Transport sédimentaire et architecture de barrières littorales silico-bioclastiques : une approche par modélisation physique

Abstract : In many areas, coastal environments, from tropical to temperate-cold zones, are characterizedby mixed sediments, i.e. made of a mixture of siliciclastic and biogenic particles. Processes oftransport that occur in these so-called "mixed" environments are difficult to quantify and modeldue to the differences in hydrodynamic behaviour between siliciclastic particles, generally ofsub-spherical shape, and bioclastic particles the shape of which is very complex. The presentPhD work is related to this topic and aims in evaluating if changes in the composition ofmixed sediments can impact significantly the dynamics of the coastline, and more specificallythe construction modes of coastal barriers. To reach this objective an experimental approachhas been developed. Experiments in unidirectional current flume (erodimeter) highlight thesingular behaviour of bioclastic debris in comparison with that of siliciclastic particles, as wellas significant differences in behavior between bioclasts from various mollusc species. Theseresults could help in improving numerical models of natural sediment transport. Experimentsin a large wave flume clearly show that coastal barriers reconstructed from mixtures of varyingproportions of siliciclastic and bioclastic sediments have different morphological characteristicsand internal architectures. Barriers with high content in bioclastic debris are thicker andnarrower compared to barriers containing more siliciclastic particles. These findings suggestthat an increase in bioclastic inputs may have a positive effect on the stability of littoral barriers.
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Alissia Rieux. Transport sédimentaire et architecture de barrières littorales silico-bioclastiques : une approche par modélisation physique. Sciences de la Terre. Normandie Université, 2018. Français. ⟨NNT : 2018NORMC268⟩. ⟨tel-02159560v2⟩

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