EFFECT OF WATER LEVEL CHANGE ON WAVE OVERTOPPING VOLUME BASED ON EXPERIMENT SIMULTANEOUS OCCURRENCE OF STORM SURGES AND WAVES

Typhoon Jebi hit Osaka Bay, Japan in 2018, causing significant damage to coastal areas due to storm surges and high waves. Although the water level due to the storm surge was lower than the seawalls, the super-imposed storm surge caused inundation damage in some areas in the hinterland, such as Kansai Airport due to wave overtopping. Inundation damage in inner bay areas was enhanced by the simultaneous occurrence of storm surges and high waves. Therefore, it is necessary to reexamine the transition state of water level rise caused by storm surges and the effects of the simultaneous occurrence of storm surges and high waves. In this study, changes in wave overtopping and overflow were measured experimentally under conditions of transitional rise in water level due to storm surge and a series of phenomena from a state in which only wave overtopping occurs to a state in which wave overtopping and overflow occur simultaneously were reproduced by hydraulic experiment. Furthermore, the results were compared with the wave overtopping to surge transition model developed by Mase et al. (2020), and the accuracy of the existing models was examined.