[nikdaheratik]

You say that, but Detroit is a pretty good counterexample. Tons of money / land just left to rust because it wasn't worth the effort. And that was just due to industrial changes not even something approaching a natural process.

If the ports not worth that much, the beaches (and tourism) has washed away, they've got a new sewage problem due to rising waters, and they can't get fresh water as easily, then what reason is there to rebuild? You need trade, fresh water, and waste removal to keep a city running, and for Miami, they're going to have problems with all three areas.