CHAPTER 1
INTRODUCTION
As waves propagate they are transformed by variations in currents and depths, along
with interaction with obstructions. The major processes of wave transformation include
shoaling, reflection, refraction, diffraction and dissipation. Shoaling is the change of wave
energy, propagation speed and wave height due to changes in the water depth and/or current
field. Refraction is the change in the direction of wave propagation due to the spatial
gradient of the bottom contours and/or current field. Diffraction is the phenomenon of
wave energy being transmitted laterally along a wave crest. Dissipation is the process of
energy loss due to a multitude of possible causes such as bottom percolation, damping
due to viscous effects, turbulence, and wave breaking. As waves approach a shoreline and
break, momentum exchanges can produce currents and mean water level variations. These
currents can be in the form of longshore currents, rip currents, or circulation cells in the lee
of obstructions. They in turn modulate the incident wave field. The process can be quite
complicated depending upon the complexity of the bathymetry, the ambient current field,
and the presence of obstructions.
Coastal engineers and planners have many reasons for wanting to obtain accurate pre
dictions of waves and currents and water elevations in the coastal rone. For instance, pre
dictions of extreme conditions are needed for site planning and erosion mitigation studies.
Harbor authorities need wave predictions for structure design and for operational decisions.
This dissertation develops a numerical model for obtaining predictions of waves, currents
and mean surface elevations in a given domain with the offshore wave conditions and the
bathymetry as the input. The model uses a linear wave equation and depth integrated
equations of momentum and mass conservation. Comparison with experimental results
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