Shallow parts in a sloping bottom toward the coast can be expected to act as a waveguide, in partial analogy with optical
waveguiding. We will present numerical simulations that convincingly show that large enhanced wave amplification
happens for tsunami waves in certain geometries and bathymetries. Since this is even the case for shallow regions that
have cross sections of the order of badly resolved numerical scales, this phenomenon may at least partly explain that
tsunami heights and coastal effects as observed in reality show such high variability along the coastline.
This report, following , supports a more concise publication that will be published soon . In this report we will
provide detailed results of extensive simulations using various wave models and different gridsizes. We will show results
obtained with the commonly used Shallow Water Equations and with a more accurate dispersive wave model. For
the latter simulations we use a recently derived Variational Boussinesq model. We will also show that relatively small
gridsizes are needed to capture the transversal flow near the waveguide; on grids that are too coarse, the enhanced
amplification will not be observable. This may provide a partial explanation that spatial variability due to relatively
shallow bottom variations will not be present in most simulations.
|Place of Publication||Bandung|
|Number of pages||16|
|Publication status||Published - Oct 2007|
|Name||CTIT Technical Report Series|