NUMERICAL MODELING OF TIDAL-WAVE RUNUP

A numerical solution for the 2 + 1 (long-shore and onshore propagation directions and time) nonlinear shallow-water wave equations, without friction factors or artificial viscosity is presented. The models use a splitting method to generate two 1 + 1 propagation problems, one in the onshore and the other in longshore direction. Both are solved in c haracteristic form using the method of characteristics. A shoreline al gorithm is implemented, which is the generalization of the earlier 1 1 algorithm used in the code VTCS-2. The model is validated using lar ge-scale laboratory data from solitary wave experiments attacking a co nical island. The method is applied then to model the 1993 Okushiri, J apan, the 1994 Kuril Island, Russia, and the 1996 Chimbote, Peru tsuna mis. It is found that the model can reproduce correctly overland flow and even extreme events such as the 30-m runup and the 20-m/s inundati on velocities inferred during field surveys. The results suggest that bathymetric and topographic resolution of at least 150 m is necessary for adequate predictions, while at least 50 m resolution is needed to model extreme events, contrary to intuitive expectations that long wav es would not interact with morphological features of such short scales .