It’s already doing that. However most of New Orleans is below sea level and that entire part of the state is a river delta/swamp. All of that low lying swampland is receding, potentially leaving New Orleans as a small island out at sea.

You can no longer just protect the city from floods, no longer just reinforce the coastline, you’d have to protect the entire lower part of the state. And it’s not just rising sea level, but floods from the entire Mississippi watershed, and hurricanes. That’s just not reasonable or sustainable