Coastal Morphological Modeling

Abstract

The coastal zone is the area where the action of waves and wave-driven-currents on the seabed is very intense, and where the bed level and sediment are almost always in motion. If the mainly seasonal climate changes, the wind and wave conditions will also change. A new waves and wave-driven-currents conditions will change the rate of sediment transport and the beach topography. Natural beaches are significant characterized by an annual cycle of seasonal erosion and accretion. In other words, natural beaches are generally in dynamic equilibrium from the balance of sediment transport budge for specific area on the beach. We can utilize the conservation law of sediment transport to describe the coastal morphodynamic evolution. It is the same way to predict beach evolution due to changes in wave conditions or caused by coastal structures. Therefore, we can utilize numerical models to predict the change of bottom topography from the spatial distribution of the alongshore and offshore sediment transport rates in real coastal area. Coastal morphological models are indispensable and powerful tools that allow harbour and hydraulic engineers to predict nearshore topography, to analyze the impact of coastal structures, and to verify the planning and design of harbours and coastal defences. Morphological models are based on various sub-models for waves, tidal currents, nearshore currents, and sediment transport, coupled with the sediment transport model. The sediment transport model solves the sediment conservation equation to calculate bed-level evolution. The local sediment transport is first calculated by wave and current sub-models, and the bed form evolution is then computed based on the conservation of sediment and its continual redistribution in time. The aim of this chapter is to describe the theories, techniques, applications and robust algorithms for computing bed level change which is flexible enough to handle the nonlinearity present in the sediment conservation equations describing bed evolution in a complex coastal area. Classification of prediction methods for morphological evolutionThe changes of coastal topography were the complex and irreversible morphodynamic processes, influenced by local bathymetry, weather, wave, tide, and coastal structures, etc. The technology of prediction morphological evolution caused by coastal structures or varied with monsoon, typhoon, and climate changes, etc. is needed. In order to predict morphological evolutions, the experience analysis with many survey data in similar cases and the results of hydraulic model tests are considered in the past.

Study on the Coexistence of Offshore Wind Farms and Cage Culture

“…This study used a hydrodynamic model that included wave and current characteristics for calculation. The numerical model first analyzed the overall coastal dynamic characteristics, and corrected some numerical calculation parameters and input/output data formats and contents according to different regions that may be affected, and then analyzed the impact of offshore wind turbines on the wave-current pattern [19][20][21].…”

Analysis and Exploration of the Impact of Average Sea Level Change on Navigational Safety in Ports

“…The numerical model first analyzes the overall coastal dynamics and adjusts specific numerical parameters and input/output data formats and content for areas that may be affected. Subsequently, the model analyzes the influence of sea level rise on the wave and flow fields [39][40][41]. The calculation of the planar wave field in the hydrodynamic model utilizes the unsteady-type governing equations for water waves, including the effects of currents on inclined slopes [42]:…”

Hydrodynamic Equilibrium for Sediment Transport and Bed Response to Wave Motion

“…To solve Eq. 1 it is required to use various numeric schemes (Callaghan et al 2006, Chiang and Hsiao 2011, Johnson and Zyserman 2002, Long et al 2008. As shown, among others by Johnson and Zyserman (2002), the numerical schemes used to solve Eq.…”

“…It will, however, demand a greater computational power of computers. If the diffusion term is correctly removed from the transport equation, the boundary value of the Courant number can be exceeded (Chiang and Hsiao 2011). This is attainable through the introduction of diffusion constants, which are chosen according to the actual environmental conditions (Cayocca 2001, Chiang et al 2010, Kuroiwa et al 2004, Struiksma et al 1985, Watanabe 1988).…”