P.S. Miranda1,2*, J.J. van der Werf1,2 , S.J.M.H. Hulscher1
1 University of Twente; 2 Deltares
* Corresponding author: p.s.miranda@utwente.nl
Introduction
Our research is under the framework of Marie Sklodowska-Curie Action Doctoral Network programme funded by the EU entitled, SEDIMARE. Specifically, our research focuses on practical morphological modeling of sand-mud mixtures.
Estuaries are systems that provide value to both ecology and human activities. However, estuaries are also susceptible to degradation from both sea level rise, and storms. One way to help preserve these systems is by understanding their morphodynamics.
The current studies on estuarine morphodynamics have mostly been towards mixed sediment systems that are sand- or clay-dominated (van der Wegen & Roelvink, 2012; Vanlede et al., 2019). However, there are estuaries which are silt-dominated that are not yet fully understood (te Slaa, 2020).
My PhD will describe the explicit contribution from each sediment component by adapting the erosion behavior and bulk density formulas. These will be validated by incorporating them into the process-based model, Delft 3D, and analyzing the resulting morphdynamics. Validation cases will be chosen depending on what sediment component is dominant (e.g. sand, silt, or clay). Finally, these systems will be subjected to long-term modeling with sea level rise, and short-term modeling with storm forcing. This is to assess the potential impact of these forcings on the morphodynamics of different types of estuaries.
Objective and Methods
The methodology will involve an analysis of the current erosion models (Chen et al., 2018; Van Ledden et al., 2004; van Rijn, 2007; Wu et al., 2018) for mixed sediments. From these models, together with available data,
Nand will be incorporated into the process-based numerical model, Delft 3D 4. These, such as the Western Scheldt (sand-dominated) and Yangtze river (silt-dominated) estuaries, and Zeebrugge harbor (clay-dominated).
Finally, numerical test cases will be done to understand the effect of sea level rise and storm conditions on the differently dominated sediment systems. We will apply the appropriate Intergovernmental Panel on Climate Change (IPCC) Shared Socioeconomic Pathways (SSP) for decadal lengths on each of the systems and then analyzing the resulting morphodynamics. Similarly, historically significant storms for each of systems will be introduced as hydrodynamic forcing in the numerical model. The immediate (timescale: hours) and short-term (timescale: days to months) impact of the storm to the morphodynamics will be analyzed.
Results
Expected result is a new formulation for erosion behavior and bulk density of mixed sediments with explicit contributions from each sediment classification. We also expect morphodynamic results in good agreement with measured bathymetry of differently dominated sediment systems. Finally, we expect to gain insight into the effects sea level rise and storm conditions have on different types of estuaries
Maps of estuaries from van Maren et al. (2020) for Zeebrugge harbor, Bolle et al. (2010) for the Western Scheldt, and Feng et al. (2020) for the Yangtze river estuary overlain on muddy coasts of the world from Hulskamp et al. (2023)
References
Bolle, A., et al. (2010). The influence of changes in tidal asymmetry on residual sediment transport in the Western Scheldt. Continental Shelf Research, 30(8), 871–882.
Feng, H., et al. (2020). Effects of recent morphological change on the redistribution of flow discharge in the Yangtze River Delta. Continental Shelf Research, 208.
Hulskamp, R., et al. (2023). Global distribution and dynamics of muddy coasts. Nature Communications, 14(1), 8259.
te Slaa, S. (2020). Deposition and erosion of silt-rich sediment-water mixtures [Doctoral thesis, Delft University of Technology].
van der Wegen, M., & Roelvink, J. A. (2012). Reproduction of estuarine bathymetry by means of a process-based model: Western Scheldt case study, the Netherlands. Geomorphology, 179, 152–167.
Van Ledden, M., et al. (2004). A conceptual framework for the erosion behaviour of sand-mud mixtures. Continental Shelf Research, 24(1), 1–11.
van Maren, D. S., et al. (2020). Formation of the Zeebrugge coastal turbidity maximum: The role of uncertainty in near-bed exchange processes. Marine Geology, 425.
van Rijn, L. C. (2007). Unified View of Sediment Transport by Currents and Waves. I: Initiation of Motion, Bed Roughness, and Bed-Load Transport. Journal of Hydraulic Engineering, 133(6), 649–667.
Vanlede, J., et al. (2019). Mud dynamics in the Port of Zeebrugge. Ocean Dynamics, 69(9), 1085–1099.
