Modelling the effect of marine processes on deltaic wetlands
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Deltaic wetlands are among the most biodiverse systems on earth, provide important ecosystem services, and are natural buffers against violent storms and hurricanes. Marine processes change the planar configuration and internal stratigraphy of deltaic wetlands, and understanding their contribution to wetlands development and deterioration processes is a key issue for society. In this thesis, field data and numerical models are used to investigate the effect of marine processes on the formation and evolution of deltaic wetlands. The first part of this work focuses on the effect of micro and meso tides on the hydrodynamics, morphodynamics, and stratigraphy of deltaic distributaries. Data from instruments deployed in Apalachicola Bay (FL) were used to investigate the hydrodynamics of river mouths. Investigating the hydrodynamics is the first step for a deeper understanding of sediment transport processes, and possible implications for the morphological evolution of these depositional environments. The effect of micro and meso tides on the morphology and stratigraphy of mouth bars is then explored by using numerical and analytical tools. Mouth bars are the building units of river deltas and continuous bifurcations around them allow delta progradation and the formation of new deltaic islands. The second part of this work focuses on the effect of wind waves on salt marsh deterioration using cellular automata and process-based models. Special attention is given to salt marsh resilience to extreme events, to the effect of variable erosional resistance on the large scale morphodynamic response of salt marshes to wind waves, and to the identification of geomorphic features indicative of wetlands deterioration. Results from cellular automata and process-based models are compared to field and literature data.