Here's what happens to engineers who can't do physics. Do you think any seawall would have held this? No, because this is not a wave! This is a giant sliding sheet of water coming towards you, like water held in a cookie tray. Put a wall in front, and it jumps it, up to 100 feet high. Putting faith in a seawall, is like assuming your plant can take an earthquake, without any thought (physics) put into it.
In the pictures, note that the plant is perfectly intact up a few stories. Can you think of a better place to put backup generators other than the basement?