The overarching research aim is to gain understanding of the three-dimensional physical mechanisms resulting in the trapping of fine sediments in tidal estuaries such as the Scheldt and Ems estuary, and the typical timescales at which sediment is imported to evolve to previously found equilibria after mud extraction.
Since the interaction between longitudinal, lateral and vertical processes, and their relative importance concerning sediment dynamics, is never systematically investigated, and their transient response to changing conditions is still largely unknown, the specific aims of this PhD project is:
1. To analyze the water motion in a three-dimensional idealized model, and assess the sensitivity of the water motion to geometry and roughness formulation (including a comparison with the results concerning the water motion obtain by Steven Kaptein using the width-averaged version of iFlow). The three-dimensional formulation will be included in the existing iFlow modeling structure (grid generation, Finite Element solution method, analysis method).
2. To analyze the three-dimensional mechanisms producing equilibrium suspended sediment patterns and ETM under regular forcing conditions, considering the formulation of the erosion function introduced by Brouwer et al (2018).
3. To determine the sensitivity of these equilibrium suspended sediment patterns to wind forcing, river discharge and geometry/bathymetry. Importantly, here we focus on the equilibrium response to non-transient forcing conditions.
4. To assess the transient evolution of turbidity under spatiotemporally varying conditions on the subtidal timescale (i.e., large compared to the tidal timescale).
To answer these research questions, a three-dimensional idealized model that resolves the water motion, sediment transport and trapping, will be developed by extending the model of Kumar et al. (2017) to include
processes that were shown to be essential to correctly model the sediment dynamics in the Scheldt and Ems estuary.