma dist?ncia de aproximadamente 800 m do mar. Atualmente, encontram-se localizadas na linha de costa, sob ataque constante dos processos costeiros (ondas, correntes, mar?s), que promovem uma intensa variabilidade morfodin?mica.Diversas medidas t?m sido aplicadas para proteger esta linha de costa contra a eros?o nos po?os petrol?feros. Entretanto, estudos de monitoramento n?o haviam sido efetuados anteriormente. A metodologia utilizada envolveu a utiliza??o de dados de sensoriamento remoto (tratamento digital de imagens orbitais e fotografias a?reas), processos costeiros (ventos, correntes, ondas e mar?s, inclusive o padr?o de circula??o local), perfis praiais, an?lises sedimentol?gicas e geof?sicas (batimetria) para caracteriza??o da din?mica costeira local em diferentes per?odos (mensal, ciclo lunar, semestral) em tr?s pontos distintos (P01, P02 e P03). Os resultados deste estudo mostram que enquanto a praia na regi?o da Ponta do Tubar?o apresentou-se est?vel com tend?ncia a deposi??o, na regi?o do Macau5 e Barra do Corta-Cachorro ocorreu uma tend?ncia ? eros?o. Isto ? confirmado atrav?s da evolu??o desta linha de costa realizada com base nas imagens Landsat de 2000, 2001, 2002 e 2003 (monitoramento anual). Observa-se tamb?m que durante o ciclo lunar de mar?o 2002 (in?cio do per?odo chuvoso) a ?rea em estudo n?o apresentou diferen?as durante as quatro fases da lua. Entretanto, no ciclo lunar de outubro 2003 (per?odo seco e ventos fortes), apenas o Perfil 01 n?o apresentou diferen?as significativas. O Perfil 02 apresentou maior deposi??o na fase de lua cheia e o Perfil 03 uma maior deposi??o na lua nova, com presen?a de barras arenosas. Os resultados da hidrodin?mica costeira mostraram que na regi?o da Ponta do Tubar?o, devido ? prote??o exercida pela ilha-barreira, as ondas s?o atenuadas e as correntes de mar? exercem um papel importante no interior da laguna. No per?odo de mar? vazante as correntes mostraram uma dire??o geral para NW, coincidindo com o sentido da deriva litor?nea, enquanto no per?odo de mar? enchente ocorre uma invers?o no sentido da corrente para E-NE. Na ?rea do Macau5 e Barra do Corta-Cachorro, que n?o s?o abrigadas pela ilha-barreira, os valores de temperatura, condutividade e velocidade da corrente aumentaram com a profundidade e o sentido preferencial das correntes foi para NW, independente da fase de mar?. O volume de sedimentos transportados pela deriva litor?nea ? da ordem de uma centena de metros c?bicos ao dia. A an?lise mensal dos dados granulom?tricos indica, no geral, uma grande homogeneidade nos resultados obtidos (acima de 90%), mostrando que n?o houve modifica??es no tamanho dos gr?os em rela??o ? sazonalidade (per?odo de chuvas e per?odo seco). Nos tr?s perfis monitorados (P01, P02 e P03), tanto a p?s-praia quanto o estir?ncio, foram classificados pela m?dia como areia fina a m?dia. Apenas a antepraia ? classificada como areia fina a muito fina. Os gr?os s?o predominantemente esf?ricos, sub-angulosos a sub-arredondados. Composicionalmente quartzo ? o mineral vi predominante, podendo ocorrer tamb?m micas, feldspatos, fragmentos de rocha e minerais pesados (< de 5% cada), bem como componentes bi?ticos. Quanto a morfodin?mica a ?rea em estudo foi classificada como reflexiva (erosiva) nos meses de outubro a abril e como intermedi?ria (inst?vel) nos meses de maio a setembro, tanto no Perfil 02 (Macau5), como no Perfil 03 (Barra do Corta-Cachorro). Aplicando o modelo de Masselink e Turner (1999) para uma varia??o m?dia de mar? de siz?gia de 3 m, a varia??o relativa de mar? - RTR (Relative Tide Range) obtida para as praias da ?rea em estudo esteve na sua maior parte entre 4 e 15, permitindo ser classificadas como praias mistas, denotando a influ?ncia das ondas e mar?s para a regi?o. Na zona submersa pr?xima ? costa as linhas batim?tricas apresentam um trend principal paralelo ? linha de costa na por??o oeste da ?rea, enquanto que na por??o leste, apresenta uma varia??o, pela complexidade morfol?gica influenciada pela Ponta do Tubar?o. Na baixa-mar ? poss?vel observar os bancos de areia expostos. O entendimento das causas da eros?o costeira e monitoramento dos processos costeiros obtidos nesta tese permitiu a quantifica??o e caracteriza??o das mudan?as na linha de costa, essenciais para elabora??o de mapas de sensibilidade ambiental ao derramamento de ?leo