Jean Pierre Lefebvre, Nicolas Gratiot, Franck Dolique, École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL), Laboratoire d’Océanologie et de Géosciences (LOG) - UMR 8187 (LOG), Centre National de la Recherche Scientifique (CNRS)-Université du Littoral Côte d'Opale (ULCO)-Université de Lille-Institut national des sciences de l'Univers (INSU - CNRS), Laboratoire d'étude des transferts en hydrologie et environnement (LTHE), Institut National Polytechnique de Grenoble (INPG)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS), École normale supérieure - Paris (ENS-PSL), Institut national des sciences de l'Univers (INSU - CNRS)-Université du Littoral Côte d'Opale (ULCO)-Université de Lille-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Nord]), Observatoire des Sciences de l'Univers de Grenoble (OSUG), and Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique de Grenoble (INPG)-Centre National de la Recherche Scientifique (CNRS)
The dynamics of the shoreline in French Guiana are characterized mainly by the northwestward migration of nearshore mudbanks. The passage of these features is responsible for significant geomorphic changes at the shoreline, such as the creation and erosion of extensive mudflats and the deviation of estuarine river mouths. Indeed, the hydrodynamic perturbation of the mean alongshore coastal currents generated by river discharge and tidal outflow from these estuaries can result in the immobilization of parts of a migrating mudbank, leading to the creation of a mudflat. Due to the general northwestward direction of coastal oceanic dynamics in this area, such mudflat development always occurs southeast (updrift) of the river mouths and consequently contributes to their northwestward diversion, forming a mudcape. Erosional processes on the marine side of mudcapes often result in a secondary outlet channel that gradually replaces the former main channel. In order to quantify the rate of these geomorphic changes, monitoring of an estuarine area was carried out at different time scales: on a decadal basis, from 1951 to 2001, with airborne sensing data, and over a shorter period covering a complete interbank situation (i.e., between the passage of two successive mudbanks), from 1999 to 2002, by means of field surveys and airborne digital videography. This short-term morphological monitoring was conducted from the early stage of mudflat consolidation and mangrove colonization to the arrival of the following mudbank at the edge of the study area. Various modes of erosion and the diversity of the eroded topography were highlighted by the study. Other aspects brought out by the work are the rate of mangrove colonization and its influence on the erosion processes, the influence of the tide on geomorphic processes, and the role of pioneer fluid mud deposits, related to the proximity of the next mudbank, on the dynamics of the mudflat system.