Case study on impact of storm waves on inundation characteristics

Modeling interactive features of storm waves and surges may be one of important but challenging tasks toward more accurate estimations of coastal hazards under severe storms. This paper discusses how storm waves and interactions of waves and surges affect amplification of local inundation characteristics through overviews of several case studies of recent coastal disasters. The paper first describes witnessed inundation characteristics caused by Super Typhoon Haiyan along the coast of San Pedro Bay and also the east coast of Eastern Samar in the Philippines. Along the west coast of San Pedro Bay, neither predicted storm surge nor storm wave can reasonably represent the following observed features: inundation around the mouth of San Pedro Bay started about an hour prior to the time when the inundation was witnessed at the inner part of the bay and the water level quickly descended after the peak around the bay mouth while it was kept high for an hour in the inner part of the bay. Along the east coast of Eastern Samar, deformation of wind wave components strongly depends on bathymetry of fringing coral reefs and refraction, diffraction and wave-wave interactions appear to have significant influence on observed locally varying damage levels and inundation characteristics. Similar locally concentrated inundation was also observed along the west coast of Batan island, the Philippines when the super typhoon Meranti passed north of the island. Significant influence of infra-gravity waves on the locally concentrated inundation characteristics was also observed in the disaster along Seisho coast on the Pacific coast of Japan when the typhoon, Fitow, hit the coast in 2007. Based on these findings, finally, this paper discusses how the numerical model should be extended for better estimations of coastal hazard with brief example of model application to South Pacific islands.