I have to admit, I'm a little taken aback by the "It's impossible!" thinking of some people in this group. It's so intense that we now have a seperate thread devoted solely to slamming the OP?! Come on!

Ok, so if this big, ugly, hairy, scary situation ever happened, you would just dig in and not even consider such a trek, no matter what. We got it.

Nobody said it would be easy. It's impractical, sure, but that's what makes the thought exercise so practical. I'm pretty sure the OP stated that this isn't the be all and end all of her preps, but rather one level of preparedness she's working on. Never did she say this is her only plan or the only scenario she's working on.

This scenario might never happen, but in working on a plan for it, might the OP actually be better prepped for more realistic situations? I think so. It's all about finding solutions. Can you carry 400 miles worth of water on your back? No. But you can carry to means to make 400 miles worth of water. If you're prepared to make 400 miles worth of water, would you be better off in a bug-in scenario? You bet you would!

There's a solution to every problem so why don't we focus on those, instead of slamming the OP. If you have nothing to add to that discussion then I recommend taking my Grandpa's advice and zipping your lip.