Wave overtopping is one of the most important processes for the design of seawalls. During the past few decades methods for predicting wave overtopping of coastal structures have continuously been developed. In this study, a numerical wave flume based on two-dimensional Reynolds-averaged Navier-Stokes equations with a VOF (Volume Of Fluid) method (Hirt and Nichols, 1981) is described. We are concerned with increasing wave overtopping volume by the sea level rise due to global warming, and numerical simulations are carried out to estimate wave overtopping quantity using the two-dimensional numerical wave flume under regular and irregular wave conditions. The influence of how the water level, wave height and wave period affect the overtopping quantity has been investigated.
A storm surge is a natural hazard causing serious damages to lives and properties. Japan has been attacked by typhoons every year, and some typhoons have brought storm surges especially in the inside of bays. Recently, Typhoon 9918 (T9918) attacked north Kyushu and Yamaguchi areas in the early morning of September 24, 1999. This typhoon resembled Typhoon 9119 (T9119) in power and course, and both typhoons generated similar magnitude of storm surge, as shown in Table 1. The storm surge by T9918 caused devastating damages along the coasts of the Yatsushiro Sea and the Suo Sea, because this typhoon hit there at the same time of the highest spring tide. But, the storm surge by T9119 didn't, because of low tide. The seawalls of New Moji port on the west coast of the Suo Sea were destroyed at 10 locations by the wave force of the typhoon and wave overtopping. A large amount of seawater by wave overtopping and a direct consequence of seawall collapse invaded upland areas and inundated the area of about 9.4km2. Therefore, this area suffered the serious inundation damage, as shown in Photo 1.(refer to the full paper)
