"Forced to Leave"
The better half and I have been talking about this for a couple of weeks now. We're both convinced that the Government (federal, state, local) lacks the legal/constitutional power to actually force people out of their homes in a "mandatory" evacuation. The relevant comparison is the right to refuse life-saving medical care. The Government cannot force you to save your own life. People have certain privacy rights, and these privacy rights are very closely tied to their homes. Indeed, this is partly a property right, or mostly a property right, depending on how you want to frame it. So I think Government lacks the authority to force people out of their own homes; it can conduct a mandatory evacuation of Government property, but only because there the Government is the landlord.
Now, Government has the authority to say: "If you stay here, we can't come back and save you. You're on your own, starting at H-hour." Again, the analogy is refusing life-saving medical care. If you decline, then you're on your own. But people have a legal right to decline to be saved. I'm convinced of that.
The reason that has been bothering us is that news anchors seem absolutely fascinated by the possibility of police or soldiers forcibly removing people from their homes. Now, generally, Governments don't do this, because it would be very impractical, not to mention a poor use of resources. But I think that there's a good substantive due process argument against it, too.
Btw, Government could condemn the properties, in keeping with the Takings Clause (although there is that "public use" problem). But it can't just issue a "mandatory" evacuation order and then force people out of their homes.