For the stability and protective function of port facilities, it is important to assess the future changes in external force acting on them. In this study, we present that the future changes in the extreme probability of external force are related to those of offshore wave height, storm surge and sea level. We also find that the occurrence probability of an external force exceeding the required performance of the facility in the future climate may be more than twice the one in the present climate.
External forces acting on port facilities such as wave force and wave overtopping rate are expected to change with climate related future changes in sea level, waves, and storm surge. The changes in external forces directly affects performances of the port facilities. Thus, the quantitative projection of the future changes in external forces is necessary to assess the performances in the future.
In design of the port facilities, it is important to understand the extreme probability of external force. Among them, the protection facilities such as breakwaters, jetties, and seawalls should keep their stability against waves and storm surges in storm events to protect other port facilities and land areas from them. In general, the stability and protective function of the port facilities are determined based on a combination of design waves and sea level. Especially in Japan, the design waves are determined by using the waves with the return period of 50 years, and the design sea level is the storm surge of a scenario typhoon on the mean monthly-highest water level or the highest high water level (MLIT, 2018). The external force computed by this combination indicates low frequency and large external force. Therefore, care should be taken in the extreme probability to assess the stability and protective function.
Authors proposed the method to assess the extreme probability of external force (Okamoto et al., 2022). Additionally, as a case study, the extreme probabilities of wave force and wave overtopping rate acting on an existing facility in the present climate was estimated with the proposed method.
