Among the natural phenomenon for which these plants were built, was an earthquake induced Tsunami.
Along some coastal areas of Japan where population density is high, Tsunami walls are extensively built as Tsunami protection. Japan is the more prominent country which has used tsunami walls to have protection against locally generated tsunami. These walls are of 4.5 metres. Theses walls are also designed to redirect water in the event of a Tsunami facilitating floodgates and channels.
Variations in height of protection in Japan varied, some up to 30 feet which appears to be based on local topographic features.
At these reactors, a design of about 16 feet was provided. This height was considered well above any conceivable scenerio. The actual wall estimated at the plant was about 45 feet.
Obviously, it's back to the drawing boards.
I understand that the San Onofre reactors at San Clemente are designed for a Tsunami of 30 feet. News to me.
