Process-based and Surrogate Modelling of Fine Sediment Transport in the Dutch Coastal Zone

Process-based and Surrogate Modelling of Fine Sediment Transport in the Dutch Coastal Zone

Kai, C.

2009-04-01

Coastal zones which are known as the interface between continents and oceans are vital and important to human beings because a majority of the world's population live in such zones (Nelson, 2007). Coastal systems are among the most dynamic and energetic environments on earth and they are continuously changing because of the dynamic interaction between the oceans and the land. Dronkers (2005) described coasts as multiform, infinitely complex, quasi-fractal, always changing and unpredictable. Sediment process, especially fine sediment transportation is a very complicated feature in many coastal zones as it is affected by physical dynamics, tide, wave, wind and their mutual interactions. Waves and winds along the coast are both eroding rocks and depositing sediments continuously, and the rates of erosion and deposition vary considerably from day to day. Tidal currents also have great effects on sediment transportation. Sedimentation causes many problems in coastal systems. Fine suspended sediment affects local morphology in coastal rivers, estuaries and shelves environments. Fluid mud, a high concentration aqueous suspension of fine sediment, impedes navigation, reduces water quality and causes environmental damages (Sowed, 2008). So it is crucial and of great interests for coastal engineers and water managing authorities to improve understanding of the underlying sedimentation processes and then further to carry out plans for water management, coastal protection, channel maintenance, land reclamation and dredging of deepwater navigational channels, etc. Along the Dutch Coast, a lot of efforts have been made to improve the prediction and understanding of sediment transport processes. Process-based models such as SOBEK and Delft3D of Deltares have been proved to be useful in simulation of 2D/3D sediment processes in the Dutch coastal areas. Delft3D solves shallow water equations and transport equations for salinity and suspended particulate matter (SPM) numerically by using a finite-difference scheme. Delft3D was used to build both large-scale and small-scale models to predict SPM concentrations and siltation rates in the Dutch coastal zones. For example, Van Kessel et al. (2007) built model of the Southern North Sea and Li (2007) built a local model focused on the mouth of River Rhine. The results from both models were satisfactory. However, simulating sediment transportations with process-based models is often quite time consuming, which restricts process-based model for widely applications. More detailed information will be introduced in Chapter 1.3. Data-driven models (DDM) have also been used in simulation of sediment processes (Bhattacharya et al., 2006). They are based on limited knowledge of physical processes and rely on the data describing input and output characteristics. Data driven techniques are used in building models to solve mathematical equations from the analysis of concurrent input and output time series instead of the analysis of physical processes. Solomatine and Ostfeld (2008) described that the model works on the basis of connections between the system state variables (input, internal and output variables) without considering too much on assumptions about the natural processes of the system.

Dutch coast
North sea
wadden sea
coastal sediment
currents
morphology
sedimentation processes
process based models
SOBEK
Delft3D
shallow water
suspended particulate matter
SPM
river Rhine
data driven models
DDM
morphological
meteorological
hybrid modelling
Delft Cluster
CT05.20
Noordzee & kust
CT05.24.11
morfodynamiek van Noordzee en kust en kustverdediging

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Delft Cluster

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(c) 2009 Kai, C.