Well a 1 in 1000 year event that may affect all the reactors in Japan. There's some geographic information you have to include in this analysis. Also, like i said somewhere else a 1 in 1000 year event could be something insignificant depending where your reactor is located...

That's not quite right. According to your math a 1 in 1000 year event affects a reactor every 3 years and leads to a meltdown. A 1 in 1000 year event could be a magnitude 6 earthquake depending on where the reactor is built so it might have no effect.

Agreed, you certainly can't plan for everything and you do try to plan for the worst case. That's why there's not just one backup system but a few different ones and the plant is designed with bigger safety factors than normal. Also each backup system is maintained by different personnel so the "human factor" can partially be taken out of the equation. It's impossible to have something that's 100% resistant to everything...

A 30 meter wall would be the same height as a 10 story building... It might also stop the water from leaving the area thereby causing more problems. These things are usually designed with pretty good safety factors and with redundant systems. If it were just the earthquake or just the tsunami we probably wouldn't have this scenario, its the combination of both that caused it... Do remember an earthquake of this magnitude is a 1 in 1000+ year event. It's not realistic to plan for those when the life of your reactor is 50 years...