Effect of Climate Change on Performance-Based Design of Caisson Breakwaters

Abstract

This paper presents a method to incorporate the effect of climate change on the performance-based design of a caisson breakwater and its application to the East Breakwater of the Port of Hitachinaka in Honshu, Japan. The up-to-date projection estimated a future sea-level rise of 0.25–0.6 m and a wave-height increase of 1.7 m (from 8.3 to 10 m) during the 21st century in this area. The influence of a sea-level rise on caisson sliding was minimal; the sea-level rise was much smaller than the water depth at the breakwater site. When the effects of climate change were not included, the performance-based design method calculated the same caisson width as that of the constructed breakwater, partly validating the consistency between conventional deterministic methods and performance-based design methods. The effects of climate change dictate an increase in caisson width of approximately 1.5 and 0.5 m for linear and parabolic increases of wave height, respectively, which are approximately 6.8 and 2.3% of the present caisson width of 22 m. Finally, it is recommended that the caisson breakwater be designed using the projected wave height and water level in 30 years from construction, if the deterministic design method is used and the effects of climate change are to be taken into account.