San Francisco and probably St. Louis are in a comparable situtation. Some day the great earthquake will come. But when? And you can't protect against an earthquake with levees. And you can't, realistically, dismantle a city either.

The Japanese and Chinese, for example, have suffered terrible earthquakes. One at Kobe, Japan, in 1985 leveled the city and killed 5,000 people. It took ten years to rebuild. 100,000 died from a quake near Tokyo before World War II.

Such risks never go away.