It is true that natural systems should be reestablished to add protection.  However, even with these intact, New Orleans is low and sinking.  The U.S. is large and there are many competing funding needs.  It is unwise to spend hundreds of billions in an effort that could ultimately prove futile and lead to greater disasters.  (Sound familiar)  New Orleans will remain a very easy terrorist target when water levels are high.

Most of the low parts of the city should not be rebuilt or protected.  Funds should be used to help dislocated folks instead.

Side note:  Water topping over levies for a long period of time is not a disaster.  The problem is when the flow of water into the city exceeds pumping capabilities.  Then you get flooding if that condition lasts long enough.