June 17-18 2004
Wrigley Marine Science Center
Catalina Island, California

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The primary objectives of the workshop are to discuss several critical issues concerning the accuracy of long-wave runup models.

1. Calculations of the moving shoreline. This is certainly not a new issue. The accuracy of the numerical algorithm used in locating the shoreline has direct consequence in estimating the maximum tsunami runup. The moving nature of the shoreline boundary makes the problem nonlinear. Various kinds of numerical treatments have been invented and some of them have caused numerical instability or dissipation. In some cases, artificial damping is introduced into the numerical algorithm, masking the instability and clouding the accuracy of solutions. However, surprisingly, these issues have not been the focus of discussions in the past workshops. With the development of higher-order models for tsunami propagation and runup, such as the Boussinesq equations, and the inclusion of more physical processes, such as wave breaking, and bottom friction, it is important to create a forum to discuss this difficult, but critical issue openly.
2. Modeling of bathymetry and topography. It is obvious that the predictability of any numerical model depends largely on the source region information (i.e., the initial condition) and the correct representation of bathymetry and topography. There are two levels of issues to be discussed as far as the bathymetry and topography data are concerned. The first is the availability and the resolution of bathymetry and topography data. The second concerns the grid resolution requirement in a numerical model and its relationship to the resolution of the bathymetry and topography data. The common practice for deciding the grid resolution has been based on the characteristic wavelength. However, there is very little understanding on the grid resolution requirement in terms of bathymetric and topographical variations; i.e., slope and curvature of the seafloor and land surface. Furthermore, different numerical schemes can be used to interpolate and/or extrapolate a given set of bathymetry and topography data to obtain approximated data at the grid points of a numerical model. The differences in the resulting slope and curvature could affect the numerical solutions for wave heights and the direction of propagation, especially in the case of long distance propagation.
3. Landslide generated tsunami. The characteristics of landslide generated tsunamis could be different from those generated by tectonic movements. For example, the wavelength could be shorter and the dispersion effects might be important. The traditional shallow water equation model might not be adequate. Moreover, the duration of a landslide is usually in the order of magnitude of a few minutes or longer. Therefore, it is hard to justify not considering the landslide motion in the tsunami generation process. On the other hand, our knowledge of the dynamics of sub-aerial and sub-marine landslides is still incomplete. The strategy for parameterizing the slide movement to provide adequate initial conditions for tsunami propagation models is an important topic to be discussed.
4. Tsunami forces on a nearshore structure. When tsunamis impinge a structure on land, the flow system is very complex. Quite often the waves are breaking and the flow filed is three-dimensional. The depth-integrated hydrodynamic models are no longer suitable for describing this complex flow. Instead, the Navier-Stokes Equations with suitable turbulence model are required. The important modeling issues include the selection of free surface tracking technique, the selection of appropriate turbulent model for wave breaking generated and boundary layer generated turbulence, and the interface between 3D model and the depth-integrated hydrodynamic model. Although there are only a few researchers are involved in this type of modeling efforts, it is a challenge that should be brought to the attention of the entire coastal and tsunami community.

Background / Benchmark Problems / Contact Information (organizing committee)
Home / Objectives / Travel Information / Participants / Proceedings / Program / Work Plan