Hydrodynamique et transport de particules en suspension dans le lagon sud-ouest de Nouvelle-Calédonie

Abstract : This thesis participates to a study that has been lead for several years by IRD which aims increased knowledge of hydrodynamics and transport of dissolved substances and particles on the South-West Lagoon of New Caledonia (SLNC). This work stands on field measurements and numerical modelling. The first step of this thesis is an attempt to synthesise the great amount of data produced by a numerical hydrodynamic model (MARS3D). Indexes having the dimension of time and related to the renewal of water masses were computed from numerical tools applied to the hydrodynamic model. The computation methods, the significance and the application of these indexes to the Southwest Lagoon of New-Caledonia (SLNC) are exposed. Examples of application of these indexes aiming to quantify the influence of hydrodynamics on biological processes are shown. Out of flooding periods, the re-suspension of freshly deposited sediments is the main source of suspended particles on the SLNC. The combined actions of waves and currents induce a bottom shear stress that is responsible for particle re-suspension. In order to access the wave field characteristics, a wave model (WavewatchIII) was implemented over the SLNC. It was validated by in situ directional measurements of the wave field. The last part of this thesis focuses on the determination of physical properties of suspended particles such as particle size distributions, density, and fall velocity, are compulsory to model particle transport. This work stands on in situ measurements and laboratory experiences performed with laser particle size analyser. Results emphasise the importance of bioaggregation in a coral reef ecosystem.
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Aymeric Jouon. Hydrodynamique et transport de particules en suspension dans le lagon sud-ouest de Nouvelle-Calédonie. Milieux et Changements globaux. Université du Sud Toulon-Var, 2007. Français. ⟨tel-01171150⟩

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